After years of resisting calls to develop an electric version of its popular hydraulic Vector stabilising fins, Sleipner has finally bowed to pressure from boatbuilders and revealed a brand new range of all-electric fins.

Over four years in development and featuring a number of new innovations to maximise the efficiency, quietness and safety of both the actuators and the fins, Sleipner is confident that its latest offering will not only match the performance of its existing hydraulically driven fins but also outperform its electrically driven competitors.

Speaking to Motor Boat & Yachting, Sleipner CEO, Ronny Skauen, said that it had taken this long to develop the new system because of his determination to ensure the same high levels of safety and reliability inherent in the company’s hydraulically activated fins.

“Hydraulics are very powerful, very quiet and very reliable and can cope with shock overloads,” said Skauen. “Even if they do fail you can always release the pressure to let the fins return to their neutral position.

“Electro-mechanical systems tend to be noisier and there’s a greater risk that the motor or gearbox could seize, leaving them stuck in the up or down position. It took us a long time to find effective solutions to these issues.”

Safety first

One of those solutions is a very unusual gearbox design called a Harmonic Drive Strain Wave gear that uses a unique elliptical cog bearing that can withstand extreme loadings while delivering exceptional reliability and very high gearing ratios. It can even slip without destroying its interlocking teeth.

Skauen admits it is a costlier and marginally more power hungry solution than traditional planetary gears but points out that there’s a reason the Mars Rover space vehicle and Lockheed F35 fighter jet also use the same type of gearing.

Article continues below…

Sleipner curved fin stabilisers put to the test

We test new zero-speed, curved fin stabilisers to see if they can create less drag and end rolly cruising

Seakeeper targets high-end motor yachts with Seakeeper 18 gyroscopic stabiliser

Resolving the noise issue also took some lateral thinking as the problem isn’t just the sound of the motor and gears accelerating and decelerating causing a distinctive (and more noticeable) rise and fall in pitch than the near silence of a hydraulic piston or background thrum of a generator, but also the actuator’s tendency to reverberate through the hull.

Skauen says that the hull moulding can act like a loudspeaker membrane with certain resonant frequencies causing it to vibrate and create noises in areas of the boat some distance from the actuator itself.

However, unlike an engine that can be isolated from the hull structure on rubber mounts, the fin mounts have to be absolutely rigid to cope with the enormous rotational torque forces. The solution was a new damping material and arrangement that retained the necessary torsional rigidity while still isolating the actuator from the hull.

Elongated cutaway shape improves efficiency

Arguably the biggest change of all is in the shape of the fins themselves. Sleipner has been championing its patented curved Vector fins for over a decade now due to the extra stability at rest and fuel efficiency underway that they offer over traditional straight fins.

This is because Vector fins splay outwards from the hull creating more vertical stabilising force and less horizontal force at anchor than a straight fin with its forces acting at a constant 90 degrees to the deadrise angle of the hull. The Vector fins also generate more lift underway at speed to help offset the drag created by any external fin.

Sleipner’s latest design, developed specifically for its new electric actuators, is its most extreme yet, boasting even more significant gains in stabilisation at rest and drag reduction at speed as well as a decrease in unwanted side-effects such as sway, yaw and anchor walk (when the fins paddle the boat forward over its own anchor).

Stability gain

They still curve upwards like the original Vector fins, only more so, but they are also considerably longer and shallower than previous designs, with a cutaway shape that keeps the faster-moving tips further away from the hull than the slower-moving leading edges.

This helps prevent an unwanted interaction between the fin and hull that was reducing the size of the efficiency gains. The end result is an unprecedented gain in stabilisation efficiency as well as increased lift underway. Sleipner’s own measurements show that these new fins are now twice as effective at anchor as flat fins of the same size and speed.

The other big advantage of the new electric fins is that they allow a larger rotational swing than hydraulic arms, which are typically limited to 35 degrees either side of neutral. This gives greater flexibility in how fast, how far and how long the fins are rotated in order to achieve the best stabilising effect.

Why curved fins generate more of the desirable vertical stabilising force and less of the undesirable horizontal one

It also enables more sophisticated algorithm controls to counter the effect of anchor walk by adding an occasional backwards paddle rather than constantly paddling one way or the other as some rival electric fins do.

The end result is Sleipner’s most efficient fin shape yet and one which will, in time, be adapted for use on its hydraulic range too. Skauen falls short of saying that Sleipner’s new electric fin systems are superior to its hydraulic ones but does admit that they have a number of advantages both for builders, who no longer need to allow for hydraulic pipe runs and electro-hydraulic pumps, and users who can enjoy all the benefits of Vector fins without some of the less desirable side effects.

Although full details and prices of Sleipner’s new electric fin stabiliser range haven’t yet been confirmed, there are likely to be five different packages with fin sizes from 0.6m² to 2.5m² covering boats from 55ft up to 130ft with fully installed prices starting from around €90,000 inc VAT.

First published in the June 2023 issue of MBY.

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This article These electric curved fin stabilisers from Sleipner could be a total game changer appeared first on Motor Boat & Yachting.

Humphree may have invented the original interceptor trim tab and the first active trim stabilisation system, but with competitors like Zipwake and Seakeeper now offering similar alternatives, the Swedish manufacturer needed to move the game on.

The new Humphree Lightning series of automatic interceptors does exactly that. Aimed at the market for 20-45ft boats with top speeds of up to 60 knots, it is said to offer better stabilisation under way, as well as improved automatic trim, pitch and cornering control, plus a number of other new features.

The most visible of these is a row of underwater lights built into the interceptor blade’s housing. The 25W LEDs are moulded in as standard during the manufacturing process and are fully adjustable for colour, although Humphree charges an extra €870 to have them enabled.

By combining both trim and underwater lighting functions into a single integrated unit, it saves space on the increasingly busy transoms and dashboards of outboard-powered craft, and avoids having to drill two sets of holes for cabling runs.

This fits in very neatly with another of Lightning’s key new benefits – easy installation. Because the brushless motor for the interceptor blades is now built into the external housing, rather than being in a separate drive unit mounted on the inside of the transom with a drive shaft connecting the two, the only through-transom fitting is for the slender watertight cable supplying power and relaying signals to and from the control unit.

All the installer has to do is screw the mounting bracket onto the transom, drill a small hole for the cable fitting and bolt the Humphree Lightning unit onto the back of it. This is sealed in the factory to ensure it remains watertight, with any software upgrades made over the air via Wi-Fi and Bluetooth.

Article continues below…

Keeping things on the level with Humphree stabilisers

Humphree takes the zero-speed fins story a stage further with its new integrated trim and stabiliser system, writes Dave Marsh

Induced drag and its effect on fuel efficiency explained

Our technical expert Dave Marsh explains how induced drag can affect the fuel efficiency of your boat

Customisable blades

Another first for Humphree is the option of a chine-shaped blade that can be cut to fit the shape of your boat’s hull. This not only looks neater but enables it to be fitted at the outermost edges of the transom where it has the maximum stabilising effect.

The blades themselves have a 2-inch (50mm) stroke and are mounted as close to the hull as possible, again to maximise the lift created and the speed of operation.

The interceptor blades trap a wedge of water creating lift on the hull

As with all interceptor-style trim tabs, they work by trapping a wedge of high pressure water in front of the blade which acts like an upside-down ramp, forcing the main flow of water down and generating lift on the hull.

Although it looks like this would create excessive drag, it’s actually more efficient than a conventional trim tab and often improves fuel consumption by optimising the boat’s running angle for any given speed.

Diagram showing how the Humphree Lightning system reduces roll

Stabilising influence

Controlling it all is a sensor unit with built-in accelerometers, gyroscope and GPS receiver. These constantly measure the boat’s speed, heading, trim (fore and aft), list (side to side), and pitch and yaw movements.

Humphree’s own software and algorithms use this information to apply the exact amount of lift needed to counteract any imbalance and keep the boat running as flat and level as possible.

This applies to everything from constant forces such as uneven loading of passengers and crosswinds to fast-changing movements such as throttle and steering inputs as well as individual waves.

The speed and precision of the interceptor blades (they can fully extend in just 0.65sec) and the algorithm’s ability to learn and predict the wave pattern also enables these trim tabs to act like a dynamic stabilisation system.

It’s not as effective as a gyroscopic or fin-based stabiliser, as it’s reliant on the boat’s speed through the water to create lift (they don’t make any difference at anchor), but Humphree claims it typically reduces roll by 35-50%.

Multiple sensors monitor the boat’s movement over waves and make rapid adjustments to the blades to counter roll, pitch, list and trim

Ironically, the faster the boat is travelling, the more effective it becomes but as most planing boats are more dynamically stable at speed anyway, that is arguably when it’s least needed.

What it does make a big difference with at speed is turning. The coordinated turn control function works by lowering the interceptor blade on the inside of the turn to reduce the amount of lean and tighten the turn itself. Humphree likens this to a ‘go-kart’ setting, enabling the boat to turn faster and flatter.

The final part of the package is a 3.5in colour touchscreen control panel that can either be frame- or flush-mounted into the dashboard. Simple one-touch settings allow the user to switch the automated functions on and off – as long as you have paid for them to be enabled.

The sealed unit has the motor built into it so it only needs one through-hull fitting for the slender cable

Humphree Lightning package options

Two sizes are available, 300mm wide and 450mm wide with either flat or chine-shaped blades. Prices for these start at around €1400 and €1600 ex VAT respectively, including the control unit and touchscreen panel.

However, this only buys you the physical kit with manual control of all the functions. Upgrading to automated trim, pitch and list control (Comfort package) costs another €1,660. Adding cornering control (Comfort PLUS) costs a further €2,110 and full stabilisation (Dynamic PLUS) costs another €2,830.

This is on top of the €870 already mentioned for enabling the underwater lights. Although this makes perfect sense, because it keeps the base price low and means customers only pay for the features they want, we do wonder whether some customers might baulk at paying thousands of pounds simply to download software.

That said, the majority of Humphree Lightning systems will be sold as a factory-fit option on brand new boats with most of the functions already enabled and factored into the options price.

Either way it is still a lot cheaper than any gyro or fin-based stabiliser system and should make for a safer, more comfortable, more efficient boat.

First published in the December 2022 issue of MBY.

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This article Humphree Lightning first look: Quickest ever auto trim and stabiliser system appeared first on Motor Boat & Yachting.

Like most boat owners, I had long wanted to fit some form of stabilisation to our 2004 Fairline Squadron 58.

In the four years I have owned her, we have made extensive improvements: new interior, electric blinds, new exterior upholstery, new teak, new helm seats, helm refurbishments, mood lighting, watermaker and much more.

There were not many projects left and I had no real desire to change the boat, so adding stabilisers was the obvious next step. The snag? Simple: cost.

There is no cheap way to stabilise a boat. I’d assumed electric fins would be cheaper than hydraulic ones – just how much can a few motors attached to some flippers cost?

Article continues below…

Smartgyro SG40 vs Seakeeper SK9: Boat stabilisers compared

Seakeeper targets high-end motor yachts with Seakeeper 18 gyroscopic stabiliser

Answer: even more than hydraulic fins! How much are hydraulic fins? Even more than a gyro. Oh well, a gyro it is then! But fitting a gyro stabiliser brought with it two problems.

Money, as I have already alluded to, but also where on earth to put it without spoiling the boat and losing space we actually used.

A chat with Seakeeper distributors Osmotech in Southampton yielded a price that, while as much as a Porsche Cayenne for a steel beach ball with some electronics attached, I could live with. So that just left the question of where to put it.

Seakeeper SK6 installation

We looked at multiple options. Crew cabin? No. We use the crew cabin for, er, crew! Utility room? Possible, but the Fairline Squadron 58 galley has very limited storage so the practicality of the whole boat revolves around the utility room, which in my case holds a washing machine, second fridge and lots of cupboard space.

There was also the small matter of getting it into the utility room, which while it didn’t faze Osmotech (we’ll just cut out the roof!) did not fill me with joy, and the idea of a smaller utility room went down even worse with my partner Joanna.

The only other fitting option was to remove the batteries from the lazarette, drop the gyro in their place and relocate the batteries. It would make the lazarette about 8in shallower but that wasn’t a problem as it was pretty deep anyway.

Finding space to retrofit the 400kg Seakeeper gyro was quite a mission

The next issue was where to put the batteries. Osmotech assured me they would find a suitable place once the boat was in bits but the hope was that they could go below the floor of the crew cabin.

Despite this uncertainty, I gave them the go-ahead and the boat was duly taken to pieces.

Unfortunately, finding a home for six very large batteries proved to be more of a challenge than expected. The crew cabin floor did not have enough depth and putting them in there would have meant losing one bunk and restricting access to the stern locker.

After much deliberation a bespoke rack was made to store the batteries in the engineroom

It would have also put a load more weight at the stern of the boat, which given that we were about to drop in an extra 400kg of Seakeeper as well, did not seem like a great idea.

We considered putting them under the port cabin beds but the cable runs would have been too long. That just left the engineroom.

On a Fairline Squadron 58 there is a void covered by a panel next to the generator. This looked hopeful. The suggestion was to split the batteries between there and another similar void on the other side.

Batteries installed with room for access and removal

The only snag was that getting those batteries out again would be a major job as the gyro would effectively block them in. At this point I think Osmotech were losing the will to live.

The Squadron 58 is generously proportioned but the engineroom is not really fit for a cocktail party and we were running out of options.

Their solution was to build a custom racking system that would allow the batteries to be stacked two deep next to the generator. This would then be boxed in and vented to keep them safe and secure from the rest of the engineroom.

Once the batteries were removed from the lazarette, the Seakeeper mount was secured to the hull and the SK6 lowered into place

This was a great idea. The batteries wouldn’t impact engineroom access and would still be reasonably easy to change. That said, to avoid having to change them for as long as possible I asked for the batteries to be given a health check.

Even though they weren’t yet causing any issues they all failed the test – so it was out with the credit card once again so a new set could be fitted.

After four long weeks and plenty of head scratching and tooth sucking, the gyro was finally in and the only thing left was to find out if it worked. Seakeeper has an app that measures boat roll with the gyro on and off.

The official sea trial showed an 84% reduction in roll and my own test in an otherwise untenable anchorage showed a similar 83% reduction.

Gyro life

Having never been out on a stabilised boat before I didn’t really know what to expect. Firstly, you can hear it spinning, which was a slight surprise. I would liken the noise to the engine fans being on.

That said, you need to run the generator all the time anyway and that drowns out pretty much all of the gyro noise. So the only time you’re really aware of it is when you return to port at the end of the day and switch off the engines and generators, at which point it takes about half an hour for the noise to subside, even though it takes a further three to four hours for it to stop spinning!

Artist Joanna can now paint on board without fear of passing wakes. See her work at: joannabenfieldart.com

The first time I took it out, there was a Force 4 blowing directly into Bossy’s home port of Cala d’Or, Mallorca. The waves were about 1.5m high and I put the boat beam on to see what happened.

To my disappointment it rolled. I went to the cockpit to better judge the size of the swell and was met with a wall of water approaching me – it really was pretty rough.

I then turned the gyro off and all hell broke loose. Lesson one: you can’t defy the laws of physics! The gyro reduced the roll and just as importantly, rather than the boat taking some time to settle after each wave had passed, it just stopped bolt upright after the initial roll.

Results of the sea trial showed an 84% reduction in roll with the Seakeeper SK6 running, enough to make otherwise untenable anchorages comfortable for Jeremy and his guests

A more real world test took place a few days later in an exposed anchorage with a swell of about one metre. The gyro removed all but the worst of it, with the control panel showing roll of between 0 and 1 degree most of the time.

Every now and then a larger wave would make the boat roll a few more degrees but it turned a marginal anchorage into a good one.

Just don’t expect it to turn a rough anchorage into a mill pond – it can reduce roll but not eliminate it altogether. A larger gyro might give even better results but a larger gyro was not practical or possible on Bossy.

Once in situ the Seakeeper is relatively discreet and any noise it makes is masked by the sound of the generator, which needs to run continuously to keep the gyro powered up

A long wavelength swell is more of an issue as the gyro can only suppress the roll for as long as the flywheel is being swung backwards or forwards on its axle by a hydraulic ram (known as precession).

There is a balance to be struck between how fast the flywheel is being moved (the force) and the time that force can be applied for. The electronics sort this out but if a roll needs three seconds of force to suppress it and only two seconds are available then the boat will roll. I am sure there is a more technical explanation but I think this captures it.

Boat wakes, on the other hand, simply disappear and an already calm anchorage becomes as still and peaceful as a marina, as we discovered during an overnight trip to Es Trenc – a huge beach with clear blue seas and a sandy bottom.

My partner is an artist and she now sits on the boat all day painting – an impossible dream in pre-stabiliser days – so overall it is pretty stable!

User friendly

Seakeeper has taken simplicity to an extreme. There is an on/off button and a stabilise/don’t stabilise button. That is it. There is also a quiet mode that reduces the gyro speed by about 1,000rpm but I can’t really see why you would want to use it given that you can’t hear it over the generator.

It is a shame there isn’t an app connected by Bluetooth as that would let you see what the gyro was up to from the upper helm without having to install a second set of controls.

The Seakeeper gyro has opened up many more anchoring opportunities

It would also allow you to turn the stabilisation off. I am sure this desire is suppressed with time but as a new owner you always want to know what it’s like without the gyro on just to remind you why you spent all that money!

It also lacks a couple of other features that strike me as obvious – the ability to automatically switch stabilisation on when it reaches operational speed and a remote start so you can programme it to begin spooling up 40 minutes before you want to leave your berth.

The only other surprise is the frustratingly basic documentation supplied with such a sophisticated and expensive bit of kit.

With Seakeeper fitted, running the boat is stable in all but the roughest conditions

The only way I have found of getting more information is by going to the FAQs section of the Seakeeper website, which covers things that really ought to be in the operating manual, such as warnings about avoiding sudden manoeuvres with the gyro on, for example. Even then the FAQ pages do not cover some real world limitations.

Seakeeper cost options

The cost will vary depending on how complex the installation is. Some newer boats already have the cradle for a gyro pre-installed during the build, making it almost a drop-in option.

As a rule of thumb for retrofitting one to an older boat, take the cost of the gyro excluding VAT and double it to give you a rough idea of the likely total cost.

Jeremy’s Seakeeper was fitted by UK installer Osmotech

Seakeeper also sells factory refurbished units for a discount of around 20 per cent, which helps make the numbers more palatable. Mine was a refurbished unit, the only difference being a one year warranty as opposed to two, but you can still extend the warranty if you wish.

Another cost you will need to factor in is running your generator all the time you are on the boat. You may do this anyway for powering the air con etc but it does rack up – in my case £100 or so of diesel every 24 hours.

Finding a trusted Seakeeper fitter

My boat is based in Mallorca but I chose a UK installer. I have known Osmotech for some years. They have a good reputation and they quoted to install a gyro on my previous boat, a Fairline Squadron 65.

I did get competing quotes in Mallorca, which were pretty similar, however I wanted to use a company that I knew had done plenty of Seakeeper installations before and from whom I had a chance of some comeback if it went wrong.

The cost of a gyro is significant, the installation itself is invasive by nature and it applies some pretty staggering forces on the hull to keep the boat upright so while I have never heard of it happening, the worst case scenario of the gyro breaking free would be pretty messy. Trying to deal with something like this in the Spanish court system doesn’t bear thinking about.

Seakeeper models

I have installed a Seakeeper 6. The SK6 is recommended for boats of up to 52 feet and 24 tonnes. My Squadron is 58 feet long and weighs 22 tonnes.

Seakeeper has a sizing tool that aims to size gyros based on eliminating 80% of roll at +/- 10 degrees of roll, with the minimum acceptable reduction of 80% at +/- 6 degrees.

The prediction for my boat was 80% at +/- 9 degrees of roll with an SK6, rising to 80% +/- 14 degrees with an SK9. The SK9 would have been overkill plus it was even more expensive and would not have fitted the spaces we had in mind.

Worth it?

Who knows? Mine is a 2004 boat and the gyro represents a decent percentage of its value. However, the knowledge that I will get much of the cost back when the time comes to sell it on makes this more palatable.

It is not a miracle cure but in the vast majority of ‘normal’ boating situations it removes pretty much all boat roll and in a really undesirable anchorage it will reduce it to a level you can tolerate.

The main thing is it makes boating a more pleasant experience for everyone and the wakes of passing boats no longer result in your lunch being deposited all over the floor.

I used to think the cost of not fitting a gyro would pay for a lot of marina nights but the bigger issue is all those anchorage days we’d have missed out on because it would have been too uncomfortable without one. For this alone the Seakeeper has already earned its keep.

Top tip

Think very carefully about where it is going to be installed and if that results in other bits being displaced – batteries in my case – where they are going to go.

First published in the February 2022 issue of MBY.

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This article Seakeeper SK6 installation: How I stopped the rock on my Fairline Squadron 58 appeared first on Motor Boat & Yachting.

Until recently boat owners looking for an effective means of stabilisation at anchor have faced a fairly simple choice between fins and gyro stabilisers. But whereas the market for fin stabilisers is well served by a number of players such as Sleipner, Trac, Quantum, Humphree, CMC and others, the options for gyro stabilisers have been rather more limited.

Thanks to the compact size and efficiency of its vacuum-sealed gyroscopes (most gyro competitors use larger unsealed flywheels), Seakeeper has become the default choice for many owners and manufacturers alike.

Now, however, there’s a new kid in town with both the technology and the financial clout to rival its American counterpart.

Article continues below…

Seakeeper 1: The entry-level unit bringing stabilisation to the masses

Could boat stabilisers spell the end of rock ‘n’ roll?

The latest developments in boat stabilisers and control systems are heralding new levels of on-board comfort, writes our technical guru

Italian start-up

Smartgyro was launched in 2014 by a small group of ex-military engineers with the knowledge and determination to build their own take on a vacuum-sealed gyroscopic stabiliser. Based in Italy’s boatbuilding heartland of La Spezia, it made steady inroads into its home market but it wasn’t until the Yanmar Group took a majority stake in the company in 2018 that things started to take off.

Now, with the financial power and the distribution network to become a major global player, it has recently launched two new gyroscopic stabilisers into the market with a further four set to follow.

The Smartgyro SG40 and SG80 were both launched at the 2020 Genoa Boat Show last October. The SG40 is intended for boats of 50-60ft weighing up to 35 tonnes, making it a direct competitor for the Seakeeper SK9, while the SG80 is for boats from 60-70ft weighing up to 50 tonnes like the Seakeeper SK16. An SG20 is due to be launched this summer for boats from 43-50ft. Larger and smaller gyros will follow at a later date.

The stabiliser breaks down into separate parts to fit through small openings

Smartgyro claims that all of its products offer very similar performance to their Seakeeper counterparts in terms of roll reduction, noise and start-up speed but with a number of significant advantages and a lower price.

The first claimed benefit is that their modular construction makes them easier to install in tight spaces, as the main components can be broken down to fit through small access hatches then assembled in situ. Provided the ball-shaped vacuum dome can be squeezed through the gap, the larger base frame will easily pass through in four separate sections.

The second claimed advantage is that they can be completely stripped down and rebuilt on board the boat rather than having to be removed and sent back to the factory when something major needs replacing, such as the flywheel’s main bearings. This is partly because the vacuum-sealed dome is initially filled with air rather than helium allowing the vacuum to be restored quickly and simply on board the boat once the repair has been completed.

Smartgyro claims a roll reduction of up to 90% when running at full RPM

Attractive price point

The third claimed difference is that when operating at planing speeds the Smartgyro will automatically lock itself as it turns into a corner, preventing it from trying to resist the boat’s natural angle of heel as it banks through a turn. In fairness to Seakeeper, this can be done manually and on the smaller boats we’ve tested it hasn’t adversely affected the handling anyway.

For many owners, however, it is likely to be the pricing that attracts their attention. Smartgyro’s aim is to undercut Seakeeper’s equivalent products by around 10% – the base price of the SG40 is €65,000 compared to $85,000 for the SK9. Installation costs will of course vary from boat to boat.

We haven’t yet tested any of Smartgyro’s products but closer inspection of the SG40’s specification certainly suggests a similar set of parameters to the Seakeeper SK9. The Smartgyro appears to use a heavier flywheel (total unit weight 650kg versus the SK9’s 550kg) which spins at a slightly slower rate (7,500rpm vs 9,000rpm) to generate a similar angular momentum (9,100Nms vs 9,000Nms).

Smartgyro’s SG80 uses a vacuum sealed flywheel to reduce air resistance and spin faster

This means they both develop a very similar level of anti-roll torque (19,000Nm vs 18,810Nm) so they should provide similar stabilisation.

Smartgyro claims that using a slightly heavier, slower flywheel gives a shorter start up time of 25 minutes vs 38 minutes before it generates meaningful stabilisation, although the total spool up time to maximum revs is an identical 55 minutes.

The downside is that it has a higher electrical draw (4kW vs 3kW on start up, and 1.5-2.5kW vs 1-2kW when running) and the extra weight may have a small effect on the boat’s performance and trim. Both units create an identical sound level of 68-70dbC when running at full revs and have similar service intervals of 1,000 hours/annually.

It remains to be seen whether these on-paper comparisons translate to similar performance out at sea but the emergence of a credible new European competitor using a vacuum-sealed flywheel in this fast growing sector of the stabiliser market can only be a positive thing for boat owners and builders alike.

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First published in the July 2021 issue of MBY.

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Be first to all the latest boats, gadgets, cruising ideas, buying advice and readers’ adventures with a subscription to Motor Boat & Yachting. Available in both print and digital formats, our monthly magazine will be sent directly to your home or device at a substantial discount to the usual cover price. See our latest offers and save at least 30% off the cover price.

This article Smartgyro SG40 vs Seakeeper SK9: Boat stabilisers compared appeared first on Motor Boat & Yachting.

It’s amazing to think that Seakeeper has only been with us for just over a decade – the very first Seakeeper stabiliser to be sold was in 2008. Today the 200-employee strong business has a range of 11 units (nine for leisure boats, two commercial) that cover most sizes and styles of boat from 27ft through to 85ft, and even larger if you install more than one unit.

All Seakeepers work in the same way. Spinning a flywheel in a vacuum at speeds of over 500mph creates a strong gyroscopic effect, the ability of the rotating body to maintain a steady direction of its axis of rotation. It’s why motorcycles don’t fall over once the wheels are rolling at speed.

Once you have an object determined to remain resolutely upright then you have something solid to push against, and it’s that ability that allows the hydraulics to resist roll. It’s a very different concept to fin stabilisers that physically push against the sea, and has the advantage of zero drag and all the mechanical parts remaining inside the boat. Plus it will work at any speed, right down to zero.

New to the range is the Seakeeper 18. Designed for boats in the 65ft-75ft range or up to 56 tonnes, it’s the same size and weight as the Seakeeper 16 but spins faster, developing 18,000 Newton-meter-seconds of angular momentum instead of the Seakeeper 16’s 16,000 Nms. It means that boats that previously required two smaller Seakeeper units to generate sufficient stabilisation can now be fitted with one more powerful unit.

The Seakeeper 18 retails for £117,144.

This article Seakeeper targets high-end motor yachts with Seakeeper 18 gyroscopic stabiliser appeared first on Motor Boat & Yachting.

Dutch company DMS Holland is hoping to revolutionise the market for stabilisers with a new design of flapping fins specifically designed for fast-planing motor boats.

The company originally made a name for itself with its cylindrical MagnusMaster rotating stabilisers for displacement boats, and last year it launched the AntiRoll ‘flapping’ fins for superyachts. Now it plans to develop this AntiRoll technology into a smaller, cheaper, more effective package for fast production boats.

The key to this new design of high-aspect ratio fin is that they attach to the transom of the boat rather than being fitted through the main section of the hull. This makes them easier to install (the hydraulic actuators of traditional fins often have to be tucked under the floor of the master cabin) and ensures that all the internal workings can be kept in the engine bay, reducing noise disturbance at night.
It also has a number of interesting dynamic benefits. Because the fins rotate on two different axes, they can be swivelled all the way round so that they tuck in behind the transom. This not only reduces drag to negligible levels at high speed, but also enables them to double up as active trim tabs, tilting up and down to correct both roll and lean in much the same way as Humphree’s Active Interceptors. This means that instead of installing separate trim tabs and stabilisers, customers will soon be able to specify one set of AntiRoll stabilisers that should cover every eventuality from trim and lean to stabilisation at high speed, low speed and at anchor.

Although DMS Holland won’t yet reveal the full details of how the new system works across such a wide range of speeds, the illustrations appear to show three different operating modes: high speed, low speed and zero speed.

High-speed mode

At high speed, the fins tuck in along the trailing edge of the transom using small rotations of the fins to deflect the water down and create the lift on one side or the other, much like an oversized trim tab. The large surface area of the fins and high pressure of the water running over them at speed means tiny movements will generate substantial lift.
When combined with fast-acting electric actuators linked to the system’s roll sensor, this should enable them to react to any lean or roll and correct it almost instantaneously. Their ability to tuck away behind the transom will also be handy when it comes to berthing in a marina or manoeuvring in tight spaces.

Low-speed mode

At slower displacement cruising speeds, the fins swivel round into their extended position where they will rotate up and down in the same way as the high-speed mode. Although the slower speed of the water passing over them won’t generate as much pressure, their greater distance from the centre of roll ensures they will still create more than enough lift to counteract any side-to-side rolling. In fact, the long, thin, high-aspect ratio design of the fins, similar in shape to a glider’s wings or the pectoral fins of a humpback whale, not only create 50-75% less drag than the equivalent surface area of conventional fins but are also more efficient at generating lift where it’s needed the most.

Zero-speed mode

Finally, when the boat is at anchor and unable to rely on water passing over the fins to create lift, it reverts to the same actuator used to extend and retract them to flap them up and down like a pair of wings.
Once again, the high-aspect ratio design of the fins, the extra leverage gained from being further away from the boat’s roll centre and the fact that the whole fin is moving up and down rather than pivoting around an axis is claimed to make them more effective than conventional fins.
Although DMS Holland makes no reference to it, we suspect that it may also reduce the paddle effect that causes some boats to ‘swim’ over their own anchor.

One-stop solution

Patrick Noor, co-owner of DMS Holland, says: “Since there is currently no single system that performs optimally at both high speeds and at low speeds as well as at anchor, often multiple roll-damping systems have to be installed on one yacht. Soon, with our new system, one roll- damping system on board will be enough without having to compromise on stability at different speeds.”

Despite these claims, there is one obvious drawback of the new system – the position and size of the fins when retracted makes them unlikely to be suitable for twin sterndrive or multiple outboard engine installations. This rules out the majority of sportscruisers below 45ft, most of which are powered by twin sterndrive setups. However, for shaftdrive or IPS-powered boats, this does look like a very intriguing new prospect.
The AntiRoll technology has already been proven to work on much larger boats – a 37m Van der Valk was fitted with it last year, winning the approval of the ship’s captain and crew, so there is no reason it won’t work equally well on smaller production craft.

Testing under way

According to DMS, a number of major shipyards and dealers have already shown interest in the system and have indicated a willingness to test it on one of their models.
Alexander Jonkers, owner of the Dutch Fairline and Jeanneau dealer, Jonkers Yachts, has agreed to help test the system on one of his craft, adding: “I can’t wait to be able to offer the system to my Fairline and Jeanneau associates. In the meantime, I will support DMS Holland in the development and the first prototype will be tested with us.”

Full details of the new system will be revealed at the METS equipment show in Amsterdam later this year with the first deliveries of production systems scheduled for early 2019. DMS Holland hasn’t yet given any indication of pricing but with
so many players now offering stabilisation systems, it will have to be competitive to make inroads into an already crowded market.

Contact: DMS Holland

Radical retractable stabiliser fins AntiRoll

We test a new dual-axis stabiliser, which promises to be the best of both worlds with retractable flapping fins.

Sleipner stabilising fins on sea trial

This is not the first time we have taken a very serious look at Sleipner’s zero-speed Vector stabilising fins

This article Motor boat stabilisers: DMS's new stabilisation fins appeared first on Motor Boat & Yachting.

They say the best things come in small packages, and thanks to the all-new Seakeeper 2, you can now enjoy a fully stabilised ride on boats as small as 27ft.

The Seakeeper 2 uses exactly the same active gyroscopic stabilising technology as the larger Seakeeper models but at a fraction of the size and price. That means you and your guests can experience all the same benefits enjoyed by dozens of Princess, Sunseeker and Riva owners the world over but in a smaller, more affordable boat.

The Seakeeper 2 is specifically designed to fit craft in the 27-32ft bracket, reducing boat roll by as much as 95%. And thanks to its compact dimensions, ease of installation and lack of any external appendages, it will work just as well on a high-speed sportsboat as it will on a single-engined displacement cruiser or outboard-powered pilothouse craft.

Measuring just 2ft 1in by 2ft 2in and 1ft 8in high, the Seakeeper 2 is small enough to fit under the seats or inside the centre console of most open-cockpit craft, while those with higher freeboards can usually fit it in the bilges. Nor is there any need for a generator, as the system is designed to run off the boat’s existing 12V domestic battery power source.

You and your guests will immediately appreciate the extra comfort, stability and feeling of security that a Seakeeper 2 offers. And because it helps prevent the rolling motion that induces seasickness, you can invite whoever you want whenever you want, safe in the knowledge that every day is a calm day on a Seakeeper-equipped boat.
To find out more about how the new Seakeeper 2 works and to see how it could dramatically improve your boating experience, visit www.seakeeper.com or contact your nearest Seakeeper dealer.



At a glance…

Vacuum-sealed casing

Enables the gyro to spin three times faster due to reduced air friction.

Reduced weight

With speeds of up to 9,000rpm, it produces the same powerful effect from a lighter gyroscope.

Sealed for life

Provides unbeatable protection for the bearings against the marine environment.

Compact packaging

Allows you to site it wherever you choose, it doesn’t have to be on the centre line.

No separate generator

DC power enables it to run off the boat’s existing 12V electrical circuit.

Reduce roll by up to 95%

Hydraulic actuators tilt the gyro fore and aft, creating powerful side-to-side torque.

Active control

Senses the sea state and reacts instantly to help prevent seasickness

This article Still waters: Make every day a calm day with the new Seakeeper 2 stabiliser (sponsored post) appeared first on Motor Boat & Yachting.

For the first time, boaters with smaller vessels can take full advantage of a technological innovation that’s been available on larger boats for nearly a decade thanks to the Seakeeper 3.

The all-new Seakeeper 3, which runs on 12v DC power and does not need a generator to operate, eliminates up to 95% of boat roll, the rocking motion that causes seasickness, anxiety, and fatigue.

It’s optimised for boats between 30-39ft, bringing a fundamentally new way of being on the water to a whole new class of boaters.

Even small centre console boats like this Contender 32 can feel the benefits of gyro stabilisation

The Seakeeper 3’s computer-controlled gyroscope relies on the power of a steel flywheel spinning at very high speeds in a near vacuum.

When the gyro’s sensor detects boat roll, it tilts, producing powerful torque to neutralize the port to starboard motion of the vessel and eliminating the rocking motion that causes seasickness.

The Seakeeper 3 is 25% smaller and 32% lighter than the previous smallest Seakeeper model, the Seakeeper 5, and can be installed in as little as two days with no major structural modifications to the boat.

The unit can be retrofitted into a readymade helm bench unit too, making refit and new build installations on centre console boats even easier. Installed in a self-contained unit within the boat, the Seakeeper 3 guarantees no drag and no external damage.

The Seakeeper 3 is 25% smaller and 32% lighter than the 5

For boaters who rely on Seakeeper, boat roll is the farthest thing from their minds. That’s because boating with a Seakeeper means no more cancelled trips due to choppy waters and no more heading back to shore early because of a bout with nausea. Seakeeper has revolutionised the boating experience and the Seakeeper 3 is bringing that new reality to a whole new group of boaters.

But don’t just take our word for it; take a look at the installation video above.

More information seakeeper.com

This article The all-new Seakeeper 3 (promotional feature) appeared first on Motor Boat & Yachting.

This is not the first time we have taken a very serious look at Sleipner’s zero-speed Vector stabilising fins. Two years
ago we were observers during the stabiliser and engine commissioning trials on a Fairline Squadron 65 (see MBY September 2014).
This time we had a different and far more comprehensive experience.
We took to sea off the coast of Norway without the distraction of commissioning engineers and spent our time testing two very different vessels (a Princess 56 and a 58-foot workboat); Sleipner treated us to a full factory tour; and during the course of our 14-hour day, we also had Sleipner’s owners and technical supremos (Ronny & Thomas & Arne Skauen) with us to answer all our questions.
There’s little doubt that there is a battle raging for the boatbuilder’s stabilising spend between the manufacturers of fins and gyros. So one of the most significant things
that emerged was Ronny’s declaration that, in his opinion, the perfect stabilising set-up would be to combine a pair of zero-speed fins (Sleipner, of course!) with a small gyro. It was a refreshing acceptance of the idea that the two systems are so different that they are unlikely to ever offer the very best of everything.
So what did we learn, and how did Sleipner’s curved vector fins perform compared with their gyro rivals, err sorry, new best friends? There are four key aspects to consider, and their importance will vary depending on your expectations and the type of boating you do.

The Princess 56 was one of our test boats

Effectiveness at speed
Driving the Princess 56 at speed in breezy conditions immediately revealed one of the advantages that fins have – the ability to correct continuously for wind-induced lean. Gyros cannot produce their corrective stabilising force indefinitely in one direction, which is why gyro manufacturer VEEM openly recommends fitting interceptors to perform this duty.
Sleipner’s control algorithms work in conjunction with the gyro sensor to provide what Ronny calls a ‘coordinated turn function’ – something I call a ‘neutral G’ turn. In other words, the system controls the heel in the turns so that your body – or even your precious gin and tonic – does not fall towards the inside of the turn, nor conversely does it get forced outwards uncomfortably. And it really does work as it should.
This coordinated turn isn’t just great for comfort though, it’s actually indispensable for the boat’s proper functioning. Unlike gyros, it doesn’t really do to switch off and lock your fin stabilisers while travelling at speed on a boat like the Princess 56. It’s fine in a straight line, but what you don’t want is two huge fixed keels (which is effectively what locked fins comprise) fighting the boat’s natural movement in the turns; when we did this, the Princess would turn flat or even lean outwards and misbehave a little. The message is; if you have big zero-speed fins, you really need to run them continuously under way. Of course, only lovers of unnecessary rock’n’roll will find this an impediment.
Another bonus is being able to fine-tune the Sleipner fins, either increasing their response or softening their reaction to rolling motions, to suit the boat’s behaviour and the owner’s preferences. If it sounds contrary – surely the complete elimination of roll is what’s required – then take my word that an over-reactive fin in particular can produce an uncomfortable ride, like a car with too stiff a suspension set-up. So it is good to have this extra control.
I wish I could tell you more about the comparative effectiveness of Sleipner’s uniquely curved and very slippery looking fins. However, although the science that underpins their functioning is undeniable, without the dream test scenario of identical boats pitched back-to-back and fitted with competing fin systems, it’s impossible to judge how much extra efficiency and/or reduction in drag they provide, or how they interact with any particular boat compared with their rivals. However, like all fin systems, the most significant advantage they have over gyros is that, as long as your boat is moving forward through the water, they will continue to generate the hydrodynamic lift that’s needed to keep your boat upright. On the other hand, when the rams on a gyro have reached the extent of their travel, a gyro cannot produce any more energy until the boat heels in the other direction and the process is reversed.
This is significant because it is to all intents impossible to pack in enough gyro power into a sub-superyacht sized boat to cancel the rolling effects of all sea states, particularly as the speed of the vessel increases, and I’ve not yet tested a mainstream planing boat where I could feel the gyro’s stabilising effect above the high teens. In contrast, the hydrodynamic lift generated by a fin is proportional to the square of its speed through the water, so a rise from say 17 knots to 24 knots would double the lift from the fins. If you want to stay bolt upright at any speed, in nigh on any sea state, fins are the only answer.

Noise
Despite our experience with Sleipner’s fins, noise remains a difficult topic to nail down. Although at arms length I could just about hear the two exposed hydraulic rams in the actuators pumping back and forth while the 58-foot workboat was stationary, even with the engines switched off my sound meter couldn’t detect any increase above the irregular noises made by the waves on the hull. On deck, I could hear the gentle swooshing of the fins as they reached the end of their stroke and disturbed the water near the surface, but nothing whatsoever from below decks.
Under way, it’s a different story. On our Princess 56 the hydraulic actuators were buried beneath the cabinetry in the owner’s cabin, so it’s no surprise that no noise could be heard at all. Whether either or both of these fin-related sounds could be heard lying in bed in a silent anchorage is difficult to say. The advantage a gyro has is that it can normally be located in a heavily sound-insulated engineroom, although in theory, like any piece of rotating or reciprocating machinery, it has the potential to generate structure borne noise. Given that both systems will be running off their generators, the night-time noise from that piece of equipment is likely to be the deciding factor.
Over the years, I’ve recorded greatly varying sound levels on similar boats with identical engines – up to 10dB(A) in extremis. So with both gyros and fins, the quality of the installation and the extent of the soundproofing is likely to prove as important as the underlying noise of the system itself. Unless you have a mate with an identical boat, you’re unlikely to find out exactly how quiet any particular system is at night.

Stability at rest is as important as it is under way

Installation
When stabilisers are designed and installed at inception, neither system is problematic. Sleipner’s beautifully engineered actuators are exceptionally low profile affairs which will delight the designers and boatbuilders who are trying to hide them away, typically at the back end of the midships owner’s cabin. A gyro is far bulkier than the equivalent hydraulic pack that powers Sleipner’s fins, but then a simple rectangular gyro box is practically all there is. Installation is very straightforward, and it’s normally a doddle for a designer to adapt and reinforce the longitudinal structure to provide landings for the gyro’s feet.
Retro-fitting is a different matter. Gyros are almost invariably easier to retrofit, although if the available space is constricted and the existing structure is disobliging, even a simple gyro can take a lot of man hours to install. Fins with electric actuators, such as Stabilis Electra from CMC Marine, have the potential advantage of electrical cables that are easier to run than hydraulic pipes, but even CMC’s smallest actuator is way taller and bulkier than Sleipner’s sleek actuators, so the trade is definitely not one-way.
Given the burgeoning popularity of stabilising systems of all stripes, it’s surely about time that all boatbuilders designed and engineered their boats for possible retrofit. For fins that would involve no more than constructing boats with the necessary hull reinforcement where the actuators would live, and leaving conduits or space for pipe and cable runs. For gyros, it’s simply a matter of designing the structure and its surrounding space with retrofit in mind, and leaving conduits for the wiring. The more forward thinking boatbuilders have already started to do this, but not all are so considerate.

Effectiveness at rest
Stability at rest has become a big issue. Whichever system you chose, or have chosen for you by the boatbuilder, it’s important to realise that neither gyros nor fins have an unlimited capacity to reduce roll at rest; given a tall enough wave or set of waves, both will eventually run out of steam simply because when the rams on a gyro have reached the extent of their travel, or a zero-speed fin reaches the end of its paddling motion in a particular direction, they cannot develop any more stabilising energy until the process is reversed.
When it comes to stabilisers, size really is important. If stability at anchor is your overriding consideration, and you have deep pockets, it’s always worth asking the question: “Could I fit the next model up?” because it will make a noticeable difference. The data we recorded on our Princess 56 (see Fig 1 Roll Comparison 1 small waves, and Roll Comparison 2 larger swell, above right) reveals two things. In small waves, Sleipner’s flapping fins (its smallest VF650 model) damped down the roll considerably, to the point where it became no more than an agreeable suppleness in the motion of the 56. The data also confirms the idea that, if a big enough swell comes rolling through (see Comparison 2) the fins will still damp the motion, but they cannot eliminate it entirely.
However, if zero-speed stability was the only issue, I’d go for a big gyro. And that’s principally because of the way a gyro generates and harnesses its energy. Because gyros from the likes of Seakeeper and VEEM are actively controlled by their rams to maximise their efficiency and provide safety stops at the end of their travel, there’s sometimes a misconception that these rams actually force the gyro to precess in order to generate the angular torque that provides the corrective heeling force. In fact, the gyro’s talent is that it is the roll of the boat itself that makes the gyro precess and hence produce the counteractive force. And because they are reacting directly to the boat’s roll, gyros act extremely quickly and extremely smoothly. I’m convinced that their distinctive operation produces a similarly distinctive stabilising action that feels different to that of zero-speed fins, and it manifests itself as a more resolute and yet more comfortable motion. It’s doubtless why Ronny’s perfect stabilising set-up would include a small Seakeeper gyro. Fortunately, even though they both use gyro sensors, the two systems would not confuse each other, they would simply enhance each other’s capacity.
PS For the record, my dream set-up would be; Seakeeper gyro, Sleipner Vector fins and Humphree’s ACTIVE ride control interceptor system. Now, where was that form for remortgaging the house?
Contacts www.sleipner.no; www.cmc
marine.com; www.seakeeper.com;
www.veemgyro.com; www.humphree.com

Sleipner curved fin stabilisers put to the test

We test new zero-speed, curved fin stabilisers to see if they can create less drag and end rolly cruising

Fairline Squadron 65 boat test

Motor Boat and Yachting: first full boat test on the Fairline Squadron 65

Radical retractable stabiliser fins AntiRoll

We test a new dual-axis stabiliser, which promises to be the best of both worlds with retractable flapping fins.

Keeping things on the level with Humphree stabilisers

Humphree takes the zero-speed fins story a stage further with its new integrated trim and stabiliser system, writes Dave Marsh

This article Sleipner stabilising fins on sea trial appeared first on Motor Boat & Yachting.

Just when you thought that the gyro versus fins debate might finally reach closure, yet another new stabilising system is announced.

This time it comes from Humphree, the manufacturer of high speed interceptors. This Swedish company has combined its existing interceptors with new zero-speed fins.

A cynic might argue that this development is not new, as it has always been possible to combine any of Humphree’s five basic interceptor systems with another manufacturer’s fins, or with a gyro instead.

And doubtless those combinations would deliver a sophisticated boat control system.

The big difference with Humphree’s system is that the myriad functions are all under the control of a single digital brain, not two non-communicating electronic minds.

Clear lines of communication

With that integration in mind, I’d suggest two key points arise. Humphree’s system includes as standard its CTOS function (Coordinated Turn Optimisation System).

In my opinion, that is significant because it adds the final element of comfort and safety under way.

CTOS provides what I call a ‘gravitationally neutral’ turn, that is, the angle of heel in a turn is controlled such that, whatever the boat’s speed, your body is neither forced towards the outside of the bend, nor left to fall towards the inside of the turn.

That constancy will also be relevant to all those G&Ts you’ve just lined up on the bar.

Secondly, this system is based around Humphree’s top-end Active Ride Control. As such it incorporates automatic control (with manual override, naturally) of roll and the associated list induced by crosswinds or a static transverse trim.

Potentially, I see this as one of its significant benefits; the ability of the interceptors at higher speeds to substantially reduce the current draw of the electric fin actuators/motors, which have a maximum rating of 80A.

Of course, modern boats are rarely short of power, but the less the generators and/or alternators need to feed the batteries the better.

Humphree’s assertion that the system controls pitch, as well as roll and yaw, needs qualifying.

Any fin system will reduce pitching to a degree simply because of the vertical damping effect of having a pair of immersed plates amidships, resisting being pulled up and down through the water.

However, I talked to Humphree’s technical guru, and the company is not claiming that pitching in waves will, or even can, be eliminated.

The pitch it refers to could be more suitably described as the bow-up, bow-down running trim, which the interceptors continuously optimise as fast as they can based on what the boatbuilder and/or owner has told the system is best.

With under 1-second from fully-up to fully-down, that is extremely quickly, and it naturally has a damping effect on pitching in more general terms.

One question is why Humphree did not combine its interceptors with a gyro instead. The effect of Humphree’s interceptors can be felt down to around 15 knots, but to exert their full degree of control normally requires 20 knots or more.

Likewise, although we all know how effective gyros are at zero speed, I’ve been on boats where their efficacy has started to tail off at speeds as low as 10 to 12 knots.

So although it wouldn’t always have been the case, combining Humphree’s interceptors with gyros might have left some boats with an uncomfortable control gap in the middle of the speed range.

This article Keeping things on the level with Humphree stabilisers appeared first on Motor Boat & Yachting.

Barely a month goes by without some new development in stabilising systems appearing – this is a terrific time for boat owners whose appetite for rock and roll is confined to Led Zeppelin and the Rolling Stones.

The last time we flagged up Seakeeper was only eight months ago, shortly after the California-based company had released its smallest ever Gyro.

Its diminutive Seakeeper 5 was notable for its compact size and a price which made it suitable for boats as small as 30 foot.

However, the US company, whose manufacturing plant in Pennsylvania covers a sprawling 90,000ft² now has a new starter model, the Seakeeper 3DC (pictured below).

At first glance the spec is perplexing – the 3DC has exactly the same compact dimensions of 30.1 x 29.8 x 24.7 inches (765 x 757 x 628mm) as the preceding 5 model. Also exactly the same starting price of $29,900. Its weight of 358kg (790lb) is also identical to the 5.

Power from a battery

The big difference, and the reason why the 3DC is such a significant development, is that the new Seakeeper can be battery powered.

Okay, the motor itself still needs to draw its 900W maximum via a true sine wave inverter (110-230V, 50/60Hz, single phase) but the 100W Gyro control system is fed from a simple 12V supply. Hey presto, modest boats without generators now have access to stabilisers!

In order to achieve that low power battery operation, the new 3DC spins at 6,400rpm instead of the 10,700rpm of the Seakeeper 5.

Consequently, its maximum 6,500Nm of anti-rolling torque is almost exactly half that of its rotationally faster sibling.

That explains why Seakeeper says it’s suitable for boats up to 40 foot, whereas the company states that its 5 model can handle 50 footers.

One significant benefit of its slower rotational speed is that the 3DC is noticeably quieter; 62-64dB(C) versus 70-72dB(C) for the 5, measured from a metre away.

Bear in mind that 65dB(A) is the generally accepted level of normal human conversation, so completely cloaking the sound of the 3DC should not be difficult provided it lives in a well insulated space.

In late April this year, Seakeeper conducted initial tests on a 35ft long, 10ft wide, 6 tonne open decked US sportfishing boat with a stepped hull called the Contender 35ST.

In conditions that Seakeeper says comprised three-foot significant wave height and 15 knot winds with gusts up to 30 knots, the company reported a 94% reduction in roll.

According to the graph (see above) with the 3DC engaged, most of the residual rolling was reduced to 1º or less, a level at which Martinis barely get shaken, let alone stirred.

Gearing up for action

Like all gyros, it takes time to spool up to operational speed. In the case of the 3DC that is 27 minutes to the point where stabilisation is engaged, and another 11 minutes to full rated rpm.

Zero-speed fin devotees like to point out that this waiting time can be a nuisance, but I feel it’s really no big deal as long as you switch the 3DC on as soon as you step on board.

By the time you have packed away your kit, carried out a safety briefing, and crawled gently out of the marina, few of us get under way in less than half an hour.

And also like all gyros, the 3DC can be sited almost anywhere convenient. For instance, on the Contender 35ST, the 3DC sat directly on deck in a small locker.

On small boats, where space is often at a premium, that is potentially a huge benefit. The only caveat to this freedom of placement is that on boats that regularly experience vertical accelerations greater than +/-1.0g, it needs to live aft of the longitudinal centre of gravity (LCG).

All told then, I feel that Seakeeper’s modest claim of a starting point of 30ft does not reflect the 3DC’s full potential.

Assuming that shouldering an extra 358kg is not going to trouble your boat (and that is only about four adults’ worth of weight, or a typical PWC) then its compact dimensions, battery power, and ability to be mounted nigh on anywhere aft of the LCG, should in theory allow it to be installed on almost any size of boat whose owner can afford its $29,000 – roughly £18,600 (plus fitting costs) as of mid July.

And given how on-board comfort is becoming an ever more appreciated aspect of boating, even on a small and inexpensive boat that seemingly extravagant £19k may feel like money well spent.

This article Seakeeper launches battery-powered 3DC stabiliser appeared first on Motor Boat & Yachting.

When it comes to stabilisers, we’ve witnessed a whole Industrial Revolution’s worth of development in the space of a few short years.

Gyros have got smaller, faster and cheaper, and what used to be simple fins now come in multiple mix-and-match forms: straight or curved, electric or hydraulic, conventional or zero-speed, and there’s even the DMS AntiRoll fins that flap like a pair of wings.

With the typical cruising boat becoming ever more corpulent and fixed hardtops adding yet more weight up top, these developments could not have come at a better time.

It’s one thing to report on these developments, better still to test drive the stabilisers. We’ve tried most of them over the years but this is the first time we’ve tested the most unusual stabilisers of all – the RotorSwing.

Our test bed was a Linssen Grand Sturdy 52.9, which we motored for about an hour in relatively open water near Emden in Germany and then subsequently up a surprisingly blustery river Ems for a couple of hours, on the way to the Linssen dealership.

The surprisingly simple system comprises a pair of rotating cylinders, driven by high-speed electric motors, which swing out at right angles to the hull when in use.

These cylinders develop their lift courtesy of the Magnus effect (pictured below). When a cylinder spins as it moves through a liquid medium, it develops high pressure on one side (where the cylinder’s surface is pushing against the flow of the water, due to friction) and low pressure on the other side (where the cylinder is pushing it in the same direction).

The effect is exactly the same that you see when Novak Djokovic hits a powerful forehand shot with topspin – that spinning produces the Magnus effect as it moves through the air and enables the ball to dip inside the base line rather than fly out the back of the court.

With their spindly forms protruding at right angles from the hull, I couldn’t help feeling how vulnerable they looked, possibly at odds with the notion of travelling up a river at close quarters with other craft.

However, during our trip along the river, Jan Linssen and Linssen’s sales manager Ed Houben, explained why they are so popular on Linssens and other boats used in a similar environment.

In fact, they don’t protrude far at all, about a metre from the exit point on the hull well below the waterline, and obviously much less from the far bemier ship’s sides, certainly less distance than you would ever hope to pass oncoming traffic.

Regardless of their protrusion, their killer feature is that when required they fold in to sit snugly along the hull reducing both the width and drag.

This is a big plus on the inland waterways, where Houben explained that the banks are sometimes so shallow and shelving that even a small conventional fin would be at risk of grounding when a boat tries to tie up alongside.

Linssen Grand Sturdy 52.9 AC Wheelhouse

That retraction can be manually triggered or there’s an auto-park function that will swing the fins in as soon as neutral or reverse gear is engaged, or when the speed drops below 3 knots.

Operation was simplicity itself, an ultra-simple control with drive and park buttons – the motion sensor and control cabinet takes care of everything else.

Our big Linssen has a slightly different hull form to its predecessors, and was better than I had anticipated at remaining steady all of its own accord.

However, the difference between RotorSwing on and RotorSwing off was marked. It was as if the water we were passing through had been removed from the scene, and we were gliding along a railway line.

That railway track became a lot bumpier when we headed up the blustery river, so we did experience up and down movement of the bow, but the transverse stability remained rock solid.

The system also compensated perfectly for driver induced roll such as flinging the boat into full lock turns at the 52.9’s albeit modest top speed of 10 knots.

Sadly, we didn’t experience truly challenging conditions for a stabiliser. However, if you have any doubt how much force the system is able to exert, check out the video below:

Houben and Linssen also explained the system’s practical appeal. Like a Gyro, RotorSwing isn’t too fussy where it is installed, and is most effective between 3 and 14 knots, very much Gyro territory.

However, RotorSwing’s electric motors are far more compact than a Gyro, so installation is exceptionally easy.

RotorSwing is not going to render other stabiliser systems obsolete. Mounting drag means they can’t be deployed above 14 knots and the standard RotorSwing does not work at anchor like most fins and gryos now do. And although they fold in they will still generate the drag that gyros do not.

In truth, no one system has all the answers, but RotorSwing clearly has a few unique solutions it can call its own.

This article RotorSwing boat stabilisers tested on Linssen sea trial appeared first on Motor Boat & Yachting.

When you live through transformative advances in technology, it’s easy to miss how fast the world around you is shifting – can it really be just five years since Apple launched the first iPad?

Pod drives such as Zeus and Volvo Penta IPS probably represent our iPad equivalent, but I reckon there’s another less obvious revolution taking place right now.

An increasingly diverse range of ever more sophisticated boat stabilisers and boat control systems (such as high speed interceptors) are creeping into ever smaller boats. And the benefits are game-changing.

Part of the momentum is driven by technology, but I think the other reason is that we’ve only just begun to fully value their benefits.

Thanks to burgeoning accommodation and weighty luxuries such as hardtops, many of our cruising boats have become taller and more top heavy. Plus, increasing numbers of boaters are now demanding stability and comfort at rest, not just underway.

My experience is that even the finest hulls now need a helping hand to please all of the people all of the time. So what are the latest developments, and what are the pros and cons of each?

Seakeeper 5 gyro boat stabilisers

Evidence indeed of a revolution, Seakeeper’s latest gyro is a tiny thing. Weighing 368kg, it takes up less space than a 70 gallon water tank. Or if you aren’t fluent in tank, that’s roughly six HP8600 desktop printers.

Its anti-roll software is optimised for sub-50 foot vessels weighing up to 20 tonnes. This means that for the first time cruisers like, say, the Fairline Squadron 48 and Linssen’s Classic Sturdy 46 are able to benefit from gyro stabilisation.

Moreover, Seakeeper’s literature talks of vessels of 30 foot and above, so as long as its $29,900 (approx £19,800) cost and its tiny footprint can be accommodated, even smaller motor cruisers will benefit.

Like all gyro boat stabilisers, Seakeeper’s 5 has pros and cons. It takes 35 minutes to spool up to 9,035rpm, the point at which it provides stabilisation, and another 15 minutes before it reaches its full 10,700rpm.

The new Seakeeper 5 is so small and light that boats as small as 30 foot can now benefit from gyro stabilisation

Compared with instant-on fin boat stabilisers, that’s only going to be a drawback if you’re in a manic rush to put to sea, and surely none of you head off without a safety briefing, a full systems check, and a cup of tea?

In my experience gyros are outstanding on a boat at rest or moving at lower speeds, and they don’t increase drag beyond the penalty that a marginal increase in weight incurs. Neither can gyros be damaged by underwater debris or incompetent travel hoist operators.

The benefit most often overlooked is noise. Structural considerations notwithstanding, gyros can be positioned almost anywhere, even off-centre according to Seakeeper, although not all the naval architects I’ve talked to are comfortable with that notion.

So gyros are far less likely than fins to be sitting under the midships master suite, where hydraulic fins are more prone to disturbing the owner’s reverie with their swooshing. Instead, gyros are likely to be hiding in heavily sound-insulated engine rooms.

Fin-based boat stabilisers

Compared with gyros, the principal advantage of fins is that, underway, they do not run out of energy. As long as your boat is travelling forward, the angled fins will continue generating a corrective hydrodynamic force.

Gyro aficionados like to point out that this force tails off as a boat slows down. True enough, but my hands-on experience suggests that as long as the fins are correctly sized this is not an appreciable problem.

Quite differently, a gyro boat stabiliser extracts the precessional energy that it uses to correct heeling by pushing the spinning gyro off its vertical axis.

Once the rams involved have reached the full extent of their travel, they can’t extract any more energy until the boat starts to roll in the other direction and the process is reversed.

This is principally why gyro manufacturers such as Seakeeper sensibly claim, say, a realistic 70% to 90% roll reduction, not 100%.

Gyros from the likes of Veem, Mitsubishi ARG and Seakeeper used to be the only choice for stability at rest, although fins have fought back recently in the form of larger fast-flapping zero-speed versions.

TRAC is introducing electronic actuators as alternatives to its hydraulic systems

TRAC is countering the hydraulic swooshing by introducing electric motors as alternatives to its usual hydraulic fin actuators, and CMC Marine already has a range of electric fin boat stabilisers.

The most radical development in fin-based boat stabilisers is DMS AntiRoll, which we covered fully in the February 2014 issue of MBY.

AntiRoll is fundamentally different to existing zero-speed fins in that the high-aspect ratio fins rotate independently around two separate axes.

This means that its zero-speed flapping function is far more effective because the whole of the fin’s area is pushing directly against the transverse rolling.

That second longitudinal axis also allows the fins to fold flush against the hull, even into a recess if so designed, which goes some way towards countering the gyro’s

Zipwake Interceptors

It used to be that conventional trim-tabs and their Interceptor siblings were thought of as no more than simple devices to trim the boat. Then along came what is still regarded as the Rolls-Royce of interceptors – the Humphree system.

Interceptors will not stop your slow-speed Nordhavn rolling around underway or at rest, as fins or a gyro will, but the latest Humphree HCS5 system is so fast acting (full-up to full-down in less than a second) and so powerful if correctly specified, that on fast boats it can serve as a complete boat attitude control system, including appreciably damping and controlling rolling motions.

Zipwake is a newcomer to the Interceptor market. It was nominated for a DAME award at the METS trade show last year, very deservedly so if the prototype system I played with proves as reliable as its terrific design suggests it might.

Currently, Zipwake uses its sensors to dynamically control pitch and roll. However, the GPS and 3D gyro sensors and motion controller it uses to do this are integral to its system.

So it would only need the necessary algorithms to be developed to provide full attitude control similar to Humphree’s system.

Zipwake’s through-hull wires are sensibly sited above the waterline

The simple interface and control system are nigh on perfect. In auto mode there’s nothing to be done except read the clear display.

The manual controls are excellent; a scroll wheel controls the bow-up bow-down running trim while a circular dial handles the lateral trim (heel). It’s far faster and more intuitive than the usual trim-tab controls.

At METS, Zipwake was refreshingly free of hyperbole. It does not see itself as a rival for high-end Humphree, instead it is aiming its interceptors at the mass market, so it has standardised its systems and produced four regular sizes of interceptor blade, which can be mixed and matched to provide the necessary muscle.

That said, I examined an interceptor that had been disassembled into its component parts, and it was anything but a budget item.

It looked as though it would laugh off the 60-knot rating that Zipwake assign. All told, one of the most significant developments in boat control systems that I’ve seen.

The end of rock and roll?

You may have no choice between fins and gyros when you buy your new boat, although even that seems to be changing.

Advances have meant that both principal types – fin and gyro – are improving all the time, so if you are faced with a choice, either on a new boat or a retrofit, nowadays it’s an impressive choice.

It could be that two of the seemingly lesser considerations, principally noise and practical installation issues, could tip the balance.

However, the overall consensus is still that you cannot beat gyros for stability at rest, but that the best fin-based boat stabilisers cannot generally be bettered underway.

And although new systems such as AntiRoll may change that notion, that consensus unfailingly matches my hands-on experience to date.

What is potentially exciting is the combination of gyro and high speed interceptor – that’s a marriage which I feel could, on particular boats, give fins a real run for their money in every department.

Whichever system suits though, for me the safety issue looms large. Controlling any boat in heavy seas is infinitely easier when it’s not rolling around.

And safety at sea definitely improves when you no longer have to abseil across a saloon full of razor-edged furniture.

This article Could boat stabilisers spell the end of rock ‘n’ roll? appeared first on Motor Boat & Yachting.

The weather was perfect – a north-easterly Force 5 blowing in across the North Sea all the way from Norway. Not something we would normally relish when sitting beam on to the sea in a 65ft flybridge boat. However, these conditions were just what was needed to put Sleipner’s new Vector stabiliser fins to the test.

Nor was this a specially arranged press event designed to demonstrate their ability to best advantage, MBY was simply invited to join the team of engineers from Fairline, Caterpillar and Sleipner taking part in the commissioning process of the first new Squadron 65 fitted with these intriguing new stabilisers.

First revealed in these pages last November, the zero-speed Vector fin stabilisers use an unusual curved design to deliver more thrust from a shorter, more compact fin design. Vector believe this compact design is a winner because the curved shape ensures the fin is closer to the horizontal than a straight fin, producing more of the useful vertical thrust needed to counteract roll. It also produces less lateral thrust reducing unwanted yaw.

Fin test on a fairline
Sleipner claims that Vector fins are 50% more efficient than a comparable straight fin at anchor and 30% more efficient underway. Crucially this means the surface area of the fins can be reduced and their associated drag through the water while still delivering the same anti-roll performance.

On a planing boat such as this, that can make a significant difference to both performance and fuel efficiency. In fact Sunseeker, which also offers them as an option on some models, reckons that Vector fins cause no discernible loss of performance.

Our Fairline 65 test boat was powered by twin 1,136hp Caterpillar C18s. We bashed out into the North Sea with the fins set in their low drag position and recorded an impressive 34 knots.

However, the real test was to bring the craft to a halt beam on to the sea to see how it would cope. Up on the flybridge with the system switched off, the swell had our camera and tripod doing its best to escape overboard. The horizon rocked violently from side to side in the viewfinder and it quickly became apparent why the crew weren’t keen to hang around like this for any longer than necessary.

Moments later, with the system switched on, it was like some invisible hand had mysteriously steadied the ship. The alarming roll was cut down to a gentle, comfortable rocking motion and colour once again returned to the faces of the crew. When we turned into the wind, as you would be at anchor, even the gentle rocking motion disappeared.

Running back to the river entrance at semi-displacement speed, again with the sea on our beam, the additional dynamic stability generated by the Vector fins slicing through the water kept us on an impressively even keel. Considering we were doing 14 knots at most I would have expected some side-to-side movement but the only movement we could see was on the helm display showing which way the fins were pointing.

A fin-tastic system?
The brain of the system is a roll sensor while the heart is a powerful hydraulic-pump rapidly pushing the big actuators back and forth and swivelling the fins to generate lift. In the right weather conditions these fins can rotate through a 76° arc in less than a second. In order to do this the hydraulic system can produce up to 3000ft/lbs (4,000nm) of twisting power.

Under way the pump is driven by the power take-off (PTO) from one of the engines. At anchor the generator kicks in automatically to keep the hydraulic pump on the go, although with sufficient battery power on tap they can run on DC power for a limited period of time.

The whole system is operated from a control panel at the helm. The SPS55 actuators used on the Squadron 65 are substantial pieces of kit weighing 100kg each with dimensions of 51x43cm (length x width). However, they are only 15cm deep making them relatively easy to locate under the floor of most craft of 50ft or more.

On the Squadron they are located under the port side heads. Sleipner is particularly proud of the way its actuators have been engineered to deliver both the power and speed needed to cope with challenging conditions at anchor. Watching the actuators at work through an inspection hatch, I was surprised to see how frequently and rapidly they react although the adjustments underway tend to be fairly small movements. At anchor they have to move further and faster to generate the lift required.

The Squadron 65 uses the smaller of the two fin options for the SPS55 actuators. Measuring 4ft 8in long by 2ft 3in wide, they have a surface area of 0.65m². The largest Vector fins have a surface area of 2m² and can cater for boats up to 130ft long but significantly the smallest fins are also suitable for boats down to 50ft, provided you can stomach the cost. The price of factory fitting this option to a Fairline Squadron 65 is around £100,000 including VAT. Retro fitment to an existing craft of similar dimensions is also possible for much the same price.

Contact www.side-power.com

Sea Sickness – what’s the cause?
Seasickness is a form of motion sickness. The cause of seasickness is usually an uncomfortable and continuous swell or rocking motion.

Many will develop immunity to seasickness after a period of time at sea and some will never defeat it. Admiral Nelson suffered from seasickness throughout his career.

Motion sickness is caused by conflicting messages being sent to your brain by your eyes and your body. It can either be motion that is felt but not seen or motion that is seen but not felt or a combination of both.

This explains why it is possible to feel queasy when watching video footage from a rolling boat even when seated comfortably on dry land.

One theory is that seasickness is linked to the body’s natural defence mechanism against poisoning. The area of the brain responsible for inducing vomiting when poison is detected is also responsible for coordinating vision and balance.

When the signals from your eyes do not match those from your vestibular system (the inner ear labyrinth responsible for balance) the brain considers you have been poisoned causing vomiting to expel the poison.

There are many means of reducing seasickness: focusing on the horizon and taking preventative tablets well in advance of going to sea tend to be the most popular and proven options. Some people also swear by wristbands with pressure beads or electronic pulses to reduce the symptoms or at least distract you from them. First published in the September 2014 issue of the magazine.

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This article Sleipner curved fin stabilisers put to the test appeared first on Motor Boat & Yachting.

AntiRoll is a radical new stabilising solution that aims to combine the best elements of both gyroscopic and fin systems.

Most stabilisers fall into one of two camps: gyro-based systems such as Seakeeper and Mitsubishi ARG, which rely on a fast-spinning weight to keep the boat steady; or fin systems such as Sleipner, TRAC and CMC, which use a pair of tilting fins to counter roll.

Both systems are capable of working under way and at anchor, but fins tend to be most effective under way while gyros are at their best at anchor.

Flapping fins

The new AntiRoll system developed by Dynamic Marine Solutions (DMS) is unique in that its fins flap as well as tilt. It claims this allows them to counteract roll under way and at anchor without any of the usual compromises.

Conventional stabilising fins only tilt around a single axis so their ability to prevent roll at anchor is limited by the size and speed of the arc each fin can sweep before having to reset itself. Under way this isn’t a problem as the water flowing over the fins greatly increases the dynamic lift each fin can generate.

Gyroscopic stabilisers, on the other hand, offer the same level of roll-resistance both at rest and under way. This means they tend to be very effective at anchor but run out of steam under way in a big beam sea earlier than a fin system would. They also have the advantage of not having any external appendages to increase drag at planing speeds.

The new AntiRoll system can rotate through two axes. When under way, the fins tilt around a lateral axis just like conventional fin systems, providing lift on each side as required. However, at anchor, the AntiRoll fins also move up and down on a longitudinal axis, creating a flapping effect similar to a bird’s wings.

Because this flapping motion is directly opposed to the direction of roll, it is far more effective than the paddling effect of a conventional fin. The fins are also a very different shape to the normal stubby winglets, being twice as long as they are wide (known as a high-aspect ratio of 2:0). This means that they only need to tilt around 15º to produce the same degree of lift. Conventional shorter fins (with low-aspect ratios of 0:5 to 1:0) normally have to tilt 30º to have the same effect.

By limiting the angle of attack to 15º, drag is also reduced, response times are quicker and the power draw is lessened. This is because there is less pressure on the trailing edge of a narrow fin than a wider fin. The shaft is also located slightly aft of the leading edge, producing some counterbalance to the pressure exerted on the trailing edge. Conventional fin systems tend to mount their shafts on the leading edge in order to maximise the paddling effect at anchor.

Fins with no drag

The big disadvantage of a long, high-aspect ratio fin is that when not in use they create more drag as well as posing a greater obstruction when berthing. So DMS has made the problem disappear at the press of a button – literally. When not in use the curved fins fold flat against the hull or into recesses. Another advantage of rotating the fins through a longitudinal axis is being able to adjust the positioning of the fins to suit each boats roll point.

With a conventional system the fins have to be set at a fixed angle, which is invariably a compromise between efficiency and the practical limitations of the hull design. Even after fitting, the DMS system can be adjusted to ensure it’s as close to the roll point as possible for maximum efficiency under way. This ability to rotate around two different axes is achieved using two sets of hydraulic actuators, one for each axis. The actuators for the lateral axis are located inside a cylindrical housing at the base of the fin.

The shaft for the fin passes through this cylindrical casing where it connects with the actuators. This whole cylindrical housing also rotates on its longitudinal axis, causing the fins to flap up and down. The fins are controlled by what DMS calls a Hybrid Power Train. The primary source of this Hybrid Power Train is a three-phase 400V AC generator. This is channelled to an AC/DC converter, which feeds two servo drive units (port and starboard) and a battery pack. The battery pack acts as a reservoir of DC current to provide a short-term boost.

The beauty of the system is that the pumps are fed by an electrically driven low-pressure supply (15-20 bar) from a central reservoir. Two small servo pumps then provide the final high-pressure boost of up to 250 bar. This removes the need for a much less efficient mechanically driven high-pressure hydraulic pump. At the moment the system is aimed at the 30m-plus market.

However, DMS claims the principle is equally effective on boats of all sizes, including planing and displacement craft. Whether it is physically and financially viable on smaller craft in the 15m to 30m bracket has yet to be seen but the speed with which the market for stabilisers on smaller boats is evolving suggests anything may be possible if the demand exists.

Contact www.dmsholland.com

Dynamic Lift

Hydrodynamic lift causes powerboats to plane and aerodynamic lift causes aircraft to fly. The scientific principles are much the same, although wings produce lift on both sides whereas hulls only produce lift on the submerged side. In that respect, stabilising fins behave more like underwater wings.

Water flowing over the fins causes positive or negative lift, depending on whether the leading edge is higher or lower than the trailing edge. The degree of lift is dependent on the angle of attack and the speed of the water flow. The angle of attack is the angle between the surface of the object and the water flow. The further the fins tilt, the more lift they generate. The same holds true for the speed of the water flow.

The faster the boat moves through the water, the greater the lift. This lift isn’t just created by high pressure on the underside of the fins pushing the boat up, it’s also produced by low pressure on the upward surface pulling the fins in the same direction. It’s the combined effect of this that generates such a powerful lifting force from a relatively small surface area.

Fins also work at rest because Newton’s third law of motion states that to every action there is an equal and opposite reaction. So when a stabilising fin is pushed rapidly down against the water, an equal and opposite force is applied up by the water. Water in cold climates is denser than water in warm climates, so fins in the UK do not need to work as hard as they do in the warmer waters of the Mediterranean. First published in Motor Boat & Yachting, issue February 2014.

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This article Radical retractable stabiliser fins AntiRoll appeared first on Motor Boat & Yachting.