Smartgyro SG40 vs Seakeeper SK9: Boat stabilisers compared

Thanks to new owners Yanmar, Smartgyro’s latest range of efficient, easy-to-install and competitively priced gyroscopic stabilisers now has the firepower to challenge market leaders Seakeeper. Let battle commence…

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.

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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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Smartgyro SG40 Seakeeper
Boat size 50-60ft 50-69ft
Boat displacement Up to 35 tonnes Up to 30 tonnes
Max RPM 7,500rpm 9,000rpm
Angular momentum 9,100Nms 9,000Nms
Anti-roll torque 19,000Nm 18,810Nm
Spool-up time to max RPM 55 mins 55 mins
Spool-up time to stabilisation 25 mins 38 mins
Spool-up power 4kW 3kW
Operating power 1.5-2.5kW 1-2kW
Noise output at 1m 68-70dbC 68-70dbC
Dimensions L x W x H mm 860 x 930 x 720 852 x 903 x 708
Weight 650kg 550kg
Price €65,000 $85,000

First published in the July 2021 issue of MBY.

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