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Old 11-18-2021, 01:22 PM   #1
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Gyroscopic Stabilization on trawler

I went to the FL boat show to look at the Nordhavn 41 with my buddy who owns a Regulator 34 center console with Seakeeper gyro stabilization.

He asked the Nordhavn rep "can you get gyro stabilization in these?"

The Nordhavn rep replied, "Trawlers aren't really a good match for gyroscopic stabilization. They are displacement boats. The N41 comes with fin stabilization...."

So, focusing on "trawlers aren't really a good match for gyroscopic stabilization."

Thoughts, comments, opinions?
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Old 11-18-2021, 02:21 PM   #2
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I hope Hippocampus chimes in here as he was looking very closely at used Nordhavns but ended up with a Nordic Tug 42 with a Seakeeper system. In short, statement that 'trawlers aren't a good match for <Seakeepers>" definitely doesn't sound right. The only functional complaint I have heard about Seakeepers is from installing under-sized systems. Just as with fins, slower you go, the bigger the system needs to be.

If you or your friend are interested, would definitely reach out to Seakeeper. I am sure they could point you to many happy customers.

I'm not a buyer of Seakeepers only because I'm not keen on keeping the generator running. Otherwise, sounds like people seem perfectly happy with them. As an FYI - my fins work fine.

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Old 11-18-2021, 02:28 PM   #3
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In my mind, it's not that an FD trawler is a worse application for a Seakeeper, it's that it's a better application for fins. On a slow boat, sizing the fins to work at zero speed will have less of a drag penalty than on a fast boat. And by having a narrower range of cruising speeds, sizing fins is easier in general (compared to fins on a faster boat).

Relative to fins, in my mind, the Seakeeper has 2 big downsides. It's heavy and it takes up a lot of space. That, and it's not instant-on.
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Old 11-18-2021, 04:41 PM   #4
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I looked at a Nordy 62 with twin Seakeepers and they reported they were horribly ineffective and a waste of over 100k.
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Old 11-18-2021, 06:11 PM   #5
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I looked at a Nordy 62 with twin Seakeepers and they reported they were horribly ineffective and a waste of over 100k.


62 or 63? I know of one 63 that was equipped with seakeepers. The second owner added fins, but didnít remove the gyros.

I donít know of any 62s with gyros.
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Old 11-18-2021, 06:30 PM   #6
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62 or 63? I know of one 63 that was equipped with seakeepers. The second owner added fins, but didnít remove the gyros.

I donít know of any 62s with gyros.
Do you know why gyros so ineffective on Nordhavn? Their biggest impact is anchor and low speed, definitely not planing speeds. Is it the weight or hull shape? I can see how zero speed would be easy.
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Old 11-18-2021, 06:48 PM   #7
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Do you know why gyros so ineffective on Nordhavn? Their biggest impact is anchor and low speed, definitely not planing speeds. Is it the weight or hull shape? I can see how zero speed would be easy.


Iím not sure, but would love to know. I suspect that itís just too heavy a boat for effective underway stabilization, but that gyros are good for at anchor. Perhaps better than fins with zero speed stabilization.

A friend has installed dual gyros plus fins in a new N68 build, and Iím interested to hear how they work. Heís big into fishing, and I think thatís where gyros shine.
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Old 11-18-2021, 07:40 PM   #8
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The weight thing is a good point. Compared to typical Seakeeper sizing for a lighter, faster boat, you may need one or more VERY large gyros to get enough stabilizing force because the boat is so heavy.
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Old 11-18-2021, 07:49 PM   #9
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Guys I know with seakeepers have them primarily for zero speed operation but rely on active fins while underway. Seakeepers allow a boat to drift - fish the trough with minimal roll. People that buy Seakeepers, rather than fins, are often times disappointed in the displacement speed performance. When neither cost nor room is an object, the combination of Seakeepers and fins is the best of both worlds. If you can only have one, fins is probably the better choice at least on displacement speed boats. I think rslifkin's comment about mass is a good part of the explanation -- Nordhavn's are heavy boats and probably require proportionately larger Seakeepers.
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Old 11-18-2021, 08:46 PM   #10
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Guys I know with seakeepers have them primarily for zero speed operation but rely on active fins while underway. Seakeepers allow a boat to drift - fish the trough with minimal roll. People that buy Seakeepers, rather than fins, are often times disappointed in the displacement speed performance. When neither cost nor room is an object, the combination of Seakeepers and fins is the best of both worlds. If you can only have one, fins is probably the better choice at least on displacement speed boats. I think rslifkin's comment about mass is a good part of the explanation -- Nordhavn's are heavy boats and probably require proportionately larger Seakeepers.
That could be it as the biggest issues I've seen with Seakeepers on slow boats is undersizing them. Builders do so to save money and they just are way too inadequate.
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Old 11-19-2021, 05:45 AM   #11
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I have/had zero speed fin stabilization on both most recent boats, and they are great when drifting. That's where I've used them the most. In our case that's watching whales rather than fishing, but it creates the same rolling in the boat.


I think part of the problem using gyros on larger displacement boats is the slower roll period. A gyro has a limited stroke over which is can counter a roll. If the combination of the amount of roll, and the period of the roll is too much, the gyro reaches it's limit and just stops countering and has to wait for the reverse roll to begin before it can do anything. Otherwise it would contribute to the roll rather than counter it. Fins provide a continuous counter-roll force for as long as needed.
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Old 11-19-2021, 08:16 AM   #12
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After two trips it’s still early days. First was eastern Connecticut to the top of west passage RI. The entire trip was into the wind and a short period chop of 2-4. Second was top of west passage to mouth of Chesapeake inside except for NJ coast. Only dealt with a significant swell in block island sound and coast of NJ.
Still, from reading and this very limited experience think the following.
Gyros need to be sized by vessel weight not loa or lwl. So by length Nordies are heavy FD boats. The NT is a moderately heavy SD boat. Both roll period and stiffness are quite different. The round bilge, lower form stability Nordie will intrinsically want to roll more than the hard chined, more form stabilized NT. Yes, the Nordie will have a much greater AVS, less down flooding risk and be a safer more capable boat in a seaway but the Nordic roll period will be shorter and will have more initial stiffness.
So the great thing about gyros is they work at any speed or no speed. Bad thing is they only respond to acceleration and have no effect on a fixed list. Also they only work in one axis. They are usually set up to damp roll not pitching. This matters less on a boat operating at or above hull speed.
Fins don’t care how you got leaned over or if it’s sustained. Their “brain” is set up to return you to a even keel. Fins are set up to respond to any rate of perturbation. Your perception (as a human) is gyros are phenomenal for wind waves and chop but for big waves and swell fins maybe better. Gyros don’t care about slow boat speeds. Well designed SD boats tend to be intrinsically more resistance to roll when at or above hull speed. You need more area for fins and slow boats. FD boats operate below or just approaching hull speed the majority of the time.
In summary if I was spec’ ing a BWB it would have fins or Magnus effect device. Fins for FD heavy boats. Magnus or fins for light, narrow higher speed boats. Works at all levels of heel regardless of how you got there. Works well with heavily ballasted boats. Having external appendages is no biggie. But for a coastal SD boat with more dependence upon form stability gyros work just fine.
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Old 11-19-2021, 09:02 AM   #13
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Might want to review hammerheads thoughtful thread. My only caviate would be if I was doing mixed use would investigate Magnus effect further. The idea of rotating them in when in skinny water or debris filled waters is quite appealing.
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Old 11-26-2021, 03:16 PM   #14
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Might want to review hammerheads thoughtful thread.
Link please, Hippo. Best, KL
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Old 11-26-2021, 03:41 PM   #15
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Gyros

Not sure why someone would suggest a gyro is not suitable for a certain design of boat, I would assume it would improve stability in any design. That being said, I had a Seakeeper in a 40í trawler design and can thoroughly recommend them.
I completed more than a 1,000 nm journey day after day with the gyro on the whole way. We were in quite rough and sloppy conditions and it worked a treat. Without it on ( and we conducted numerous on/off tests) you could really feel the difference.
At anchor the gyro is incredible and the Admiral always wanted it on even if there was a slight sign of chop. It even impressed my boating mates who were sceptical.
They are an expensive piece of kit but they do the job .. I now have a 60í trawler with fin stabilisation .. not the same result and in my experience, not as effective, although difficult to compare.
If you want to invest the money to install a gyro I doubt you would be disappointed.

Cheers and happy boating.
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Old 11-26-2021, 03:56 PM   #16
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That being said, I had a Seakeeper in a 40’ trawler design
What was the hull shape of that 40-footer, Illerom? I had a sharpie-design 40' trawler, with flat aft sections and a hard chine (so high initial stability and rapid roll accelerations in confused seas). My feeling is that different hulls respond to different stabilisation approaches. The present vessel, 30 tonnes, deep draft and rounder hull respond very well to the paravane stabilisers we have fitted to her, but my sense is that these would not have worked as well on the sharpie.
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Old 11-26-2021, 04:16 PM   #17
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I’m afraid my technical knowledge of the hull will probably not meet your expectations, however, she was a full displacement hull, with, I would say, an almost flat aft section. From memory.. approx 20 tonnes (??). I acknowledge that different hull designs would be more or less effective but once you flick that switch(keeping in mind the gyro takes 45 mins or so to get up to speed) the difference was incredible.
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Old 11-26-2021, 04:28 PM   #18
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Illerom, my experience with a Gyro in a 45 ft boat is as you have described. Worth every Penney. Many people on here jump in whenever they can to make negative comments about them, but have never owned one or used one for extensive cruising. One poster on here was making various claims about them over a 1 year period, including that they were “dangerous”. He subsequently bought a boat with a Gyro. Steve D Anatonio is one of the most knowledgeable boat and system people on the planet. He has written about them, likes them, and has worked with owners who have had them installed on numerous boats, including trawlers. I generally stay out of these discussions these days, but only chime in periodically so that people who may be interested in them hear from someone who has actually used one, for 600 hours.
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Old 11-26-2021, 04:34 PM   #19
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Well, let me put my cards on the table: I have not owned or used a Seakeeper, but the technology appeals tremendously. Yes, you do have to run the generator to use one, but just like our paravanes, there are plenty of occasions where the sea is calm and airs are light, and so would not be needed. My partner does not have much offshore experience, and she really liked the difference when we dropped the fish in on our last trip to Sydney. Some kind of stabilisation is needed on long passages, I believe.
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Old 11-26-2021, 04:36 PM   #20
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I have had Seakeeper 6’s in two trawlers and both were installed well after the original build. The first boat was 47 OAL, twin engine, flat bottom, hard chine, 16’ beam, at 25 tons displacement. Did nothing for pitch but that was easily accommodated by adjusting course to take more on the beam. On the beam the system remove 80% of roll from an already very stable platform. Second is a 42’ twin engine with similar underwater characteristics, beamy with hard chimes, 40 tons displacement in all steel. Similar results. I sold the first boat and replaced it with a vessel with fin stabilization but I still prefer the gyros.
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