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Gyro Stabilizers for mid-sized yachts

Discussion in 'Stabs, Tabs & Gyros' started by Viceroy, Jan 15, 2020.

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  1. Viceroy

    Viceroy Member

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    No, I didn't win the lotto but have had a hankering to custom build a displacement/semi-displacement motor yacht with an internal stabilization system. Our Pacific Northwest coast can be rife with logging debris and other water borne dangers for exterior vanes. Similarly, our ambitions extend to the Caribbean where seaweed (Sargasso) can be problematic. In the design stage is a steel hull with aluminium topsides, no gross displacement/weight, to date...just not light weight nor a speedster...but in the 65' to 74' LOA, to be commanded (comfortably) by a knowledgeable owner and well skilled wife (both in our 60's with both sail and power backgrounds).
    I don't necessarily wish to fill these pages if a Thread already exists, dealing with detailed pros and cons relative to gyro stabilizers but do ask if there are any informative publications, papers, opinions, etc. by authors unbiased by a manufacturer that can be gleaned on the internet? Naturally, I will also welcome direction to an existing Thread and comments from the forum. Cheers, Richard.
  2. Capt J

    Capt J Senior Member

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    I'm not sure why seaweed would be a problem in the carribbean for traditional fins, both gyro's and traditional fins are cooled with sea water.

    That being said, I have been VERY impressed with sidepower curved stabilizer fins, they are awesome at anchor, slow speeds, fast speeds. Better than a gyro in every aspect, especially at fast speeds. Seaweed is no issue for traditional fins, although a log might be a different story......generally at displacement speeds the bow wake pushes the log far enough away from them.

    That being said, the seakeepers are the only Gyro I would recommend and do a very good job at anchor and slow speeds, BUT you're going to have to size it correctly for your weight. The current trend is 2 smaller appropriate sized seakeepers on outbound sides of the boat, than one massive one, it seems to work better. Based on my experience I would NOT consider any other brand of Gyro......and definitely not the air cooled one.
  3. JWY

    JWY Senior Member

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    Be sure to check out the "warm-up" times and the energy consumption on the gyros to make sure that fits it with your cruising plans. If you're at anchor in the Bahamas, you might not want to sit with your generator running in orfer to support the stabilizer system.

    I'm waiting for the "perfect" steel trawler to be built. Would love to see a new thread on what you're intending. You might get some good input from YF.

    Judy
  4. mapism

    mapism Member

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    I'm not sure if the subject was already debated in this forum. It certainly was - extensively! - in the European forum, on YBW website. And there's also plenty of other documentation around the web, nowadays - it's just a matter of investing some time with a search engine.

    But in a nutshell, leaving aside the obvious (no external components vs. somewhat large moving parts sticked to the hull), the main difference between gyro and fins stabilization is that the first can't contrast the boat rolling whenever, due to sea conditions, the length of the roll gets longer - to the point of being more akin to listing on one side for some time, and then list to the opposite side, and so on.

    In these conditions, gyros (regardless of brands, it's a matter of physics) run out of precession excursion, and after the imitial "kick", they can't contrast the rolling movement anymore. In sharp contrast with that, fins can keep contrasting the roll forever, for the same reason why a boat keeps running around in circle for as long as you keep her rudder(s) steered. And imho, this difference alone is more than enough to leave gyros to fast(ish) boats, where it's more desirable to not have any external component, and also the typical rolling behaviour is different vs. heavy displacement boats. For the latter, which as I understand is what you are interested in, fins would be my choice with no hesitation.
  5. Nigel Oakey

    Nigel Oakey New Member

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    Best explanation on limitations of gyros I’ve read anywhere. Thanks.
    explanation
  6. mapism

    mapism Member

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    Thanks to you for appreciating! :)

    Btw, I forgot to mention that the above is also the main reason why gyros are very good at anchor (slightly better than zero speed fins in fact, for equally well designed equipments), when long ocean swell that make the boat slowly list either side, depending on the route vs. the waves direction, is a condition that practically can't materialize.
    Last edited: Jan 17, 2020
  7. olderboater

    olderboater Senior Member

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    The size boat the OP is talking about is a challenge for stabilization. Do you go gyro or fin and, if fin, do you go zero speed. Some larger boats now, like Westport, are going to both fins and gyros. Makes sense for anchoring out but in a boat that also cruises at 20 knots.

    Now, when we bought our Sunseeker Manhattan 65 a few years ago, they offered gyros but the route we went was the Sidepower/Sleipner Vector Fins. I read all the promotional material, even the comparisons on real boats and I still wasn't fully convinced. I wasn't too worried though since we were using the boat for the loop. Well, they did everything they were advertised to do. They were incredible at speed and at anchor. If I purchased any boat in the 40 to 80 ft range, that's what it would have. Larger, I'd have to do more research. Clearly this blog post is a promotional blog for them, but it's also interesting in explaining the theory.

    https://blog.side-power.com/en/how-to-choose-the-right-stabiliser-for-your-boat
  8. Viceroy

    Viceroy Member

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    Many thanks to all responding. I'll keep researching and building a file and hopefully a consensus for the direction to follow into specifications to current model builders and/or marine architect. I will eventually let the the thread readers know of my progress but please keep relevant comments coming. Cheers, Richard.
  9. mapism

    mapism Member

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    I would agree with the gyro vs. fins part, but the real reason why they stress also the supposed higher efficiency of curved fins is, quite simply, that they managed to patent them.
    Just about every fin stabilizers I tried were very comparably effective, when properly sized and commissioned: Naiad, ABT, CMC, Wesmar, Sleipner (also before their "Vector" stuff).
    In fact, I've yet to see any kind of scientific comparison between curved and flat fins aimed at checking (let alone confirming!) what Sleipner claims.
    Not saying they aren't good, mind. Just that all fins are.

    Brand aside, I understand your preference for fins in a boat as large as a Manhattan 65, even if (relatively) fast.
    For anything smaller, and possibly even faster, gyros do make sense, though.
    In this respect, I wouldn't go as far as choosing fins down to 40'. Not for planing boats, at least.
    But that's irrelevant for the OP anyhow, considering the type and size of boat he has in mind.
  10. olderboater

    olderboater Senior Member

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    To match the capability of fins at speed, you're going to need a lot of gyros or a very oversized one in a 40' boat. I don't know why you say gyros make sense for faster boats, for planing boats. They're every ineffective at speed when compared to fins.
  11. mapism

    mapism Member

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    I'm saying that because it's not even worth trying to stabilize a 40' (or also 50') boat capable of cruising at 30+kts.
    With such vessels, whenever sea conditions are decent enough to keep going, the ride can be kind of hectic and uncomfortable, but not due to roll.
    It's more a matter of wave impacts - which can be softer or harder, depending mostly on the hull deadrise and shape, but which neither fins nor gyros can contrast.
    So, gyros can still make sense, but just for those interested in usage at anchor - or possibly when pootling around at hull speed.
    But if you ask me, in boats like for instance the Magnum Bestia I would neither want fins nor gyros...
  12. Capt J

    Capt J Senior Member

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    Maoism, I believe the curved fins are a lot more efficient than regular fins when anchored due to their shape and movement. I’ve run a lot of gyro boats and the side power fins blow the gyros away in every aspect and every other brand of fin I’ve used. I have also noticed the issue with gyros at speed in a beam sea where it will keep the hull flopped over for a period of time.
  13. olderboater

    olderboater Senior Member

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    I would agree on the Magnum Bestia but not because of length, because of beam, so I'd say no on narrow beam high performance boats.
  14. mapism

    mapism Member

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    Well, my experience is different. If properly sized, I would call gyros better than fins, at rest.
    Slightly better as I said, but better nonetheless, particularly for coping with sudden navigation waves coming out of nowhere, which is the most annoying reason for rolling in many Med anchorages. In this situation, fins (regardless of their shape) can only rely on half of their theoretical stabilizing power on the first stroke, because when coming from a stable situation they are bound to be centered.

    That aside, I've been on boats equipped with ABT and CMC zero speed (straight) fins, whose performance at anchor was totally comparable with curved fins.
    But if you have ever seen any half decent real world test supporting what the builder of curved fin claims, I'd be delighted to read it.
    So far, I only came across theoretical charts made by them, with a remarkable lack of any reference to actual tests performed.
  15. mapism

    mapism Member

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    Mmm.... Actually Magnums (as well as Itamas, just to name a similar style boat) are built upon rather beamy hulls, for any given length.
    The real high performance league (Fountain, Outerlimits, Cigarette, etc.), where it takes three digits to measure speed, that is where hulls are indeed narrow.
    But in those boats, drag alone (whose relationship with speed is exponential, not linear) is more than enough to not even remotely consider fins.
    Not to mention that they could contribute to spin out the boat while turning - which can happen already at 50kts or so, with relatively small boats...
  16. Pascal

    Pascal Senior Member

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    When you get into the “slightly” range it s all very subjective. The only way to get a valid result would be to have two identical boats, anchored closer to each other subjected to the same conditions...
  17. Seasmaster

    Seasmaster Senior Member

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    Gee, and I thought you were a total Cape Horn advocate!!:);)o_O
  18. mapism

    mapism Member

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    I couldn't agree more: that's precisely the type of test which I have yet to see not only between gyros vs. zero speed fins, but also curved vs. flat fins.
    Most debates and articles on this subject are focused on theoretical/technical considerations alone, and in this respect, I tried to contribute with a few points I'm aware of.
    On the other hand, when it comes to personal experiences alone, mine are as right (or wrong!) as any others, obviously...
  19. mapism

    mapism Member

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    Haha, JWY surely has been, and I guess still is.
    But at the same time, she's realistic enough to know that perfect they were not - as well as any other boat built to date!
    With boats, it's all about finding the one whose compromises you consider more acceptable, rather than stick to wishful thinking...
  20. olderboater

    olderboater Senior Member

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    Interesting that you say "In my experience" but yet you have no experience with Sidepower/Sleipner Vector Fins. They do have real world tests they've run on Princess boats and a others from my memory. They don't have everything they've done on their web site. I've also got experience with Zero Speed straight fins. I've got actual experience on identical Sunseeker's with Gyro and with Vector Fins.

    Now, based on my experience, at anchor I wouldn't claim there's a detectable difference in Gyro, Vector and Zero Speed, with all three superior to regular straight fins. However, at speed, then I give fins a huge advantage and I give Vector fins an advantage over straight on 50-80' boats. I've never used Vector on larger boats although they are installed on some. Now, I would personally choose Vector or straight (Zero) over Gyro because of the significant advantage at speed and also because of the spin up time of Gyros.

    On larger boats, I do find the combination of Gyro and straight to be interesting but haven't gotten deep enough into it to fully understand why builders are going that route rather than zero speed.

    Another comment on experience with vector on typical cruising boats is that the loss of speed isn't there. Now I would suspect there would still be a loss on high performance boats and I'd be concerned as to impact on handling. In a couple of weeks, I'll be having a discussion with AB and I'll be interested in getting deeper into this subject with them and the options and impact on their boats which brings the additional factor of jet drives into it.

    That brings me to a final comment. I would lean heavily toward actual experience a builder has with various options on their boats, where they have such experience. Unfortunately some haven't tried different approaches. However, I would prefer not to be their first use of any form of stabilization as sizing and location and design of hull can all figure into how well a system performs. I was very fortunate with Sunseeker that they had experience with three variations and that I could actually test the identical boat with vector and with gyro. My views are also influenced by the fact I anchor far less than many here, I run at slow speeds far less, and I run at cruise far more. I would then encourage others to take their own usage into consideration.