Gyro Stabilizers for mid-sized yachts

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

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.

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.

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.

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...

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.

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...

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...

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...

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...