Active Fin Stabilizers

Curious what size and type boat you have seen Active Fin Stabilizers used on? We had them on our N40's (Full Displacement Hull) trawlers and would not buy a FD boat without them. Has anyone seen them used on a smaller (LOA) boat?

Curious what the group thinks on semi-displacement hull boats. Having lived on both coasts we find the west coast with its major distances between ports and large ocean swells stabilization is required to enjoy the longer coastal trips.

John T.

I've got ABT stabilizers on my 47' Grand Banks which is a planing. I love them and would never consider a boat without them, assuming there is room to fit them. But I think that becomes a real problem with boat my size and smaller. On the BG there was thankfully an alcove space available in a good location, but I think you could be just as unlucky as I was lucky. I think your 40s are at the very low end of the size range where there is room, and I'm sure the Nordhavn was designed explicitly to provide room where most boats in that size range don't consider it. Bottom line, I think you would be hard pressed to find room in a boat 45' or less unless it was designed from the get go to accommodate them.

Then there is the economic question. Just to use a round number, let's say stabilizers cost $50k installed. The smaller the boat and the lower the boat value, the harder it is to justify a $50k option.

And then there are the waters where people boat. If you are up and down the ICW, doing the great loop, or in many of the protected or semi-protected waters of the US and Canada, the benefit is much less.

If you want to see the gruesome details of stabilizers going into my Grand Banks, check this out Adventures of Tanglewood: Installing Stabilzers on a 47' Grand Banks

Paravanes

I agree with Twisted Tree. I have 6' NIADS on my Hatteras. They need about 4 sqft at the fins and 4 sqft at the tank and valving. There is also the drag of the blades to consider. My experience with semi- displacement boats under 40' is that they have a lot of primary stability which might be difficult to overcome with fins anyway. The cost last time I checked was about 45k for parts. A stay sail or paravanes might be more practical at slow speed. At planning speeds there should not be much roll as the ride firms up.

N4061 said:

Curious what size and type boat you have seen Active Fin Stabilizers used on?

Curious what the group thinks on semi-displacement hull boats.

Having lived on both coasts we find the west coast with its major distances between ports and large ocean swells stabilization is required to enjoy the longer coastal trips.

John T.

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We have 9 square-foot Wesmars on our 64' Mikelson. I believe the hull is properly classified as semi-displacement, with a max cruise speed of about 17 knots. Most of my time is at 10 knots or below, when stabilizers are most necessary. They work really well, at least in terms of eliminating roll. My trips are all west coast and typically offshore and multi-day, and are planned well in advance. We don't cancel except to avoid a named storm (insurance restriction), so we often find ourselves in poor conditions. The fins don't do anything for pitch, but it is truly remarkable how they handle a large, intimidating swell, even on the beam. The boat just seems to magically rise up with very little of the expected roll.

A friend has a similar size (and displacement) OA, but with 6 square foot fins (I can't recall whether they are Wesmar or Niads). He is not at all happy with the performance of his.

Once you get use to stabilizers you'll never want to go without them. The one caution I'd advise is to talk to your boat builder and get what they have experience with and have tested on your boat, installed exactly as they say. Today we were coming down the coast of Washington and had beautiful weather but still the swells wouldn't have been nearly as pleasant without. And a few days ago conditions were far worse. We hadn't been in such swells on the east coast as then. Our experience has all been Naiad and the boat we're on at the moment has Naiad Multisea II.

Stabilizers. Wouldn't leave the dock w/o 'em.

And as a note, we don't have a full displacement boat. They work equally well on other hull types. And the fear some have over loss of speed isn't really one necessary with a proper installation. The data shows typical loss is around 0.1 knots, or so minimum as to not be noticeable. Now in terms of what it does to practical operating speed, you are able to go faster simply because of the stabilization. Yes 0.1 knot off at given rpm, but we cruised today at 22 knots and never would have been as comfortable doing that without stabilization.

We love our 6 sqft Wesmars but whatever you choose make sure you take care of them. We had the fins pulled for seal service at 7 years (5 recommended) because of a tiny rusty drip and just missed needing a new shaft. As with anything on a boat, don't ignore the warning signs.

Dave

How often should the system be serviced?

Oil—change the oil in the reservoir every three years or 4000 hours of use.

Oil Filter Element—replace when the DIRT ALARM approaches the yellow arc when system is operating in either CENTER or ACTIVE.

Accumulators & Noise Suppressors (if applicable) - Check nitrogen pre-charge every 6 months.

Lower Seals—replace every three years or 4000 hours of use.

Cooling Water Pump—Check the water pump impeller for wear periodically and verify adequate flow.

Zinc Anodes—Check monthly on heat exchanger(s) if applicable.

This model are in my 50· Marine Trader - full Displacement:
Roll Reduction Technology, Reduce Roll at Zero Speed
Its Pneumatic cero electric!
very, very good.
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Norbert

My OA is 50ft, SD hull. And the Naiad's are 7.5 sq ft. They are trouble free and perform brilliantly. They were a about $60k yard fitted. As noted above, unless designed-in at the outset for 40+ fters finding the space for them could be very difficult

Don't have the space for either stabilizing fins or gyro.

I also have the Niads stabilizers with the multi sea control on my 48 Hatteras LRC, we installed 9 sq ft fines and boy do they work good. Would never cruise off shore without them.


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Capt. Don

We love our Naiad active fin stabilizers and most Defevers have them. What was said about keeping up with the service is very true. We use them all the time even today when getting passed by large fast boats throwing big wakes on the ICW to heavy weather with beam seas makes for a much more comfortable trip.

The only issue is to beware of skinny water with those fins protruding down.

gwkiwi said:

The only issue is to beware of skinny water with those fins protruding down.

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Of course, I understand that the pitch of the boat will change the bottom clearance to either side, but could you guess at what the draft is to the fin when the boat is level?

We have 9 sqft ABT Trac and would not be without them. Despite a lot of what gets written here about the potential for damage to them, I have never met anyone who actually lost a fin or had any damage from them hitting anything. On our boat, 58' with twin skegs, draft about 5' 4", the tips of the stabilizers are at least 12-18 inches higher than the lowest point of the keels and about 2' or more inside the beam. On FD hulls, I think that is pretty average. It would take an awkward grounding on a real slope to damage the fin/shafts.

N4061 said:

Curious what size and type boat you have seen Active Fin Stabilizers used on? We had them on our N40's (Full Displacement Hull) trawlers and would not buy a FD boat without them. Has anyone seen them used on a smaller (LOA) boat?

John T.

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So far those responding with fins seem to be above 40' LOA. I'm interested in this subject too. So far the only active stabilizer I've heard of on shorter boats is a gyro system in a magazine. It was installed in a 35' planing hull.

I have seen paravanes installed on smaller boats but not active fins.

Are there issues hauling out, do they get in the way?

BruceK said:

Are there issues hauling out, do they get in the way?

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Nope.

Bottom clearance

This a 48 lrc with 6' fins. So far so good on grounding. Actually I haven't grounded on anything yet with this boat.

Scary said:

So far so good on grounding. Actually I haven't grounded on anything yet with this boat.

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You scare me.

healhustler said:

Of course, I understand that the pitch of the boat will change the bottom clearance to either side, but could you guess at what the draft is to the fin when the boat is level?

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Haven't measured yet, but the one time I've seen our Defever 44 hauled, it appeared to have about 1.5 to 2 feet between the bottom of the keel and fin tips.



As for space, I don't know if Art designed his engine rooms for active fin stabilizers or not, but god bless him for building in enough room for them . . . plus enough left over for a small bowling alley.

Fin installation is typically midship, but can be +/- 20% of that and still be OK. A good install is inside the beam and above keel level. Even on SD hulls this should be readily achievable. Steve Dashew ripped one off - apparently he 'just brushed' something, but actually it would take a decent hit to do it. The GRP fin is designed to break off so the actuator shaft does not get any significant shear force and damage the hull integrity.

On many RPH boats the engine room bulkhead is midship, so stabilisers installed just behind that is perfect. I would have done that had I known my fuel tanks were going to be replaced, and taken a bit out of the lower part of the tanks to fit them in. As it was we managed to fit them in just forward of the ER bulkhead. Stb one was in a void outboard of the master suite wardrobe, port one was in the shower area. The shower tub is a stepped type, and we had to reduce its floor area by a couple of inches to make it work. Pic shows actuator installed, and you can see where the tub sits. On the seat part of the shower tub there is now a hatch about 15'x10" for access. It turned out pretty good, although I don't have a pic to prove that.

Me Gyro Gale Stabilizer has 4 Fins , sometimes its better tu find 4 other places in the Boat when in the middelpoint no are place.
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Norbert