Stabilizers

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Fletcher500 said:
I am not debating which system is better, because a lot of people have fins and love them. There are positive and negatives for any system. We are having a Seakeeper installed in a 45 ft. Trawler new build, and I have not heard anything from the builder or yard regarding lack of room. They are putting in a hatch above it to allow install and improve access. A lot of these Gyros are going in on new builds these days, including retrofits on existing boats.
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How heavy is your SeaKeeper? The dude in the Panbo article says his was 1200 lbs and it was installed in the lazarette. In reading through his Loop blog, it gives the feeling it added several inches to his draft. He ended up moving several things toward the bow to compensate for additional weight on the stern. Isn't it best to install the SeaKeeper in the middle of the boat?
 
Donsan said:
How heavy is your SeaKeeper? The dude in the Panbo article says his was 1200 lbs and it was installed in the lazarette. In reading through his Loop blog, it gives the feeling it added several inches to his draft. He ended up moving several things toward the bow to compensate for additional weight on the stern. Isn't it best to install the SeaKeeper in the middle of the boat?
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I have avoided commenting much about this because I have never had a boat with stabilizers. Everything I know is from reading and talking to others.

Long story short:

Seakeeper did a computer generated analysis of our boat, weight, etc. It will be the first Helmsman to get a Gyro. They came back and said the SK 9 model would result in the most roll reduction. As noted, the 9 is $ and heavy.

They also provided data for expected roll dampening for the 5 and 6 models within our boat. The 5 and 6 models are much less money, smaller, and lighter. I felt the 5 or 6 would provide the best solution with all factors considered. The 6 is essentially a 5 in regards to size, but with more advanced components so it provides about 20% more torque.

The 5 was available to ship from SK right away, and it was heading to a container with other gear the builder was sending over to the yard. I therefore went with the 5 model.
 
Regarding location, yes, the Lazarette location probably resulted in that. A lot of Express Cruisers are now getting these. The engines on EC's are already located aft because the designers are squeezing every inch of space/volume to get more cabin space below. Combine that with Pods is resulting in a lot of weight aft. They are still managing to get these in boats in 40 - 50 ft. range. In these type of boats instances, it would be cramped.
 
Unless things have changed since I looked at them, one "issue" with the gyros is that you have to have a pure sine generator AND keep it running while requiring the stabilization.
 
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Re: Seakeeper

Last summer we installed a Seakeeper 6 in our DeFever 45 RPH. I am not entering into a debate between fin vs. gyro, just that the gyro worked for us. We didn’t want any protrusions from the hull and it was not that much more than a fin system.

The gyro works at any speed, 0 to 12 kts. If you can go faster than 12 kts, than your planing hull shape obviates the need for a gyro at high speeds. Ours weighed in at 800 lbs and we did have to re-balance the boat. But then again, it had an inherent list that I needed to correct anyway! It does take 45 minutes to “spin up”, but we start at the dock before we depart, so it is running we we need it. With the engines running under way, the generator noise is negligiable and at stop, what little generator noise we have covers the gyro. Actually, you can’t tell it’s running with everything off when plugged in to shore power.

It is designed to handle roll actions. So, like the fins, it will subdue beam waves and also help with the squirrelies with following seas. Again like the fins, it does nothing for the pitching action you get when pounding into a sea, except helping to keep the boat flat if you take one on an angle.

Stabilizers are not necessary, but neither is airconditioning. They just make the cruising far more comfortable and thus enjoyable and after all, isn’t that what it’s all about - enjoyment.

Gary
 
Yours is by far the most relevant example/experience for this group since your boat is typical of TF trawlers. So many seakeepers have been in stalled in sport fishing boats and fast cruisers which is not a good example for a slow trawler.
 
We were fortunate that we had room in the engine room and did not have to do any modifications to the compartment. The gyro is mounted off-center and the installers did reinforce the stringers for the gyro mount - one inch thick aluminum plate glued to the stringer and then glassed over. The gyro can be mounted anywhere aft of the fore/aft center of moment.
Gary
 
Delfin said:
Good summary. The only disagreement I would have is the statement that active fins result in a reduction in speed due to drag. No doubt true on boats moving at fast speeds, but for trawlers, IMO, there is no speed penalty in a typical seaway since a stabilized boat feels less drag overall than one rocking and rolling.
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The evidence for KK42’s suggests actively stabilized vessels loose about 0.5-1.0 kts at cruise rpm, as compared with unstabilized vessels. We loose about 0.5 kts from cruise when our paravanes are in the water.

Jim
 
JDCAVE said:
The evidence for KK42’s suggests actively stabilized vessels loose about 0.5-1.0 kts at cruise rpm, as compared with unstabilized vessels. We loose about 0.5 kts from cruise when our paravanes are in the water.

Jim
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I know that is what they say Jim, but it doesn't make much sense to me. For example, paravanes operate by directly creating drag - it is the whole principle of their operation. If paravanes create .5 knots cruise reduction with chains or cables attached in a KK42, plus a forward slopping dolphin being dragged through the water, then how does an active hydrodynamic fin create the same or more drag? Further, the most slipperly presentation of a hull in not when it is swaying from side to side, as it is more prone to do when rolling, nor when it is presenting greater wetted surface when heeled, but rather when it is upright.

With active fins, at least on Delfin with her hull shape, turning on the fins has zero impact on speed, or at least none that I can detect with GPS, so whatever drag there is comes from inefficiencies in the fin hydrodynamics, which don't intuitively seem like would be much.
 
Delfin said:
I know that is what they say Jim, but it doesn't make much sense to me. For example, paravanes operate by directly creating drag - it is the whole principle of their operation. If paravanes create .5 knots cruise reduction with chains or cables attached in a KK42, plus a forward slopping dolphin being dragged through the water, then how does an active hydrodynamic fin create the same or more drag? Further, the most slipperly presentation of a hull in not when it is swaying from side to side, as it is more prone to do when rolling, nor when it is presenting greater wetted surface when heeled, but rather when it is upright.



With active fins, at least on Delfin with her hull shape, turning on the fins has zero impact on speed, or at least none that I can detect with GPS, so whatever drag there is comes from inefficiencies in the fin hydrodynamics, which don't intuitively seem like would be much.
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My point was comparing the same hull and propulsion system, with and without active stabilizers, whether they are operating or not. I would concede that properly maintained active stabilizers are at least as good and probably better than paravanes, but the latter can be removed from the water and no longer contribute drag.

The problem with Delfin, unless you can do trials with the same hull and propulsion, with and without stabilization it’s hard to determine the implications to performance (speed).
 
I think up to 1/2kn loss by adding fins is about right. I can't give data because I changed engines and made other changes to my displacement # at the same time I added fins.

The fins probably have greater wetted surface area than paravanes, but a more efficient foil shape that will offset that increased area in terms of drag comparisons. And mine, like most, are not retractable so I cannot know my speed now without fins.

The point is, it's quite small. But the benefit is huge.
 
The evidence for KK42’s suggests actively stabilized vessels loose about 0.5-1.0 kts at cruise rpm, as compared with unstabilized vessel
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Exactly what evidence?

turning on the fins has zero impact on speed, or at least none that I can detect with GPS
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The true test would be your boat with no fins at all vs one with fins.
I agree with your observation about paravanes. Of course the nice thing about them is you can take them out of the water when conditions are calm.
 
caltexflanc said:
Exactly what evidence?



The true test would be your boat with no fins at all vs one with fins.
I agree with your observation about paravanes. Of course the nice thing about them is you can take them out of the water when conditions are calm.
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The problem with this analysis is that there are so many variables. Clearly, in smooth water Delfin would likely add some speed without the fins, but I doubt as much as a half knot although I can't quantify that. However, as soon as you introduce any kind of roll, the loss of hull efficiency without stabilization is a factor that has to be weighed against any increase in drag. One thing I can tell you is that if we are in rolling conditions, my SOG goes down if the fins are off, not up. Turn the fins on and the vessel stabilizers, moves through the water more upright and shows a very slight increase in speed of maybe .1 to .3 knots, but I won't pretend to be able to measure it with precision.

Just one man's opinion....
 
The before and after on our Grand Banks was about 1/2 kt. Not enough to matter, and a very small price to pay for the benefit.
 
twistedtree said:
The before and after on our Grand Banks was about 1/2 kt. Not enough to matter, and a very small price to pay for the benefit.
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Again, I think the total cost is a function of hull form and wave action. I can imagine that a shallower hull might have different characteristics than one drawing 7 1/2'.
 
My stabilizing sails typically add a half knot with wind on the beam. :D
 
caltexflanc said:
Exactly what evidence?

The true test would be your boat with no fins at all vs one with fins.
I agree with your observation about paravanes./QUOTE]


Exactly that. There are enough examples of KK42’s with and without active stabilizers with Lehman 135’s. Those with the active stabilizers loose about half a knot or more. We talk to each other, you know ;-). One vessel I know travels at less than 7 kts with Wesmar stabilizers. We travel at 7.5 at cruising RPMs.

Jim
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Delfin said:
Again, I think the total cost is a function of hull form and wave action. I can imagine that a shallower hull might have different characteristics than one drawing 7 1/2'.
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That's entirely possible, but way beyond my knowledge to assess.
 
twistedtree said:
I don't think this is correct, at least not the fin stabilizer part. We have about 25,000 miles on two different boats with ABT stabilizers and have never experienced anything by positive results in all seas, following included.
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+1 to Twistedtree's comment. We have ABT Trac fin stabilizers and have found them to be very effective in all conditions. Using them is like hitting the button on stabilized binoculars. Night and day difference.

Seakeeper gyros and active stabilized fins reduce roll. Not effective controlling pitch. What if a Seakeeper gyro is "mounted sideways" in a hull. Would it help with pitch? Maybe the pitch forces are too strong to be controlled compared to roll?
 
Miss Rachel said:
+1 to Twistedtree's comment. We have ABT Trac fin stabilizers and have found them to be very effective in all conditions. Using them is like hitting the button on stabilized binoculars. Night and day difference.

Seakeeper gyros and active stabilized fins reduce roll. Not effective controlling pitch. What if a Seakeeper gyro is "mounted sideways" in a hull. Would it help with pitch? Maybe the pitch forces are too strong to be controlled compared to roll?
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When I was researching Seakpeer a few months ago, I didn't read about anyone who had these mounted sideways to dampen pitch. I'll take a guess and say you are right regarding the potential pitch forces, but I don't know. It may also be that two systems (SKs mounted to control both) would have trouble working together in tandem to control the various motions. The Seakeeper brains may not be that evolved yet.
 
Miss Rachel said:
+1 to Twistedtree's comment. We have ABT Trac fin stabilizers and have found them to be very effective in all conditions. Using them is like hitting the button on stabilized binoculars. Night and day difference.

Seakeeper gyros and active stabilized fins reduce roll. Not effective controlling pitch. What if a Seakeeper gyro is "mounted sideways" in a hull. Would it help with pitch? Maybe the pitch forces are too strong to be controlled compared to roll?
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The Seakeeper gyro can operate in either orientation as the internal rate gyros only sense up/down movement and compensate accordingly. Theoretically they could be mounted sideways to dampen pitch forces. However, roll forces act along the longitudinal axis of the boat and the dampening effect is lateral (the shorter distance). Whereas pitching forces act on the lateral axis and dampen longitudinally, a longer distance. Longer distances mean a longer arm of momentum for the gyro and this would require a greater torque to dampen the pitching force. Greater torque equals larger gyro with a higher weight and cost. As an example, the Seakeeper 9 produces 9000 N-M-S of torque with a weight of 1200 pounds and eat. cost of $72,000, plus install. A Seakeeper 6 produces 6000 N-M-S of torque, weighs 800 lbs, and cost of $40,000, plus install.

Theoretically it is possible. But actually, it is impractical to do it. As an aside, there are several boats, to include the US Navy, that have more than one gyro installed, but these are all oriented to dampen more roll than a single gyro can handle.
Gary
 
Miss Rachel said:
+1 to Twistedtree's comment. We have ABT Trac fin stabilizers and have found them to be very effective in all conditions. Using them is like hitting the button on stabilized binoculars. Night and day difference.

Seakeeper gyros and active stabilized fins reduce roll. Not effective controlling pitch. What if a Seakeeper gyro is "mounted sideways" in a hull. Would it help with pitch? Maybe the pitch forces are too strong to be controlled compared to roll?
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If the bow of your boat was rising to climb the face of a large wave, would you want the gyro to hold it down and bury it into the face of the wave? The same in a following sea: I would want the stern to be able to lift to the overtaking waves, not be held down and pooped.
Conceptually, this is a bad idea.......
 
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Good points regarding roll vs. pitch control for SeaKeepers.

There are some good YT videos on the web showing multiple SK's controlling roll, especially on the big Sporty's.
 
Flatten out pitch? You want your props out of the water? Think about it!

I see posts like these and wonder if some people have any concept as to how a boat moves in the water.
 
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caltexflanc said:
Flatten out pitch? You want your props out of the water?
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Agree, left my thinking cap off when I posted that response. Should have pondered more and held back on the keyboard. Can I go back in and delete? :)
 
Fletcher500 said:
Agree, left my thinking cap off when I posted that response. Should have pondered more and held back on the keyboard. Can I go back in and delete? :)
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Sure. I've learned a lot of things by starting off dumb... make that almost everything.. the key is to stop being dumb once you've learned, and can't say I've mastered that either!
 
Bulbous bow fitted to your boat will dampen pitch, and have the added benefit of increasing LWL. Can be done cheaper than experimenting with a side mounted Seakeeper gyro.
 
My boat came with paravane stabilizers. Stabilizers were not even on my radar as something I wanted in a boat, but after trying them, I would never consider another boat without some form of stabilization. We use them almost all the time. Even on calm summer days, as they make such a difference with wakes from other boats. About .5 knots seems about right for how much they slow us down, but it is more than worth it, they make boating so much more fun. We used them extensively at speeds as low as 1.5-2.5 knots last summer while trolling for King salmon off the Pacific coast of Vancouver Island last summer, and they were surprisingly effective even at those slow speeds. Some day I am going to get around to building some flopper stoppers to hang off the poles while at anchor. The fish do not have enough surface area to really do much while at anchor.
 
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