[AMG]

You are right Bill and this is also what I said in post nr 7. This combination has to be tested out carefully, but on small and not too fast yachts I think they can be good since the yacht will maintain a pretty straight course which isn´t always the case with the active fins. Especially in following seas they can have problems and sometimes cause more rolling than if you shut them down. This has to do with how you trim the autopilot so the rudder speed and angle doesn´t accellerate the rolling...

[Billy1119]

Understood. Thanks for the input. Now that I re-read your post, I realize this is what you were talking about.

Maybe a little off topic, but I was talking with someone a while ago about utilizing trim tabs (modified versions, of course) as a form of stabilization while underway on higher speed vessels. This, of course, would have adverse effects on the autopilot and what not, but I suspect it could be compensated for. This way you could have a fairly simplistic (okay, well, more so than typical systems) method of stabilization with fairly low costs without any hull protrusions. Sure, it probably wouldn't be as effective, but may help out. On the other hand, maybe it'd be better just to utilize a gyro stabilization system if you couldn't deal with the hull protrusions... I haven't put a lot of thought into this, so there may be a big hole (never a good thing on a boat) in the idea, but thought I'd mention it and try and get some feedback.

[AMG]

You are right again. There are stabilized trimtabs for fast boats already...

[Billy1119]

Well, I must be smarter than I thought I was (a joke, of course. I'm really very humble. No, really, I am) . So, how effective are they and have they been applied to yachts? If yes, what was the outcome?

[AMG]

I have no personal experience, but Naiad has been supplying such systems to fast yachts and ferries. Here is a PDF;

http://www.naiad.com/2003-09DATUMFly...20trim-tabs%22

[Billy1119]

Neat stuff. Thanks for the info.

[Innomare]

Quantum also has active trimtabs www.quantumhydraulic.com. Click on Stabilizers, then on Archer and Arrow. They are a.o. on the "World is not enough" from Millenium and on many others and are said to be effective.

Interceptors do the same example www.humphree.com. Instead of a trimtab, it's a blade that creates pressure on the hull bottom. Many of the fast italian and french boats have this system.

-> Bill
As to passive and active working against each other: increased passive stabilization will always be beneficial. Any hull has it's own passive roll damping, but bilge keels jsut add to that. A hard chine hull has more roll passive roll damping than a round bilge. In a sailing boat, it's the keel and rudders that provide a lot of roll damping.

Benetti is now working on a system which one could call "retractable bilge keels". When the vessel is at anchor, huge panels hinge out of the hull and provide passive roll damping. When the vessel is sailing, they are hinged back in for less resistance.
They are planning to make this system active in the future (comparable with active fins).


_____________________________________________
Bruno
www.innomare.com
Naval Architect - Owner's Representative - Marine Surveyor

[MYCaptainChris]

This thread is great, one of the most interesting yet. Thanks AMG.

I often wondered about the trim tab idea also.

My thoughts were that the planning hull would have to be moving faster for them to be affective, and in many conditions that you would need them on a planing hull you wouldn't be going at planning speed. Perhaps if you had super large tabs to counter act the loss in forward motion and thus amount of water travelling over the tabs????

[Innomare]

Chris,

you're right, they become more effective as you go faster.

Trimtabs are more effective at lower speeds than interceptors (but they are also more complicated and expensive).
The lower the speed at which you want them to be effective, the bigger their size should be. But you're limited by the length of straight edge you have on the bottom of your transom (their width is more important than length).
The advantage of the interceptor is that it doesn't have to be straight.

________________________
Bruno
www.innomare.com

[YachtForum]

Originally Posted by Innomare

Quantum also has active trimtabs www.quantumhydraulic.com. Click on Stabilizers, then on Archer and Arrow. They are a.o. on the "World is not enough" from Millenium and on many others and are said to be effective.

This is a system developed by Kelly Archer, hence the product name "Archer". Because the foil is mounted as an extension to a conventional-style trim tab, it will not work for Chris, assuming his ride is a true displacement hull.

Originally Posted by Innomare

Interceptors do the same example www.humphree.com. Instead of a trimtab, it's a blade that creates pressure on the hull bottom. Many of the fast italian and french boats have this system.

Again, this system is not intended for full displacement apps. The plates are intended to mount vertically on a transom. On a side note… I really don’t like this concept. There’s something fundamentally wrong about it!

[AMG]

Originally Posted by CCamper

The plates are intended to mount vertically on a transom. On a side note… I really don’t like this concept. There’s something fundamentally wrong about it!

I agree Carl, still I have put them on a boat where they work really well!

But on our boats with stepped hulls they doesn´t work at all since there is too little waterflow. They doesn´t give the support of real casted offshore tabs either, so for speedfreaks I think the traditional trimtabs are better.

[Innomare]

Carl,

you're right. We were all led off-topic by Billy1119. For a displacement ship trimtabs or interceptors don't make sense.

There you have to choose between fins, magnus-effect rotors, passive or active anti-rolling tanks, gyros, flopper stoppers, rudder stabilization and probably a few others that I am forgetting.

Oh yeah, some fishing boats have a small triangular sail on the aft deck just for roll stabilization.

Cheers,

________________
Bruno
www.innomare.com

[AMG]

There was a stabilizer system with a weight sliding sideways on rails. Maybe from KoopNautic, and I have seen it on a Moonen 72 where it was on the forward bulkhead of the engine room.

It was also working at anchor, but created some noise and it was scary to be in the engine room when it was moving forth and back...

[Billy1119]

Originally Posted by Innomare

you're right. We were all led off-topic by Billy1119

Uh, yeah, sorry about that. My curiosity got the best of me.

Originally Posted by AMG

There was a stabilizer system with a weight sliding sideways on rails.

Seems like that would have to be quite a weight. How big (heavy) are we talking about? Seems a little archaic, but hey, if it's effective...

[MYCaptainChris]

surely it would be more advantageous for the sliding weight to be higher up on the vessel rather than down in the engine room??? Maybe it was there because of the noise and cosmetics?