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Old 05-07-2016, 03:18 PM   #1
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Trim tabs to stabilize?

So I must be missing something, otherwise it would exist. I was wondering about the feasibility of using your trim tabs to stabilize your boat, like the humphree interceptors. Can this be done? Could I buy the humphree electronics but leave my old Bennetts on there?

The only real issue I can see, assuming they would integrate, is the rate of actuation of the trim tabs. They might be a little slow

Anyone know anything about this?
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Old 05-07-2016, 03:39 PM   #2
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Bennett trim tabs would be much too slow.


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Old 05-07-2016, 03:47 PM   #3
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Yes, I think it's about the speed of the actuators, the size of the trim tabs (much smaller) compared to normal stabilization fins, and the positioning along the hull.
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Old 05-07-2016, 03:48 PM   #4
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Quote:
Originally Posted by djmarchand View Post
Bennett trim tabs would be much too slow.


David
Right. Fins swing from stop to stop in a second or less. That's pretty fast.
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Old 05-07-2016, 05:38 PM   #5
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I had that same idea and mentioned it to Lenco at the 2015 Miami International Boat show. He looked pretty surprised and then told me they were working with a stabilizer company to develop that idea. Yes the trick is fast acting tabs and good software. It's more than a year later and still not on the market. I guess it isn't easy.
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Old 05-07-2016, 05:42 PM   #6
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Gabe,
The stabilization you seek should IMO be attained through other means.
Tabs are so very very draggy and ineffective at slow speeds.
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Old 05-08-2016, 10:29 AM   #7
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Hmm. Great. Thanks everyone for the food for thought.

I'll keep looking at the options....
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Old 05-08-2016, 07:36 PM   #8
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Quote:
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I had that same idea and mentioned it to Lenco at the 2015 Miami International Boat show. He looked pretty surprised and then told me they were working with a stabilizer company to develop that idea. Yes the trick is fast acting tabs and good software. It's more than a year later and still not on the market. I guess it isn't easy.

How could it be. With the front of a 50 foot boat going up on a 4 foot wave it would take a monstrous trim tab to correct that motion and force the bow to plow into the wave. It would be even harder to correct roll from the rear corner of a boat.
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Old 05-08-2016, 10:12 PM   #9
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What barnacles, what barnacles!

most stabilization does not work to reduce pitch but rather roll... gyros, birds, etc.

I wasn't thinking about pitch but why couldn't you adjust the boat's pitch with trim tabs to compensate for wave motion, at least partially? their normal function is to adjust the boat's pitch albeit somewhat slower

It sounds like the trim tab idea would work if you could put a really fast piston on them. they do have "interceptors" such as volvo, humphree, and a few others. These do work, I'm told. The boat has to be underway but thats what I was thinking with regards to the trim tabs as well. The interceptors have an electric ram that I dont fully understand but I think the vertical action of these makes for more lift with less travel as well...

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Old 05-08-2016, 10:18 PM   #10
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Active trim tabs provide roll, pitch and trim control. - Image - Naval Technology
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Old 05-09-2016, 07:17 AM   #11
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And that active trim tab spells monstrous to me.

It would take a pretty good amount of electrical power to move that tab with enough force to counter roll, pitch, what have you.

And once you lift the stern up forcing the bow back down, how do you force the stern down when the wave gets there and pitches the rear up even more? I havent seen too many bow tabs.
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Old 05-09-2016, 10:08 AM   #12
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retract the tabs and most of our boats will squat to some degree while under way. I'm not saying it will negate ALL pitch. I dont understand why you dont think trim tabs can modify a boat's pitch? Isn't that their primary function, maybe not just as fast as needed to compensate for waves, etc?

what I really want to negate anyway, would be a little bit of roll as I'm cruising with a beam sea. taking waves on the bow is generally not when I break the beer(/wine) glasses in the cabinets.
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Old 05-09-2016, 10:18 AM   #13
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I think Lenco is thinking their tab/stabilizers will be used on planing hulls. You would set the bow angle to reduce pounding and the tabs will control roll.
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Old 05-10-2016, 07:06 AM   #14
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It's not that I dont think trim tabs cant control pitch. Its that I dont think most can afford the power needed to make them be effective at a high rate of speed. It's the old F = M*A equation.

The wave that rolls your boat in a beam sea is acting on a very large area so it has a pronounced affect. The trim tab that is needed to counter that either needs to have that big of an area M, or work very fast A.

Obviously you cant be dragging around 20 foot tabs. The tabs in the picture are massive compared to lenco's electric tabs both in area and physical construction. To move them at the rate needed to generate a counter force would take lots of power.

It would probably be a lot cheaper to use acrylic wine glasses.

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Old 05-10-2016, 04:52 PM   #15
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Maybe something like this:

Auto Tab Control (For Hydraulic Systems) - Bennett Marine

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