Use of Trim Tabs

[JOHNPEET]

Just wondering if any other of the Forumites have had similar un-nerving experiences when using Trim Tabs while on the plane.

Was out on Sunday in absolute perfect conditions with 5 adults on board including myself.
Normally go boating single handed so the boat generally felt quite different with the extra load.

On the return journey, just after starting off, using tabs full down to get on the plane then raising them up and accelarating up to about 21/22 knots - all going well.

Then decide to use the tabs independantly to adjust the lateral trim of the boat to allow for the uneven loading of the accompanying crew.

Applied an amount of port tab down a little bit at a time then completely out of the blue and without warning, the boat made an extremely tight turn to starboard which I was unable to steer against and I quickly pulled the power off, by which time we had accomplished a 180 deg turn in about 20 metres!!

The crew then shouted and swore at me while I checked everything out and then we set off again, eventually up onto the plane without a problem - this time without correcting lateral trim and motored for 3 or 4 miles and then a further 6 miles or so later without a further problem. I left the tabs level throughout.


I have since checked the tabs and there is no damage to them.


Advice and comment welcome!


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[Happy1]

Sorry I can't help I don't have them on mine, but you have my sympathy, scary or what!!! I will be interested to see what it could be as my next boat will have them.

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[DavidJ]

I remember the same happening to me on a Sealine 195 over a decade ago. The trick is to bring the trip tabs fully up as soon as you get on the plane. I haven't experienced it with larger boats but maybe its because you don't need such extreem correction since the boat weight to passenger weight ratio is more favourable.

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[Matthewb]

What happened to you sounds a bit extreme and makes me wonder if you ended up with one of your t/tabs all the way down while the other was completely up. From my own experience I have found that using the trim tabs at all at anything above about 18 knots on my Sealine has some very unpredictable and often unnerving results. In fact, according to the Sealine boat manual, and I quote, "Steering and handling difficulties may result if trim tabs are used fully down above 20 knots".

I know several people with bigger boats who use their t/ts all the time even at high planing speeds but it seems that on smaller/lighter boats the effects of even minor tab correction can cause the boat to lean alarmingly. and behave strangely. Normally, killing the power is the quickest way to stop what's happening, just as you found.

Matt

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[MickJ]

I have a 25ft Sealine, If I leave the tabs fully down, she literally falls of the plane and dives to port at about 16 knots. Very, very unnerving. I have found that I only ever need to use half the travel of the tabs (and nothing past 20 knots), anything over just causes instability. If weight distribution is very uneven, a couple of very short dabs on the button seems to right things.

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[JOHNPEET]

Thanks for the advice.

Your comments pretty much confirm my own assumptions.

One hell of a scare though - I don't like that feeling when something happens and things just seem that little bit out of control!

John.

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