Trim Tabs Q?

[CaptainCaveman]

Not sure but what ive heard they are used to lower or raise each side of the boat depending on how much weight you have on either side, but do they have an effect on how quick the boat gets on the plane? and also if both sides of the boat are equal in weight is it better to have both trim tabs fully up or down?

thanks
CC

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[Deleted User YDKXO]

Yes, most boats will get onto the plane faster if the tabs are trimmed down. Again generally speaking, once on the plane, the tabs should be trimmed up again in order for the boat to achieve its maximum speed. Apart from using the tabs to correct side to side trim, you can also use them to trim the bow down in a head sea for a more comfortable ride but, in a following sea, the tabs should always be up. Be careful how you use trim tabs on some smaller boats as, in some cases, they can affect the handling characteristics of the boat

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[maxtorque]

All of the earlier replies plus: don't leave them down at high speed, they will get damaged. Once you use trim tabs, the boat becomes a little 'skittish' and sensitive to the slightest helm demand.
Great for planing at low speed.

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[tcm]

Re: contoversy break out about trim tabs

Now, i agree with most the above except that tabs affec big boats too, and ...i have not heard that you can't usem at high speed?

Anyway, to answer original question, yep, they can be used to flatten the boat if weight distrbution is so bad that it rides to one aide or another. But they are there to adjust the ride of the boat either to get more speed at a given engine speeed by tilting the boat a little bit, or if the sea comes at you from the side, so the boat again can be trimmed flat.

The time they mustn't be used is when reversing, which I often forget, but not ripped them off yet...

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[DPH]

All of the above plus

I find I use trim tabs more often to counteract the effect of a side wind more than weight distribution. I’d also say that for most boats once you reach planning speed then tabs should be fully up.

On my last boat when coming out of the marina I’d always put both flaps fully down. This kept the nose down at displacement speeds, slightly increases the water line and thus by the law of displacement will give a little extra displacement speed. Because the engines were only turbo-charged this also greatly helped getting on the plane. Never measured it but probably saved 5 seconds on the acceleration, and a lot of strain and black smoke.

Once planning I’d put the flaps fully up and then adjust one or the other to achieve a flat ride. Then once at cruising speed I’d adjust the trim of the drive legs to achieve the best speed.

Coming in to a harbour I pretty much reverse the process, good idea to get into the habit of always putting flaps fully up when you come off the plane to stop any corrosion/fouling on the rams.

Not sure if this is the “experts” view but it worked for me. You can also trim a boat by varying the trim of each outdrive. Obviously you need two engines for this and I’m sure I read conflicting advice in Volvo’s manual about this.

Incidentally, don’t know why flaps are trimmed up and down while drive legs are trimmed in and out. I still can’t remember if in is up or down!


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[whisper]

Re: contoversy break out about trim tabs

I also have mine down slightly at high speed as it does not seem to harm the efficiency and makes the ride more comfortable in any sort of a sea. If the boat tends to lean over due to a strong side-wind I only try to correct it in flat seas as I feel that in moderate seas it impairs the safe handling somehow. Whether this is actually the case or not I don't really know.

<hr width=100% size=1><P ID="edit"><FONT SIZE=-1>Edited by whisper on 17/06/2003 11:58 (server time).</FONT></P>

 

[TwoStroke]

When trimming drive legs - in is down - out is up.

When getting onto plane - trim leg in fully - also keeps bow down on plane for smoother and faster ride. When coming into marina - trim out slightly.

<hr width=100% size=1><font color=red>... too late now, I've bought the boat... must remember the kill cord next time!!

 

[Deleted User YDKXO]

Re: contoversy break out about trim tabs

Of course you can use them at high speed but on some smaller boats, the handling is affected. I once had a Sealine 305 which, if you tabbed down too much at speed, occasionally the boat would quite suddenly and disconcertingly roll and veer off course. Not dangerous in itself but scary

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