Trimming for head and following seas

M

mutski

New member
A friend recently pointed out that trim tabs can push the bow down, but only motor trim can push the bow up. That was a break-through in my understanding of how to trim my 22-Cruiser for following seas. I had been simply raising the trim tabs and finding the bow still dug into the wave ahead. But using motor trim to lift the bow, I find I can cruise downwind in 3' seas with no tendency to broach. Much better!

Going into the wind, I can use both motor and trim tabs to bring the bow down and achieve a reasonably smooth ride at 12-15 mph. Even running into the chop, motor trim seems to have a much greater effect than the trim tabs. It seems the trim tabs are most useful for leveling the boat from side-to-side while the motor is most useful for raising or lowering the bow.
 
To get the best ride also add a Permatrim foil to the motor.

Some like more weight in the bow---and that can be contraprodutive in following seas. It is harder to trim the bow up.

There is always a balance--and the reason that the trim has to be worked just like the throttle and steering, especially in challenging seas. There is a reason that offshore race boats have a helmsman, and a throttle man who tends to both throttles and trim. Full time job in these fast boats.
 
(I see Bob made much the same point while I was typing.)

Another thing to remember about trim tabs and foils is that their effects are related directly to the speed of the boat. In neutral, or at anchor, or sitting at the dock, you can adjust the tabs and foils all you want and the attitude (pitch, roll, or yaw) of your boat will be unaffected. On the other hand, at WOT you need to be careful how quickly and how far you adjust tabs and foils. The effect of a sudden change in foil angle at high speed can be dramatic! At moderate speeds, the effects of tabs and foils are, well, moderate.

The lesson I take away from this is that you should do everything you can to keep your boat in good trim with weight distribution. You might put a lot of weight in your bow to help keep the nose down when going into chop thinking you will rely on your foil to raise the bow as needed when going with the waves. If the seas are in such a state that you really need to slow down, guess what - at slower speeds your tabs and foil will have less effect on controlling your bow. The same principle applies in side-to-side balancing.

When I was heavily loaded for long range cruising, I tried to keep significant weight in gear and supplies in duffel bags that could easily be moved around to assist in trim control.
 
I find my trim tabs to be very effective above 20 mph and I just about always travel at slower speeds. So I enlarged my tt's with stainless steel plates and they are much more effective at my usual speeds of 12-18 mph. Had to make my own Permatrims to avoid interference between the tt's and pt.

MTCW, Jay
 
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