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VOL. 9 NO. 5
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Trimming tips

How to handle your boat at cruising speeds

Trimming tips

Most boats handle best when running on their lines, or parallel with their at-rest waterline. A slight bow-up trim will increase the efficiency of a planing hull, but excessive bow-up trim increases slamming in a chop and impedes visibility ahead.

A little bow-down trim can give a more comfortable ride and better steering at slow speeds or in a chop, but it may also increase spray and cause bow steering or bury the bow at cruising speeds in following seas.

Trimming your drives

Outboards and sterndrives typically provide a powered adjustment for the trim angle of the drive unit. When the drive is trimmed out (away from the transom), the bow will rise. When the drive is trimmed in, the bow will fall.

Generally, you will trim the drive in for steering, visibility and wave-handling at slower speeds unless you need some bow-up trim to counterbalance weight in the bow. Drive-in trim will also help you accelerate to a plane by lifting the stern. Once on plane, you will probably want to trim the drive out, but if you go too far, the bow may begin to porpoise up and down; trim in until this stops.

Using trim tabs

A trim tab is a hinged plate mounted at each side of the transom’s bottom edge. When a tab (or flap) is in the raised position—flush with the bottom, it has little effect. When it is lowered, it lifts its side of the stern and depresses the opposite bow. The flap’s angle is controlled hydraulically from a pair of rocker switches at the helm.

Because each trim tab can be controlled separately, you can adjust side-to-side as well as fore-and-aft trim. When both tabs are trimmed down, the stern will rise and the bow will drop. This can be essential for getting an inboard boat to plane and can also augment a trimmed-in outboard or sterndrive.

Once on plane, adjust the tabs to suit. Raise them to decrease drag, keep the bow up in a following sea or fall off plane again, and lower them slightly to maintain planing at a lower speed or to reduce slamming in a chop.

If your boat is unevenly loaded, you can level it side to side using one trim tab. Similarly, if you’re heeling into a crosswind, lower the tab on the side of the boat you want to raise. Do it incrementally. Gauge the effect of the trim before you lower the tab farther.

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