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From: Mike Maurice (no email)
Date: Tue May 17 2005 - 13:33:49 EDT
Trim tab theory is easy enough to grasp, but the practical use takes some
experimenting.
Generally the control buttons are arranged such that pushing the fwd left
trim tab pushes the bow down on the left side of the boat and similar for
the right hand side, and conversely for the aft buttons. However, I have
seen every other possibility which is confusing to say the least. Sometimes
the buttons are all working and sometimes not and about half the boats have
no indictors to let you know how far down the tabs are. And sometimes the
indicators are not both working. So much for things being what they seem.
In general the tabs should be retracted as much as possible and still bring
the boat to the desired state of trim. The "desired state of trim" implies
running at such an angle that the boat is making the highest speed possible
for the conditions and the setting of the throttles. I normally set the
throttles and adjust the trim tabs, while watching the gps speed reading.
And adjust until I think the maximum speed has been achieved. This is not
as simple as it sounds, since the gps speed may not be stable enough to
really know if the speed has or has not changed by a tenth of a knot. This
is one factor that you have to learn. Trim tabs are also useful to adjust
the side to side trim to compensate for too passengers on one side of the
boat or for fuel or water tanks that are not balanced as well as they
should be. Note that it can be dangerous to allow the trim to get badly out
of balance and be relying on the trim tabs to solve the problem. The tabs
are not effective at slow speeds or at rest and the out of trim could
result in the loss of the boat if the conditions are rough enough.
In a following sea or any gnarly conditions the tabs should normally be
backed all the way off. However, you may recall that I can almost always
provide some exception to every rule. Sometimes in chop I will drive the
bow down and push the throttle setting up in order to go fast and keep the
bow from bouncing up from the impact of the small waves. I have used this
on a lot bigger chop than you might imagine. Some boats like the big
Tollycrafts respond well to this sort of tactic.
For instance, if you are getting beaten up in a fast planning boat and
can't run directly up wind or wave, then striking off at an angle with bow
forced down and zigzagging across the waves may allow you to run fast
without pounding and get to cover, say back at the beach in some cove or
anchorage. Sometimes this will require several long tacks in order to get
to the desired waypoint. Remember these long tacks are being done in a
power boat ,not a sailboat. Power boaters tend to ignore tacking since they
generally have a lot of power. But there are many uses for sailboat type
tactics in power boating and this is one of them.
There is much to learn about using trim tabs to their best advantage.
Regards,
Mike
Capt. Mike Maurice
Tualatin(Portland), Oregon
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