Join Date: Jun 2005
Location: New Orleans
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Most new sailors tend to overtrim, since a sail will "tell" you when it's undertrimmed (by luffing) while an overtrimmed sail won't give you such an obvious reminder, you'll just be going slower.
Off the wind, the old saying is,"When in doubt, let it out".
When you sail closer than a beam reach, you'll have to trim in more than you think, because your speed has a greater tendency to "pull" the apparent wind forward, and you have to trim in to avoid a luff.
Think about iceboats..they can go 60 knots in a 20-knot wind, because their speed creates much more apparent wind speed than does the "true" wind. Same thing with your boat, but to a much lesser degree. This is why you may be at 45 degrees to the true wind close-hauled, but the apparent wind (on you telltale yarn) may be more like 25-30 degrees. It's like those vector problems you used to do in geometry.
All this will come with experience. Eventually, try some racing (crew for someone to start with) and you'll see more clearly how critical proper sail trim is for speed.