You should reef any time you start to suspect that things could get out of control. If you get a gust or two that are little pushy your probably ok. If your getting pushed pretty far over, If you find your getting headed up, then having to fall back into the after ever gust. you should have already had a reef. It will make you a faster and safer sailor. A good pratice would be to reef your sail any time there is some good wind blowing. Then when you get out there, if your not moving worth a darn, you can shake the reef. This will give you a lot of quick pratice. Later when you need to reef on the quick you'll be ready.
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