While Sailing the I20 last weekend with a mainsheet that was considerably too long (it wasn't my boat so I wasn't about to start chopping lines), I handed the sheet to David after just assuming the lead, tacking, and popping out on the wire. David went to sheet it in and realized we had an issue. The slack had dropped in the water and wrapped around the windward rudder. We tried flying a hull and everything and couldn't get it to come free. David finally had to go in and raise the rudder because we wouldn't have been able to tack otherwise.

The mainsheet should be long enough that the crew can run it from the trapeze while the skipper hangs on to the traveler leaving two to three feet of slack between them.