Join Date: Feb 2012
Location: New Orleans Louisiana
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Re: Mainsheet size?
Med, if you want to be able to hand sheet it primarily, with the winch available as a backup, then you should probably size it based upon controlling it that way. Assuming a 1500lbs max load trimmed by hand, you would need something like a 30:1 purchase arrangement. This is why on mid boom sheeted mains they pretty much have to be winch controlled. The rough number is that a person can exert around 50lbs of force on a line for brief periods. Beyond this it isn't practical. On my Trip 40 we had a 24:1 and a cascade 48:1 on the main, but it was still pretty marginal.
By switching to a winch, you immediately get somewhere in the 40:1 range in low gear, meaning even a 2:1 or 3:1 additionally while nice, isn't really necessary. The downside to additional purchases is that you also increase the amount of line you need to crank in, and the amount of tale left in the cockpit. Which may or may not be an issue depending on your boat.
If I was setting up a winch driven system, I would just assume that I was going to use it most of the time. Otherwise on a sail this big you have to have a major increase in necessary purchase.