Westsail Owners Alliance - Post: "Question For Engineering Types"
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Post: "Question For Engineering Types"

12,268 posts on 2,444 threads   •   From Mar 07, 2004 - Jan 08, 2012


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- Archived Message from Inactive Forum -

Kevin Donahue and Marilyn Falconer

If I understand your question correctly the number you are looking for would be the mainsheet/mainsail load divided by the purchase. So two fiddle blocks 4:1 would result in a 50% reduction of the load for each sheave the line passes 180 degrees around on the fiddle blocks.

A sailmaker can give you some load numbers for your mainsail based the sails dimensions and different windspeeds.

A simple example: 400# mainsail load in 30 knots of wind passing thru a 4:1 purchase.
400 divided by 4 = 100# load

Don't know if this helps...

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