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

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


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Question For Engineering Types

Gary and Charlotte Burton

So I have a fiddle block with cam cleat for my main sheet (end boom sheeting). The way the cleat is arranged makes it very awkward to cleat the sheet in.
My idea is to get rid of the fiddle block with cam cleat and replace it with a regular fiddle block and then use a swivelling cam cleat with fairlead mounted on the boomkin..
The question is: What will the load on the swivelling cam cleat be? When not in motion, does it take the full load of the end of the boom?

Gary and Charlotte Burton

Just to be clear, there will still be 2 fiddle blocks but the bitter end of the sheet will go through this fairlead and cleat

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...

Gary and Charlotte Burton

Kevin - yes, that answers the question pretty much. I wonder if this type of block/cleat is appropriate for this use. I have visions of the whole thing bending over under load.
It does look pretty beefy though and according to schaefer is strong enough

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