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Old 12-23-2012
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Re: Size Numbering on Winches

Try this site

Winch comperarison - Self-tailing models
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Back in the water in Grenada - with new main and #2 and cockpit canvas (Santa came early). Will spend the winter and early spring in the Caribbean and then head to Bermuda and the northeast US. Still trying to decide if we will bring the boat to Canada, either in 2015 or 2016.
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Old 12-27-2012
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Re: Size Numbering on Winches

I never serviced my winches until they seized completely. Never needed the hole-in-cardboard-box trick because there simply would be no loose parts to lose.
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Old 12-27-2012
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Re: Size Numbering on Winches

Originally Posted by killarney_sailor View Post
Thanks for the link and OP! Good question and the answers make me feel very silly.

I was told a long time ago (by someone who SHOULD have known!) that the winch number was the manufactures rough estimation of the length of boat for which the winch would serve as a primary. It wasn't really an issue for me, so I accepted it. However, I often wondered why my Lewmar ST 40's (and me) sometimes get worked in a good blow on my 30 foot boat. I thought: "I'm not exactly a small guy, and 40's should be overkill!"). I could always head up, but thought that I shouldn't need to with my guns and the mighty ST 40's.
Now, I can stop fighting it. Whew....what a relief! (no ego here!)

I do wonder how they match the winch to the probable load. Is there a formula for sail size to winch power ratio?
I assume the power ratio on the chart is for low gear (on two speed winches), as they would want to rate the most power you could expect from the winch, when push comes to shove. Correct?

Regarding the winch service issue: I found a small plastic bucket in the paint department at the hardware. I cut the bottom out and it fits nicely around the base of the winches to retain parts when I service them. If it needed to be bigger, I could have removed more of the lower section of the bucket to fit.

Last edited by L124C; 12-27-2012 at 04:50 PM.
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Old 12-27-2012
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Re: Size Numbering on Winches


There are formulas that can generate expected sheet loads based on sail area and wind speed. When you combine this with the maximum work output of 50lbs peak, you can pretty easily figure out the minimum power ratio you need on a winch.

The issue is that while most builders use 50lbs, many people prefer an easier workout and want more power.

The formula btw is:

SL = SA x V≤ x 0.00431

SL = Sheet Load in pounds
SA = Sail Area in square feet
V = wind speed in knots


ML = E≤ x P≤ x 0.00431 x V≤)
(√P≤ + E≤) x (E - X)

ML = Mainsheet Load in pounds
E = Foot length on main in feet
P = Luff length of main in feet
V = Wind speed in knots
X = Distance from aft end of boom to mainsheet attachment point
killarney_sailor and L124C like this.
Greg Rubin
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