This might be off topic but does a chart for sail area vs line size strength with wind speed exist? Lets take say the fishing line in the light air and 180 sq ft of sail needs to be what test ? Then with the same sail you will need a -- size line in a 20 knots? You may also need to change your choice of knot on the clew. Regards. Lou
Thanks Lou. Whenever I learn something interesting I try to share it online. I've learned so much myself from others who do the same.
Like stumble said, my understanding of jib sheets is that for the most part you are sizing up for ease of handling.
My light air spinnaker sheets are 1/8" vectran core. They have a tensile strength of about 2000# and could certainly handle the loads in heavy air too, but in anything over 15 knots they start cutting through the gloves. 25' boat.
I think of it this way. The winch on my mast is the same size as my primaries. I weigh about 200#, and get winched up the mast fairly often. I see how much effort is needed to get me up the mast with that winch, even though I usually help with my legs, and i can say with confidence that I never put nearly that much strain on my primaries while trimming the sheets, even beating or trimming the guy on a hot angle. So it is unlikely that the sheets have to handle any loads greater than that of my 200# (plus friction so to be safe I say 300#). Obviously you want some room for error, but still this gives a ballpark figure in my mind.
I have winched my 250# father up the mast of his 32' keelboat, and found that on his (larger) primaries, the strain in low gear while winching him up is about equal to the max strain in low gear on the primaries while trimming, so for his 32 footer a minimum working load of say 375# is required, plus a margin of error. So 1/4" sta set polyester double braid, with a tensile strength of 2350#, and a working load for non critical applications of about 460# (tensile strength/5), could theoretically handle the loads. But it would be tough as hell on the hands and there may not be enough room on the winch for the number of turns you would need to make it manageable!
I tend to overestimate loads on my own boat, it helps to be able to put things in perspective.