UK-Cherub Forum
Cherub Chat => Tech Chat => Topic started by: Alex Slatter on September 04, 2013, 08:16:22 PM
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Guys,
I have a fully carbon windsurf top section which fits perfectly as a pole as I have tested it. Would it work or would I have to go and make a new one ?
thanks
Alex
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I'm guessing it'll be a bit floppy? We've used glass tips as mandrels with good success.
Bottom line is how bad is it if you break it? If in doubt, sail with it and see if it breaks is a valid mantra.
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I used one as a boom for kokopelli, brill.
look at the carbon content, the more it is generally the stiffer it is. use the biggest sections you can as well. should be fine but you wont know til you use it.
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On reflection the other mantra
"why do it, is why is this better than what is there and works"
also needs careful consideration.
Jim, Will, Phil and several others have been there and done this - I'm sure they will comment shortly...
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The carbon windsurfer mast was the standard thing to use in the 1990's for a bowsprit. They generally worked perfectly well for '91 rigged boats without reinforcement, perhaps a tad bendy for '97 kites but perfectly serviceable. My guess is the extra length and loading from an '05 kite would mean it might need beefing up a bit.
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Hi Alex,
I have built 2 poles for my self and helped build a third for others.
The first one was a compromise as we wanted it to fit in the bow of Slippery When Wet which limited the diameter but needed it to be quite long (2.8m) to get the tack far enough forward of the mast so the kite would set correctly. It worked fine for us a light weights and when single wiring. In fact when the pole bent I bore away a bit so meant we were always making good VMG. twin wiring or tight reach in lighter conditions meant that it bent opening the luff of the kite and closing the leach. This gives you more side force and less drive and backwinds the main more. I suspect you will see some of this effect and not get the full potential of the sail. A larger diameter pole and slightly shorter pole as we built for E-Numbers dosen't have this problem and provides more downwind power than we can handle. I.E. we reach a limit of righting moment or control before the pole starts bending significantly.
We used the rule of thumb that the tack needs to be about 4m in front of the mast (perhaps a bit less on a 97 rules boat and a bit moe on the 05 rules boat. For the first pole we used a byte C2 top mast section that we had spare as the mandrel, for the second we used the class pole mandrel. The pro built poles (C-tech, Ardspar) can be thinner because they use high modulus carbon. We used low modulus but i know have some medium modulus uni cloth.