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Polar Diagrams for beach catamarans?
by TexasTuma. 07/01/25 04:16 PM
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Pre-Load on Carbon Fiber snuffer poles... #7129
05/17/02 09:29 AM
05/17/02 09:29 AM
Joined: Mar 2002
Posts: 138
California!
Inter_Michael Offline OP
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Inter_Michael  Offline OP
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Joined: Mar 2002
Posts: 138
California!
Some spin equipped boats, when fully rigged have a significant amount of "bow" on their spin poles,...others have no load. Is there any reason to have or not have a pre-loaded pole?



On the inter 20 with snuffer, the midd point (where forestaty attaches) is higher than both ends.



Good, bad, or indifferent?


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Re: Pre-Load on Carbon Fiber snuffer poles... [Re: Inter_Michael] #7130
05/17/02 11:25 AM
05/17/02 11:25 AM
Joined: Jun 2001
Posts: 196
San Diego, CA
whitecaps Offline
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whitecaps  Offline
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Joined: Jun 2001
Posts: 196
San Diego, CA
The main thing is that you don't want the tip of the pole bowed up, as the pole is weaker in this position and invites failure. It's OK if it's straight, but remember that everything on the boat stretches/bends when sailing under load (mast, hulls, lines/halyards, forestay/shrouds, sails, etc).



If you start out with a straight pole, when everything stretches it allows the pole tip to be bent up, weakening it. To prevent this, they are usually rigged so that the pole tip is bent downward a little when at rest, as a pre-compensation for the pole tip bending upward when under load.



You want enough "pre-bend" (downward), so that the pole never bends upward past the straight position.



All of the above is much more pronounced on hooter/reacher poles than on spinnaker poles, as the reaching sails are under much higher luff tension and sheet tension than spinnakers. The hooter pole on my previous P19 had maybe 5x the bending force of my current I20 pole. For more hooter info see http://www.whitecaps.net.



Sail fast and have fun,

Alan Thompson

I20 - San Diego

Re: Pre-Load on Carbon Fiber snuffer poles... [Re: whitecaps] #7131
05/17/02 12:59 PM
05/17/02 12:59 PM
Joined: Mar 2002
Posts: 138
California!
Inter_Michael Offline OP
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Inter_Michael  Offline OP
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Joined: Mar 2002
Posts: 138
California!
If you were to run a line from the bowl to the base at the beam, what would be the avg. distance? (Between the line and mid pole)

Re: Pre-Load on Carbon Fiber snuffer poles... [Re: Inter_Michael] #7132
05/17/02 03:25 PM
05/17/02 03:25 PM
Joined: Jun 2001
Posts: 196
San Diego, CA
whitecaps Offline
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whitecaps  Offline
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Joined: Jun 2001
Posts: 196
San Diego, CA
On my boat, it came with the wires cut to induce about 2" of prebend in the pole (i.e. you have to push the tip of the spinnaker pole/snuffer down 2" in order to connect the spin-pole wires to the hull tang.



Alan


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