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PostPosted: Tue Sep 18, 2007 8:32 pm 
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Location: Northfield Minnesota
Who, what, why? Huh? This is a foreign concept to me. Why do I want more/less bend. Spreader rake? The tuning guide shows the old style setup, do I measure from the same places?


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PostPosted: Wed Sep 19, 2007 6:20 am 
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Location: Oklahoma City, OK
More diamond wire tension = more pre-bend = de-powering of the main. The spreader rake determines how much pre-bend is applied to the mast with the diamond wire tension. Two schools of thought: Little to no spreader rake and you can tension the diamond wires to stiffen the mast and have max power to the main. Stock spreader rake (approx 2") allows de-powering of the main by applying more diamond wire tension. I prefer the tunability of the diamond wires and typically have 2-2.5" of spreader rake. Light winds = 200-300lbs diamond wire tension, Med = 400-500lbs, Heavy = 600+.


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PostPosted: Wed Sep 19, 2007 8:57 am 
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Get a loos gauge for sure, or you can borrow mine. I have noticed a big difference with JUST ONE TURN on the spreader buckle. Talk to John Volkman next time you see him. He's a technician on the 20/17 and has taught most of us 20 guys up north how to set up.


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PostPosted: Wed Sep 19, 2007 6:45 pm 
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Location: Northfield Minnesota
My mast has very little prebend to it. CW I think it measured 34 on the loos gauge when we checked it at Yankton.

Adding prebend depowers the boat. This is done with diamond wire tension. So more spreader rake allows for less tension to get the same amount of prebend? Why not fix the spreader bars and just have one control? What do I gain by adjusting the rake then?

Speak slowly, lowly 16 sailor hoppin' on a hot rod boat here.


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PostPosted: Thu Sep 20, 2007 7:19 am 
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Well, you have to have a certain amount of tension on them - they support the mast as well. Loose diamonds are a good way to break or bend a mast. So the spreaders need to be moveable as well so that you have a greater range of adjustment in prebend while also keeping the diamonds tight enough.

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PostPosted: Thu Sep 20, 2007 8:51 am 
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Location: Raleigh, NC
While adding prebend may depower the boat past a given point, it is important that you prebend your mast to correctly fit your sail. If the mast bend isn't concurrent to the cut of the sail, then you will not achieve optimum power and shape from your sail. Your best bet here is to find someone who knows what to look for in sail shape and reaction and get them to help you out in person. Good luck...

PS: the same rules also apply for diamond tension. Less diamond tension doesn't necessarily mean you'll be faster in lighter winds...

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PostPosted: Mon Sep 24, 2007 1:36 pm 
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Location: North Carolina
What Trey said, prebend is about making the mast fit the sail. Downhaul is about depowering or flattening the sail. Check the Hobie Europe site for proper prebend info. All their boats incorporate prebent masts, Fox, Tiger and the FX. The US Hobies do not typically need prebend for their sails to fit the mast, ie 16, 18 and 20. My 18 with a Tiger main however does need prebend which is difficult due to the location of the spreaders and wires.


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