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Author Messages Oldest First Newest First Bruce Artman Posts:5 09/28/2007 11:15 AM   I am getting ready to build a new mainsail and want to take the opportunity to re-think the amount of prebend in the mast. What is the advantage of having any prebend? It seems to me that with the backstay eased and the forestay at max length (Im on the Chesapeake, we have a lot of light air!) wouldn't I want the mast as tall as possible and the sails as deep as possible? Doesn't that imply a minimum of pre-bend? Thoughts? Bruce William Wildner Posts:29 10/04/2007 4:52 PM   Bruce, My thoughts on mast pre-bend. One reason to have some pre-bend is to prevent the mast from inverting when the backstay is on very lightly, I don’t think it would be good to have the mast moving around (pumping) and I think that the pre-bend helps prevent this, which in turn maintains mainsail shape. The forestay length has as much to do with balancing the boat as anything. One of the reasons to rake the mast in light air is to get the boat to have slight weather helm when beating. This will help greatly when sailing upwind in light air. If lengthening the forestay is ruining your mainsail shape (making it too flat?) you may need to move the mast step or where the mast is blocked in the partners. Moving the mast step forward, or aft at the partners will reduce mast bend and help with adjusting the draft in the mainsail. Also note that as the cap shroud is slightly aft swept when we tighten the caps we have slight pre-bend without the back stay attached. Again these are my thoughts, I’m not an expert or a sailmaker, others may have a differing opinion that I would welcome. Bill Wildner Mr. Bill’s Wild Ride Bruce Artman Posts:5 10/04/2007 5:33 PM   Interesting thoughts. I hadnt considered the pre-bends ability to stop the mast from pumping. So, it sounds like a minimum amount of prebend is the best policy, but put enough in to keep the rig from pumping itself to oblivion. Seems like the kind of thing that I dont want to test to failure.... B
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