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| bowing of side rails http://www.hobie.com/au/en/forums/viewtopic.php?f=14&t=39783 |
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| Author: | scott smallwood [ Tue Nov 08, 2011 11:11 pm ] |
| Post subject: | bowing of side rails |
Reading through previos posts, I notice some folks suggest pre-bowing the side rails before lacing the tramp, while one other mentioned that bowed side rails reduces leverage while trapezeing. I would go with the second. Any thoughts? |
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| Author: | srm [ Wed Nov 09, 2011 4:42 am ] |
| Post subject: | Re: bowing of side rails |
You're only looking at a difference of trapeezing leverage (righting moment) of somewhere on the order of 1% due to bowed siderails, so the influence on performance is really miniscule. On the other hand, having the boat as tight as possible is really important to getting the most performance, so it most certainly makes up for the slight loss of leverage. Just look at the racers' boats, they all run a super tight tramp with bowed sidebars. By the way, if you really want to get the max trapeezing leverage, you wouldn't trap off of the sidebar, you'd trap off the side of the hull since it sticks out several inches farther than the sidebar. sm |
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| Author: | scott smallwood [ Wed Nov 09, 2011 7:01 pm ] |
| Post subject: | Re: bowing of side rails |
Thanks, I appreciate your knowledge. How would one accomplish this bowing of the siderails to get the best performance out of boat? |
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| Author: | dbevisjr [ Wed Nov 09, 2011 8:07 pm ] |
| Post subject: | Re: bowing of side rails |
I've not had to lace one yet myself but have seen a couple guys do theirs. They use a ratcheting tie down strap. Wrap around the side rails and hook the ends together underneath. Then you can ratchet the strap until you get adequate pressure on them. Then lace your tramp tightly and when you release the strap the rails will pull it nice and tight. I have no idea how much pressure is adequate but I'm guessing you wouldn't want to get too carried away since you will have a mechanical advantage. My boat is stripped down for hull refinishing so I will have to figure this out soon. I've heard of people using their 6:1 main system to do the same thing but have not witnessed that. Afterthought: Just to clarify, you want to hook the hooks at each end of the strap together. Don't hook them to anyplace on or around the hulls. You probably already know that but I'd hate for you to mess up your boat over a misunderstanding. |
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| Author: | srm [ Thu Nov 10, 2011 7:18 am ] |
| Post subject: | Re: bowing of side rails |
Quote: How would one accomplish this bowing of the siderails to get the best performance out of boat? To clarify - the actual bowing of the side rails doesn't have any effect on performance. The bowing of the side rails is simply an indicator that the trampoline is pulled about as tight as it can be. Having a tight trampoline improves performance by creating a stiffer boat because it reduces the amount that the trampoline frame flexes. So for racing, you want to make your trampline tight enough that the rails visibly bow inward by about an inch or so. If you're not racing, then you probably want to back off the tension slightly so there is less risk of pulling out grommets. Here is a relevant thread on the subject of tightening the tramp. http://www.hobiecat.com/forums/viewtopic.php?f=14&t=33674&p=133919&hilit=tramp+tension#p133919 sm |
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| Author: | Tim H16 [ Thu Nov 10, 2011 10:42 am ] |
| Post subject: | Re: bowing of side rails |
If you have already stiffened your frame by gluing it (except the side rails), then I am assuming that there is no benefit to deliberately bowing your side rails unless you want your tramp to feel more like a trampoline. |
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