Date: Sat, 6 Aug 1994 15:42:42 -1000 From: bb11807@medtronic.COM (Brian A. Blow) Message-Id: <321e6i$3q1@gazette.medtronic.COM> Organization: Medtronic, Inc. Subject: Sail stretch on spin-off I know that there have been several articles recently posted on sail stretch, but it was just recently that I realized that the sail on my 8' spin-off has stretched. There is a noticable sag in the sail when I set the kite on its 'stomach' (bridle side down). I don't remember exactly what it was like when it was new, but it has definitely stretched. I have noticed that the kite seems to buffet (sp?) a lot when I am flying in winds >15mph. It's like the nose of the kite is jerking back and forth. I am guessing that the sail stretch has modified the kite shape enough so that it is no longer stable. I have tried some minor bridle adjustments, but I have not successfully eliminated the instability. So, how do I fix this? Do I put in longer wiskers and/or cross spars? This will modify the shape from the original, but at least the fabric will be stretched tighter. Or do I have to rip out some stitching in the sail and remove some of the material? This seems like it could be a lot of work and I could easily make it worse than it is. Thanks in advance for your help!! Brian Blow email: brian.blow@medtronic.com Medtronic, Inc., Minneapolis, MN Phone: (612) 574-4030 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Alcohol and mathematics don't mix... Don't drink and derive. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = Date: Sun, 7 Aug 1994 23:45:55 -1000 From: rolf@login.dknet.dk (Rolf V. Oestergaard) Message-Id: Organization: DKnet / EUnet Denmark - Login Tjenesten Subject: Re: Sail stretch on spin-off Brian, >So, how do I fix this? Do I put in longer wiskers and/or cross spars? >This will modify the shape from the original, but at least the fabric >will be stretched tighter. Or do I have to rip out some stitching >in the sail and remove some of the material? This seems like it >could be a lot of work and I could easily make it worse than it is. You better get started right away: Sew a new sail for Your Spin-off! This time You might want to add some strips of 10mm dacron reinforcements on the back of the sail, from the leading edge to the trailing edge. This will reduce the strech, but might also change the kite in other ways....If You try it, let me know how it worked. BTW, I got a Speedwing clone with the sail streched a lot, and it actually improved the kite I think! I strong wind, it flies very well - the kite seems to be more "radical" than the new Speedwing. Guess that only aplies to kites as simple as the Speedwing, but... Rolf V. Oestergaard, Copenhagen, Denmark -------------- \ /\ / email: rolf@login.dknet.dk \/ \/ = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = Date: Thu, 11 Aug 1994 18:38:10 -1000 From: tanaka_be@swam1.enet.dec.com (Bert Tanaka) Message-Id: <9408120435.AA17183@mts-gw.pa.dec.com> Organization: Division of Applied Sciences, Harvard University Subject: Sail stretch on spin-off /Subj: Sail stretch on spin-off /I know that there have been several articles recently posted on sail /stretch, but it was just recently that I realized that the sail on /my 8' spin-off has stretched. There is a noticable sag in the sail /when I set the kite on its 'stomach' (bridle side down). I don't /remember exactly what it was like when it was new, but it has /definitely stretched. /I have noticed that the kite seems to buffet (sp?) a lot when I am /flying in winds >15mph. It's like the nose of the kite is jerking /back and forth. I am guessing that the sail stretch has modified /the kite shape enough so that it is no longer stable. I have tried /some minor bridle adjustments, but I have not successfully eliminated /the instability. /So, how do I fix this? Do I put in longer wiskers and/or cross spars? /This will modify the shape from the original, but at least the fabric /will be stretched tighter. Or do I have to rip out some stitching /in the sail and remove some of the material? This seems like it /could be a lot of work and I could easily make it worse than it is. /Thanks in advance for your help!! /Brian Blow email: brian.blow@medtronic.com ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ I never have had much luck with this problem on TOL kites. I had a couple of NSR's, and like most of the TOL kites, this one too had a deep sail with a lot of billow. So, when it stretched, it even had a little bit more material to work with than some other kites. I had the same problem on my Hawaiian Team kites, too. I don't remember this being a big problem on the Spinoffs, but then, I never bought that model. I tried using longer cross spreaders and longer whiskers but didn't like the way the kites handled after that. The most success I had was to put a fold in the sail that took it in about 1", including the trailing edge. I drew a line on the sail that bisected the top spreader connection, and the lower whisker connection on one side of the sail and repeated for the other side. I folded the sail along this line and sewed it 1/2" in so that it gathered in the sail 1" along the line. There were slight variances for symetry. With a very loose stitch, this flap was sewn flat against the inside of the sail just to be out of the way. Because the sail panels will not line up precisely, the pattern will be mismatched. Mostly what I learned was that a stretched sail pockets the wind and contributes greatly to poor performance. Typically, a kite with a severely stretched sail will pull out of the sky easily unless you use very low bridling to compensate, and there will be a big improvement of this characteristic, but it still won't be as good as a new sail. Other characteristics of a stretched sail may include: more pull, and less forward drive. This might explain the "buffeting" or loss of tracking you're experiencing. If you really like the Spinoff, you may want to consider just buying a new sail. If you can get one that uses Icarex, so much the better. Good Winds, Bert = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = Date: Fri, 12 Aug 1994 18:08:44 -1000 From: lord@eskimo.com (David Lord) Message-Id: Organization: Eskimo North (206) For-Ever Subject: Re: Sail stretch on spin-off When you design a delta stunt kite two of the parameters you are concerned with are aspect ratio and close up angle (sets the amount of billow). The aspect ratio of the spin off was set to minimize spar cutting or wastage. Two 32 1/2 in spars for each leading edge,two for the lower spreader, one for the spine and 1/2 a spar for the upper spreader. My point being that the aspect ratio was not optimized for flying characteristics. Sail billow probably was varied to find what seemed to work best. If the sail billow changes due to stretch then it can be redeemed by adding a spacer to each lower spreader and the upper spreader. You should strive for the same close up angle as the original. If you get the billow in the ball park and readjust the bridle because of the aspect ratio change the kit should fly pretty close to the original, maybe better. I have always preffered higher aspect ratioi designs. In commercial designs extra cutting of spars or spar waste runs the cost of the kite up substantially at the retail level. Dave Lord = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =