Date: 23 Feb 93 03:00:47 GMT From: jeffy@syrinx.umd.edu (Jeffrey C. Burka) Message-ID: <18638@umd5.umd.edu> Organization: University of Maryland at College Park Subject: cure for a flat sail In article <1993Feb22.210248.3370@samba.oit.unc.edu> Matthew.Appler@launchpad.unc.edu (Matthew Appler) writes: >The plans I had were wrong, and ended up doing a lot of research >and guesswork to get it to fly. Were you working from published plans? >It is a basic delta pattern, the spars it has are : a spine, 2 wings, and >a top and bottom spreader bar. The sail is currently ONLY conncected to >the wings...and hangs off the back of the frame. This is the only way I >could get it to fly. Now, of course I want it connected to the spine >also, but then the sail is stretched flat, and it doesn't fly. So, since >I know how deep I want each air pocket, and I know the size of the frame, >how cna I calculate out the plans for the sail??!!?? Several comments: First of all, if the sail is attached only to the leading edges and not the spin, it sounds like your basic configuration is that of a Speedwing (which has no spine, and this only has one "pocket" in the sail, as opposed to your standard spined swept wing stunt kite which has a pocket (or 'billow') on either side of the spine). Based on this, I'm confused as to how you could know how deep you want each of the two pockets when you're basing everything you currently know on the one pocket configuration. That said, let me address this: >I have taken up >through 3rd year calculus, so don't worry about getting too mathematical. I dont' know of any kitemakers who actually bother themselves with calculus when they're designing stunt kites. This isn't to say they don't exist; for all I know, Marty could handle all his geometry this way. But basically, most of the folks I know tend to base their patterns on trial and error and the classic method of TLAR ("that looks about right"). What these two methods would suggest in your situation would simply be to shorten your spreaders. If you shorten only the bottom spreaders, you will also induce a camber by the leading edge; this may or may not have a favorable effect on the kite's performance. Shortening your spreaders will lower the aspect ratio, but that doesn't mean the kite won't fly. You may be interested in checking out Mark Cottrell's book _Swept Wing Stunt Kites_, which I'm told includes formulas for all sorts of different things. I dont' know if it would address the sort of thing you're looking for, though. And, I've never actually read the book myself, so I can't give first-hand reviews of it. Good luck! Jeff (who barely remember anything from the calculus class he took in high school, but still generally manages to get things to fly...) -- |Jeffrey C. Burka | "Fairies are the perfect people to do this | |(suffering Bad Grammar) | sort of work. Biologically, their upper | |jeffy@syrinx.umd.edu | bodies are strong enough to wield a pickaxe...." | = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = Date: Tue, 23 Feb 1993 04:24:03 GMT From: Matthew.Appler@launchpad.unc.edu (Matthew Appler) Message-ID: <1993Feb23.042403.21490@samba.oit.unc.edu> Organization: University of North Carolina Extended Bulletin Board Service Subject: Re: cure for a flat sail Yup, they were published plans. They were in the book "One Hour Kites". The author's name escapes me at the moment, but they are the plans for the crusader stunt kite in the back of the book. In the plans, the author gives 2 different measurements,one on the drawing and one in the text, for various parts of the kite. None of them seem to add up quite right. I upgraded the materials in the kite also....I used ripstop and fiberglass instead of Tyvek and tape....:)... I think what I'll do is obtain some Tyvek or cheap nylon and experiment with it a little. The problem with the current design is that the sail will flatten when you take it too hard into the edges....You must understand, this is the first "swept wing" stunt kite I have ever had. I am a ppor college student who has flown Peter Powell diamonds for years and years, and want sto go on but has no money..;)...I've also had a blast designing the thing, so it's not been too frustrating or anything. I will attempt to do some guess work and piece together some stuff to make the billows right....once I have the sail set right, I will remake it out of ripstop. Thanks much Jeff.... Matthew -- The opinions expressed are not necessarily those of the University of North Carolina at Chapel Hill, the Campus Office for Information Technology, or the Experimental Bulletin Board Service. internet: laUNChpad.unc.edu or 152.2.22.80 = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = Date: Tue, 23 Feb 93 08:34:18 GMT From: salanne@convex.csc.FI (Simo Salanne) Message-ID: <1993Feb23.083418.11111@nic.funet.fi> Organization: Finnish Academic and Research Network Project - FUNET Subject: Re: cure for a flat sail In <18638@umd5.umd.edu> jeffy@syrinx.umd.edu (Jeffrey C. Burka) writes: >In article <1993Feb22.210248.3370@samba.oit.unc.edu> Matthew.Appler@launchpad.unc.edu (Matthew Appler) writes: (text deleted) I posted my follow up before reading Jeff's reply. We gave similar replies: "speedwing", shortening spreaders, low aspect ratio - we must be right:-) Simo = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = Date: Thu, 25 Feb 1993 20:49:17 GMT From: sasaki@netop3.harvard.edu (Marty Sasaki) Message-ID: <1993Feb25.204917.16042@das.harvard.edu> Organization: Harvard University Subject: Re: cure for a flat sail In article <1993Feb23.042403.21490@samba.oit.unc.edu>, Matthew.Appler@launchpad.unc.edu (Matthew Appler) writes: >I think what I'll do is obtain some Tyvek or cheap nylon and experiment >with it a little. The problem with the current design is that the sail >will flatten when you take it too hard into the edges Try adding some whiskers/standoffs to the kite. It isn't unusual for a really flat kite to do what you say. After that, try increasing the nose angle before you put the sticks in. This will make the kite less flat. This should make it more stable, meaning that it should easily fly straight. One of the problems that I have as I experiment with making kites is that time is now my primary resource. As a result, I am always torn between making a kite out of first rate materials (I know that chances are small that I will remake a kite to use better materials) and using inexpensive stuff (if the kite doesn't fly, then I haven't invested a lot of money in it). Usually I go with the more expensive materials and design in graphics that I think I can live with. -- Marty Sasaki Harvard University Sasaki Kite Fabrications sasaki@noc.harvard.edu Network Operations Division 26 Green Street 617-496-4320 10 Ware Street Jamaica Plain, MA 02130 Cambridge, MA 02138-4002 phone/fax: 617-522-8546 = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =