Article 26969 of rec.kites: Path: tug!ibmpcug!laura.pcug.co.uk!hole.news.pipex.net!pipex!tube.news.pipex.net!pipex!dish.news.pipex.net!pipex!news.be.innet.net!INbe.net!news.nl.innet.net!INnl.net!hunter.premier.net!news.uoregon.edu!newsfeed.internetmci.com!in2.uu.net!news.ner.bbnplanet.net!das-news2.harvard.edu!harvard-gateway!andrew From: Andrew Beattie Newsgroups: rec.kites Subject: Chevron Progress Date: Wed, 26 Jun 1996 23:46:29 +0100 Organization: Division of Applied Sciences, Harvard University Lines: 141 Sender: news@das.harvard.edu Message-ID: <9606262346.aa18095@tug.com> NNTP-Posting-Host: endor.harvard.edu Originator: mss@endor After my success with the 5m Chevron, I figured that I should go a little larger and try a 10m. I did the work on the plan shortly after finishing John Gabby's black and white 5m, but it had been lying around the house waiting first for fabric and then while I worked on the second 5m. When Matthew Hurrell dropped me a line and said that after toying with the idea for several months, he had decided that he wanted a 10 (and that having made the commitment, he wanted it sooner, rather than later), it was time to pull my finger out. First problem was the size. I build full-size plans of the skins, so that I can cut and mark accurately and quickly. My cutting floor isn't really big enough to build a 10, so this tedious stage took longer than ever. There is a problem when you are designing with the bridle points. In order to calculate the bridles accurately, I need to know where the bridle attatches to the rib. In order to apply the re-enforcing patch to the skin, I need to know where the bridle pierces the skin. Trying to calculate one from the other is not reliable to withing the accuracy that I want. On previous kites, I have marked the skin and sewn the bridle re-enforcing on the rib to meet the mark. On this kite, I decided to mark the rib, then take the patches to the sewing machine and stick on the patches as I sew. This means that I must stop sewing just before I reach the mark on the rib. This method failed completely. I am simply not capable of pating sufficient attention to what I am doing to stop sewing before I reach the mark. This wasn't the only problem. I have now built 14 soft foils of different descriptions. You would think that I would have the hang of it by now, but no, I still manage to find a different way to mess up each one. This particular kite has a panel seam that's been put together in-side-out (so that the seam allowance is on the outside of the kite), so it has a french seam across the lower panel to tidy it up. *sigh* I had intended that the kite would be ready for Matthew to fly at Scheveningen last weekend. We had decided to car-pool to the festival to keep the costs down, so it would be an ideal time. Despite working hard, at the time Matthew arrived, the kite was sewn and the primary bridle was fixed, but there was no cross-bridle. We discussed the options for the cross-bridle together and wound the line round the jig, but since we were short of time, we didn't build the secondary bridle, nor join anything togeter, so we opted to bang some nails in a piece of wood and use that to store the bridle till we were ready. Chevrons these days have a 3-stage bridle. The primary bridle is the 4 lines which attatch to each rib. To this, I attatch a extentions, to bring the primaries down to the length that I require, as a single line, rather than 4 lines. I then attatch this secondary bridle to the cross bridle. When we were in the channel tunnel, we got the Spectra out, and measured, cut and attatched the secondary bridle. Later, when we got to Scheveningen, we found a sheltered spot behind one of the beach cafe's where we tied on the cross-bridle and hand-tuned the tips. The wind at Scheveningen was more suited to a 3.5m^2 kite rather than a 10m^2 kite, so testing had to be rather restricted. We popped it up on the bridle to have a look. Everything looked fine, so we left it on the bridle and I used it extensively for buggying. Despite the terrifying appearance of using so much kite in such strong wind, the experience is rather dosile. Robbed of the ability to scoop up large slices of sky, the kite accellerated the buggy only slowly. It takes more skill than usual, because there is no room to recover, but the kite was forgiving and I soon had the hang of turning about well enough to give tandem rides. The following day, the wind had subsided a little, and we put it up on lines. It behaved fairly well, the cross-bridle working as well as we had hoped, but as is usually the case, the calculated bridle left the kite both underpowered and slow. The 10m kite felt asif it was only somewhere in the region of 6m^2. I was pretty clear in my mind how I wanted to fix it, but in the strong wind, the "problem" was actualy an advantage - the kite would have been unamanagable if it had been flying properly, so we left it. Matthew now gathered up the courage to fly it and spent some time getting aquainted with the kite which was his in theory, but which only I had been flying... Matthew is a repeat customer. He bought one of the 3 7m^2 early black and white Chevrons. I took the chance to fly this kite again. I had been wanting to do this, because I felt sure that I could improve on it by applying what I had learned about bridling in the intervening time. I was in for a rude awakening. It wasn't flying anything like it should be. It clearly needed some primary bridle work. Matthew had envisaged that he would come home from Scheveningen with a new kite. On the contrary, I took the 10 off him so that I could power it up properly, and took the 7 back off him too, so that I could do similar work on that... Yesterday, I went buggying with Andy Hawken, who had a 10m Icarex cross-bridled Sputnik 4, which would make a fair comparison. We buggied at Lunchtime at Southsea, and I was clearly not performing correctly. It was a struggle to keep up with him, so I started work on the 10m Chevron bridle. Later that evening, we went buggying again, or rather, he went buggying, while I continued untying, adjusting and re-tying. When I was done, the difference was marked - It flew faster, turned better and pulled significantly harder. Upon trying it, Andy immediately confirmed that it was pulling much better than his. (so now, we're working on his one...) I'm not quite ready to send Matthew his kites back just yet (I think there is a little more power to come from the 10 without any drag penalty), but all the signs are that the success of the 5m is going to smoothly transfer to the 10m. I'm not sure what the next project will be. I'm looking at: Build a 5m and try to get it right first time (no tuning) Build a 10m with slightly different dimensions to get minumum fabric waste Work out what 7m or 8m kite should look like. The 10 is very stiff - could I push the aspect ratio further again? How will it fit on the fabric? Matthew had a very nice 3.5 kite at Scheveningen. I had been puting off building a 2.5m kite because it is so highly specialised in a wind range that I have little experience of, but 3.5m^2 is an interesting size to play with. I need to do more work with bladders. I have some Orcron. Maybe a very small chevron could be interesting... My single skin chevron failed miserably. I have been thinking about it, and maybe I could fix everything with the judicious application of a knife... I am very pleased with the performance of Icarex and I avoid Carrington like the plague, but really, I should make a Carrington kite, so that I can learn exactly how bad the problem is... Anyway, if you're interested in owning the results of any of these projects, drop me a line and I might do that one next... Andrew We've discussed this before. It's in http://www.kfs.org/kites/archive