Date: Tue, 22 Jun 1993 06:58:16 -1000 From: ar12@quads.uchicago.edu (Andre Robotewskyj) Message-Id: <1993Jun22.165816.7509@midway.uchicago.edu> Organization: University of Chicago Subject: Anyone add ribs to Flexi design? Hi there, Having just completed construction of my first flexi, I'm already thinking about building another... I'm toying with the idea of doubling the number of ribs from 11 to 22 (for a 6'). It seems that this should result in a much faster kite. As is, there is a lot of "billow" between the ribs which results in pretty extreme distortion of a large percentage of the sail >From the ideal airfoil profile. Has anyone tried this? Andre = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = Date: Tue, 22 Jun 1993 21:05:50 -1000 From: andrew@tug.com (Andrew Beattie) Message-Id: Organization: Negligible. Subject: Re: Anyone add ribs to Flexi design? In article <1993Jun22.165816.7509@midway.uchicago.edu> ar12@midway.uchicago.edu writes: >Having just completed construction of my first flexi, I'm already thinking >about building another... I'm toying with the idea of doubling the number >of ribs from 11 to 22 (for a 6'). It seems that this should result in a >much faster kite. As is, there is a lot of "billow" between the ribs which >results in pretty extreme distortion of a large percentage of the sail >from the ideal airfoil profile. Has anyone tried this? A thought: It'll be slightly heavier. It'll take twice as much work. (But you knew those) The curve the skin in a normal flexi bears only a passing resemblence to the curve of the rib, particularly where the width of the cell is significantly more than hight of the rib (at the rear of the cells). By changing the rib spacing, you will change the skin shape more at the back than at the front. Since the shape of the foil at the rear is unusualy important (it pushes *down*), you may upset the balance of forces and adversely affect the kites ability to fly. I'm not saying that it won't work, just that it *may* have unexpected side effects. Andrew -- Work: gaffer@plx.com Phone: +44 793 614 110 Fax: +44 793 614 297 Play: andrew@tug.com Phone: +44 256 464 912 = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = Date: Thu, 24 Jun 1993 00:51:50 -1000 From: jkn@ohm.york.ac.uk (John K Nicoll) Message-Id: <1993Jun24.105150.15610@ohm.york.ac.uk> Organization: Electronics Department, University of York, UK Subject: Re: Anyone add ribs to Flexi design? In <1993Jun22.165816.7509@midway.uchicago.edu> ar12@quads.uchicago.edu (Andre Robotewskyj) writes: >Hi there, >Having just completed construction of my first flexi, I'm already thinking >about building another... I'm toying with the idea of doubling the number >of ribs from 11 to 22 (for a 6'). It seems that this should result in a >much faster kite. As is, there is a lot of "billow" between the ribs which >results in pretty extreme distortion of a large percentage of the sail >from the ideal airfoil profile. Has anyone tried this? > >Andre Haven't actually tried this, but the `Speedfoil' variant I have made has more ribs than a standard flex - I seem to remember around 15 ribs. I agree that this should increase the speed due to less distortion on the profile, but haven't got a `real' 'flexi for comparison. The designers of the `Speedfoil' plans claim a worlds speed record with a version with (If I remember aright) 100mm rib spacing. Hard to sew! I've made a 3m flexi with around 125mm rib spacing. I wonder if anyone has done any work on the rib shape? It's supposed to be `critical', but noone _really_ knows how they work anyway... john N -- john nicoll (jkn@ohm.york.ac.uk) Department of Electronics University of York Heslington YORK YO1 5DD U.K Tel +44 (904) 433221 Fax +44 (904) 433222 = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =