Stuart Eggerton Posted November 7, 2022 Share Posted November 7, 2022 Hi, I am going to be building the Sagitta XC glider this winter, it uses 11/32 brass tubes, joined with a metal wing joiner rod for the main wing joining method. Can anyone suggest a good manufacturer that can supply this diameter of wire. The brass tube is 8.73mm outer diameter. Can anyone recommend a diameter of wire which will fit, not too tight or loose?!!! Quote Link to comment Share on other sites More sharing options...
Nick Cripps Posted November 7, 2022 Share Posted November 7, 2022 I think I'm right in saying that the K&S tube sizes and wall thickness are designed to fit inside one another as you step up/down in tube diameter. That means that you would need 5/16" diameter piano wire for a sliding fit. Doing some simple sums confirms this as the wall thickness of 0.014 is a touch under 1/64 so with an od of 11/32, subtract 2 x 1/64 and you get 5/16. Note also that 5/16 is just under 8mm so if the fit is a bit loose then go up to 8mm. Have you got any suitable size drills to test in the tube? As for suppliers, there are plenty to be found using your favourite search engine. 1 Quote Link to comment Share on other sites More sharing options...
Piers Bowlan Posted November 8, 2022 Share Posted November 8, 2022 I sometimes substitute a carbon fibre rod, in the case of strait joiners (no dihedral), as it doesn’t bend like a wire joiner, lighter too. If the fit is a little loose, I wrap a short length of sellotape or similar around the rod as a shim. 1 Quote Link to comment Share on other sites More sharing options...
Ace Posted November 8, 2022 Share Posted November 8, 2022 True carbon is lighter but some of these old designs had no wing retainers and relied on the flex to grip the wire and stop the wing coming off. Of course sellotape over the joint works with carbon. Quote Link to comment Share on other sites More sharing options...
Engine Doctor Posted November 8, 2022 Share Posted November 8, 2022 Those old wire joiners often bent and modern so called piano wire is more likely to bend than the old stuff. Find some brass tube and carbon rod to replace as it's far stiffer and will probably be easier to find than the metal wire /rod. Even carbon tube is extremely strong and very stiff compared to wire. Good luck with build. Quote Link to comment Share on other sites More sharing options...
Gary Binnie Posted November 8, 2022 Share Posted November 8, 2022 You could use imperial Standard Wire Gauge (SWG) wire and tube as they work together, this is my Roger Pullen Medicine Man. It has a three-piece wing with 6 SWG and 10 SWG tube and wire joiners for the tip panels (joint is just outboard of the airbrakes). I wouldn't use carbon as a joiner myself as it breaks without warning, I've bent plenty of piano wire joiners on windy bungee and winch launches but they never broke. I would use carbon if it was obviously oversize for the job and/or was the original design. 3 Quote Link to comment Share on other sites More sharing options...
Mike T Posted November 8, 2022 Share Posted November 8, 2022 Maybe this as an alternative? https://www.gliders.uk.com/12mm-x-2mm-Steel-blade-and-Brass-box-x-1M/productinfo/GLB12/ Quote Link to comment Share on other sites More sharing options...
Stuart Eggerton Posted November 12, 2022 Author Share Posted November 12, 2022 (edited) Hi Nick, thanks I checked and the 8mm drill bit fitted the brass tube perfectly:-). I hadn't thought about such a simple solution. I have found a good supplier. This will allow me to start making the spar for the Sagitta XC. I had used carbon before but had it shear in a hard landing. Thanks for everyone's comments and help, it's been much appreciated. Edited November 12, 2022 by Stuart Eggerton Quote Link to comment Share on other sites More sharing options...
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