Bob Cotsford Posted July 24, 2014 Share Posted July 24, 2014 I've just joined a pair of wing halves for a Bullet and it got me thinking about the glass bandage we use. Traditionally we run the strip of glass across the chord so that the weave is square to the wing. This means only half of our glass strands run spanwise, the rest are superfluous at most holding the spanwise strands in place. Well. I haven't got any bandage, but I have got plenty of 25gm cloth, so I put on 4 layers cut with the weave at 45 degrees, so both warp and weft cross the join and all the strands should be pulling their weight. I hope! I also used differing strip widths so I ended up with a soft edge. One bonus of using lots of thin layers is that it needed very little sanding So have I built a self-destruct wing? Quote Link to comment Share on other sites More sharing options...
Andy Green Posted July 24, 2014 Share Posted July 24, 2014 Hi Bob Check this out from Probuild. There are also example of how I do it on my website. Andy Edited By Andy Green on 24/07/2014 17:49:43 Quote Link to comment Share on other sites More sharing options...
Bob Cotsford Posted July 24, 2014 Author Share Posted July 24, 2014 b****y he** - 3 layers of 80gm cloth? Seems a bit excessive to me! I notice Probuild's diagram shows the weave at 45 degrees so I'm not the first to think that way. Quote Link to comment Share on other sites More sharing options...
Chris Barlow Posted July 25, 2014 Share Posted July 25, 2014 No but you thought of it before me! Chuffin good idea and I'll be doing it that way in future! Quote Link to comment Share on other sites More sharing options...
Hangar 9 nut Posted July 25, 2014 Share Posted July 25, 2014 Hi Bob I have just built a Bullet using carbon rod with no bandage just a couple of things left to do and she will be ready for the maiden ! Watch this space ! Quote Link to comment Share on other sites More sharing options...
Andy Green Posted July 25, 2014 Share Posted July 25, 2014 I have 3, 4 & 5 in glass bandage and I just use the one that gives me about 1/2 in outside the fuselage, and use filler to blend to the wing. I always add addition glass around undercarriage wells and mounting blocks. Not had a problem to date. Andy Quote Link to comment Share on other sites More sharing options...
Paul Jefferies Posted July 25, 2014 Share Posted July 25, 2014 I think foam wings joined with Glass tape are massively strong and probably much stronger than they need to be...... Has anyone ever had a foam wing fail at the centre join in flight? Correct me if I'm wrong but I seem to remember that in the original Wot 4, Chris Foss used an open weave CLOTH (not glass) tape stuck on/impregnated with PVA glue. Admittedly it was a pretty thick wing but it never failed under quite severe stress. I think it will be fine Bob...... and please do tell us if it fails! Paul Quote Link to comment Share on other sites More sharing options...
Bob Cotsford Posted July 25, 2014 Author Share Posted July 25, 2014 Yes Paul, it used to be common to reinforce built up wing centre joints with a layer of medical bandage glued on with balsa cement, then later it got hi-tech by using PVA to bond the bandage on foam wings. In actual fact all we are doing is linking the veneer, thats where all the strength is in tension. Anything beyond that is to resist the wing seat digging in Quote Link to comment Share on other sites More sharing options...
Bob Cotsford Posted July 25, 2014 Author Share Posted July 25, 2014 H9N - last night I boxed in the cowl, as it is it would make a very effective burglar deterrent or baseball bat. Probably 30% of the wood I I spent yesterday gluing on will now be planed back off. Edited By Bob Cotsford on 25/07/2014 08:11:50 Quote Link to comment Share on other sites More sharing options...
Alan Gorham_ Posted July 25, 2014 Share Posted July 25, 2014 Bob After years of slapping on the horrible, thick glass bandage and trying to fair and smooth it down to the veneer without cutting into the veneer I gave up and started doing it the way you have. It works.... With your method it's also possible to extend a few layers of the cloth further out into the span of the wing to spread the stress. Actually it seems that you've done that too, so I wouldn't worry Quote Link to comment Share on other sites More sharing options...
Bob Cotsford Posted July 25, 2014 Author Share Posted July 25, 2014 Just spent a couple of hours in the garden with razor plane, detail sander and sanding block while the window fitter does his business plies his trade on the front of the house. It don't half feel lighter and look better now! Pictures a bit distorted but: Quote Link to comment Share on other sites More sharing options...
Former Member Posted July 25, 2014 Share Posted July 25, 2014 [This posting has been removed] Quote Link to comment Share on other sites More sharing options...
Former Member Posted July 25, 2014 Share Posted July 25, 2014 [This posting has been removed] Quote Link to comment Share on other sites More sharing options...
Former Member Posted July 25, 2014 Share Posted July 25, 2014 [This posting has been removed] Quote Link to comment Share on other sites More sharing options...
Bob Cotsford Posted July 25, 2014 Author Share Posted July 25, 2014 and that makes three! I could understand you having a problem with polyester resins (Davids and the like from Halfords), they do stink, but most epoxy laminating resins are pretty odour free. They also have the added bonus of not melting foam. I use Z-Poxy simply because it was what was available last time I bought some. Quote Link to comment Share on other sites More sharing options...
JOHN ADAMS Posted February 4, 2021 Share Posted February 4, 2021 Posted by Andy Green on 24/07/2014 17:48:50: Hi Bob Check this out from Probuild. There are also example of how I do it on my website. Andy Edited By Andy Green on 24/07/2014 17:49:43 Andy, Enjoyed reading your build threads on your website. Always considered building a BarFli, with a Phil Kraft design you know it’s going to fly well. In the process of completing Doug Spreng’s Twister from about the same era, electrifying it which I’m not convinced about but guess it’s the way ahead. John Quote Link to comment Share on other sites More sharing options...
Phil McCavity Posted February 4, 2021 Share Posted February 4, 2021 I've heard of a method where an elongated rhombus is used instead of a square or rectangle of cloth so that the warp and weft are at 45° to the wing span, that is so the widest part of the rhombus is parallel with the main spar. Never tried it nor seen it done in real life but it is a thing according to other forums. Quote Link to comment Share on other sites More sharing options...
Piers Bowlan Posted February 4, 2021 Share Posted February 4, 2021 I have seen that done on foam winged DLGs where minimum weight with maximum strength is required. Quote Link to comment Share on other sites More sharing options...
Matt Carlton Posted February 4, 2021 Share Posted February 4, 2021 I usually cut a couple of full depth 1/16" ply joiners one extending about 6" into the wing and the other about 4" which I epoxy in place. Replace the veneer/sheeting and then use a single rhombus of glass cloth over the joint to avoid a stress point at the edge of the cloth. Quote Link to comment Share on other sites More sharing options...
Martin McIntosh Posted February 4, 2021 Share Posted February 4, 2021 Just saw the latest post on this thread and in my opinion you are all over engineering this. Years ago we would purchase a wing bandage kit which comprised of some very heavy GF and resin which we applied to the join after gluing with epoxy. Talk about an overkill, you could jump up and down on the thing and it would not break. A while now since I made a foam wing but one 2" wide layer of 25-50gm cloth is quite enough. Ever tried to rip thin cloth by hand? A couple of years ago I built another TN 72" Spit. but this time got rid of all the spruce and most of the ply. It has two wing joints which have no braces and relies on the small overlap of the 18gm cloth at joins. 4 3/4lb saved. I throw this around quite a bit and not broken anything yet. Quote Link to comment Share on other sites More sharing options...
Matt Carlton Posted February 4, 2021 Share Posted February 4, 2021 Well there is a point that the less weight the less required strength but in my case cutting my teeth on slope models, the joint needed to withstand the odd cartwheel, so over engineering was the order of the day. Quote Link to comment Share on other sites More sharing options...
Geoff S Posted February 4, 2021 Share Posted February 4, 2021 Most of the models I build are built-up wings but one method I've used I copied from Precedent. Their foam wing Fun Fly (the current kits are built up, I think) kit had slots cut into the wing and you insert a supplied 3mm plywood brace that is at the correct dihedral. I used the same method on my 1/4 scale Percival Mew Gull (it took a bit of courage to cut the slots on my bandsaw) and it flies beautifully. No wing bandage at all so no change of section with its potential stress point. The wing brace is the full depth of the wing so is highly unlike to break. Another Fun Fly tehnique I've also adopted is to cut a chunk of foam out at the leading edge join point and replace it with soft balsa which takes the location dowel. Much better than glueing it into foam - especially at the join where there's hard, cured epoxy. Geoff Quote Link to comment Share on other sites More sharing options...
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