McG 6969 Posted October 26, 2016 Author Share Posted October 26, 2016 I do hope you're right, Peter. As for me, as I can't rely on any experience, I'm not sure at all how it will feel like once put together. But indeed, I project it to be quite 'stiff' in those short dimensions. On the other hand, the purpose of my test-piece is mainly to check how the glassing will behave regarding adhesion and integrity with the Depron. I also intend to test different kinds of resin for the glass fibre. Thank you for commenting, sir. It keeps me motivated. Hakuna matata Chris BRU - BE / CTR Integrity Control Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted October 26, 2016 Share Posted October 26, 2016 Chris The only point I would make on a purely structural note is to do with the thickness of the Depron 'web' between the spar flanges. In a spar the forces on the web (both shear and compression) are a good bit less than the tension and compression forces in the flanges themselves but balsa is so much stronger than Depron there is a danger that ultimately the web fails before the flange, in other words the whole spar 'kinks' before it actually breaks. With substantial spar flanges it is better to make the Depron web the full width of the spar. But as Peter suggests I would not worry, yours will be massively strong anyway. Now next time if you are really trying to save weight without sacrificing strength....... Quote Link to comment Share on other sites More sharing options...
Peter Miller Posted October 26, 2016 Share Posted October 26, 2016 I have always looked on the web as serving two main jobs. First it holds the two flanges apart and stops them beding and secondly it forms the last side of the D box leading edge which makes the wing so stiff in torsion. Quote Link to comment Share on other sites More sharing options...
McG 6969 Posted October 26, 2016 Author Share Posted October 26, 2016 Thanks again for your assistance, gents. @ Simon > I'm afraid this time I'm a bit (totally !) confused... I made my test-spars the same as you are showing on your drawing (the Depron example at the right side of it). It is also the same as it was on my 'project-drawing' posted earlier. The only difference being that the Depron I have isn't actually 6mm but 5,6mm and I cut my balsa flanges at 6mm without knowing it. So after the construction board picture was taken, I sanded the few tenths off the balsa to make the top and bottom flanges the same thickness as the Depron web, doing the same at the rear spar. @ Peter > I can only totally agree with your words. So, I'm terribly confused here as I don't understand what I'm doing wrong... and than of course I feel as much confused that I don't know 'what' or 'where' to correct for the 'real wing'... Lots of 'matata' here Chris BRU - BE / CTR No Control Quote Link to comment Share on other sites More sharing options...
Peter Miller Posted October 26, 2016 Share Posted October 26, 2016 You are doing anything wrong. It doesn't matter if the web is narrower that the spars. The spars fit into the slots in the ribs. The webs normally go between the ribs. so the spars are one piece from end to end and the ribs are in one piece from front to rear. The webs can be short peices betwen the ribs. Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted October 26, 2016 Share Posted October 26, 2016 Chris I did say it was a purely technical point if you are after the maximum possible strength to weight with the materials involved. What you are doing is perfectly sound. Peter also points out that when building a wing there can be some advantage in using 'one piece' wing ribs with the web in pieces between. It is really a matter of personnel choice. For example: My Endurance wing uses a complete balsa/Depron/balsa spar with two piece ribs. On the other hand the Petiterina uses one piece ribs with the Depron web in pieces between them. In this case the top flange can only be added onnly when all the Depron webs are in place. Its a bit "six of one, half a dozen of the other" as to which gives the better result! I hope this helps. Quote Link to comment Share on other sites More sharing options...
McG 6969 Posted October 26, 2016 Author Share Posted October 26, 2016 Thank you both, gentlemen. I was really thinking I was missing a point somewhere, even possibly due to my the lack of English technical terms and understanding. Now i feel quite reassured that I'm not bringing the Bella into total chaos territory. And promised Simon, next time I'll really try to build with a better understanding of 'weight to strength' ratio... but I'll need some extra guidance, then... For now, I think I'll stick to my first "half a dozen" intention, being full spar and split ribs as I believe it can give the best result given the 3mm Depron skinning and the additional glass 'anti-ding' structure protection. Thanks again for your help. Hakuna (less) matata Chris BRU - BE / CTR Six Control Edited By McG 6969 on 26/10/2016 19:34:04 Quote Link to comment Share on other sites More sharing options...
McG 6969 Posted October 27, 2016 Author Share Posted October 27, 2016 Hello to all, A bit of progression with the wing test-piece today but I don’t have that much to show as I have to wait for the glued bits to dry. When both spars were fixed, I cut the ribs to dimension to be prepared for a faster progression afterwards. I also fabricated a simple ply jig to allow the ribs to be placed more accurately and… faster. Not that important for this test-wing but as I intend to have 24 ribs for the wing, I’ll better be prepared… Next is to start cutting all those ribs and to make some ‘sandbags’ for the next assault… being the Depron top covering to be weighted down. Hakuna matata Chris BRU - BE / CTR Assault Control Quote Link to comment Share on other sites More sharing options...
Rosco Posted October 27, 2016 Share Posted October 27, 2016 Don't stress Chris.I wish I had your level of patience!I just want to get stuff up and flying so I've got no patience for test pieces but if it keeps you in the build.......Somehow, I think you'll make sandbags but if I can put my suggestion in......just use some magazines laid ontop of the skin. Put a few ontop of eachother for some weight. They'll curve to the shape underneath and spread the weight across the skin to hold it down whilst your glue dries..... I'm still here Rosco Quote Link to comment Share on other sites More sharing options...
Peter Miller Posted October 27, 2016 Share Posted October 27, 2016 I have some old club catalogues and Argos catalogues for that purpose.. If you city has big ones, telephone directries are good too. Quote Link to comment Share on other sites More sharing options...
McG 6969 Posted October 28, 2016 Author Share Posted October 28, 2016 Well gentlemen, you both are geniuses. Why couldn't I think about magazines and/or catalogs just by myself. Now the sandbags will probably be heavier by volume but the magazines might be quite easier to use, of course. I certainly don't have a lot of magazines at hand, no telephone directories neither... but of course I can always make my life a bit more difficult by combining the two methods... Cheers & thanks Chris Quote Link to comment Share on other sites More sharing options...
Peter Miller Posted October 28, 2016 Share Posted October 28, 2016 WE all see ideas and think "Why did I never think of that" I do it on a regularbasis and so does everyone that I know. I am sure that I Picked up the catalogiue idea from someone else. Quote Link to comment Share on other sites More sharing options...
McG 6969 Posted October 28, 2016 Author Share Posted October 28, 2016 Hi to all, @ Peter > yes, I guess you’re right but this ‘weight story’ should have been an easy one to think of… Anyway, as soon as I got back to the building board, I added the ribs to the bottom plate together with the false leading edge. Better than words, here are a few pics… … and finally, a close-up of the ‘high-tech-bottom-sheet-wig’… you are all entirely allowed to smile, of course, but at least this time, it is simple, adjustable & fully usable for the length of the full size ‘real’ wing… In the meantime, I’m still looking around for big magazines or catalogues. Hakuna matata Chris BRU - BE / CTR x Control Quote Link to comment Share on other sites More sharing options...
Peter Miller Posted October 28, 2016 Share Posted October 28, 2016 The man who comes up with every "simple" idea would be a genius. Quote Link to comment Share on other sites More sharing options...
McG 6969 Posted October 29, 2016 Author Share Posted October 29, 2016 Well Peter, I don't even think it is 'my' idea. Must have seen it somewhere during my research... Cheers Chris Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted October 29, 2016 Share Posted October 29, 2016 Chris Very nice. Nothing wrong with that. When it has the top skin on it will look similar to my 'broad spar' test piece I built a bit back. It will be interesting to see the 'glass' surface.. Quote Link to comment Share on other sites More sharing options...
McG 6969 Posted October 29, 2016 Author Share Posted October 29, 2016 Thank you for the kind words, Simon. It would be very pretentious to think that it can look like your 'test' piece, but indeed the general shape shouldn't be too far away, hopefully. Is that a test portion for your planned 'full plan size' Ballerina wing? To be honest, I'm starting to wonder about that 'fiber glassing' myself. We'll see after a bit of patience... Hakuna matata Chris BRU - BE / CTR Glassing Control Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted October 29, 2016 Share Posted October 29, 2016 Chris No it was test piece I made for a proposed Depron electric glider like this. But 50% bigger at 3.1 m span! But I chickened out. Quote Link to comment Share on other sites More sharing options...
Worden Posted October 30, 2016 Share Posted October 30, 2016 Chris I don't think you need worry about the strength of your spar or wing as you intend to build it. I used a very similar construction on my Gentle Giant and although it was designed as a slow flier and never intended for any aerobatics it was 16ft wingspan. Same 6mm Depron spar capped with 6mm square balsa and 3mm webs either side except around the dihedral brace where the webs were balsa. The only covering over the 3mm Depron skin was film around the brace area. The completed wing with 2 full size servos and lengthy extension leads was under 2 1/2 Kg. There are some photos in one of my albums or thread here 16ft Depron Wing Worden Quote Link to comment Share on other sites More sharing options...
McG 6969 Posted October 30, 2016 Author Share Posted October 30, 2016 Hello gents, @ Simon > I can fully understand that you had some 'doubts' with a 3m wingspan. I have them already at 1.6m... @ Worden > Thank you for visiting and commenting. I discovered your Gentle Giant some time ago with a lot of pleasure, enjoying that 'floating' flight... even if you didn't land on that foam dolly... I remember that you used some Depron/balsa additional webbing as well. I don't think I'd need them in regard to the Bella's wingspan, except maybe some thin balsa at the dihedral brace to spread the gluing surface. I'm now really convinced that it will be strong enough thanks to Simon's advises and Peter's comments, but of course, thank you for your reassuring opinion too. I think my following concern now will be finding a good compromise to join the two half wings nicely together. But one thing at the time, first I want to see how the surface fiber glassing goes and what polyurethane or epoxy to use for best. Thanks again & more to come soon. Hakuna matata Chris BRU - BE / CTR Glassing2 Control Edited By McG 6969 on 30/10/2016 18:46:59 Quote Link to comment Share on other sites More sharing options...
McG 6969 Posted October 31, 2016 Author Share Posted October 31, 2016 Hello again to all, After allowing some drying for the ribs and bits, I could sand down both spars and the false leading edge to shape, the ribs being protected with a few lengths of masking tape. Regarding some weighting down, I remembered that I was donated some old catalogues together with the crashed Graupner glider: the Graupner ’96 and a Robbe ‘97/98. That allowed me use the ‘geniuses’ method to weigh down the top sheet. It seems that I truly like that picture as it hides all the possible mistakes and blemishes I’ve made, but it also allowed me to combine the magazine method with some sandbags… I hope that the weight will not be too much for my 20cm wide test-piece, but at least the poor Por will feel the ‘assault’… and that’s what sandbags are meant for, ain’t it? … Hakuna matata Chris BRU - BE / CTR Po(o)r Control Quote Link to comment Share on other sites More sharing options...
Iris Vlieghe Posted October 31, 2016 Share Posted October 31, 2016 Oh dear, there are my freezer bags in 'La Grotte'! I wondered... I just bought some and wanted to freeze some food. Mysteriously my new roll seemed so slim. And you are using it for... SAND? Not the sand intended for my tropical plants I hope? Mister, I need to talk to you... Iris Freezer Bag Stockcontrol Quote Link to comment Share on other sites More sharing options...
Peter Miller Posted October 31, 2016 Share Posted October 31, 2016 That's right. tell hime to buy his own freezer bags Quote Link to comment Share on other sites More sharing options...
Iris Vlieghe Posted October 31, 2016 Share Posted October 31, 2016 Posted by Peter Miller on 31/10/2016 21:05:14: That's right. tell hime to buy his own freezer bags Yeeeeaaaaaa! Thank you Peter, you are so right! Chris, dear, get your own freezer bags! Quote Link to comment Share on other sites More sharing options...
Peter Miller Posted October 31, 2016 Share Posted October 31, 2016 Well naturally. I buy my own. Quote Link to comment Share on other sites More sharing options...
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