Snorbitz Posted September 22, 2010 Share Posted September 22, 2010 So i spent an hour at lunch time doing touch and go's with my current favourite my 71" CMPro Zero and having completed dozens of touch-n-go's without incident i decided that i'd do one more before packing up and well lets just say i miss judged it and caught a wheel on the way in on a rut ripping it completley out the wing and doing all kinds of naughtiness to the wing itself. (Trying hard not to be potty mouthed here as i'm sure many will understand!!). So i gathered the poor girl up and i've started to strip the wing back already to see what i need to do. I've taken some pics and your comments would be appreciated. The leading edge is intact but as you can see the middle spar's are missing (still attatched to the u/carriage) and whats left is cracked through. I'm not sure you can see in the picture but where the rear edge of the ribs meet the traling edge is also cracked. It'll serve me right for beefing up the mountings too much...SIGH. Anyway onwards and upwards. The main damage was where the retract was but i've removed a lot of the sheeting to see what lurks below...good job i have too by the look of some of the ribs!! I need a cuddle!! Quote Link to comment Share on other sites More sharing options...
Snorbitz Posted September 22, 2010 Author Share Posted September 22, 2010 Are ribs normally made from lite-ply?...its hard to tell when they're only 2.5mm think. Balsa sheeting obviously for the skin but is there anything else i should be aware of? The covering is very thin and i'm not sure what it is...i'll ask the manufacturer to be sure. Could be a nightmare to match. Quote Link to comment Share on other sites More sharing options...
Pete B Posted September 22, 2010 Share Posted September 22, 2010 Can't help with the specifics, Shuglu, but hard-grade balsa for the ribs should be fine, I'd have thought. I'm not offering a cuddle either - but you'll get all the moral support you need from the forum - most of us have been there............ Pete Quote Link to comment Share on other sites More sharing options...
Snorbitz Posted September 23, 2010 Author Share Posted September 23, 2010 Being a warbird its wings are asymmetrical and narrows towards the tip which makes things extra tricky. Top and bottom sheeting needs replacing along with quite a lot of structural stuff, but lying the wing flat is going to be all but impossible as it has a few degrees of diehidral so i need to try to figure a way of getting round that problem first. Then i'll start with the main structural wood first the the ribs then the sheeting last (obviously!). If anyone thinks i should do it another way please shout up. Its looking a bit daunting but with the cost of a new wing set as much as the plane was new its not an option. I found a great "how to" elsewhere and will be able to use a lot of the advice on there about recontructing the broken ribs then cutting out new ones from the templates etc etc. I'll have to make a shopping list for the balsa. As the retract mount came out complete i'll try and get it back in in one piece too. Edited By Shuglu on 23/09/2010 09:50:48 Quote Link to comment Share on other sites More sharing options...
Steve Hargreaves - Moderator Posted September 23, 2010 Share Posted September 23, 2010 My initial thought was that it looks pretty dead, maybe try & get a new wing from Perkins & then I saw that a spare wing is £190 so I thought again!!!! A whole new model is only £50 more!!! Anyway for a bit of wood it might be worth attempting a repair...where bits have been displaced & destroyed replace with new, anything cracked double up with some new wood. avoid sudden changes in section (eg the main spar) as these induce weak points...always try & taper the section. For the wing skin I would cut the edges square so its easier to get a join & then fit sections of sheet under the edge of the existing wingskins to give the new wood something to glue to. Peter Millers articles in the mag recently repairing his Spacewalker gave some excellent ideas... When re-assembling it keep the wing flat to the board & pack the LE & TE to keep it straight & square whilst you pin it down. Also consider using one of the PU glues (like Gorilla glue) this stuff foams a little on curing & will fill any inevitable gaps.....obviously gaps are undesirable & should be avoided where possible but with these sorts of repairs they are almost impossible to eliminate. All parts should be clamped/pinned when using this glue too as the foaming can (& does) move the parts around if you're not careful (& no I'd rather you didn't ask me how I know this...) When complete I would compare its torsional stiffness to the unbroken side & see if its similar...if so its probably as strong as new (or stronger even!!) Good luck... Quote Link to comment Share on other sites More sharing options...
Flanker . Posted September 23, 2010 Share Posted September 23, 2010 Check out my blog HERE on how to fix the impossible - just glue it all back with cyno like a jig saw, and stiffen it up with glass n carbon. light, fast, easy. n very very very strong. Go on fix it and get it up! Go well, F Quote Link to comment Share on other sites More sharing options...
Snorbitz Posted September 23, 2010 Author Share Posted September 23, 2010 Flanker having flicked through your YAK rebuild i feel so much better and in comparison mine is but a surface wound. Still its not the repair that scares me so much as putting a 7kg bird back in the sky and have the confidence to pull back in a turn without fear of the wing giving out.They always say you should get straight back on when you fall off don't they. Thing is i don't even class this as a crash as such, just a rough arrival on the strip. I'm taking my pulse xt40 out today just to get over my incident yesterday. I don't want to be overly critical of the build quality of the plane but i've a few things to say......what main spar...it doesn't really have one as you can see or not in the photos!! and more glue on the joints would be nice....neither would have prevented the damage you see but i can see why folk build there own.....i built a Precedent T180 a few years ago and i think i went overboard compared to this. Quote Link to comment Share on other sites More sharing options...
IanN Posted September 23, 2010 Share Posted September 23, 2010 Posted by Shuglu on 22/09/2010 17:38:42: having completed dozens of touch-n-go's without incident i decided that i'd do one more before packing up The trick is to never say actually "just one more", or "just one last flight" etc. In my experience that is usually tempting fate Quote Link to comment Share on other sites More sharing options...
Snorbitz Posted September 23, 2010 Author Share Posted September 23, 2010 Tell me about it. Its always hard the first time you break your pride and joy. I should be thankfull most of the airfame is intact (ref Flanker's crash). I'll post the rebuild pics on here though as i know pictures say a thousand words and if someone else can learn from my rebuild then some good will have come from the whole thing. Quote Link to comment Share on other sites More sharing options...
Steve Hargreaves - Moderator Posted September 23, 2010 Share Posted September 23, 2010 Ah yes.....what lies beneath.....its aways a bit scary seeing whats underneath the covering of an ARTF.....poor wood, not much glue & have they really used balsa spars on this wing!!! Quote Link to comment Share on other sites More sharing options...
Snorbitz Posted September 23, 2010 Author Share Posted September 23, 2010 Its not full blown soft balsa but then its not ply either....its somewhere in the middle so i expect the repair to be stronger then the rest when its all done......but yes scary is how i would describe some of the work too.!! Quote Link to comment Share on other sites More sharing options...
Biggles' Elder Brother - Moderator Posted September 23, 2010 Share Posted September 23, 2010 In my experience my skill with the covering materials might not be upto the standard of a high end ARTF - but I'd back my airframes against theirs any day of the week! BEB Quote Link to comment Share on other sites More sharing options...
Steve Hargreaves - Moderator Posted September 23, 2010 Share Posted September 23, 2010 Ah but thats because ARTFs use the covering to hold the airframe together BEB........I bet you use that old fashioned stuff....oh! what's it called now...yes thats right...GLUE!!!! I've heard various things about the ARTF factories.....someone told me that the glue represents 30% of the cost of a typical ARTF so they don't use much (I find that a bit hard to believe but there you go) & I also heard that with these CNC cut & tabbed assemblies they are assembled dry & then the whole framework dipped in a great big vat of very thin glue & then hung up to dry (allowing the excess glue to drain away). Certainly if you look at many ARTF airframes you can often see fillets of glue in the corners..... Who knows but as long as we keep buying them they'll keep making 'em & lets be honest if you can buy an ARTF WOT 4 95% finished for LESS than the cost of a Chris Foss Wot 4 kit (minus tank, wheels, covering etc etc) then most people will buy the ARTFs!!! Quote Link to comment Share on other sites More sharing options...
Biggles' Elder Brother - Moderator Posted September 23, 2010 Share Posted September 23, 2010 We might be wondering just tiny bit "off thread" here but I'm sure the mods will be tolerant! You raise an interesting point there Steve that I have sometimes pondered myself. With CNC cutting being so accurate I sometimes wonder if, paradoxically, the parts don't fit a bit too well! Most glues have a fairly high viscosity and high surface tension - PVA, Epoxy, PU etc. They wont "wick" into a really tight joint well. Thin CA will - but there is always the possibility that the stuff soaks into wood before it "wicks" into the joint. Anyway CA is probably far to expensive for ARTF manufacturers to use. Its a potential issue and may account for at least some of the "poorly glued" jonts we see in ARTF's. BEB Quote Link to comment Share on other sites More sharing options...
Steve Hargreaves - Moderator Posted September 23, 2010 Share Posted September 23, 2010 I think we are wandering a bit here BEB...we're hijacking poor Shuglus Zero rebuild thread so I won't comment further...there are lots of "poor build ARTF" threads after all..... Shuglu...back to you & on with the rebuild.... Quote Link to comment Share on other sites More sharing options...
Biggles' Elder Brother - Moderator Posted September 23, 2010 Share Posted September 23, 2010 Oooo - sorry Shuglu - over to you BEB Quote Link to comment Share on other sites More sharing options...
Snorbitz Posted September 23, 2010 Author Share Posted September 23, 2010 Anyway as i was saying... Quote Link to comment Share on other sites More sharing options...
Ernie Posted September 23, 2010 Share Posted September 23, 2010 Touch and gone? ernie Quote Link to comment Share on other sites More sharing options...
Snorbitz Posted September 23, 2010 Author Share Posted September 23, 2010 MMMM quite Ernie...thanks for that...lol.....so i've stripped the wing back now to something i can work with and ordered the balsa and ply that i need. It all came to a little over £10 plus post so if thats all it costs me plus some epoxy and a recover i'll be a happy bunny. I'll start making some cardboard replicas of the broken ribs this weekend while i wait for the wood. The supplier quotes 3-5 days so it could be next week before i really get my teeth into it. Quote Link to comment Share on other sites More sharing options...
Snorbitz Posted September 23, 2010 Author Share Posted September 23, 2010 Oh yes and i've just remembered i need a new prop too so there's another £12ish. Quote Link to comment Share on other sites More sharing options...
Flanker . Posted September 24, 2010 Share Posted September 24, 2010 Glad you enjoyed the YAK fix blog shuglu, I hear that you have ordered wood. Looking at your photo all you need to do is cyano all the bits back and then run some glas cloth (medium/heavy) or a bit of carbon across the joins and they will be stronger than ever. Then just bang the skin back on and filler the cracks. Trying to splice in new timber will drive you nuts, unless you like that sort of thing. With glass n epoxy the job will take less than an hour. As to strength the wing you have looks fine, nice and light. Everything we used to build was well over engineered in my opinion. BUT they did put up with a little tumble ok. I tell you straight that Glass cloth over balsa is stupidly strong. An example. My Middle phase hit the deck pretty hard and was very smashed. A nice man told me how to fix it. with glass and I did. It was 1979 and I was using dry cells so it was only a matter of time until... Yep the batteries gave out in such a way as to get the poor model to go in vertically at a VERY high speed. This time instead of smashing to bits it just stuck 10" into the ground with no damage except a loose servo mount ! There is alot of waffle in the blog but there is all you need to know about glass repairs right there. Go well and very good luck oh Moderators you may give Shuglu my e mail if he asks, then I can help direct if needed. Go well. F Quote Link to comment Share on other sites More sharing options...
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