mightypeesh Posted October 7 Share Posted October 7 Hi folks.      My long languishing Great Planes Little Toni has made it back out of the dusty 'to be repaired' pile in the loft and onto the workbench again. Last time she flew (a good seven years ago) the undercarriage pulled out and the spats punched great big holes in both wings! 🤕 Now she is out again, I am going to electrify her. I have a 4 Max 50/65 360 motor with matching esc ready to go, to run on 6s. To this end I will need to cut a battery hatch in the fuse, and I want to repair all the cut-outs in the cowling from the engine and re-spray. The wing is no problem as its the usual balsa traditional construction.   The bits I need advice on is,  A, The type of adhesives to use to glue plywood reinforcement to the glass fuse where I cut the hatch - epoxy I am guessing?  B, The best type of resin and glass to repair the big holes in the cowling?  I have only used 'finishing resin' with glass cloth before for finishing, and as adhesive. Any advice as to the best products I need would be much appreciated!       Cheers, Simon   Quote Link to comment Share on other sites More sharing options...
Allan Bennett Posted October 7 Share Posted October 7 In my opinion you should use epoxy resin, rather than polyester resin, for all repairs because it will stick to any type, whereas polyester might not stick to epoxy. Naturally you need to roughen up the old glass where you want to make a bond.  I've only ever used West Systems 105 epoxy with their 206 hardener and for filling holes I might start with 100g or 200g cloth. For creating new parts from a mould I generally use 100g in several layers. 1 Quote Link to comment Share on other sites More sharing options...
mightypeesh Posted October 8 Author Share Posted October 8 Thanks Allan. Sounds like the stuff I need!  Cheers, Simon Quote Link to comment Share on other sites More sharing options...
Jolly Roger Posted October 8 Share Posted October 8 May be worth also checking out Easycomposites? They offer all the materials you could need, at competitive prices and with good technical support if you get stuck (or, not stuck!😆). I find their EL2 epoxy resin is excellent and versatile.  Hope the repairs go well! 2 Quote Link to comment Share on other sites More sharing options...
Engine Doctor Posted October 9 Share Posted October 9 (edited) Polyester for polyester and epoxy for epoxy. They dont like each other and wont form a proper bond. A mate ignored this and lost a model . He assembled a Flair warbird with polyester fuselage. Then built and fitted a battery box. After a few flights the model became tail heavy so he put the nose down , then it became nose heavy . Ah I think the battery box has come loose he shouted. It was moving about altering CG this went on for a while as he tried to line up to land then after another sharp clinmb and dive he lost control as battety lead seperated. The polyester and epoxy had seperated . Yes it  had been cleaned and abraded . With very heavy abrading you will get a bond but it still eonf ge as hood as using like matetials. Edited October 9 by Engine Doctor 2 Quote Link to comment Share on other sites More sharing options...
Allan Bennett Posted October 9 Share Posted October 9 6 minutes ago, Engine Doctor said: Polyester for polyester and epoxy for epoxy. They dont like each other and wont form a proper bond.  If you don't know what the original is (how do you test?), use epoxy because it will bond to polyester. Not vice versa. 1 Quote Link to comment Share on other sites More sharing options...
RottenRow Posted October 9 Share Posted October 9 If you use some coarse abrasive paper to rub down the (unpainted) inside of the mouldings, then smell them, polyester has a distinctive car body filler smell, whilst epoxy generally doesn’t smell at all.  Obviously don’t breathe in clouds of dust whilst doing it.  Brian. 3 Quote Link to comment Share on other sites More sharing options...
Paul De Tourtoulon Posted October 9 Share Posted October 9 8 minutes ago, RottenRow said: polyester has a distinctive car body filler smell Like Almonds. 2 Quote Link to comment Share on other sites More sharing options...
mightypeesh Posted October 10 Author Share Posted October 10 (edited) Thanks for the advice, I will get my little bit of sandpaper out and give it a sniff! 😀  The Prices look good on Easy Composites too Edited October 10 by mightypeesh Quote Link to comment Share on other sites More sharing options...
Jason Channing Posted October 10 Share Posted October 10 (edited) Use a good epoxy adhesive and it sticks perfectly to polyester if it has been cleaned and keyed correctly. Important to remove any last remaining wax also. laminating resins are not always the best adhesives, Edited October 10 by Jason Channing 2 Quote Link to comment Share on other sites More sharing options...
Martin McIntosh Posted October 10 Share Posted October 10 The West system is by far the best for laminating or finishing but gets a bit expensive initially if you include the pumps. 1 Quote Link to comment Share on other sites More sharing options...
Dale Bradly Posted October 10 Share Posted October 10 The vast majority of commercially produced "fibreglass" products are polyester resin based product, because it's cheaper to produce for several reasons. The vast majority of commercially produced polyester resin based products have a wax added to the resin to aid the curing process. Needless to say, any subsequent processes don't want to stick to wax. So give the item a through clean with hot soapy water to remove any remaining wax. (And any other subsequent contaminants that have appeared since). And do this prior to any scuffing, or you just drive the wax into the scuffs, thus defeating the reason for scuffing it in the first place. 1 Quote Link to comment Share on other sites More sharing options...
Nigel Dell Posted October 10 Share Posted October 10 Henkel stablit express is pretty good for this work as is the Deluxe materials Fusion or Super Crylic I used to bond plastic glazing into epoxy moulded helicopter fuz with Super Crylic and in a whoopsie the moulding delaminated but the glue joint didn’t fail. 2 Quote Link to comment Share on other sites More sharing options...
Paul De Tourtoulon Posted October 12 Share Posted October 12 On 10/10/2024 at 15:24, Nigel Dell said: Henkel stablit express If that won't stick, nothing will ! 1 Quote Link to comment Share on other sites More sharing options...
Guvnor Posted October 13 Share Posted October 13 I always use West Resin, used in the full size industry for a reason... Quote Link to comment Share on other sites More sharing options...
Jason Channing Posted October 13 Share Posted October 13 5 hours ago, Guvnor said: I always use West Resin, used in the full size industry for a reason... What reason is that? AS it was designed for marine. Quote Link to comment Share on other sites More sharing options...
mightypeesh Posted October 14 Author Share Posted October 14 I have given it the sandpaper test and am getting next to zero smell from the fuse or cowling, so It looks like epoxy resin is the way to go.  I am quite please about this given how smelly polyester is to use 🙂. I will go shopping later for resin and cloth and will post the results when it happens.  Thank you all for you input, Cheers, Simon   1 Quote Link to comment Share on other sites More sharing options...
Guvnor Posted October 14 Share Posted October 14 15 hours ago, Jason Channing said: What reason is that? AS it was designed for marine. It was, but it has got a good name amongst the aircraft homebuilders, mainly I think because of the availabilty, range of resins and hardeners and good quality control. Quote Link to comment Share on other sites More sharing options...
Michael Barclay Posted October 16 Share Posted October 16 Epoxy will bond to polyester but will not make a successful bond to itself. 1 Quote Link to comment Share on other sites More sharing options...
Dickw Posted October 16 Share Posted October 16 15 minutes ago, Michael Barclay said: Epoxy will bond to polyester but will not make a successful bond to itself. ?????????????? Epoxy glass motor mount bonded into a kevlar/epoxy fuselage with epoxy adhesive - takes 5kW power OK. Â Dick Quote Link to comment Share on other sites More sharing options...
Michael Barclay Posted October 16 Share Posted October 16 I have a lifetime of using epoxies and polyester resins in full scale yacht construction. In the case you show the bond area and stress involved will let you get away with that, but technically speaking, epoxy will not make a successful chemical bond to itself. Quote Link to comment Share on other sites More sharing options...
Dickw Posted October 16 Share Posted October 16 2 minutes ago, Michael Barclay said: I have a lifetime of using epoxies and polyester resins in full scale yacht construction. In the case you show the bond area and stress involved will let you get away with that, but technically speaking, epoxy will not make a successful chemical bond to itself. Point taken, and I suppose it depends on your own definition of successful in any given application. Do you have any advice on what will successfully bond to epoxy? Cyanoacrylate seems to work, but does it really?  Dick Quote Link to comment Share on other sites More sharing options...
Don Fry Posted October 16 Share Posted October 16 (edited) 9 hours ago, Michael Barclay said: I have a lifetime of using epoxies and polyester resins in full scale yacht construction. In the case you show the bond area and stress involved will let you get away with that, but technically speaking, epoxy will not make a successful chemical bond to itself. Yes accepted, once cured it can’t make chemical bonds to other another cured sheet, no cross bonding possible, but why can’t the normal forces like van de walls force hold it together like any normal glue. If you superglue  2 thin, as in 0.25 mm) sheets togeter to form a trailing edge, you can use it like an axe until the sheets break. Edited October 16 by Don Fry Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted October 16 Share Posted October 16 I suspect this is a major factor in why bonded structural parts in full sized epoxy glass gliders use generous fillets of epoxy impregnated cotton flock.  However, properly done, the resin should be abraded back until the glass fibres are feathered slightly so the new resin permeates them, so it isn’t purely an epoxy to epoxy bond. 1 Quote Link to comment Share on other sites More sharing options...
Tim Flyer Posted October 17 Share Posted October 17 (edited) The “rule “ quoted above epoxy for epoxy and polyester for polyester is not correct “.  Epoxy resins stick very well to properly keyed polyester resin surfaces. Epoxy is commonly used, and has been for decades in boat repair.  However polyester resin is less flexible than epoxy so it is not a good idea to use polyester on top of an epoxy resin surface.  The important thing when repairing is providing a proper key by degreasing and surface abrading down to the matting.   Many new moulded components still have release agent on them so preparation is very important with kits or new parts Edited October 17 by Tim Flyer Quote Link to comment Share on other sites More sharing options...
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