Tony Harrison 2 Posted February 13, 2016 Share Posted February 13, 2016 Last night I managed to glue the mylar hinges, previously fixed to the fin of my glider, into the rudder - but the thin cyano set too quick for me to jam them all the way home. I wonder how big a gap (if any) is advisable anyway? Mine is slightly uneven, 3-4mm at the top so that the rudder hangs slightly out of square... To re-do it, is there anything to dissolve cyano bonds? Or will I have to cut it apart then either insert fresh mylar hinges offset, or use these nifty Robart 3/32 jobs I've come across - ? Thanks, Tony Quote Link to comment Share on other sites More sharing options...
ken anderson. Posted February 13, 2016 Share Posted February 13, 2016 hello tony..either cut them off flush and re do them or cover each side with some see through tape..sellotape or similar....up to you...i would re do them then seal with tape.... ken anderson...ne....1..... sealing dept. Quote Link to comment Share on other sites More sharing options...
Tony Harrison 2 Posted February 13, 2016 Author Share Posted February 13, 2016 Posted by ken anderson. on 13/02/2016 13:56:34: hello tony..either cut them off flush and re do them or cover each side with some see through tape..sellotape or similar....up to you...i would re do them then seal with tape.... Thanks Ken. Would you insert fresh mylar on top of (properly speaking, alongside) the buried stubs of the previous ones, or put them in a different position? Why the sellotape...? rgds Tony Quote Link to comment Share on other sites More sharing options...
ken anderson. Posted February 13, 2016 Share Posted February 13, 2016 ian...i would reposition the mylar hinges on both surface.....along side the cut off ones..... the tape is used on a lot of gliders to hold the elevators etc on...no hinges.....only the tape....works ok...i use it to seal the hinge line completely on most of my models...here is a pic of the tape in place....... ken anderson....ne.....1...... sealing dept. Edited By ken anderson. on 13/02/2016 14:32:33 Quote Link to comment Share on other sites More sharing options...
Geoff S Posted February 13, 2016 Share Posted February 13, 2016 I know it's too late for you this time but I always fully fit the hinges, then run the thin cyano in. Trying to do it the way you attempted this time is always to risk its grabbing before you want it to. I then always pin both sides with cocktail sticks, again glued in place with thin cyano after fitting. You can release the hinges with either a propriety cyano release fluid (mine in called Unstick from 5 Star but they're hard to deal with right now) or acetone. Nail varnish remover is acetone based but I'm not sure if it's full strength. Geoff Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted February 13, 2016 Share Posted February 13, 2016 Tony For maximum efficiency a conventional control surface wants no (or at least as small as possible) gap between it and the fixed part so air cannot leak through. This is particularly important for wings as there is a pressure differential across them all the time when in flight so an aileron gap reduces the wing's efficiency. The rudder is slightly different as most of the time the fin is 'neutral' to the airflow so a gap between it and the rudder is not too serious although it would reduce the effectiveness of the rudder when it was applied. Quote Link to comment Share on other sites More sharing options...
Tony Harrison 2 Posted February 13, 2016 Author Share Posted February 13, 2016 Thanks chaps. I just tried some acetone but couldn't make any impact on the hinges. Looks like either I leave the ugly gap, or hack it off and re-do the hinges, which would be tedious and might leave ugly scars. I see the point of that clear tape now: I have some 3M tape for repairing foamy models that might be suitable - or sellotape. rgds Tony Quote Link to comment Share on other sites More sharing options...
john stones 1 - Moderator Posted February 13, 2016 Share Posted February 13, 2016 You may be able to slide a scalpel blade into the side of the mylar and free them, pretty tough stuff mylar. John Quote Link to comment Share on other sites More sharing options...
Geoff S Posted February 13, 2016 Share Posted February 13, 2016 Tony, the acetone may take a while to effect the release and it will also help if you slide a scalpel blade down the side as John suggests. I succeeded in removing a big plastic moulding from a Multiplex Blizzard wing by application of acetone with a little mechanical assistance. It does work. Give it time and a few more applications. Leave it soaking in overnight. Geoff Quote Link to comment Share on other sites More sharing options...
Allan Bennett Posted February 13, 2016 Share Posted February 13, 2016 I've removed and replaced mylar hinges in the past by first, simply cutting through them to release the control surface, then sliding a knife down each side of each remaining half to release it, and then gripping with a pair of needle-nose pliers and pulling hard. Sometimes a bit of balsa comes out with the hinge, resulting in a larger-than-required slot, so I just fill the slot with a suitably sized thin piece of balsa glued in, and then re-cut the slot. An issue for me when installing hinges is ensuring that they don't get pushed too far into either part. So I stick a pin through the centre of the hinge before inserting it, so it can't go more than half way. When everything's pushed up tight, I then remove the pin, push a little further (to take up the gap created by the pin), move the control surface each direction to make sure it's not too tight, and then dribble in some thin cyano from either side using a long thin nozzle. Quote Link to comment Share on other sites More sharing options...
PatMc Posted February 13, 2016 Share Posted February 13, 2016 Allan, I like your idea using the pin as a limit stop but I suggest that you drill a 1.5 - 2mm hole in the centre of where you are going to put the slot for each hinge. You can then just put a few drops of thin cyno into the hole either side of the mylar. The cyano will spread by capillary action across the face of the mylar down the depth of the drilled hole/slot. Edited By PatMc on 13/02/2016 21:51:21 Quote Link to comment Share on other sites More sharing options...
john stones 1 - Moderator Posted February 13, 2016 Share Posted February 13, 2016 Or better still use those furry hinges, they suck it up good whilst they're fitted. John Quote Link to comment Share on other sites More sharing options...
PatMc Posted February 13, 2016 Share Posted February 13, 2016 I was shown the hole down the centre trick by a clubmate who used furry hinges. Hmm, this is starting to sound slightly pornographic !!! Quote Link to comment Share on other sites More sharing options...
john stones 1 - Moderator Posted February 13, 2016 Share Posted February 13, 2016 Yep last two posts have potential Quote Link to comment Share on other sites More sharing options...
Tony Harrison 2 Posted February 13, 2016 Author Share Posted February 13, 2016 Some great advice here... I've just come in from my cold, damp, cheerless garage (aka workshop) where I did all that running scalpel blades down alongside the hinges, drilling out my cocktail-stick pieces, soaking with more acetone. Will see what it's like in the morning. Thanks to all, I'm learning as I go! rgds Tony Quote Link to comment Share on other sites More sharing options...
Caveman Posted February 13, 2016 Share Posted February 13, 2016 Tony, watch this https://www.youtube.com/watch?v=QpwEvmhpAjY Cheers GDB Quote Link to comment Share on other sites More sharing options...
Allan Bennett Posted February 14, 2016 Share Posted February 14, 2016 The hole idea sounds good, to give more chance for the cyano to get all the way in. Though, having said that, I've never had a hinge pull out in all the years I've been using both the furry and non-furry mylar ones. Thinking about it a bit more, I'd want to be careful the hole doesn't go all the way through the trailing-edge spar or whatever block the hinges slot into, otherwise the cyano might run all the way through and make a mess on the inside of the covering material. Quote Link to comment Share on other sites More sharing options...
Peter Miller Posted February 14, 2016 Share Posted February 14, 2016 Posted by Allan Bennett on 14/02/2016 08:36:49: The hole idea sounds good, to give more chance for the cyano to get all the way in. Though, having said that, I've never had a hinge pull out in all the years I've been using both the furry and non-furry mylar ones. Thinking about it a bit more, I'd want to be careful the hole doesn't go all the way through the trailing-edge spar or whatever block the hinges slot into, otherwise the cyano might run all the way through and make a mess on the inside of the covering material. Never had any problem with CY inside the control surfaces. I don't think it shows up even if it does go right through Quote Link to comment Share on other sites More sharing options...
leccyflyer Posted February 14, 2016 Share Posted February 14, 2016 Posted by Allan Bennett on 13/02/2016 21:09:56: I've removed and replaced mylar hinges in the past by first, simply cutting through them to release the control surface, then sliding a knife down each side of each remaining half to release it, and then gripping with a pair of needle-nose pliers and pulling hard. Sometimes a bit of balsa comes out with the hinge, resulting in a larger-than-required slot, so I just fill the slot with a suitably sized thin piece of balsa glued in, and then re-cut the slot. An issue for me when installing hinges is ensuring that they don't get pushed too far into either part. So I stick a pin through the centre of the hinge before inserting it, so it can't go more than half way. When everything's pushed up tight, I then remove the pin, push a little further (to take up the gap created by the pin), move the control surface each direction to make sure it's not too tight, and then dribble in some thin cyano from either side using a long thin nozzle. Yes, those are great tips. In the case in the OP it would probably be very simple to just slice the mylar hinges with a sharp scalpel then grip what remains with some side cutters and work them out. Then redo them, as you've just described for a nice gapless hinge line. Quote Link to comment Share on other sites More sharing options...
Tony Harrison 2 Posted February 14, 2016 Author Share Posted February 14, 2016 Success! This morning I managed to extract the hinges from the rudder, and though somewhat battered by my surgery I should be able to re-insert them and glue properly this time. I don't know to what extent the acetone helped: I think it was largely using a scalpel repeatedly, pushed down each side of the mylar to cut through the glue bonds. I must say, since this is the first time I've ever done this hinge business, it has reassured me that mylar hinges fixed with thin cyano - and anchored additionally with cocktail-stick inserts - are very tough indeed, unlikely to come apart in flight I'd have thought. Still tempted to use those neat Robart hinges next time since they seem sort of more satisfactory in an engineering way, and possibly easier to fit too. Thanks for all the advice. Tony Quote Link to comment Share on other sites More sharing options...
leccyflyer Posted February 14, 2016 Share Posted February 14, 2016 Don't reuse the old hinges if you can help it - like you say they have been somewhat battered - best to bin them and fit new ones. Quote Link to comment Share on other sites More sharing options...
ken anderson. Posted February 14, 2016 Share Posted February 14, 2016 well done ian..forgot to mention that when i use mylar types...i use the pointed end of a knife blade to score them before putting into the slots...try some epoxy instead of cyno...give you time to line them up and insert them home...or delayed set cyano...i have some that is 30 sec before it go's off... ken anderson...ne....1 go's off dept....... Quote Link to comment Share on other sites More sharing options...
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