dr_gn Posted March 15, 2015 Author Share Posted March 15, 2015 (edited) ] On 15/03/2015 at 0:09 AM, Ascoteer said: G I can ask the Sqns if you would like Yes ple] Edited August 27, 2017 by dr_gn 9 Link to comment Share on other sites More sharing options...
Cheshiretaurus Posted March 15, 2015 Share Posted March 15, 2015 Done like a boss 1 Link to comment Share on other sites More sharing options...
perdu Posted March 15, 2015 Share Posted March 15, 2015 (edited) "Well Oliver that's another fine mess you've gott'n us OUT of!" Looks marvellous, was that your first pull? If so it proved the concept immaculately I had doubts about the extension frames, but they have worked rather nicely You see, here I am already learning how to do it Edited March 15, 2015 by perdu 1 Link to comment Share on other sites More sharing options...
Fritag Posted March 15, 2015 Share Posted March 15, 2015 Looks like proof of concept to me Doesn't look like the filler/primer transferred with heat - or that the master degraded (?) One of the frustrations is that any speck of dust etc. can ruin (depending on your standards - and we know yours are the highest G) a canopy. Have to say tho' that even your first effort looks to compare well with the Pavla offering for clarity. 1 Link to comment Share on other sites More sharing options...
dr_gn Posted March 15, 2015 Author Share Posted March 15, 2015 Thanks guys. Yes, that was the first one - shoulders of giants and all that... I just did another, but have still got little pimples all over it on the inside. Might try re-flatting the mould. I think static attracts dust to the sheet too. I wonder if I could leave the backing film on...? Link to comment Share on other sites More sharing options...
dr_gn Posted March 15, 2015 Author Share Posted March 15, 2015 Just tried one with the backing film on - works OK, but still getting the flaws - which look like bubbles in the canopy. The plug itself is fine. Strange. Link to comment Share on other sites More sharing options...
CedB Posted March 15, 2015 Share Posted March 15, 2015 Looks good to my newbie eyes... what a great WIP thread for education. Also looks as though the creature from 'Alien' is looking over your shoulder in the second picture, reflected in the sheet you're holding. Dangerous stuff. 2 Link to comment Share on other sites More sharing options...
Fritag Posted March 15, 2015 Share Posted March 15, 2015 I've had bubbles form in PETg sheets on heating. When it has happened they have appeared very quickly and it has always seemed to me to be as a result of over heating or perhaps too rapid heating as it occurred when I'd allowed the heating element of my dental vac machine to get red hot before presenting the PETg to it for heating. I've generally avoided it by not switching the heating element on until I'm actually trying to heat the PETg. Could the oven temperature be a bit high? I know that you chose a sensible temperature - but? It's also right to say that any pinprick like dimple in the master will get transferred. Frustrating aint it 1 Link to comment Share on other sites More sharing options...
Cheshiretaurus Posted March 15, 2015 Share Posted March 15, 2015 Just tried one with the backing film on - works OK, but still getting the flaws - which look like bubbles in the canopy. The plug itself is fine. Strange. This is the problem I am still trying cure, I think its called blooming and occurs only where the PETG has physically contacted a surface. Even does it when it contracts pure metal like the base place of the vac machine, but any area that has been heated but didn't touch anything is unaffected. 1 Link to comment Share on other sites More sharing options...
Cheshiretaurus Posted March 15, 2015 Share Posted March 15, 2015 Does it look like this? ignore the bigger bubbles that was muck. the smaller imperfections. If you are able to look at a Rob Taurus canopy they have managed to solve it somehow. click for bigger 1 Link to comment Share on other sites More sharing options...
dr_gn Posted March 15, 2015 Author Share Posted March 15, 2015 Not quite as bad as that, the bubbles don't seem to break the surface, but form small lumps, just one or two noticable ones. Link to comment Share on other sites More sharing options...
spike7451 Posted March 15, 2015 Share Posted March 15, 2015 Did the canopy arrive mate?....Should have gotten it by now as I gave it to the postie to put in the bag as he was emptying the postbox last Saturday lunchtime... 1 Link to comment Share on other sites More sharing options...
dr_gn Posted March 15, 2015 Author Share Posted March 15, 2015 Did the canopy arrive mate?....Should have gotten it by now as I gave it to the postie to put in the bag as he was emptying the postbox last Saturday lunchtime... Nope, nothing as yet. Still hopeful though because I'll use it if it's better than these vacform ones. Link to comment Share on other sites More sharing options...
Cheshiretaurus Posted March 15, 2015 Share Posted March 15, 2015 Nope, nothing as yet. Still hopeful though because I'll use it if it's better than these vacform ones. Its been used on the postmans tonka! 2 Link to comment Share on other sites More sharing options...
perdu Posted March 15, 2015 Share Posted March 15, 2015 I wonder if there's a need to raise the temperature more slowly? You showed us a warm up blower to use first, might it be an idea to use that to soften the PETg, maybe getting a slower heat transfer would reduce the bubblings Not being as good or careful as you I didn't notice bubbles on the Scout I wonder if attempting to use ordinary acetate sheet in your rig would be better I got a sheet of A1(? blo-dy big) sized acetate from my local artist's supply shop They sliced it down to A4 size for me and I found it worked better than PETg p.s. just searched my off cuts box for unused vac'd Scout cockpits, yes in the PETg ones some signs of internal bubbling The odd acetate ones seem clearer 1 Link to comment Share on other sites More sharing options...
eng Posted March 15, 2015 Share Posted March 15, 2015 Does the heat gun warm up the mould significantly? I wondered if the temp of the mould might be something to do with the slight bubbles in the transparency. Very very impressive results, can't believe how clear this is. Eng 1 Link to comment Share on other sites More sharing options...
perdu Posted March 15, 2015 Share Posted March 15, 2015 My friend and branch mag editor John D who posts here occasionally uses a heat gun for vac moulding demos at the club premises Plenty of heat from one of those 1 Link to comment Share on other sites More sharing options...
dr_gn Posted March 15, 2015 Author Share Posted March 15, 2015 I tried again this afternoon, without the heat gun, oven on direct heat, not fan, plus I lowered the temp a bit. I also dusted the sheet with a microfibre cloth before putting it in the oven. Pretty much eliminated the bubbles, at the expense of slightly worse conformance to the lower flared frames. I've got two ones that might pass. I can try again maybe tomorrow I guess, until I get bored. Next job is to find some very, very thin plastic strip for the frames. Tamiya tape didn't really work for the riveting tool, so I need something between plastic and tape. Maybe the Tamiya stuff posted previously might be OK. 1 Link to comment Share on other sites More sharing options...
perdu Posted March 15, 2015 Share Posted March 15, 2015 Can you cut thin strips of plasticard for that? I used it on my Jaguar canopy to reasonable effect Good news getting a better version All techniques need practise, and often fortunate conditions Link to comment Share on other sites More sharing options...
dr_gn Posted March 15, 2015 Author Share Posted March 15, 2015 It needs to be about twice as thick as tamiya tape at the most I'd think. Been painting the pilots tonight...never been very good at modelling figures, but I thought these would give some scale. Link to comment Share on other sites More sharing options...
Cheshiretaurus Posted March 15, 2015 Share Posted March 15, 2015 I tried again this afternoon, without the heat gun, oven on direct heat, not fan, plus I lowered the temp a bit. I also dusted the sheet with a microfibre cloth before putting it in the oven. Pretty much eliminated the bubbles, at the expense of slightly worse conformance to the lower flared frames. I've got two ones that might pass. I can try again maybe tomorrow I guess, until I get bored. Next job is to find some very, very thin plastic strip for the frames. Tamiya tape didn't really work for the riveting tool, so I need something between plastic and tape. Maybe the Tamiya stuff posted previously might be OK. I wonder if a tack cloth on the mould and sheet would do the same??? I'm trying making the frames on the Meteor canopy from a very thin vinyl paint mask on a digital cutter at the moment. If your able to come up with a pattern with the curve that you need I could cut it for you and you can see how that goes. Alternatively there are rolls of very thin self adheasive aluminium tape on ebay you could cut to the right shape that might work. 1 Link to comment Share on other sites More sharing options...
dr_gn Posted March 15, 2015 Author Share Posted March 15, 2015 (edited) I wonder if a tack cloth on the mould and sheet would do the same??? I'm trying making the frames on the Meteor canopy from a very thin vinyl paint mask on a digital cutter at the moment. If your able to come up with a pattern with the curve that you need I could cut it for you and you can see how that goes. Alternatively there are rolls of very thin self adheasive aluminium tape on ebay you could cut to the right shape that might work. I doubt I'll need to profile the hoops - they are near enough straight for all practical purposes, and at the thickness I'm looking at, they should bend out of plane easily (if required!). Not sure how to stick them yet, maybe pva, cyano wicked around the outer edges, then dip in Klear. Edited March 15, 2015 by dr_gn 1 Link to comment Share on other sites More sharing options...
perdu Posted March 15, 2015 Share Posted March 15, 2015 Do dip in Klear before getting cyano near them G I lesson I had to work hard to understand 1 Link to comment Share on other sites More sharing options...
Fritag Posted March 16, 2015 Share Posted March 16, 2015 I've got two ones that might pass. I can try again maybe tomorrow I guess, until I get bored. I now what you mean. It can be hard to know when to stop in the pursuit of the holy grail of a perfectly formed, perfectly clear canopy. I think it's probably a a race between boredom, awareness of the just how much expensive PETG is being wasted, and dawning realisation that there's always something wrong with the canopy you've just does - and maybe the second or third one wasn't so bad after all...... If you've got a couple that are just about good enough then I'd put one of them to one side for safety and choose the other (or one that's nearly as good) and see if you can improve it by smoothing and polishing with micro mesh followed by a dip in Klear. If you can - Bingo. If not then no harm done. 1 Link to comment Share on other sites More sharing options...
perdu Posted March 16, 2015 Share Posted March 16, 2015 (edited) I really advise trying acetate sheet instead The PETg setup you have achieved is ideal for a materials changeover I still haven't seen any bubbles in my acetate mouldings Edited March 16, 2015 by perdu 1 Link to comment Share on other sites More sharing options...
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