Andy J Posted December 19, 2021 Share Posted December 19, 2021 Need to make a new canopy for my Seagull Sparrowhawk as when I acquired the airframe the canopy had a large crack running around the base which could not be hidden. Not at all sure if I am tackling the manufacture of a canopy plug on which to form a new one is correct as I intend to use the old canopy as a mould. Have made a simple cockpit conning to the same profile as the model and my thoughts are to simply attach the old canopy and whilst holding it vertical such that the open rear end of the canopy is at the top fill the void between the conning and the canopy with plaster of paris. Once the assembly is set solid will remove the old canopy and make any corrections to form the plug. To avoid the plaster of paris sticking to the inside of the canopy will give it a liberal coating of Vaseline or possibly WD40. Assume this process will work or will I be proven wrong? Quote Link to comment Share on other sites More sharing options...
Murat Kece 1 Posted December 19, 2021 Share Posted December 19, 2021 That works perfectly.. I do my plugs with plaster of paris too. I don't even use any vaseline or WD40.. Quote Link to comment Share on other sites More sharing options...
Andy J Posted December 19, 2021 Author Share Posted December 19, 2021 Thanks MK. Is there any alternative to Plaster of Paris? Quote Link to comment Share on other sites More sharing options...
Paul De Tourtoulon Posted December 19, 2021 Share Posted December 19, 2021 Yes, polyurethane figurine moulding resin it won't stick and will harden it around an hour,,, I use it for moulding my pilots. 1 1 Quote Link to comment Share on other sites More sharing options...
Andy Stephenson Posted December 19, 2021 Share Posted December 19, 2021 I've used plaster of Paris very successfully but it does take some days to dry out. If you do use plaster, you don't need to use anything to stop it sticking to the original canopy. Anything you do use may cause a rough surface on the plug. Every little detail will be transferred to the new canopy when you vac-form it. I once got a hair on the plug and it was perfectly replicated. Quote Link to comment Share on other sites More sharing options...
leccyflyer Posted December 19, 2021 Share Posted December 19, 2021 3 hours ago, Andy Joyce said: Need to make a new canopy for my Seagull Sparrowhawk as when I acquired the airframe the canopy had a large crack running around the base which could not be hidden. Not at all sure if I am tackling the manufacture of a canopy plug on which to form a new one is correct as I intend to use the old canopy as a mould. Have made a simple cockpit conning to the same profile as the model and my thoughts are to simply attach the old canopy and whilst holding it vertical such that the open rear end of the canopy is at the top fill the void between the conning and the canopy with plaster of paris. Once the assembly is set solid will remove the old canopy and make any corrections to form the plug. To avoid the plaster of paris sticking to the inside of the canopy will give it a liberal coating of Vaseline or possibly WD40. Assume this process will work or will I be proven wrong? Yes, that should work a treat, if you have an existing canopy and can use it to make a male Plaster of Paris plug. Worked for my Cub and Beaufighter - pop bottle for the Cub and home made vacformer for the Beaufighter. 1 Quote Link to comment Share on other sites More sharing options...
Paul De Tourtoulon Posted December 20, 2021 Share Posted December 20, 2021 12 hours ago, leccyflyer said: Yes, that should work a treat, if you have an existing canopy and can use it to make a male Plaster of Paris plug. Worked for my Cub and Beaufighter - pop bottle for the Cub and home made vacformer for the Beaufighter. Me to,,,,,the original one was too short,,, Quote Link to comment Share on other sites More sharing options...
Andy J Posted December 22, 2021 Author Share Posted December 22, 2021 What is the recommended method of attaching the existing canopy to the balsa coming? Thinking unless there is a positive seal the plaster of paris is simply going to run out. Quote Link to comment Share on other sites More sharing options...
Andy J Posted December 24, 2021 Author Share Posted December 24, 2021 Plaster of Paris arrived today so thought I would do a quick pour just to seal the edges. Little came out so continued to pour more and more into the mould. Thought the plaster would take hours to dry but found it set almost immediately which took me by surprise. Tapped down the plaster as I poured it in so I hope the plaster got into all the corners. Will leave it till boxing day just to be sure its fully set. Quote Link to comment Share on other sites More sharing options...
Murat Kece 1 Posted December 24, 2021 Share Posted December 24, 2021 It does not take long Andy.. I use it after a couple of hours. Quote Link to comment Share on other sites More sharing options...
Paul De Tourtoulon Posted December 24, 2021 Share Posted December 24, 2021 I brush a coat on first then fill with what's left p then ush a lump of wood into it to use later as a handle, then hold it on my fretsaw table to vibrate the bubbles out. Quote Link to comment Share on other sites More sharing options...
Andy J Posted December 26, 2021 Author Share Posted December 26, 2021 Removed the old canopy today and found some minor damage to the plaster plug which I have attempted to fill using additional plaster. Very messy business working with Plaster of Paris which I assume will be the case when I start to sand the surface using wet and dry sandpaper. Plug still feels very damp to the touch so will leave it a couple more days before I do any final sanding. Interested to know if its worth adding say a skim of fiberglass wing finishing gel to harden the surface of the plaster as sure I will need to pull several canopies. Quote Link to comment Share on other sites More sharing options...
Tosh McCaber Posted December 28, 2021 Share Posted December 28, 2021 Hi Murat- which method do you use to form your canopy- heting a pop bottle- ot vac form? Quote Link to comment Share on other sites More sharing options...
Murat Kece 1 Posted December 28, 2021 Share Posted December 28, 2021 Heating a pop bottle. Quote Link to comment Share on other sites More sharing options...
Andy J Posted December 28, 2021 Author Share Posted December 28, 2021 Left the mould in the airing cupboard yesterday and now that the surface is dry you can easily see the defects, so will definitely have to do a bit of sanding. Next job will be to make a simple vac form box. Trip required to B&Q to see if they sell peg board or similar as it will be a hassle to have to drill a ply plate. Quote Link to comment Share on other sites More sharing options...
Andy J Posted December 30, 2021 Author Share Posted December 30, 2021 Do I need to harden the surface of the plaster of paris? Thinking I could give it a coat of finishing gel or Poly c. Quote Link to comment Share on other sites More sharing options...
Murat Kece 1 Posted December 30, 2021 Share Posted December 30, 2021 I have not needed hardening at all. Quote Link to comment Share on other sites More sharing options...
martin collins 1 Posted December 30, 2021 Share Posted December 30, 2021 What method do people use to scratch build a mould for a canopy, i have built a KI-61 tony mini fun fighter and just have the plan and the completed plane to work with, do you make a balsa plug then use filler over the top to make a smooth finish? Quote Link to comment Share on other sites More sharing options...
Andy J Posted December 30, 2021 Author Share Posted December 30, 2021 I used the old canopy as a mould outline but filled most of the void with balsa Martin. Then I back filled with 1kg of Plaster of Paris. Warning... its gets very messy working with Plaster of Paris but its very easy to sand and conversely its very easy to mark the plug. If you don't have an old canopy to use as a mould then dont think PoP will be any good as its far too runny to mould into a free shape. So suggest you make a balsa plug to the outline shape and then use a car body filler to get a good surface into which you can carve or sand to the correct size. Quote Link to comment Share on other sites More sharing options...
Denis Watkins Posted December 30, 2021 Share Posted December 30, 2021 (edited) 29 minutes ago, martin collins 1 said: What method do people use to scratch build a mould for a canopy, i have built a KI-61 tony mini fun fighter and just have the plan and the completed plane to work with, do you make a balsa plug then use filler over the top to make a smooth finish? If you start at the other end Martin, with your ability to vacform. In schools, we could vacform a 4" deep canopy on an 1 8" square bed without creases, using a solid wood former that was finished with beeswax so as not to stick. 1 mm sheet with care of 2mm sheet more easily. So how deep is the canopy? 3" - 4" deep, is best achieved with a wooden block, with canopy frames glued on made from stripwood. The block can be made up from thinner sheets, even plywood, and finished absolutely smooth, by any means, as every crevice finishes up on the final canopy. A small Tony canopy, is more easily made on a stick of wood, up to 2" deep, pushed into a trimmed pop bottle, heated carefully with a heat gun and pulled tight to the former. Edited December 30, 2021 by Denis Watkins Quote Link to comment Share on other sites More sharing options...
martin collins 1 Posted December 30, 2021 Share Posted December 30, 2021 Thanks Denis, yes i was going the pop bottle route as the canopy is not large, wingspan on the Tony is about 36". Quote Link to comment Share on other sites More sharing options...
Andy J Posted January 7, 2022 Author Share Posted January 7, 2022 Well having completed the plug thought it would be fairly cheap to make a simple vacuum former however the price of materials, particularly the metal to form a frame to hold the PETG makes the whole thing impractical given the number of times I will ever use it. Wondering therefore if the frame could be made out of wood and the PETG sheet attached say using staples. The heat would be provided by a heat gun before the whole arrangement is simply pushed over the mould which I pictured in previous posts on this thread. Another option is to make the plug itself into a vacuum plenum with holes drilled around the base onto which the plater shape sits. Quote Link to comment Share on other sites More sharing options...
Denis Watkins Posted January 7, 2022 Share Posted January 7, 2022 Screw down the wooden frame, Have some sort of gasket to seal it Quote Link to comment Share on other sites More sharing options...
Andy Stephenson Posted January 7, 2022 Share Posted January 7, 2022 (edited) 1 hour ago, Andy Joyce said: Well having completed the plug thought it would be fairly cheap to make a simple vacuum former however the price of materials, particularly the metal to form a frame to hold the PETG makes the whole thing impractical given the number of times I will ever use it. Wondering therefore if the frame could be made out of wood and the PETG sheet attached say using staples. The heat would be provided by a heat gun before the whole arrangement is simply pushed over the mould which I pictured in previous posts on this thread. Another option is to make the plug itself into a vacuum plenum with holes drilled around the base onto which the plater shape sits. Andy, If you contact [email protected] <[email protected]>, they can vac-form from a plug you send them. Edited January 7, 2022 by Andy Stephenson Quote Link to comment Share on other sites More sharing options...
leccyflyer Posted January 7, 2022 Share Posted January 7, 2022 2 hours ago, Andy Joyce said: Well having completed the plug thought it would be fairly cheap to make a simple vacuum former however the price of materials, particularly the metal to form a frame to hold the PETG makes the whole thing impractical given the number of times I will ever use it. Wondering therefore if the frame could be made out of wood and the PETG sheet attached say using staples. The heat would be provided by a heat gun before the whole arrangement is simply pushed over the mould which I pictured in previous posts on this thread. Another option is to make the plug itself into a vacuum plenum with holes drilled around the base onto which the plater shape sits. Yes. it's entirely possible to make the frame out of wood rather than metal. Mine is made from a wooden photo frame attached to a simple wooden box, with a perforated plywood base plate, created by drilling a uniform pattern of holes in the ply. The plastic sheet is retained by staples and some strategically place aluminium tape with heat resistant adhesive, often used in theatrical lighting, as a belt and braces solution. Quote Link to comment Share on other sites More sharing options...
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