discussion Crash forming canopies

[Dave W]

As any of you who have been following my build of the Avro Anson will know,I managed to break the canopy.I glue it back together and polished it,but it still looks awful.So I decided to have a go at making a replacement.I remember Tony (Yak face) used the crash forming method when making a replacement canopy for his Comet racer.So I revisited his build to see how he did it.First i made a former from the existing cracked canopy.Used a two part mix that dries rock hard (the blue stuff in my photo's).Then I cut a hole in a piece of plywood slightly larger than the former.I then got a piece of acetate sheet and clamped it across the hole in the plywood.Next I heated the acetate with a heat gun and when I thought it was soft enough I pushed the former into it.My first attempt went straight through it as the material was too thin.I then 'found' some thicker acetate sheet at work and had several goes with that.Finally I thought I had got a useable canopy. But the former was stuck to it. So I realised I needed some sort of release agent.So I tried smearing some bearing grease on the former.This seemed to do the trick.I haven't yet got a canopy I'm satisfied with.But I'm close to achieving the result I'm after.I think I need a different material.Any advice would be appreciated.I must say its been fun experimenting.I now know I can make simple parts using this method.The Anson canopy might be a bit too ambitious. But I've got to try or the models wrecked.The photo's below are of some of my many attempts. I started of with the wood on its side in my vice. Then realised the acetate was sagging away from the former. So I put the wood flat on the edge of my bench.Much better.

 

[Guest]

Milliput works very well as a former. I made a BRM F1 former with it tonight, in fact. The ally powder-filled stuff you can get in the Pound shop is also very good as it dissipates the heat well. Epoxy putties will stand up to about 230-250 degs. C.

Very hard wood will also do it, but the heat will get to the grain eventually.

Try not heating it so much. Generally if the plastic sinks, then comes up again and then starts to sink again, it's ready.

You will get there eventually. Of course the best way would be to make the frame, then glue in separate pieces!!

No, I probably wouldn't do that either:twisted:

Martin

 

[yak face]

Hi dave , keep at it mate , it takes a few "experiments" before it comes out right! I also found some acrylic materials better than others , i ended up saving anything that had clear plastic , ie. washing up/ bubble bath bottles , fruit packaging ,anything really ,and trying them all till i got one that gave the result i was after.Like you I had quite a few tries where the stuff was just too thin and went straight through or came out way too flexible and unusable. I also found that making the former as smooth as possible helps with getting it out of the formed canopy , i primed mine to fill in all the tiny imperfections in the filler moulding. Im positive youll get a usable one dave , keep going! cheers tony

 

[Dave W]

Thanks Tony.On second thoughts I think the material will do the Job.Need to refine the former though.Will have to wait till Monday when I'm back at work as Ive run out of acetate sheet!.

 

[yak face]

Dont forget too dave, Christmas is coming , loads of throwaway packaging , probably with lots of clear plastic sections on it! cheers tony

 

[Dave W]

Spent a bit of time this evening trying to make a canopy.After many attempts I finally made something pretty close to what I want.I reckon I can make one even better though.Tomorrow I will make another former and have another go.The lack of any framework will make painting difficult.So I will buy a set of masks for it.Seen one on Hannants web site,but will have to wait until

after the Christmas break to get it through the post.

 

[Guest]

thats awesome looks really good better than original

mobear

 

[Dave W]

Thanks ole.Not quite as good.But good enough to save my build

 

[Guest]

Well Dave you got there in the end. At least you had fun and got to save the model at the same time, double bonus in my books. Good luck with the rest of the build.

Andy

 

[Ian M]

Looks pretty good to me. Should be fine by the time its painted up.

Ian M

 

[Guest]

That looks well smart Dave .... fair bit of patience you have too

I have to agree with Ole, the front half of the cockpit looks a lot clearer, smoother and "even" than the rear section on my monitor ... it may just be the light etc but it's a hell of a good job never-the-less.

 

[yak face]

Great result dave, good idea with the masks too, the canopy frames are a difficult bit on a crash moulded part, due to the thinness of the material its a tricky op! keep at it mate its going to look great , cheers tony

 

[Guest]

May I ask why you all call this "crash" moulding? I've always called it "push" moulding.

Martin

 

[yak face]

Dont really know martin, its just a commonly known phrase , ive also heard it called smash moulding , I suppose its all in the nature of the action - crashing ,smashing , pushing through the molten plastic!! I vote we rename it "poke moulding"!!LOL tony

 

[Dave W]

I called it crash moulding because that's what Tony called it in his Comet racer build!.Although I have heard it called that in modelling magazines.

 

[Guest]

Poke moulding? I could go with that as you do tend to poke around a bit before you find the hole in the plywood:1newwink:

Martin

 

[Dave W]

Just fitted my home made canopy to the Anson.So I'm very pleased to say the build is back on.I fixed some plastic card tabs to the rear canopy to give the new part a solid fixing.Then I filled the gap at the front of the new canopy with two part epoxy.This is to make it solid and stop any flexing which would crack the final layer of filler.Before I glued my home made canopy on I coated it with Klear to stop the superglue fogging it.Ive also ordered a canopy mask set from Hannants.But with the new year approaching its anyone's guess when that will turn up.In the mean time I've lots of other bits to be getting on with.So relieved to sort the canopy as I really want an Anson for my collection.

 

[Guest]

you took your time with it and it turned out real nice 10/10 mate

mobear