New canopy?

[Tony Kenny]

In this old plane I'm renovating, the canopy was smashed so I need to create a new one. My "plan", not being experienced in the workshop, is to build up a block of balsa, sand it to shape and then try to find some sort of clear plastic that I can warm with a hot air gun and try to get it to conform.

Does that sound like a reasonable plan? Is there a particular material that might be able to do this?

Thanks in advance! again!

[john stones 1 - Moderator]

Yep, loads of us have made plugs n shrunk a pop bottle to it.

Which one depends on your favourite drink i made it a little oversize so you can cut back to a clean edge.

[Keith Sharples]

Hi Tony.

The idea is fine, I use plastic water bottles but be warned that when you heat the plastic up it shrinks. I make a plug the right shape and size that I want out of MDF (not tried balsa) shape and sand it smooth making sure it is tapered from the top of the canopy to the bottom (most are anyway). This allows you to extraxt the plug after you have shrunk the plastic on to it. I put the plub inside a sutable sized clear plastic bottle and apply the heat gun keeping it moving all the time and SLOWLY shrink it tight around the plug. When done cut off just enough so you can extract the plug and then tripp the canopy to fit. Some forumites make a small vac forming box and heat sheet plastic up, quickly put it into the vac box with the plug underneath it and use a household vac to suck the air out from underneath thus sucking the heated plastic over the plug. There are lots of videos of both methods on Utube. Best of luck, Keith.

[Tony Kenny]

fantastic, thank you, i'll get this bottle of D&B finished off then and need to get a plug shaped up. I'll see what I've got lying about and hope to get this ready for the Great Orme! I supposed it won't be the end of the world if I don't have a nice canopy, so long at the plane stays together.

[Chris Barlow]

The smoother you make the plug the clearer your canopy will be.

I spray mine with primer and gloss paint, sanding between coats to get as good a "finish" I can. It pays off in the finished canopy.

[Tony Kenny]

In wish case, I'll shape it on my baby's bum! Failing that, I'll use a fine grain emery for the finish.

Come to think of it, I'll use this same method to make a new front end too which will save some fibre glass work, I'm assuming I can sand the plastic rough and it will take paint, or leave it smooth and use solar film?

[kevin b]

If you make your cowl that way, you could always paint it on the inside. No worries about damaging the paintwork.

[TIM Shaw]

Posted by Tony Kenny on 23/09/2017 22:07:54:

In wish case, I'll shape it on my baby's bum! Failing that, I'll use a fine grain emery for the finish.

Come to think of it, I'll use this same method to make a new front end too which will save some fibre glass work, I'm assuming I can sand the plastic rough and it will take paint, or leave it smooth and use solar film?

I'd be wary of film - you might find the heat you need to shrink the film on would distort your moulding. Strapping / combat tape would be OK though. Might be a bit brittle for the impact zone though?

[Mowerman]

Painting clear plastic (pop bottle) mouldings, if done on the inside gives a good high gloss finish. Great for cowls.

[Stevo]

<WATCHING>

[Tony Kenny]

I'll try it out soon and post back on results.

This thread and my previous questions about design books have got me thinking now that I'll try and make a whole RC model from pop bottles! Worth a go even if just to try some techniques and see if I understand the books

[Peter Miller]

If you use balsa as your plug face it with thin ply to stop the corners crushing. I use cheap co-op lemonade bottles as they have fewer ribs which will always show up on the final moulding.

[Tony Kenny]

I had a go at this to see how the material works and what I'll need to be doing. Learned a lot along the way and it looks like I'll need to create a decent plug for the nose, or just shape one side then turn it round and to the other.

It gets a bit wrinkly at the narrow parts so I'll allow for that with extra length to cut off later. Not bad for a first go, this might work quite well as a temporary thing to protect the motor before I make the real thing! Naturally, I'll need to cut some slots for cooling the motor The canopy will come later

[Mark Kettle 1]

Hi Tony, many years ago one of your club members Deepak Chopra filmed a video of Pete Willbourn, who was at the time also a BMAC member. He stood up at a club night and did a show and tell on the art of plastic bottle moulding, I'll post it.

Pete Willbourn features in the video - whom is also a forum member.

 

Edited By Mark Kettle 1 on 25/09/2017 00:40:37

[trebor]

Thanks for showing the video, I might give it a go as I've got a wing tip light cover to make. I've always struggled to make a good job of glueing them. They always look rough round the edges and I end up sticking tape over to cover the bad bits up. Any tips on other glues besides canopy glue which I find too runny to use ?

[Kevin Wilson]

Pop bottle method works really well.

I used mdf for the plug and a few coats of varnish. 

I used to do rc cars and the trick for painting the inside is to use a green nylon scouring pad to lightly scuff the inside of the clear plastic to give the paint a key.

I found a worn one worked well and the fine scratches disapear in the paint. It's the smooth outer surface that gives the gloss shine.