Making new canopies without a vac-machine

[Cees Broere]

Hi there,

 

Can anyone give some tips how to hotform a new canopy without using a vac-machine?

I read a lot things about heat and smash forming. What's the best thing to start with?

 

I have several kits on the bench at the moment which need new canopies as they are

either inaccurate or not very clear.

 

Thanks for your help

 

Cees

[LDSmodeller]

Hi Cees,

 

I can only go from my own experience with plunge forming new canopies from acetate (I buy it from a news agent /binding store that sell plastic front covers for binding etc).

 

The canopies I have done,are mostly 1/72. Filled the canopy with milliput/epoxy and a piece of dowel/thick sprue (after shaping canopy/part to right shape)

 

For the 1/72 full canopy I cut an oblong shape only marginally larger than the canopy in a piece of wood (about 1.5cm thick) cut a piece of acetate @ 60x60mm, tack it over the hole, place it under the broiler/grill in the oven for @ 20/25 sec (time will depend on type of oven) when the acetate is floppy (but not discolored) slowy plunge the canopy/spue handle into acetate until the canopy touches bottom of hole.

 

You may need to do it a couple of times, trim it up and voila a new canopy (I frame mine with strips of aluminum foil) As I said this works well for smaller canopies. I have done it for 1/32 scale TA 4J windshield and it worked well. (can't say how well for a full bubble top canopy). I attach it with either white glue/crystal clear

 

Some years ago I read an article in a magazine (SAM I think) where a guy made a a BAe Hawk canopy (1/32) by simply fixing the canopy as described above, placed the whole thing in a mount (vice?) placed two pieces of wood on the egdes of a large piece of acetate heated it then simply pulled the hot acetate over the canopy. Worked a treat had a nice clear and in scale Hawk canopy.

 

I have read of making canopies using clear nail polish (painted over old canopy) but have never tried it. (any one???)

 

There are gents on this forum who far more experinced in these things than me but, this has worked for me.

 

Regards

 

AlanW

[Cees Broere]

Hi Alan,

 

Thanks for the tip. Looks to be simpler than I thought.

 

I will try it on the Halifax canopy.

 

Cheers

 

Cees

[Radub]

I finally managed to put some stuff on the "Hints and Tips" page of my website and as it happens it is related to this subject. http://homepage.eircom.net/~radub/

Please check the "Crash Moulding" page.

I will add more tips soon.

HTH

Radu

[stusbke]

I finally managed to put some stuff on the "Hints and Tips" page of my website and as it happens it is related to this subject. http://homepage.eircom.net/~radub/

Please check the "Crash Moulding" page.

I will add more tips soon.

HTH

Radu

Thanx for the tip However IF I don't use a kit part but make a new one from balsa do I need to take the thickness of the plastic sheet in to consideration or not? And also what is better thin plastic or thick?

 

I'm curious as I need to replace my clear parts on some of my future builds and I aslo need to form some plastic

 

Greetz STB

Frederick Jacobs

[Radub]

Hi Frederick,

With some practice, this method can be used to make very nice canopies.

If you use the kit clear part, make sure that you fill it with miliput or plaster, otherwise it will buckle from the heat and deform. You will probably draw a few canopies before you get a satisfactory one, so if the mould buckles in your first attempt, you have a problem.

When crash moulding a new canopy, the resulting canopy will be slighlty larger but if the canopy is posed open, no one will be able to notice. The canopy will be "larger" by a slim factor determined by the thickness of the plastic used - if you use 0.3mm or 0.4 mm plastic, which will actually stretch and thin even more when crash moulded, no one will possibly be able to spot such a difference.

 

I would recommend 0.3 or 0.4 mm plastic.

I never tried balsa to make a mould, so I cannot comment, but it is a good idea to take into consideration the thickness of the plastic.

 

HTH

Radu

 

 

 

Thanx for the tip However IF I don't use a kit part but make a new one from balsa do I need to take the thickness of the plastic sheet in to consideration or not? And also what is better thin plastic or thick?

 

I'm curious as I need to replace my clear parts on some of my future builds and I aslo need to form some plastic

 

Greetz STB

Frederick Jacobs

[stusbke]

Ok guys I 've got some problems with the smash forming

 

I can't seem to get a good all detail copy of the clear part

 

Could it be that the shape of the clear part has something to do with it

 

here are a few pictures to show you guys what I mean

 

 

As you said radub I filled up the canopy with putty and I tried several times and eventualy one good one came out however

 

 

I can't seem to get the bottm sloped edges to form properly does this mean I need to make the framing seperately or am I doing something wrong here. Love to know as I plan on replacing the clear parts on my F-4F to gain some space next to the instrument panels

 

Greetz STB

Frederick Jacobs

[Radub]

Hi Frederick,

When crash moulding, it is not possible to draw (or push) the pastic into resesses. That is the biggest limitation of crash moulding. Crash moulding is useable only for simple shapes.

You need to vacuum form that canopy - vacuum will draw the plastic into resesses.

HTH

Radu

[stusbke]

Hi Frederick,

When crash moulding, it is not possible to draw (or push) the pastic into resesses. That is the biggest limitation of crash moulding. Crash moulding is useable only for simple shapes.

You need to vacuum form that canopy - vacuum will draw the plastic into resesses.

HTH

Radu

Ok yes it does then I have to make me one of those vacuum forming thingies

 

anyway thanx for the reply

 

Greetz STB

Frederick Jacobs