vacform canopies

[nev]

OK, will soon be needing to cut out and paint my vacform canopy on my Mirage 4000.  The only other time I've done a vac-form canopy was on my Aeroclub 2 seat Lightning.  I managed to bodge my way through it, but I though at the time "there has to be a better/easier way of doing this".

Any tips and advice welcomed.

[Ollie]

Try highlighting the edges of the frames and the whole canopy with a pen before cutting ans masking.  It makes things much more clearer.

B)  

[Leigh]

I use a pair of straight again STRAIGHT, not the curved ones, toenail clippers that way I can just keep trimming closer and closer to where I want the cut. Don't try and take off too much at once and be careful on curves but great for taking off small slivers.

[NARSES2]

Nev

I use a small pair of scissors to trim a bit at a time (Leigh's idea sounds good though) but I have also filled the canopy with blue-tack and then used a very new, very sharp scalpel. When fitted use clearfix to blend any errors .

Chris

[PR19_Kit]

No apologies for bumping this, it's exactly the right thread title for my question.

Of one doesn't have a grille, and I don't, what the best way to heat up the Thermoform stuff to plunge mould a canopy? Does a hair dryer work OK, or is there something else more obvious?

[kitnut617]

I've got some sheets for doing plunge form canopies. It says on the instructions to make a clamp-able frame so that it can grip the sheet on all sides at once, it then says to heat the sheet over a lit candle and as soon as the sheet begins to sag, pull it over your master.

I have to say I haven't tried it yet   

[PR19_Kit]

I think that's the same stuff as I have Robert, did yours come from Squadron? The instructions for mine are so ancient that I can't read half of them, but I'm less than happy about trying the candle thing.

I'll have Mrs_PR19 on hand with a fire extinguisher if I go that route I think............ 

[kitnut617]

I think that's the same stuff as I have Robert, did yours come from Squadron?

Yup! Squadron Clear Thermaform it's called, only the instructions actually show a person holding the clear sheet in his hands over a candle    

Think I must have read somewhere else about holding the sheet in a frame

[sandiego89]

I only got one decent canopy from the squadron sheet method, and about a dozen failures   

I am sure operator error was part of it...

[kerick]

You have to be careful with a point heat source like a candle. Don't hold the plastic too close to the candle or you get a small soft spot and the rest is too hard to stretch. I've never tried a hair dryer but the heat gun for removing paint has plenty of heat to soften the plastic. Plus if someone helps you they can keep the heat gun pointed at the plastic sheet as you pull it over the mold so it doesn't harden up right away. Definitely use the frame to hold the plastic sheet plus some leather gloves.

[JayBee]

I use a hot-air gun paint stripper, like a hair drier on steroids.
Set at the lowest temp you still have to be very careful.

As to the material used, I use Acetate sheet which you can get in any good aeromodelling, ie flying type models, shop.

Heat the whole surface evenly by wafting the airflow side to side. Heating one spot like with a candle will give an uneven softness to the material which will affect its performance when you are plunging the male mould in.

For trimming I use a pair of curved nail scissors, but these are only used for removing most of the waste material.
The final trimming is done with a very sharp scalpel, but mostly with a very fine grade sanding disk in my mini drill.

[PR19_Kit]

Excellent stuff guys, thanks very much.

I'll do some preliminary tests and report back.

[kitnut617]

I was going to suggest a heat gun, used one when I was pre-forming plastic for my Airbus A410 project.  Needs practice though ---