Canopy help needed

[kitbasher]

Help!  I've got an Aeroclub vacuform Harvard canopy that's begun to yellow quite badly.  Can this be reversed, and if so, how?

[Brian da Basher]

I'd try giving it a wash with dish soap and hot water first and then move on to either lighter fluid or paint thinner. Maybe polishing it with toothpaste would do the trick. I also hear good things about micro-mesh but I've never used them.

Brian da Basher

[noxioux]

And if repolishing fails, you could just run with it and go with the tinted canopy look. . .

[Ed S]

I don't know of any way to get rid of the yellowing in clear parts like that.  IIRC it's a reaction in the plastic as it ages, particularly with exposure to UV.  If you can't live with a "tinted" canopy, then you might be better off making a new one.  What I've done in the past is to wipe some vaseline on the inside of the old canopy.  Then fill it with epoxy.  I usually use the clear 5 min or 30 min, since that's what I have on the work bench.  Then once it's cured, you can pop it out and use it as a mold to make a vacuformed or stretch formed replacement.  Also, if I'm going to stretch form a new one, I stick a piece of heavy sprue or a small nail in the epoxy before it cures.  This provides a way of holding the mold. Stretch forming is pretty easy.  You can get clear sheets (Squadron, I know sells them), heat one over a stove until it starts to sag then force it downover the epoxy mold.  It may take a few tries, but you should get one you can work with.

Ed

[kitbasher]

Thanks chaps.  It is a yellowing rather than a scratching problem (sounds like some sexually transmitted disease!).  I've sretch/plunge formed a couple of canopies in the past using a Milliput master, but haven'y yet tried using epoxy.  The canopy is for a whif that I plan tackling next year, so making a replacement as Ed S suggests would seem a good way of going forward as the canopy will probably need a little modding anyway.