Profilm / covering film techniques

[mjcp]

I am about to re-cover a pair of 2m wings - they are built up and previously had a profilm type covering on them (which removed easily, no residue etc)

In the past I have struggled with technique - I can tack down the film, spread it out ripple free and then "seal down" the edges no problem... however, the large expanses between the edges I find troublesome:

Is the idea to:
1. "shrink" the middle of the film, but leave it unattached, using the tension of the shrink, plus the adhesion on the edges giving a nice flat ripple free covering

Or,

2. Iron-on/adhere the large areas too, working middle out and then "reattach" once at the edges...?

(hope that makes sense)

Marc

[Barry_Cole]

I just seal mine down all round the edges and then attack with a heat gun. Rub it down onto any woodwork as you shrink it down.

Works for me..



BC

[Peter Balcombe]

Marc,
As Barry indicates, you need to tack down all edges, then seal all around (using a coolish iron).
If you use the diagonals method (see Solarfilm instruction sheet or similar) you should be able to get the material fairly evenly stretched all over.

Then as Barry says, it is easier to shrink back using a heat gun, steadily shrinking back the whole thing by working the gun over the whole structure without applying pressure. Then when it is all shrunk enough to contact the wood underneath, you can press down with a soft cloth onto the structure whilst the adhesive cools enough to grab & then also finally shrink the unsupported areas.
If you do find that you are getting excess material crinkles etc, these areas need heating without pressure to allow the film to shrink/form a large flat bubble, before pressing in contact.
I find that Profilm needs rather more heat than say Solarfilm, but the bubbles/wrinkles will go. Just keep a heat gun moving to avoid scorching & smooth down when ready with a soft cloth/covering sock.

Note that ifyou have undercambered areas then you need to make sure you still have enough slack left to allow the underside to contact the rib caps to retain the intended wing section before pressing down.

Just be careful not to overtauten any covering, particularly on lightweight open structures as you can overdo one side or the other, leading to a warped structure.
Peter

[mjcp]

Thanks both!

I now have a project for the weekend

Marc

[Jez_B]

On sheet surfaces, I have found a light application of spray adhesive surface works well to position it and prevent sagging. Yes you can brush on PVA or Balsalock (then allowing to dry) to achieve the same effect, but I have found the former to be far more secure. Also, the spray is not water based so won't raise the grain. That said, removing it for repairs may be tricky.

[mjcp]

Fab idea! I have had issues (well, more annoyances) where I use PVC tape on the fuse <-> wing joint and the tape lifts the film when removed... suspect this would sort that out too!

cheers,
Marc

[mjcp]

Well tonight was the night… and it went well I think:

and

This is the underside of the Stb wing - 1 side down, 3 to go, using the tack down the edge (~135d C on my iron, with "sock") then heat gun on "low" setting to shrink and press down with tea towel (don't tell the wife!)

Happy days!

Thanks all,
Marc