Film Over Film

[Trevor]

I know it is always best to minimise the area of overlap when building up a colour scheme from film (in this case a polyester ‘but not really Profilm’ product). However, particularly when the joint line is over an open wing structure, this isn’t always possible and a large area of overlap is a sure fire recipe for trapped air bubbles.

So my question is: Is there anything to be gained by perforating the area of film that is about to be overlapped?

Trevor

[Allan Bennett]

Perforating bubbles after they've formed, and then ironing around the pin-prick, is a way to get rid of them. If you pre-prick the covering you'll probably end up with holes not where the bubbles are!

Depending on your colour scheme, a sometimes easier way is to use self-adhesive trim, like SolarTrim. If you wet the base surface with water with detergent in it, you can then slide the trim around until you've got it positioned correctly, and then squeegee the water out so that the trim sticks to the base. After leaving it to dry out you can shrink it where necessary to match a curved surface, and there will be minimal bubbles because of the way you smoothed it down while it was wet.

[John Lee]

TopFlite do a dedicated accessory, the Woodpecker

Edited By John Lee on 19/12/2017 21:19:18

[extra slim]

I initially use a cooler setting on the iron, and take my time, you can usually easily lift it if you do get a bubble, then I gradually wind the temp up... works pretty well for me

[PatMc]

Cover the open area with heavyweight [It's not actually heavy] tissue. Water shrink the tissue the apply film with minimum necessary overlap - about 5 - 6mm should be enough.

The tissue actually stiffens the open structure more than the film does.

[Trevor]

Thanks everyone for the responses. In reverse order:

Pat - I haven't used tissue for more than 50 years! Even in the late 60s when I went into a model shop and asked for heavyweight Modelspan tissue to repair a control line plane, the lad behind the counter looked puzzled, disappeared out the back to be replaced by an old fellow beaming nostalgically from ear to ear, saying "What did you say!?". So I'm surprised to hear that it is available again.

Slim - That is the technique I've used before, with variable degrees of success. Generally it seems to work well on solid surfaces where you can initially almost rub the film down to clear the air, with very little help from the iron. I'm not so confident about it over an open structure though.

John - Thanks for the link to the Woodpecker. I don't intend to buy one but the very fact that it mentions using it on film at least reassures me that perforating the film isn't a totally stupid idea.

Allan, I agree, using vinyl or trim and floating it on is a much easier approach. On this occasion though the second colour has to go around the leading edge and wingtip so I need the heat shrink properties of film.

I think I'll do some stabbing with a pin or scalpel blade and see how it goes. Watch this space!

Trevor

[John Lee]

Posted by Trevor on 20/12/2017 08:45:53:

Allan, I agree, using vinyl or trim and floating it on is a much easier approach. On this occasion though the second colour has to go around the leading edge and wingtip so I need the heat shrink properties of film.

Trevor, Solartrim is self adhesive and is also heat shrinkable over compound curves just like Solarfilm. Check the instructions at the Solarfilm Website.

[Glyn44]

I have a woodpecker and it is very efficient when used on sheeting before covering. Also nice tool to transfer plan onto wood. Roll a single wheel, they are removable, along the outside of the part outline, and finally run along the holes with a pencil/pen.

[Trevor]

Posted by John Lee on 20/12/2017 09:38:51:

Trevor, Solartrim is self adhesive and is also heat shrinkable over compound curves just like Solarfilm. Check the instructions at the Solarfilm Website.

We live and learn - I never knew that! Probably because i've tended to use vinyl for trim in recent years and it's quite a while since I used genuine Solartrim.

Thanks Glyn for the experience of the Woodpecker. Why is it that things like this always come to light just too late after one has been pestered by well meaning family with "What do you want for Christmas, you are so difficult to buy for!"?

[Simon P]

Perforating the underlying film is the technique advocated in the book 'Tom's Techniques' published alongside other Harry Higley books. I'd say it is a good idea and will go a long way to reducing the chance of trapped bubbles. Careful work ought to take you the rest of the way. Solarfilm and Monokote both tend to be bubble prone in my experience while Oracover is significantly easier in that regard and can be applied over the other two brands if wanted.

[Trevor]

Just to round this off, there are now a couple of pictures of my perforation experiment now online at:

**LINK**

Thanks again for the help and advice,

Trevor