Shrink Film Covering Technique

[Andy J]

About to undertake the covering of a large airframe using HK film. Having made a hash of other models in the past so have read up on the correct techniques for heat applied coverings.

Interestingly I note that one US site recommended the use of what was called a Woodpecker tool to avoid air being trapped under the film on solid surfaces. Believe the item was sold by Top Flite and was called a Woodpecker Perforating Tool but understand this product is no longer available. Has anyone used one or could recommend an alternative product.

[Cuban8]

Never needed one of those woodpecker tools, to me they are quite unneccessary and I suspect the claims made for them anyway. Don't waste your money. When one uses the correct technique there won't be a problem.

To avoid bubbles on sheeted surfaces, I find that the vital thing is to work along the material,sealing it as you go, preventing trapped air from forming in the first place. A bit like applying a giant decal, I suppose. Allow the job to cool and then go over it several times to final shrink and bond flat. On no account use the 'open structure method' of tacking around the edges and then shrinking - guaranteed to give bubbles. Leave a couple of edges open and work towards them. Sounds counter intuitive and the opposite philosphy to the woodpecker,  but I always use a surface sealer on sheet e.g Balsaloc, to give a good bond - take your time with a covering iron (never used one of those 'orrible heat guns) and work across the job with a soft cloth to press the work down. Always a variation on a theme and I guess you'll work out your own technique. HK film is great BTW!

Good luck.

 

 

Edited By Cuban8 on 14/06/2020 10:29:40

[Dale Bradly]

Link

[Andy J]

Dale, that link does not work.

Cuban8 ..Will look again at the instructions for large sheet areas as don't have sufficient film for repeat attempts as the wingspan is 84 inches. Assuming its best to stick down a line, mid chord tip to centre span then work back to the TE and then forward to the LE.

[Bob Cotsford]

As Cuban said, tack down a couple of strategic points around the edge just to keep the film under control but seal it working from the centre out in a radial pattern. I, on the other hand, only ever use a sealer such as Balsaloc on hard surfaces such as ply. Never found the need for anything on balsa sheet!

Those woodpeckers are really designed for film on film trim where you would 'peck' the base covering where the coloured trim is to go. I have no idea whether they work but they sound like a good idea. I've always gone round after adding trim puncturing bubbles with a pin then ironing them down.

[Tosh McCaber]

Hmm- Link worked for me! - AliExpress Pricking Wheel! Maybe try again?

[Andy J]

Works for me now. Found a very similar product on flea bay by doing a search for "Perforator Tracing Tool Perforating Marking Leather Fabric Paper Card Plastic"

Edited By Andy Joyce on 14/06/2020 12:59:31

[Ron Gray]

Despite what others may say I use the woodpecker tool and find it very good especially when overlapping film coverings. But when used on sheet material or film you end up with no bubbles with very little effort. You can see me using it in the thread for my SIG Rascal refurb.

The only problem is getting hold of one!

[Craig Carr]

I’ve always worried about using sealer on the balsa before the film.... my understanding was that bare balsa does a better job of “absorbing” air. Other than that I do exactly the same as already suggested.

Give the model a good going over with a tack cloth to remove any unwanted debris before starting

[kc]

If any bubble arises then you can use a pin to prick through the film. But shouldn't be necessary.

If you spend 90 minutes watching the video of Derek Hardman - inventor of Solarfilm etc, etc,- giving all the hints on film covering, you will find it time well spent.   If you are in a real hurry just wind the video to about 18 minutes in and he shows covering sheeted surfaces.

Edited By kc on 14/06/2020 16:29:15

[Andy J]

Given the Seagull balsa (what left of it) is like soft butter used Eze Kote to harden the surface. Well impressed by that product and was tempted to continue to use it and cover the model in light weight cloth. However cost would be significant given I think I paid £17 for a bottle.

Will watch the video as the whilst the flat surface went ok the turtle deck covering has a few small wrinkles.

[Bob Cotsford]

It's always worth at least considering whether large panels couldn't more easily be covered in two or more pieces. As long as the film comes of the same roll joins will be pretty much invisible.

[Cuban8]

Posted by kc on 14/06/2020 16:20:21:

If any bubble arises then you can use a pin to prick through the film. But shouldn't be necessary.

If you spend 90 minutes watching the video of Derek Hardman - inventor of Solarfilm etc, etc,- giving all the hints on film covering, you will find it time well spent. If you are in a real hurry just wind the video to about 18 minutes in and he shows covering sheeted surfaces.

Edited By kc on 14/06/2020 16:29:15

In all the years I've been using film coverings, I've never actually watched the Solarfilm film until yesterday! The sheeting part is very good, but for me I wouldn't start in the centre, and DH mentions the formation of creases radiating out from the 'bowl' created. As I mentioned before, my preference is to work from two lightly sealed edges and manipulate the material whilst sealing across the workpiece. Again, no right or wrong but what works for the individual or a mixture of various techniques.

So sad that Solarfilm's pioneering expertise was allowed to wither away and choke itself to death because of outdated production and lack of investment - thereby handing their business to a big thinking German company that had the foresight to diversify. **LINK** Same old story....

Edited By Cuban8 on 15/06/2020 10:01:44

[Andy Stephenson]

Posted by Andy Joyce on 14/06/2020 17:36:58:

Given the Seagull balsa (what left of it) is like soft butter used Eze Kote to harden the surface. Well impressed by that product and was tempted to continue to use it and cover the model in light weight cloth. However cost would be significant given I think I paid £17 for a bottle...

Andy,

I have found that Dulux Diamond Glaze is very similar to EzeKote and a lot cheaper. You do have to buy 1litre minimum at about £40 but if you price EasyKote by the litre it works out at £226. Diamond Hard glaze is available in gloss and satin also in various tints. It can be thinned with water to make it go further.

A.

Edited By Andy Stephenson on 15/06/2020 11:10:15

[Trevor]

I had a recent project where an overlap was unavoidable. A very crude home made perforator worked surprisingly well. Details on this page (you’ll have to scroll down)

**LINK**

[Andy J]

Well covering was going really well until I got to the bit where the fuselage side flairs out as a double compound curve to blend into the wing as seen in this picture.

Flat surface is ok but the double compound curve is begging to wrinkle.

would it be best to trim this lower section off and use a separate section of film going around the fairing?

 

Edited By Andy Joyce on 17/06/2020 11:29:14

[Nigel R]

Concave bits are difficult.

Check Ron Gray's posts on the warbirds replicas LA thread, he used film to do a wing fillet.

[Andy J]

Posted by Nigel R on 17/06/2020 11:34:35:

Concave bits are difficult.

Check Ron Gray's posts on the warbirds replicas LA thread, he used film to do a wing fillet.

Nigel, what was that forum topic called? Alternatively a link would be great.

[Andy J]

Posted by Andy Joyce on 17/06/2020 11:46:08:

Posted by Nigel R on 17/06/2020 11:34:35:

Concave bits are difficult.

Check Ron Gray's posts on the warbirds replicas LA thread, he used film to do a wing fillet.

Nigel, what was that forum topic called? Alternatively a link would be great.

Found the thread and went through all of his posts on the LA but could not find that section.

Anyway wondering if putting some slits running vertically would fix the issue in one axis at least. Obviously the V shaped gap could then be filled with a small infill fillet under or over the main covering.

[Trevor]

Best to cover the fairing separately. The golden rule is that a planned joint in the covering is always far less conspicuous than wrinkles so resist the temptation to do too much in one piece!

Trevor

[Andy J]

Think you could well by right Trevor. Just put some balsalock on the fairing to assist stick down and will try a couple of slits in the tight compound curves areas fist before I rush cutting off the entire lower section and replacing.

[Douglas Groutage]

Although I am by no means an expert, last fillets I did - the fillets were laid first, started at the edge and worked my way up into the curve; I used a strip quite bigger than what the area was to handle shrinkage and giving an edge to grip and stretch. Then cut the edge on the fuselage where I wanted the seam.

Doug

[Andy J]

Well having completed the fuselage so now need to recover the tail surfaces. Given I cant dismantle the joined tail plane as it is stuck firmly in place it will be a hassle to remove the existing shrink film. Will it be possible to simply cover over the existing film or am I likely just going to end with a poor surface with lots of trapped air?

Edited By Andy Joyce on 21/06/2020 15:19:22

[Tosh McCaber]

Don't want to hack the present conversation, but, on a slightly different tack(!), I'm converting an older little pattern plane, Cox Tee Dee .049 powered, to electric. The old Solarfilm covering came off without too much difficulty, although it was pretty well adhered.

However on the underside of the fuselage, there's a slight tackiness, which may have been from fuel penetration. Has anyone any thoughts on whether there's any coating that could provide a seal, prior to when I recover with Solarfilm, (I've still got the original fluorescent green and orange Solarfilm in my store cupboard!)

Perhaps Balsaloc- is it still available?  Or A.N.Other?  I'm a bit confused!

Edited By Tosh McCaber on 21/06/2020 16:05:17

Edited By Tosh McCaber on 21/06/2020 16:27:21

[Tosh McCaber]

Looks like I've solved my problem- I've saturated the area with thin superglue, which has completely hardened the surface.