Finishing a foam core/veneer wing

[Peter Jenkins]

Hi, I'm building an old Gangster 75 kit that I was lucky enough to buy. I've now reached the wing finishing point and want to get a good surface on the veneer before film covering.

I was thinking of using sanding sealer and talcum powder but wondered if the sanding sealer would penetrate the veneer and dissolve the foam core.

I'm sure there are lots of you with ideas on how to proceed so await your answers.

Many thanks.

[Former Member]

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[Peter Jenkins]

Thanks for those suggestions Percy, I might just get my 800 and 600 grit paper out and rub down the veneer gently and then go over the wings with a tack cloth before applying the fllm.

[TigerOC]

You could give it a couple of coats of water based polyurethane (Ronseal diamond hard) which will both give a hard surface and reduce hanger rash and with 400 - 600 grade wet sanding provide a beautiful surface. I finish my foam core/balsa sheeted wings with 18g fibre glass cloth and WBPU and they are very strong and have a superb surface. It doesn't add much weight either. 60" wing glider wing this added 20g.

Rob

[chris Ibbotson]

Hi Peter,

Try using "Eezy-Coat" water based Pu sealer. Apply one coat to the wing using a good quality synthetic brush( 1to 2 inch wide) and let fully dry over-night and then sand with 800 grit wet/dry and apply a second coat . Allow to fully dry over-night and then sand with 1000 grit wet/dry and using tack rags to remove any dust. Superb finish and superb product.

As for the comment about film overlaps not staying stuck use a product called "prymol" follow the instructions on the tin and this will enhance the overlap/glue joint strength.

Used these both for the last 6 years and never failed.

[Former Member]

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[Nick Cripps]

Hi Percy,

Have a look at the Solarfilm website, there is lots of useful information on using their products. The instructions for covering with Solarfilm include the use of Prymol exactly as Chris describes.

Edited By Nick Cripps on 06/08/2016 08:01:08

[Former Member]

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[Bob Cotsford]

In years gone by we used to prepare veneered foam wings by covering with tissue and dope. I don't remember taking any precautions other than making sure there were no gaps for the dope to seep down to the veneer. I can't remember a wing done this way ever failing through the dope wicking through the veneer, but iron on films made it easier quicker and cleaner to get a nice finish on veneer, not to mention lighter for those without a spray gun and skill!

For covering a veneered wing with film, I'd think that using a sealer will make it difficult to eliminate bubbles as the sealed surface will trap small air pockets which can't migrate through the veneer's grain..

Edited By Bob Cotsford on 06/08/2016 09:42:32

[Former Member]

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[Peter Jenkins]

Wow! Thanks for the input guys - much appreciated. As ever, there appear to be pros and cons with sealing the surface although glassing with 18 g cloth does sound appealing but likely to result in a less than perfect outcome for a first timer!

The next problem will be deciding the colour scheme! The undersurface is decided - quarters of black and white on each wing and tailplane so I don't get confused which way is up! The top and sides are what are currently challenging me. Any hi vis colour schemes you can recommend? Oh, they must be in keeping with the 1980s though!

[Former Member]

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[Peter Jenkins]

Thank you Percy. Strong Wot4 influence there I see!

[Bob Cotsford]

[Engine Doctor]

For sealing down the edges on iron on film then Clear coat or prymol are great if using solar film but the prymol doesn't work on polyester based covering like pro film etc. These edges can come unstuck after some time and can be difficult to seal down . I have tried various methods to seal down overlaps on polyester covering but best results have been from using canopy glue. Clean any fuel off with meths and allow to dry. Then paint a thin coat on both edges and allow to dry until clear then iron down . Seems to stick down really well and is fuel proof . 

[Peter Jenkins]

Nice scheme Bob - one that should help when checking for wings level as the model flies towards you.

Thanks for that input ED. Will have to decide on whether to use Solarfilm or Profilm. Anyone had any experience of using the Hobby King coverings?

[Richard Wood]

Hi Peter,
I haven't tried it yet but the Hobby King covering seems to be well regarded.
Solarfilm works well on veneered foam wings but can show the grain if ironed down
firmly, even on a very smooth sanded surface.
Profilm & Solarfilm Supershrink can be better for this application.

Edited By Richard Wood on 08/08/2016 11:30:24

[Richard Wood]

This is standard Solarfilm on a veneered wing. You can get a reasonable finish with it by
going easy with the iron & not sealing too firmly. Make sure edges are well ironed though!

[Bob Cotsford]

I'm using HK film on pretty much everything these days. I find it very similar to Profilm/Oracover and WMToughlon in use.

[Peter Jenkins]

Thanks guys. Your help is much appreciated. I hope to post a picture of the finished article but don't hold your breath as it might take me some time!

[Philflyer]

 

Pete, if this is any help I have almost finished my Maestro (early 90s semi-kit bought from ebay). The veneer was separating from the foam in lots of places because the original contact adhesive had dried out. I slit the veneer over the areas that had lifted, squirted pva underneath and taped the veneer with masking tape until it dried. I did not want to use film covering and had never tried glass cloth but decided to give it a go with the water based Poly-C. So glad I did. It is very easy to use with very thin glasscloth even for a beginner if you follow the instructions on the RC World website. Much easier than applying film but obviously takes longer. I keep my models flying for years and have always had trouble with film peeling eventually. The finish is great after 3 very thin coats, it dries in 20 minutes, and is ready for the rattle can treatment.

Edited By Philflyer on 09/08/2016 09:34:50

[Peter Jenkins]

Sorry for not responding earlier Phil - life got in the way! Yes, I'm tempted to have a go but.....then I'll have to paint it with rattle cans and I'm not brilliant at that!

[Peter Jenkins]

More questions on flim.

Can you mix Profilm and Solarfilm or do they object to sticking to each other? I've got a mixture of these two films and the ideal colours and split between them!

Does Profilm give a better finish on veneer and balsa - assuming both are finished with 1200 grade paper?

Thanks in anticipation!

[fly boy3]

Hi Peter I had the same problem on a 20 year old veneered wing. The veneer had split in many places, and raised itself off the foam. After putting PVC under the raised strips I then taped them down. Still a bad finish even after trying Profilm sample. Removed the test piece and carefully sanded the veneers. Also due to the cost of Profilm, I decided to cover in brown paper. I was amazed at the result. See if I can find a picture.This was the first ever attempt at BPand emulsion.  Cheers

Edited By fly boy3 on 22/08/2016 19:10:58

[john stones 1 - Moderator]

Yes you can mix films, profilm would look better over blemishes it's a little thicker, H.K films worth a try if you've not used it Peter, excellent stuff, don't let the price mislead you.

John