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Building Tips and technical articles. => Paint and finishing => Topic started by: Joseph Patterson on March 08, 2012, 09:16:56 PM
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Other than SLC covering, what covering has the lowest temperature adhesive quality for applying directly to foam wings? I have tried Top Flite Econocote and Towercote and I'm having to get the iron up to about 220 deg F to get adhesion with the result being the foam starts breaking down. I'm using 1.0-1.5lb. white foam-the stuff members of this forum recommended. I believe this foam breaks down well below 200deg. I want to build simple stunters to tear up, so don't want to get into LE/TE/FAUX RIB caps balsa sheeting of the wing. I welome any advice and recommendations.
Doug
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Joe,
I'm guessing your wing has spars? Something has to bee there for strength. Correct?
Although I've never seen it done, you could cover the wing with the vinyl that's used for lettering and graphics.
Stuff already has a built in adheasive, is fuel proof and cleans up easily. Looks like paint!
Available in a crap load of colors and this material can also be used for trim colors.
Everything I've made in vinyl, generally is placed on painted models or models with ARF coverings.
I can send you a sample of the material OR you can walk into any sign shop and ask for scraps. They will have a bunch.
Let me know!
Charles
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I think Solar film ( not sure if you can get it still) or Black Baron are both pretty low temp. I cannot remember the temp for adhesion on Ultracote, but thats what I used over Jessicas RM+P foam wing As I recall
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I've used econocote with good results on the Gotcha combat planes. If you have SLC I'd use that, lightweight and paintable I believe. I bought some sign vinyl years ago, too heavy. Not bad to use for field repairs, but 2" shipping tape works for that also.
Steve
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Hi Joseph,
What's wrong with SLC? Other than it is clear? No problem straight over foam. and you can paint it, Phil includes instructions on painting.
BIG Bear
RNMM/AMM
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I used Solarfilm for many years for foam combat planes. It is (or was) made in England and sold here under many aliases. One caution is that some colors are much heavier than others. White is heavy. Fluorescent colors are very heavy. Red is light. I used red. There may be better stuff available now.
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I can give a big thumbs up for Solarfilm as well, It's probably more popular over here (UK) than other films and goes well over foam. Also I can recommend Litespan (Also made by Solarfilm). Requires Balsaloc or similar as adhesive but sticks down with a very low temp iron. Also it's an excellent base for most paints needing very little if the underlying Litespan colour is the same or similar.
TTFN
John.
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Thanks fellows for your input. I would prefer a film covering with color and will try to locate some solar film or its equivalent. I am going to use SLC as my second choice, in fact, have ordered 100' from Phil C. along with some kits. Should get the stuff in as soon as he gets his machinery going. I have some rolls of Ultracote which it's packaging says is multi-thermal. I'll have to give it a try on some foam scraps. It may be my technique that is the biggest problem. I think I should have used my heat gun more and the iron just to tack. I've monocoted many planes with built-up structures over the years, but have never messed with foam structures. By the way Charles, to answer you question about spars- This particular wing has double main full span spars top/bottom/ no joiners, but with ply doublers in the middle. It has a single rear spar about 1/3 span. Added the rear spar because the wing has wide root chord/ long thin taper after the airfoil high point.
Doug
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I've used Ultra Cote over foam successfully. It sticks better than Econocote and is more fuel proof. Monokote obviously won't work. It doesn't even start to shrink until well after the foam has melted. Any film that you can get to shrink before the foam melts can be made to work. How well it works depends mostly on the type of plastic and how much it was stretched during manufacture, and the adhesive.
SLC is 75 guage(.00075 in.)
This site has a nice listing of coverings weights from .5 um to .003 in.
http://www.homefly.com/reference/Covering%20Weights.htm
The trick to covering directly over foam is to NOT use a heat gum. Generally, by the time the covering starts to shrink it's already transferred enough heat to start melting the foam. You should use an iron, with the temperature set just hot enough that if you hold it in one place for about 30 sec. the foam just starts to melt.
Start covering at the highpoint at the center of the wing. Use the iron to push the covering smoothly out and away from the start. The covering will show a kind of circular ridge ahead of the iron. Pull on the covering and push with the iron, keeping the iron moving continuously. Don't iron round and round in the same spot, it will just melt the foam. When you get to the edges and tips heat the film past the edge of the surface and stretch it around the edge. Iron the edges down smoothly, wiping the iron from the film out across the edge so the edge seal down tightly. That leave no place for spilled fuel or oil to wick under the edge. On the SLC covering if the edge ironed down properly you won't be able to feel the edge.
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Thanks Phil for stepping in here with such good advice. That's what I needed to know. Having never applied film covering to foam, I now know I was doing it wrong. You are right about the econocote- about the time it decides to stick the foam decides to melt.
Doug
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I cover my foam wings with silkspan and thinned carpenter's glue prior to the iron on film. It doesn't add much weight, it stiffens the wings considerably, improves the surface appearance, and improves the covering's adhesion. If you've never done it, here's the quick overview. This assumes you are starting with a plane that would otherwise be ready to apply the iron on covering.
1)Thin some Titebond glue or similar with water, approx 1 part glue to 1 1/2 parts water. The exact ratio doesn't seem critical. Put it in a wide mouth jar, or a cereal bowl to make it easier to use.
2)Cut 4 pieces of medium silkspan to size. I cut them to the same size as the foam shucks, but about 1/2" more chord. Cutting them to size first is much easier and faster in my opinion, but you can cut them extra big and trim them later if that's how you like to do it.
3) lay a piece of silkspan on a towel and spray it with a water bottle until it is uniformly wet, but not dripping. Blot it on the towel as required.
4)Position the damp silkspan on the wing panel so that there is about equal overhang on the leading and trailing edge. Using a 2" foam brush, paint the thinned glue onto the silkspan. It WILL soak through to the foam. Scrape the surface with a playing card, working towards the TE and wingtip to remove the wrinkles and excess glue. Wrap the overhang around the TE.
5)Immediately do the other side of the same wing panel in a similar manner. This will avoid curling the trailing edge due to uneven shrinkage. Once done, the covering can be blotted with paper towels if it is still excessively wet.
6)Repeat for the other wing.
7)Let dry for a day, and sand lightly with 220 paper. If you sand through anywhere, smear it with a bit of un-thinned glue. Marvel at how much smoother and stiffer the wing is.
8)Wipe the wing with a tack rag, and proceed to the iron-on covering.
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I cover my foam wings with silkspan and thinned carpenter's glue prior to the iron on film. It doesn't add much weight, it stiffens the wings considerably, improves the surface appearance, and improves the covering's adhesion. If you've never done it, here's the quick overview. This assumes you are starting with a plane that would otherwise be ready to apply the iron on covering.
1)Thin some Titebond glue or similar with water, approx 1 part glue to 1 1/2 parts water. The exact ratio doesn't seem critical. Put it in a wide mouth jar, or a cereal bowl to make it easier to use.
2)Cut 4 pieces of medium silkspan to size. I cut them to the same size as the foam shucks, but about 1/2" more chord. Cutting them to size first is much easier and faster in my opinion, but you can cut them extra big and trim them later if that's how you like to do it.
3) lay a piece of silkspan on a towel and spray it with a water bottle until it is uniformly wet, but not dripping. Blot it on the towel as required.
4)Position the damp silkspan on the wing panel so that there is about equal overhang on the leading and trailing edge. Using a 2" foam brush, paint the thinned glue onto the silkspan. It WILL soak through to the foam. Scrape the surface with a playing card, working towards the TE and wingtip to remove the wrinkles and excess glue. Wrap the overhang around the TE.
5)Immediately do the other side of the same wing panel in a similar manner. This will avoid curling the trailing edge due to uneven shrinkage. Once done, the covering can be blotted with paper towels if it is still excessively wet.
6)Repeat for the other wing.
7)Let dry for a day, and sand lightly with 220 paper. If you sand through anywhere, smear it with a bit of un-thinned glue. Marvel at how much smoother and stiffer the wing is.
8)Wipe the wing with a tack rag, and proceed to the iron-on covering.
Have you use this method with any 60 size stunters ?
If so, was it with cored or solid foam cores ?
Have you measured the weight gain of this process ?
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I have not done this on a stunt airplane, only carrier and combat, typically 300-450 sq. in. The wings are typically solid foam, occasionally cut out for internal controls. I have not measured before/after weight. You can weigh the silkspan, which is next to nothing, so really the weight is all in the glue. If you start with 2-3 oz of glue, some of which is water which will evaporate, add more water which will evaporate, and then consider that the majority of the glue gets scraped off anyway, there's not much weight there.
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I have not done this on a stunt airplane, only carrier and combat, typically 300-450 sq. in. The wings are typically solid foam, occasionally cut out for internal controls. I have not measured before/after weight. You can weigh the silkspan, which is next to nothing, so really the weight is all in the glue. If you start with 2-3 oz of glue, some of which is water which will evaporate, add more water which will evaporate, and then consider that the majority of the glue gets scraped off anyway, there's not much weight there.
HI Bill,
Very interesting technique. I have only done it in the "opposite direction". I cover the wings of my foam wing stunters with SLC first, then the silkspan which can be doped on and then finished as a regular silkspan finish. BUT! The wing will now really resist any punctures due to the SLC underneath.
(the other)Bill
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Oh, the irony! On my last two carrier Hellcats, I did foam cores covered with silkspan, then covered with SLC, then painted. Sure seals the seams nicely compared to traditional iron-on films. :)
(Just to be clear, I am talking about covering directly over the foam, not wood sheeted foam.)
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I've used Solarfilm but not in many years as it just seemed to disappear from the shelves awhile back. My only problem was that it would delaminate the film from the glue over a period of time say about a year, or faster in prolonged exposure in the sun.
I really did like a method that Phil Cartier used on his profile models that he still offers. He uses silkspan and wallpaper paste and it really is cheap and effective at strengthening a foam wing. You then used a low temp film to finish the job. Did one of his Zlins many years ago and it lasted so long I got tired of looking at it and passed it on to someone else.
Dennis
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I really like SLC, but I am horrible at doing wing tips with it......... :'( y1 :X
BIG Bear
RNMM/AMM