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  1. #1

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    Covering sheet balsa surfaces on small R/C planes (under 3 lbs)

    There is plenty of info on the internet about covering built up structures with tissue, but I haven't found anything concerning covering sheet surfaces like fuselage sides and tail surfaces typically found on small glow RC planes.

    Therefore, I'm thinking of a thread documenting my experiences with covering small RC planes with tissue instead of silkspan. Is anyone interested? If so chime in here and I will continue with the discussion. If not I'll not bore everyone with this and assume I am just re-inventing the wheel. Maybe others will benefit and maybe some will pass along their tips as well.

    Covering sheet balsa surfaces on small R/C planes (under 3 lbs)

    I would like to start by telling everyone that I am by no means an expert model airplane builder or finisher although I have been enjoying both for over 40 years. I am a sport modeler seeking a finish that will protect my models for their expected lifespan of 5 to 10 years. Any model with an expected lifespan less than this gets an iron on finish! Finally I am not an expert with rubber powered, tissue covered models. I do have extensive experience with typical silkspan and dope finishes. I have tried to adapt tissue to the silkspan methods over the years with dismal results until recently. Tissue is foreign to me but intriguing because of it’s light weight and vast array of available colors and patterns. It is my hope that others can benefit from my efforts.

    Small aircraft present unique problems when finishing because they are very sensitive to weight. Because I prefer the economy and easy transport of small glow models, a durable, fuel proof, light weight finish that looks good has been my holy grail for over 40 years. Small models typically do not require a “Front Row” finish, they simply can’t carry the weight but they should still look good.

    The ideal finish for balsa should provide the following benefits:

    Protection from expelled oil and fuel from glow engines
    Protection from moisture, dirt and other contaminants
    Increase durability of the airframe
    Strengthens the wood to prevent dents and dings
    Easy application
    Attractive appearance
    Inexpensive - Small planes should be economical!

    Although iron on coverings are commonly used these days, many people including me, are unhappy with the constant wrinkles, sagging, and peeling edges that can't be ironed back down. Iron on coverings rarely provide long life and become brittle with age.

    Therefore I prefer a painted surface.
    Last edited by 049flyer; 07-13-2014 at 07:03 PM.
    I fly aircraft at the leading edge of trailing edge technology!

  2. #2
    skaliwag's Avatar
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    I used Doculam for years with the inside (Glue side) sprayed with Krylon interior / exterior rattle can.
    Unfortunately they changed their formula and the glue and the paint no longer "meld". Wish I could find a substitute.
    Real Airplanes have Round Engines and Two Wings.

  3. #3
    MJD's Avatar
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    I love using tissue on small sheet surfaces for all the same reasons, although I don't mind light film on sheet surfaces as much as I hate film on fuselages. Non-tautening nitrate to apply the tissue (I far prefer nitrate over butyrate for applying tissue/fabric) and enough thinned coats to seal the surface, then light sanding with 320 grit, then primer and paint of choice. Nitrate dope is a nice surface-active base coat that is compatible with a wide variety of paint systems, and the sealed tissue surface requires only light coats to cover. The surface is nicely ding resistant and it adds a good degree of toughness to a light airframe.

    Yes - it would be great to post about your finishing methods, that will be interesting.
    Marine GOOP = magic faerie boogers in a tube, sticks everything.

    Revver Bro #231

  4. #4

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    Honestly, I find that lightweight fiberglass is as light as tissue with none of the chance for warpage that dope has on thin balsa. If you've never done it you'd be surprise. You apply the glass and sand until you have a thin, non-porous surface that is extremely thin. I think it can be even lighter than doped tissue.
    Work is what I do for the love of it. A job is how I pay for it.
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  5. #5

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    Several of us have used doculam on small glow models with poor results.

    Somehow the fuel and or oil always gets under the doculam and it soon starts peeling off the model. The problem is less of a problem when applied to foam, seems to stick better. I have tried both the high temp doculam and the low temp variety with the same results. The models hold up well for a couple of months then you notice some discoloration under the doculam. Once it starts there isn't much you can do, just fly until it's too heavy with oil.

    I have also tried painting doculam with generally poor results. Sometimes the paint sticks OK but usually it peels off within a year or so and always seems to peel off if masked. Pull up the masking tape and up comes the paint. I have not tried painting the glue side of the doculam though. I have tried every conceivable method of preparing the doculam prior to painting and can't seem to find anything that works reliably.

    I have had good success with doculam covering on wings that are built up and then trimmed with other iron on coverings. Works well as long as the wing doesn't see too much oil or fuel. I have a lifetime supply of the stuff and am always experimenting with it.
    I fly aircraft at the leading edge of trailing edge technology!

  6. #6

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    MJD

    Thanks for your vote. I too prefer the tissue for all the reasons mentioned. I am currently finishing a scratch built Phil Kraft Flea Fli which is a .15 - .19 version of his famous Kwik Fli pattern plane from the 1960's. I have covered it with orange tissue and it took only one coat of orange paint to get outstanding coverage.

    CaffeenMan - Check out the magnetic building jig hanging on the wall, on the upper left edge of the photo. One of yours I think!

    I have tried to use fiberglass cloth on many occasions and the planes always seem to end up heavy. Plus dealing with the epoxy is always a pain for me, too messy. Probably my technique.

    In any event I think tissue is more easily obtained, cheaper (especially the drugstore variety), plenty strong, and takes less pigmented paint when painting the same color as the tissue. Looks great with just clear dope over color tissue, no color paint required. Less paint means less weight. One other advantage is not much sanding is required, I don't like sanding!

    I guess I'm just old fashioned!
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    Last edited by 049flyer; 07-13-2014 at 01:18 PM.
    I fly aircraft at the leading edge of trailing edge technology!

  7. #7
    MJD's Avatar
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    That looks pretty good to me!

    To me the front end of the little guys gets blathered with so much raw fuel and oil that I sleep much better with a painted fuselage with no covering seams waiting for grunge to creep underneath and ruin everything..
    Marine GOOP = magic faerie boogers in a tube, sticks everything.

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  8. #8
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    Quote Originally Posted by CafeenMan View Post
    Honestly, I find that lightweight fiberglass is as light as tissue with none of the chance for warpage that dope has on thin balsa. If you've never done it you'd be surprise. You apply the glass and sand until you have a thin, non-porous surface that is extremely thin. I think it can be even lighter than doped tissue.
    What materials/weights are you using? Always interested in better ways to cover models, and glass is certainly the most rugged. Never turns out light for me though.
    Tiger Flyer #49

  9. #9

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    MJD

    Thanks for the kind words. I am trying Nelson Hobby Paint on this model, it is water based. You can apply it with a foam brush and it looks like it was sprayed. Hope it sticks!

    Eventually I want to be able to apply latex color with the clear Nelson Hobby Paint over the top as a fuel proofer. This is my first foray into water based paint. So far so good.
    I fly aircraft at the leading edge of trailing edge technology!

  10. #10

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    Finishing sheet balsa surfaces part 2

    Finishing balsa presents several unique considerations:

    First, water and water based finishes on bare balsa results in warped balsa - not good.
    Second, how to fill the grain to get a smooth surface.

    So what has been the solution for modelers so far on larger planes?

    Apply epoxy or polyester resin directly to the bare balsa to fill the grain and strengthen the surface followed by painting.
    Cover the balsa with fiberglass cloth, or synthetic fabric attached with epoxy or polyester resin then paint.
    Cover the balsa with silkspan attached with dope then painting.

    The first two choices are too heavy for small planes, plus there are compatibility issues with certain commonly used paints when applied over polyester resin or epoxy. The third choice comes closest to what I am looking for but still comes out a bit heavy due to the fact that the silkspan requires a good bit of dope to seal and fill the grain.

    I need something lighter!

    The solution is to cover the sheet balsa with modeling tissue then painting the covered surface with fuel proof paint.

    Advantages to covering with tissue:

    Cost - tissue is cheap!
    Tissue is already pigmented - takes less color paint to cover.
    Light weight
    Tissue is easy to apply if certain guidelines are followed.
    Tissue has a very tight weave that fills and seals easily.
    Tissue adds significant strength and stiffness to balsa.
    Color tissue with a clear finish looks great by itself, don’t need color paint!
    Tissue can be used for color trim
    Tissue applies easily to compound curves

    By now you are likely thinking what are the downsides to tissue? First, tissue is delicate, especially when wet and therefore may be difficult to apply. Second, there is a great variety in types of tissue, some apply easily while others are nearly impossible to apply. Third, applying tissue WILL take a bit more time and effort than applying iron on finishes.
    I fly aircraft at the leading edge of trailing edge technology!

  11. #11
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    Actually, I just finished a model in Liquitex water based acrylic spray paints, with clear LustreKote over top as fuel proofer. Once I finish vacation and finish the plumbing and Rx battery install, I'll soon find out how that's going to work on a 1/2A. Some pretty neat colors in the chart. Goes on matte, but glosses up with a clear coat.
    Marine GOOP = magic faerie boogers in a tube, sticks everything.

    Revver Bro #231

  12. #12

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    I've had nothing but bad luck with LustrKote.

    Have you tried clear butyrate over the Liquitex? I am hopeful that the clear Nelsons Hobby Paint will work well, it's fuel proof to 40% nitro with the cross linker. It should work well over any water based paint.
    I fly aircraft at the leading edge of trailing edge technology!

  13. #13
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    With such light weight radio gear and plenty strong 1/2A engines and props to choose from, I don't mind investing some weight allowance towards having a well painted [at least well sealed] fuselage. I can live with having iron on film on the wing, but it sure is nice to have a well sealed, totally fuel proof fuselage and tail group that doesn't need to be meticulously wiped down after every flight to look good years later.
    Some Moneykote Gurus can keep their planes looking great year after year, but none of them are honest about how compulsive / obsessive they need to be with their planes when nobody is watching.
    WHO GUNNA FEED MAW KEEEIDS..???

  14. #14

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    I like to cut my wings from foam and cover with tissue or doculam, sometimes both. My foam wings are not quite as light as a built up wing but they are much stronger, more durable, dead straight, quick to build and cheap. I've been experimenting with covering them with doculam and/or tissue with great success. My current wing project is covered with orange tissue and painted with water based Nelson Paint.
    I fly aircraft at the leading edge of trailing edge technology!

  15. #15

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    Lazy me, I just use rattle can clear. Anything else and they would think I bought it from a good builder. Money kote on the wing.

  16. #16
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    I have tried to use fiberglass cloth on many occasions and the planes always seem to end up heavy. Plus dealing with the epoxy is always a pain for me, too messy. Probably my technique.
    What I have had success with is the VERY fine woven fibreglass cloth applied with dope, NOT polyester or epoxy resin.

    Goes on like magic, is easy to sand the fluffy edges off. It will need some filling before paint though. - John.

  17. #17

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    Those look like my original style fixtures. I've had the drawings on my site since forever so they could be ones I made or ones someone else made unless you know you got them from me. You've got to love building with them. If you ever want to update them to the current system let me know.

    Sometimes I get the urge to do a tissue job just because so no argument from me on that. I do find that glass sands a lot better though than dope though. The idea is not to put too much resin down in the first place and then actually let it get hard. It sands very nicely.

    Personally, I wouldn't hesitate to use it on a plane as small as an R/C .020 job. Seriously. So to me the work is easier than tissue, but that's just a matter of personal experience and preference. I use nothing but clear over glass all the time. Check these out:

    http://www.airfieldmodels.com/galler...stik/index.htm

    http://www.airfieldmodels.com/galler...k_30/index.htm

    http://www.airfieldmodels.com/galler...s_01/index.htm

    All are glassed. Some are coated with clear epoxy paint and some are coated with clear oil based poly.

    All your other statements are certainly true - tissue is definitely more widely available and far less expensive.
    Work is what I do for the love of it. A job is how I pay for it.
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  18. #18

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    Quote Originally Posted by thailazer View Post
    What materials/weights are you using? Always interested in better ways to cover models, and glass is certainly the most rugged. Never turns out light for me though.
    I use either 0.5 ounce or 0.75 ounce. Someone was asking about glass not too long ago and I posted detailed photos of glassing the fuselage in his thread for him. I can't remember what thread it was though.
    Work is what I do for the love of it. A job is how I pay for it.
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  19. #19

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    Quote Originally Posted by MJD View Post
    That looks pretty good to me!

    To me the front end of the little guys gets blathered with so much raw fuel and oil that I sleep much better with a painted fuselage with no covering seams waiting for grunge to creep underneath and ruin everything..
    One of my favorite finishing methods is a hybrid to save some time over a fully painted model while still having a fully fuel-proof fuselage. I use iron on for the wing and control surfaces and glass and paint the fuselage.
    Work is what I do for the love of it. A job is how I pay for it.
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  20. #20

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    OK, I don't want to further hijack this thread. If anyone has any questions about glassing then please start a different thread and pm me with the link. I'm happy to help.

    This is the old thread where I was explaining my glassing technique which explains how I do it. And it is very light.

    Scroll down to post #16.

    Special Fail, simple lesson learned

    So now I'm going to chill and see how tissue is done. It's been a very long time since I put tissue on a whole plane.
    Last edited by CafeenMan; 07-17-2014 at 02:06 PM.
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  21. #21
    Duane-RCU's Avatar
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    I've glassed the stabilizer on my Simple 400, and used it as a hinge at the same time. I put the cloth on waxed paper, apply resin, work it in and credit card squeegee the the resin, then applied it to the part, squeegee it on, remove the wax paper, and it is smooth.

  22. #22

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    The last time I covered anything with silkspan & Silk was about 40 years ago. It is an Andrews Aeromaster that I still have Hanging in my Shop. It was done with Dope and Talcom power and then painted with colored Dope . I remember when that was the only way to finish a Plane. Boy have times Changed LOL.

    Van in Colorado

  23. #23
    MJD's Avatar
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    Quote Originally Posted by 049flyer View Post
    I've had nothing but bad luck with LustrKote.

    Have you tried clear butyrate over the Liquitex? I am hopeful that the clear Nelsons Hobby Paint will work well, it's fuel proof to 40% nitro with the cross linker. It should work well over any water based paint.
    Not yet, I only started using the Liquitex. I just found it in a local art supplies shop and it has some groovy colors which was the motivating factor. I suspect clear butyrate would be absolutely fine overtop, I should try it sometime soon. I sued Lustrekopte clear because I have a couple of cans. I don't like the color paints, but the clear is convenient for a number of jobs.
    Marine GOOP = magic faerie boogers in a tube, sticks everything.

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  24. #24

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    CafeenMan:

    Those jigs are ones I bought from you a couple of years ago and they work great! Thank you.

    Have no fear about hijacking the thread. This thread concerns various ways to finish sheet balsa surfaces. I am kicking off the discussion by offering my own technique using tissue. My technique is by no means "The way to do it", just the way that works for me.

    Finishing smaller planes is different than finishing large planes, the parts are more fragile and the weight more critical.

    So I invite everyone to offer their own techniques so that we can all learn a few new tricks.
    I fly aircraft at the leading edge of trailing edge technology!

  25. #25

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    Finishing Sheet Balsa Surfaces Part 3


    Not all tissue is created equal!

    Tissue comes in a variety of colors, weights, weaves and strengths. Some tissue is not much stronger than bathroom tissue while others are as strong as silkspan. The easiest to use and most desirable for our purposes is tissue that is resistant to tearing even when wet.

    Hobby suppliers realize that the folks that buy tissue are probably rubber power modelers so the tissue they select to stock is often chosen for it’s suitability to rubber power where weight is more important than strength, this tissue may or may not be suitable for RC applications. What about drugstore varieties? Will they work as well? How to tell what will work and what will not?

    Some tissue comes with a noticeable sheen or gloss on one side, while the other side is flat and more unfinished. My experience has shown that there is a relationship between how glossy the finish is and how strong the tissue is when dry and wet. More gloss = more strength. Glossy tissue therefore usually works pretty well. Fortunately you can usually determine the gloss just by looking at the tissue while still in it’s plastic wrap while shopping in the store.

    But what if the only gloss tissue you can find is pink with purple poodles, can non-gloss tissue be used? The answer is maybe. Non gloss tissue purchased from a hobby supplier will probably have enough strength for RC use but may be a bit more difficult to apply or require a little different technique. Some non gloss tissue is indeed strong enough to apply wet but it is impossible to tell without testing it. Fortunately tissue is readily available and cheap, so buy a few samples and give them a spritz with water and see how easy it is to tear.

    So lets say you bought $10.00 worth of tissue and tested a sheet from each package. Grade them as to their resistance to tearing both dry and wet. Grade the sheets in some way, like this:

    Grade 1 - Falls apart like wet bathroom tissue, just disintegrates in your hand.
    Grade 2 - Some resistance to tearing but not as strong as wet medium weight silkspan
    Grade 3 - Surprisingly strong, more resistance than the others, about like wet medium weight silkspan.
    I fly aircraft at the leading edge of trailing edge technology!


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