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Author Topic: Finishing foam wing  (Read 1235 times)

Offline Harold Brewer

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Finishing foam wing
« on: May 20, 2021, 10:53:45 AM »
I am finishing up a Jim Walker Firebrand half A combat wing.  I need suggestions.  I could cover it with plastic film, but have neither the patience or the skill set to do it.  Are there any rattle can spray paints that I can use that are fuel proof and will not attack the foam?  Also, what can I use as a filler to fill the dings and nicks?

Best regards,

Harold Brewer

Online Dan McEntee

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Re: Finishing foam wing
« Reply #1 on: May 20, 2021, 12:51:50 PM »
I am finishing up a Jim Walker Firebrand half A combat wing.  I need suggestions.  I could cover it with plastic film, but have neither the patience or the skill set to do it.  Are there any rattle can spray paints that I can use that are fuel proof and will not attack the foam?  Also, what can I use as a filler to fill the dings and nicks?

Best regards,

Harold Brewer

      I have one of those kits, it doesn't have balsa skins, does it? If not, regular iron on films won't work because you will melt the foam, you need low temp iron on materials. You could skin it with any kind of tissue or silkspan with thinned white glue. This is how some f the earlies mentions of foam wing construction I had ever read were finished. I think it was Rn St.Jean did a series of articles in the late 60's about it. It really toughens up the foam also. The resulting hard shell can then be painted. You could just g with colored tissue for a base color and trim also. If you can find some Fas-Cal, that is a self stick material that combat guys used to cover their all foam wings with, but I understand it is disappearing from the market. Think along those lines as you search the forums here and the internet in general. I know Bob Hunt has some ideas along these lines also and maybe a PM to him through the list here will get you some good information. I saw a video once a LONG time ago about some sort of R/C combat model that was finished with latex house paint!! That is fuel proof from what I understand but not necessarily light!! Good luck!!
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Offline Robert Whitley

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Re: Finishing foam wing
« Reply #2 on: May 20, 2021, 10:57:13 PM »
Last year I built six stunt trainers using foam cores.
I covered them with Dr. paper and white glue thinned about  50/50 with water.
The weight gain was rather small and the results were quite good for utility models.

If you wish I could dig up the weight figures and application process for you.

Offline dave siegler

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Re: Finishing foam wing
« Reply #3 on: May 25, 2021, 06:33:46 AM »
Gloss clear spar varnish.  Minwax.   
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Online MikeyPratt

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Re: Finishing foam wing
« Reply #4 on: June 01, 2021, 05:01:11 PM »
Brew,
There is always the old silk-span and white glue that works pretty well.  Thin the white glue to the consistency of clear dope and apply a coat to the entire surface (use foam brushís and toss them when finished).  When dry, them apply the silk-span wet but only lightly damp.  Attach the silk-span around the outside edges and trim off the excess covering.  When that dries, apply to the bottom surface.  When the wing is covered and dry, brush on a coat over the silk-span and allow to dry throughly and lightly sand the surface.  At this point you can, if desired, and a second coat of the thinner whit glue.  Not the fastest way but it does work well on foam, then you can use a spray on rattle can finish.  In the past Iíve used this on free flight models and they held up very well.  You could also try the C/M and Tight-bond II method that Bobby Hunt uses also.

Later,
Mikey

Offline Robert Whitley

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Re: Finishing foam wing
« Reply #5 on: June 01, 2021, 10:59:17 PM »
I used white glue (PVA) because of itís longer working time before starting to dry as well as itís less tacky characteristics.
That lets you more readily smooth out any wrinkles.

If you do get minor wrinkles just sand them off when dry and apply a bit more glue.

Almost any finish can be applied including the lower heat iron ons. I used a catalyzed polyurethane since I have lots of it and am willing to put up with a bit of a weight gain for the benefits of total fuel proofing, durability and being cheap since they are just utility stunt trainers.

Since this building and covering method is so cheap just try stuff as you have very little to lose.

Offline Christopher Root

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Re: Finishing foam wing
« Reply #6 on: July 28, 2021, 07:46:30 AM »
How do you bend the sheet of balsa around the curvature of the foam wing?

Online Dan McEntee

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Re: Finishing foam wing
« Reply #7 on: July 28, 2021, 08:09:07 AM »
How do you bend the sheet of balsa around the curvature of the foam wing?

    To bend the balsa sheeting, soak the wood in water for the tight radius' like the leading edge, and for the top and bottom it just dampen the outside surfaces. That make the fibers on that side expand and starts the wood curving. For the leading edge, position the already soaked sheet in place on the leading edge and wrap with an ace bandage and then let it dry for 24 hours. Then when you remove the wrap the balsa will be in the same shape. Then just apply the glue for the leading edge and then wrap it again until dry. The remove the wrap and continue with the rest of the sheeting. Since you are using preshaped wing panels this may be your only way to do it. If the wing panels were cut by hot wire you should have the foam beds that they were shipped in to help with the process.
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Offline katana

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Re: Finishing foam wing
« Reply #8 on: July 28, 2021, 12:04:40 PM »
  regular iron on films won't work because you will melt the foam, you need low temp iron on materials.

Strange as back in the day, I used to use regular Solarfilm over white foam combat wings, using nothing more than a regular domestic iron to stick and shrink - no problems with melting here!

Offline john e. holliday

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Re: Finishing foam wing
« Reply #9 on: July 28, 2021, 01:37:21 PM »
 I have done this since reading it in an RC article on finishing foam wings.   Brush white glue(Elmers) over the surface to be covered.  Let dry.  Then lay silk span, doc paper or poly span on the surface.  Set your iron to where you can hold it in your hand.  This will activate the white glue.   Once it is down, brush another coat of white glue, thinned over every thing.  Eye ball the surface looking for pin holes.  Or lightly start spraying the primer coat.  Go lightly giving it time to dry before it attacks the foam if there is any pin holes.  Yes it takes time and once the primer coats have been sanded and no pin holes go with what ever type of color you want going with very light coats.  Remember if you spray too heavy it may soften the lower coats and get to the foam.

If you are in a hurry, go with low temp iron on covering. H^^
John E. "DOC" Holliday
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Online jerry v

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Re: Finishing foam wing
« Reply #10 on: September 05, 2021, 11:23:21 AM »
I am finishing up a Jim Walker Firebrand half A combat wing.  I need suggestions.  I could cover it with plastic film, but have neither the patience or the skill set to do it.  Are there any rattle can spray paints that I can use that are fuel proof and will not attack the foam?  Also, what can I use as a filler to fill the dings and nicks?

Best regards,

Harold Brewer
White foam wing size 48 x 9 inches , 1.35 Inch thick with spruce spars, balsa TE and LE , balsa block with adjustable leadouts -4 oz.
Patch filled with 3M - 4.55 oz.
One coat of heavy silkspan and 50/50 Elmers white glue- 5.43 oz.
One more coat of medium silkspan and 50/50 Elmers glue and water - 6.24 oz.
One coat of Minwax polycrylic clear - 6.59 oz.
All weight figures are after drying. Accumulation of weight is a weight of the wing after each application.
Silkspan soaked with the glue on the plastic bag surface and applied as a wet sheet over a dry wing.
Now water based enamel can be applied with brush or sprayer. Paint is rugged enough to withstand beech landings and glow fuel.

Jerry
Variety is the spice of life.

Online jerry v

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Re: Finishing foam wing
« Reply #11 on: September 05, 2021, 11:27:20 AM »
Pictures

Jerry
Variety is the spice of life.


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