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Old Sep 12, 2013, 12:59 PM
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United States, OR, Portland
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Finished wood vs. film covering

I'm contemplating leaving a fuselage of an airplane un-covered to show off the wood as apposed to using film. What type of varnish and or sealing techniques would work for this? I would even consider doing this for the Sheeted portion of wings as well....

Thanks!
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Old Sep 12, 2013, 05:29 PM
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The boat people do it all of the time. The technique is to apply fiberglass with epoxy resin. If desired, the wood can be stained before the fiberglass is applied. Wood sheeting sealed only with lacquer or varnish is subject to warping and cracking. Applying a layer of tissue or fiberglass on top adds a lot of strength without too much weight and prevents the wood from eventually splitting and cracking. A layer of 0.5 ounce fiberglass cloth will be all but invisible and will allow the wood grain to show through as if the fiberglass wasn't there. This post shows a boat done in that fashion.

Larry
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Old Sep 12, 2013, 06:31 PM
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Skin it with Clear Film.
Choose from Doculam to any of the Hobby Films, as they can usually be had in Clear.
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Old Sep 12, 2013, 06:34 PM
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I've done a couple of models in doculam to get a clear finish, and it works quite well.
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Old Sep 12, 2013, 06:59 PM
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you guys think just regular cover rite in clear would stick well to wood that has been varnished? ... and look good? that sounds easier and more familiar to me than resin and fiberglass
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Old Sep 12, 2013, 09:19 PM
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Films do stick better to non porous surfaces.. given the opportunity.

Glass and Epoxy can be a PITA imo.
Epoxy is cantankerous, sticks to everything in the immediate area and is a real mess to clean up after.
Also Epoxy can remain rubbery for a Looong time.
Using Waterbased Polyurethane Varnish as the 'resin' to fix glass cloth, is far more user friendly, albeit at some loss in strength over the epoxy. Small price though imo :-)
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Old Sep 12, 2013, 10:02 PM
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Quote:
Originally Posted by Bare View Post
Films do stick better to non porous surfaces.. given the opportunity.

Glass and Epoxy can be a PITA imo.
Epoxy is cantankerous, sticks to everything in the immediate area and is a real mess to clean up after.
Also Epoxy can remain rubbery for a Looong time.
Using Waterbased Polyurethane Varnish as the 'resin' to fix glass cloth, is far more user friendly, albeit at some loss in strength over the epoxy. Small price though imo :-)
If your epoxy is rubbery there's somethng wrong it it.
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Old Sep 13, 2013, 09:48 AM
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To do this you'd have to cover first with the film, them mask off the edges of the film and finally finish the wood.

The covering actually reinforces the wood more than you realize. Models done with a clear finish, dope is the standard here, tend to split the wood more easily in harder "landings" then if the wood is covered with a film or with tissue held on with the dope.

I know that epoxy and fiberglass results in an all but totally clear finish. But it's not that light unless the cloth is VERY thin. But luckily we have 1/2oz cloth available. If applied neatly with epoxy it'll give you a very good woody looking finish.

I've used this cloth with dope for a light skin. But the optical properties of the dope did not match the glass strands of the cloth so it was still "cloudy" looking. The trick to making glass cloth disappear is to match the optical properties of the glass with the binding glue. I know that epoxy does this well. You'd have to play around with some varnishes to see if you can get the same results if you don't want to use epoxy.

Mind you if you're doing a larger model and the wood is something other than balsa then this could be a good look. For example luan door skin plywood used instead of Lite Ply on a bigger model would look pretty darn nice if neatly finished in varnish. Birch aircraft ply also looks good in a varnish finish.

For balsa the old time classic is nitrate or butyrate dope. It builds well, sands well and is relatively light. Oh, and it's also fuel proof if you use the butyrate on a glow model.
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Old Sep 13, 2013, 10:52 AM
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Thanks everybody ... Good stuff. I'm going to build a Big Bird sailplane from Skybench. Leaning heavily towards glassing the fuse clear to show off the wood. If someone knows how to make glassed wood really clear to show off the grain (possibly stain the wood very lightly before glassing) please tell me how and what to use. Thank you all.
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Old Sep 13, 2013, 11:57 AM
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You mean like this? Lightweight glass cloth stuck down with water based polyurathane...
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Old Sep 13, 2013, 01:02 PM
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Beautiful!! That is EXACTLY what I want to do. I would love to see more of this bird and get more specific about how you did that. I am so glad you replied and posted that work of art.

...also, is that just clear tape holding the wing halves to the fuse?
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Old Sep 13, 2013, 01:28 PM
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Quote:
Originally Posted by Bare View Post
Skin it with Clear Film.
Choose from Doculam to any of the Hobby Films, as they can usually be had in Clear.
This there is completely clear film.
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Old Sep 13, 2013, 03:53 PM
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Cut light fg strips into top/sides/bottom strips. Light mist of 3m77 on glass, apply to fuse and gently brush on minwax water based polyurathane. Let dry, apply two more coats. (very light sanding before final coat)

I also bought a used OLYIII and stripped it, sanded the heck out of the fuse, recovered the wings, and did the same treatment to the fuse.
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Old Sep 13, 2013, 04:58 PM
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Do you slightly overlap the fiberglass kinda like you would monocote? And with the Minwax, Do you sand in between each coat? What grit sandpaper?

Did you modify The spoilers or did you build them as the plans suggest? They look a little bigger.
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Old Sep 13, 2013, 05:26 PM
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They are 3 bays, I think the plans call for two, not sure. The plane flies great, a nice moderate size, tough as nails, and looks better than any other plane at the field....unless someone shows up with a Skybird....oh, that may be me, being a smart @ss...
Yes, apply, slightly overlap like monocoat...bottom first no overlap, sides next, overlaping bottom, top last, overlapping side. Overlap not much, be gentle brushing next to cut edges as they fray easily. I just lightly sanded with one of those "fine" sanding sponges, wiped off the dust, and put down final coat Some put medium on front, lighter on tail, but don't overthink it. Really pleased when I put down the orange ultracoat, really please when I say how the grain showed through on the fuse. Maybe use a scratch piece of balsa and stain it with tea, let it dry, and cover it with a test piece to see if it looks better. I'm in the desert, so I stay away from dark fuselages because of the sun/heat. Some say epoxy is stronger than water based poly, but the fuse wood is strong enough, don't need the weight of epoxy. It looks like wood sculpture, and flys like a bird, I rest my case.
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