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Old May 04, 2012, 09:54 AM
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Graham 65's Avatar
Chipping Norton, UK
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Best finish for foam obechi covered glider wing

I have a big glider wing on order which is blue foam covered in obechi. Not sure what to cover it with, some film is on order but wondered if laquor and paint was a better solution?

Any other ideas?

Graham
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Old May 04, 2012, 10:17 PM
Visitor from Reality
United States, VA, Arlington
Joined Dec 1996
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This might be a little odd, but a 'few' years ago, I kit reviewed a veneered foam winged model for RCMW magazine. I finished the model in tissue paper applied with regular house wall paint - 'emulsion' as it was usually called then.

Painted a couple of coats onto the wood, with sanding when dry. Laid tissue on area, rubbed emulsion paint onto and through the tissue. Another coat went atop the tissue, to give a little paint to sand rather than the tissue. Another two coats, IIRC, gave a good surface finish. Colour was the then popular 'magnolia' - a pleasant pale cream-ish colour. As it was glow powered, the paint got a top coat of 'fuel proofer', which glossed It up some.

Different, but it looked good and worked in service.

Hope that helps

Dereck
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Old May 05, 2012, 12:42 AM
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The 'Wack, BC, Canada
Joined Oct 2002
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The problem with using latex house paint is that it tends to be a little heavy. And it also tends to build a fairly thick layer if you're not careful.

Graham, one option I've seen used to good effect was to stain the wood with an aniline wood dye/stain. Just don't use an oil based stain or it'll make the epoxy unable to cure well.

Epoxy? Yep, after the alchohal aniline stain drys to where you can't smell it you can then coat and fill the wood grain with pure epoxy laminating resin. The trick was to use a small resin scraper to minimise the amount of resin needed. You want to fill the wood grain and give the outer surface a very light coat. When cured well you can wet sand it and then apply a spray coat of a clear gloss varnish or lacquer over the epoxy. The results are very slick looking.

For some color you can also apply a colored art store tissue at the time of the epoxy. Simply squeegee the tissue trim to the wood with a little more epoxy over top of the first coat. Just go lightly with the tissue over the wood.

I've seen wings done this way both with and without the wood stain. They are actually quite spectacular.

One option is that since it's often wise to make the bottom darker is to use a dark stain on the lower side and no stain on the upper. Just using the epoxy resin produces a nice darkening and rich looking tone to the obechi. So really stain can be an overkill to many folks. But darkening the underside is never a bad idea for visibility reasons.
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Old May 05, 2012, 03:17 AM
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Oh wow, that'd be nice!
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Old May 05, 2012, 04:43 AM
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Back in the olden days of soaring (70's) when foam was the new wonder material, gift wrapping paper was cheap. Never seen a pair of wings covered with Mr. Men?????? Adhesive of choice was either wallpaper paste or for a tough finish, Epoxy.

Regards Ian.
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Old May 05, 2012, 11:41 AM
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I am doing a combat hurricane. Last night I laid down a polycrylic base coat from Minwax, today I'll do some fine sanding and I'm going to use paints my brother has used on foam before with stellar results. It's available at Wallie World for $2.50 for a 2 ounce bottle, Apple Barrel. http://www.plaidonline.com/apple-bar.../5/product.htm

I got my 6 primary colors so I can mix all my own colors.
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Old May 05, 2012, 04:59 PM
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Graham 65's Avatar
Chipping Norton, UK
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Thanks for all the suggestions.

A little experimentation is required, it is a glider so weight is an issue.
Mr Men!!! Must see if there is a Mr Thermal Hunter.

Will test out some polycrylic and see what it weighs if used on similar wood. Maybe it could be used with coloured tissue?

I would like to be able to leave at least some of the upper surface as a natural finish and agree that a dark underside sounds good.

Got a feeling that this plane is going to have a retro look, bring on the flairs
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Old May 05, 2012, 11:37 PM
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The advantage of the epoxy over something like Polycrylic is that the epoxy will fill the grain and not shrink as it cures. Also in using some Minwax Polycrylic I found that the final film after drying remains quite a bit more rubbery than with a polyurethane varnish such as Flecto Varathane.

On a boat hull I did some years back I used epoxy on the sides and bottom and for some reason elected to use Varathane only on the top deck. Even after four coats, then wet sand then another three coats and wet sand and top coat that the upper deck STILL has some of the grain showing due to the finish shrinking. The epoxy filled and sealed sides and bottom came out glass smooth with far less coats needed.

And if you scrape it on thinly enough you'd be surprised at how much coverage you get from an ounce or so of epoxy. Just be sure to use a sharp edged but flexible scraper to apply and spread. And puts on more than you need at first then scrape most of it off before it begins to thicken. In particular don't leave any ridges that require sanding off.
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Old May 06, 2012, 03:01 AM
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All the more reason to collect those credit cards in the mail!
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