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Fiberglassing - help

Old 02-27-2009, 03:33 PM
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KitBuilder
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Default Fiberglassing - help

I'm building a CraftAir Firebird from the late 70's? early 80's? (think more boxy ultrasport).
The fuse is all balsa with no lightening holes so I'm thinking it will be my first candidate to fiberglass. I have never done this before other than using minwax poly on small glider pods, with very good results, however I'm looking for somthing more durable. The entire fuse shell and tail surfaces are balsa sheet. I'm hoping to use covering for the wings only.
I've done some reading on this but not clear on the steps. With talks of resins and hardeners, etc. I'm not sure of the products to use. I believe I'm looking at some sort of two part mix that is brushed on over the glass with the excess squeezed off? Is it wise to spary a very light mist of 3m sticky spray to hold the glass in place? I was planning on a very light weight glass cloth as it was only going to have ultracote on it anway so strenght is of prime concern.

I was planning on painting with Lustrekote spray as this is said to be fuelproof from the can. How does one "tape" off the design? painters tape, etc. I would hate to have the colors bleed underneath.

Lots of questions i know and apologize but basically it comes down to:
Glassing: If two parts? what are they? what weight of glass? 3m to tack down the glass first? Best way to mask a design?
Mike
Old 02-27-2009, 04:11 PM
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Default RE: Fiberglassing - help

First of all you will probably get a lot of different answers to your questions and none being really wrong just different ways of achieving the same goal. Personally i would use polyester cloth and Minwax Polyc. I have done some testing over the past week or so and find the results exceptionally good. If that is not what you are looking for, I have used 3/4 ounce fiberglass cloth with Zap or West Systems epoxy resin. That is a good way to go but too much work for me. (i am just speaking for myself here). As far as the tape goes, my preference is 3M Scotch Plastic Tape. If applied correctly it will not bleed under. I believe it is a vinyl material and you can make some curved lines with it as well. I get it from a local auto parts store. It is not cheap by any means but it does the job. Lusterkote is good paint too. Apply it in light, even coats and your finish will come out great. I have been using some household latex lately on gasoline powered models and it is a good way to go but has to be fuel proofed for a glow powered plane.
Old 02-27-2009, 04:18 PM
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Default RE: Fiberglassing - help

ORIGINAL: OldScaleGuy

...... Personally i would use polyester cloth and Minwax Polyc. I have done some testing over the past week or so and find the results exceptionally good. If that is not what you are looking for, I have used 3/4 ounce fiberglass cloth with Zap or West Systems epoxy resin......
I have used the minwax poly but didnt' think it would hold up strength wise. With the Zap or West systems expoxy resin.. are they one part or pre-mixed? Is there any sort of minimal sealing of the balsa that should be done prior to applying minwax or the resin so the balsa doesnt drink it up? This is what Im looking to glass over when it's complete
Mike
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Old 02-27-2009, 04:30 PM
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Default RE: Fiberglassing - help

Zap and West Systems are 2 part epoxy finishing resins. They both will add strength to the surface and help avoid nicks and dings but the added structural strength is minimal.
Old 02-28-2009, 12:35 PM
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Default RE: Fiberglassing - help

If you're not going to use the WBPU method, then go over to airfieldmodels.com and look at Paul's method for glassing.

I use the EZ Lam two part resin from acp-composites.com in Livermore, CA. You can use either .5oz or .75oz fiberglass cloth (available from ACP or find it on Ebay). The resin is mixed two parts "A" to one part "B". The big decision then is do you dilute it with some acetone, or just put it on full strength? I usually put in little acetone (~10%), some folks dilute it more, and some put the resin on full strength.

I don't treat the sanded balsa with anything, nor do I use hairspray to hold the cloth down. I cut a piece of cloth to fit the surface, smooth it out by hand, then brush on the epoxy, working from a strip down the center outwards to the edge. Once the cloth is covered, use a plastic credit card to squeeze excess resin out of the cloth (I go over the cloth from center to edge, then lengthwise, then diagonally... the more you get out, the less weight you add). Then use a roll of toilet paper to soak up any extra.

Once this has dried, you can lightly sand the edges of the glass (220 grit) to feather the edges, then flip the part over (a wing or stabilzer) and lay down the next stip of glass. Once you have the entire project covered and it's dry, put another layer of resin down, again squeezing off as much as possible. Once the second coat of resin is dry, lightly sand the whole surface with 220 grit abrasive paper and use primer to fill the weave of the cloth.

Using the resin method takes more time than WBPU. It's not any more difficult, but takes longer to dry. Either way, you then get to do the "put on primer and sand it off" routine so many times you'll look at a roll of Ultracote and question your sanity for even thinking about paint

As for the masking problem, one thing to try is to mask off the surface, then spray a layer of clear coat or the underlying paint color over the edges of the masking tape. That seals the paint line, so your top color shouldn't bleed through.

Old 02-28-2009, 03:03 PM
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Default RE: Fiberglassing - help

As for the masking problem, one thing to try is to mask off the surface, then spray a layer of clear coat or the underlying paint color over the edges of the masking tape. That seals the paint line, so your top color shouldn't bleed through.
This a great method. You can also you the same base color of paint and achieve the same results. Either way will work fine.
Old 03-01-2009, 10:57 PM
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Default RE: Fiberglassing - help

Thanks for all the good info. Much appreciated.

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