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Fiberglassing Wing Center

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Old 03-14-2006, 07:27 PM
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Default Fiberglassing Wing Center

When fiberglassing the center section of a wing, which glue/resin works best. I have seen epoxy glue, finishing resin, and thin CA mentioned for the bonding material.
Would the CA be as strong as the epoxy or finishing resin?
It seems other than the smell, the CA method would be the easiest.

Greg
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Old 03-14-2006, 07:50 PM
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Default RE: Fiberglassing Wing Center

Hi OldRookie,
Any of the methods you described will work, CA is the quickest, but I would think that the epoxy or resin will be produce the strongest joint. Ben
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Old 03-14-2006, 10:48 PM
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Default RE: Fiberglassing Wing Center

You can use a credit card to smooth/feather the epoxy if the patch extends past the fuselage. It works well.
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Old 03-14-2006, 11:05 PM
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Default RE: Fiberglassing Wing Center

I've used 30 min epoxy, finishing resin, and thin CA. 30 min epoxy was the worst. It was too thick to easily soak into the weave of the fiberglass, and I had difficulty spreading it without moving the fabric or getting bubbles. Thin CA worked fine, but I suspect it is more brittle, and cures to a very hard surface. I like finish cure epoxy resin the best (stuff I get is Bob Smith Ind 20 min). It is thin enough to soak through well, and has enough working time to smooth it out.

Just a note, if using Nylon mesh (like Goldberg supplies in their kits), I use CA, as it seems to adhere to the nylon better.
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Old 03-15-2006, 02:12 AM
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Default RE: Fiberglassing Wing Center

Thanks to all for the replies.

Can you use 3M-77 to hold the fiberglass cloth in place and then work in the finishing resin?
This is a twin engine plane, and I would like the strongest center section possible. It seems as if all are agreed that resin would be best for strength.

Greg
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Old 03-15-2006, 07:02 AM
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Default RE: Fiberglassing Wing Center

The little trick i do is to just tack a couple places of the cloth with CA then use resin.
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Old 03-15-2006, 10:11 AM
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Default RE: Fiberglassing Wing Center

Greg, yes, you can use the 3M spray, but use a light coat.

BTW, I see you're in Prior Lake, did you come to the TCRC Auction last month?
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Old 03-15-2006, 06:24 PM
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Default RE: Fiberglassing Wing Center

Hi old rookie
just my 2 penn'orth to the mix! I agree completely that thin epoxy resin is best - it soaks into the top layer of the wood giving a great bond, the layer can be thinned right out for minimum weight gain and if you wrap the joint while wet in thin polythene sheet you get a fantastic smooth and shiny finish. Food wrap (cling film) or solarfilm backing plastic works fine. Hope this helps!
all the best
Rick
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Old 03-15-2006, 10:21 PM
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Default RE: Fiberglassing Wing Center

Minn,

Didn't make the auction.
I was at the Warehouse the day before, and did in the better part of $250.00. I figured I did enough damage to my cash flow.

Greg
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Old 03-16-2006, 12:42 AM
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Default RE: Fiberglassing Wing Center

a light mist of spray glue will help a lot to hold the fiberglass cloth instead of fraying and it also stay put when you lay the resin/epoxy. I have no problem in getting 30 mins to do such job. Very easy. Don't forget to wear gloves and in well ventilated place.
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Old 03-17-2006, 10:34 AM
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Default RE: Fiberglassing Wing Center

For very large areas, a light, amount of 77 sprayed over the cloth before you lay it down works well. I prefer the finishing epoxy, but 30 minute thinned about 50% pure alcohol works fine too. I use an old credit card to smooth out the cloth and squeze out excess epoxy. If you are doing multiple layers of thinner cloth, then you can apply the second layer over the wet first layer before you squeze out the exess. This will allow the excess help to bond the second layer over the first more smoothly. I usually cut the second layer a little larger than the first, so I get a smoother feathering. I like two thin layers better than one thick layer. I think it comes out stronger IMHO. Good luck with your project.

Mike Boyd
AMA 7197

ORIGINAL: OldRookie

Thanks to all for the replies.

Can you use 3M-77 to hold the fiberglass cloth in place and then work in the finishing resin?
This is a twin engine plane, and I would like the strongest center section possible. It seems as if all are agreed that resin would be best for strength.

Greg
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Old 03-17-2006, 11:18 AM
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Default RE: Fiberglassing Wing Center

I like to use 30 min epoxy, strong and has work time. But.. first I put two parellel strips of 2" masking tape, one one either side of the glass. I cut the tape to the right size then lay it between the tape after I pre wet the wood between the tape lines with the epoxy. Then I wet it down from the surface. Now.. to get good wetting, I run my heat gun over the epoxy, keep back, don't let it get too hot, just bring it up to about 140 degrees or so. The epoxy thins out like water, but work quickly becuase the heat excellerates the cure time. I use a old credit card to wipe off any extra. As soon as the epoxy starts to jell, pull of the masking tape for a nice clean line. If the glass joint will be exposed, I do one of two things. If I am going to glass the entire plane as part of the finishing, I use light wieght bondo to taper and fill the heavy center glass. If I am using a film covering, I use wood colored light wieght balsa filler. The Bondo is hard to sand but is stronger and dent resistant.. but it leave a distinct red color and, covering tends to bubble over it. Balsa filler is very soft but sands easily and hides well under covering.

Best regards,
Randy
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Old 03-17-2006, 12:09 PM
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Default RE: Fiberglassing Wing Center

how much fiber do you use?
i mean how wide is the piece of fiber
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Old 03-17-2006, 02:24 PM
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Default RE: Fiberglassing Wing Center

Hi!
The best method is to use either 24 hour epoxy or polyester resin. I mostly prefer polyester resin as it is much easier to mix than 24 hour epoxy that often has odd mixing quantities like 38/100. Mixing polyester resin is soo easy as you just pour in some drops of of hardener in a spoonful of base resin and mix it together.
Using hobby stuff epoxy like 30min epoxy is no good as it is too thick, soft and difficult to sand, and has to be thinned with metanol ...which makes it even more sticky and hard to sand...plastic film will not adhere well to it either.

When people mention that they use Ca glue to secure glass fiber I just shudder...[:@] Can't understand why they mess with Ca glue when it is soo difficult to use together with thin 25g -50g glasfiber and so damn hard to sand compared to polyester resin or 24 hour epoxy.

It's soo easy just to lay the 25g glassfiber weave onto the wing and just pour the resin onto it...no spray glue is needed, spreading with a "Flash" or "SIG" yellow plastic spreader or just using a small brush to spread the resin. Do not use a credit card, they are too small, too hard and don't give the right "feel " compared to the "Flash" or "SIG" spreader . It is soo easy! It only takes a couple of minutes to completely cover the center section of a .40 size airplane wing.
I use 4-5 pieces of of different shaped 25g glassfiber weave on my sport .40 airplanes.
Never just use one single piece of heavy glassfiber cloth that you often see in model airplane kits...the wing will most likely brake at the outer sharp edge of the glassfiber cloth.

Regards!
Jan K
Sweden


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Old 03-17-2006, 03:13 PM
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Default RE: Fiberglassing Wing Center

Has anyone ever used a roll of toilet paper to take up the extra resin?
I've seen this in a demo once.

Greg
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Old 03-17-2006, 05:10 PM
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Default RE: Fiberglassing Wing Center

Hi!
Yes I do soak up exessive resin (both polyester and 24 hour epoxy), but I use a roll of kitchen papper instead of toilet paper.

Regards!
JanK
Sweden
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Old 03-18-2006, 08:15 AM
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Default RE: Fiberglassing Wing Center

Here is my take on how it is done:
http://www.theflyingknights.com/phpB...opic.php?t=137

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