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Author Topic: Fiberglass Cloth Trick  (Read 6214 times)

Offline Colin McRae

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Fiberglass Cloth Trick
« on: July 27, 2024, 01:24:45 PM »
I am currently building a Brodak Yak-9 kit. The wing is mounted on the profile fuselage.

Since the wing is attached t the fuselage only on the top side on this particular model, some have suggested to add a fiberglass cloth strip with epoxy along the fillet area joint for some added strength. I am using some 3/16" balsa triangle stock to form the filet area.

My question is if there is a trick to minimize fraying of the fiberglass cloth during application. I do plan to cut the cloth with a pinking shear which should help. But are there any other recommendations?

Thanks in advance.

Offline bill bischoff

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Re: Fiberglass Cloth Trick
« Reply #1 on: July 27, 2024, 02:14:41 PM »
I spray the cloth with a light mist of hair spray and let it dry before cutting. This helps it hold its shape without distorting, and allows better cutting. Of course, super-sharp scissors are a given.

Offline Motorman

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Re: Fiberglass Cloth Trick
« Reply #2 on: July 27, 2024, 03:28:32 PM »
I would not use pinking shears if wanting to minimize fraying. The less you handle the cloth the better. Cut it and let it sit where it falls until you pick it up to apply it.
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Offline Colin McRae

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Re: Fiberglass Cloth Trick
« Reply #3 on: July 27, 2024, 05:31:36 PM »
I spray the cloth with a light mist of hair spray and let it dry before cutting. This helps it hold its shape without distorting, and allows better cutting. Of course, super-sharp scissors are a given.

Interesting idea. I assume hair spray doesn't affect the epoxy bond.

Thx

Offline Dan McEntee

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Re: Fiberglass Cloth Trick
« Reply #4 on: July 27, 2024, 08:44:34 PM »
    The old Hot Stuff "How To" videos had a neat trick for this. Spray the cloth with a light coat of 3M 77 spray adhesive. That's what they used in the video, but I imagine for this any spray adhesive would do. Then lay the glass cloth on a sheet of wax paper and smooth it out. Now when you cut the strips that you need, use good sharp scissors and it won't fray. When you have everything ready to lay down the cloth, just peel the wax paper backing off. I'll bet you could brush down a coat of epoxy , lay the cloth on the surface and then smooth it out before pulling the wax paper off, and continue with the epoxy.

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Offline Dave Hull

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Re: Fiberglass Cloth Trick
« Reply #5 on: July 27, 2024, 09:45:34 PM »
If you are going to be doing much work with glass fabric, consider getting a rotary fabric cutter used on a cutting matt. Far better than any scissors approach to reduce fraying especially on complex cutout shapes. If you are just doing the one plane or occasional reinforcement you can manage without. But forget about the pinking shears....

For the job you are describing, stiffening the fabric as Bill suggested helps. Then, if you paint on the thin epoxy to the bare wood and aren't using too coarse a grade cloth you can drape the cloth (you get one shot to get it right doing it like this), then lay some Saran wrap over the whole area and work the joint with your fingers without making a sticky mess.

Conversely, you can spread the epoxy on the peel layer (Saran? Wax paper?) then lay your glass on it, then lay it on the plane. That way you have a lot more to hold onto. Good and bad features there: more to hold and get you lined up (Sharpie marks) but the excess plastic can make it harder to get into the corner.

Everyone finds a way that suites their tools and skills. Lots of ways to skin a cat....


PS--The attached picture shows the small rotary cutter and the (very) small cutting matt. The matt should be larger than the largest piece you expect to cut out. I didn't have a picture of doing the fish filets, but you can get some ideas maybe from this cowling. The fabric here was cut on a 45, which allows a significant amount of warping (stretching) to contour to the compound curves. It is done in one piece, and as a traditional wet layup. Using low viscosity epoxy (EZ-Lam) painted thinly over the wood surface with the China-bristle brush, then drape the precut 0.58 oz cloth overtop. The better your aim, the smaller the piece of glass you can try. With the thin epoxy you can do some over-brushing without ruining the weave. Else, lay Saran over the wet assembly and work it with you fingers or in some cases a squeegie. A flexible credit card offer thingie works pretty good, or a piece cut from a cereal box.

« Last Edit: July 27, 2024, 10:06:39 PM by Dave Hull »

Offline doug coursey

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Re: Fiberglass Cloth Trick
« Reply #6 on: July 28, 2024, 04:11:13 AM »
I did the nose of my nobler using 3/4 ounce cloth and stuck it down with thinned  clear dope working from the center out,its easy to trim the excess cloth after that .then i brushed on the epoxy,its easy to work with because the cloth doesnt move..
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