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Smoothing fiberglass cloth

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Old 02-09-2018, 04:46 PM
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jrf
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Default Smoothing fiberglass cloth

Fiberglass cloth comes neatly folded in a small package. I have never been able to get the folds smoothed out so that the applied glass doesn't show the folds. I have tried water and ironing the cloth before application, but neither worked. Help!

Jim
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Old 02-12-2018, 06:25 PM
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tubig
 
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Not sure what your application is, but have you tried tacking one end down and then lightly stretching the cloth while applying the resin?
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Old 02-12-2018, 06:47 PM
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blvdbuzzard
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Try a touch of hair spray. it should be just tacky enough to hold down the fold lines. I have also used a very lite mist of 3M77.
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Buzz.
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Old 02-12-2018, 11:06 PM
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EloyM@twc.com
 
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The basic problem is either too much or too little resin at the point of the fold. Must be all even. Try thins: After applying the resin, lay a couple (or 3) layers of plain toilet paper over, The cheap kind, not the one with embossed flowers or any pattern on it. Now hand rub firmly all over the paper. This serves two purpose (1) it assures that all the cloth, including where the folds were, get saturated with resin, and (2) it eliminates all existing puddle or high buildup of resin. The result is an even resin coat that will require little sanding. Another coat of resin, then on to primer and color.
Another good idea: googles and vinyl gloves.
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Old 02-13-2018, 08:26 AM
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Thanks for the tips. I will experimented and found that rubbing with denatured alcohol will smooth out the folds before applying the cloth. I think I will try thinning the resin (saw that on YouTube) or squeegeeing the resin off the first coat, which has been recommended by several folks.

Jim
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Old 02-13-2018, 12:25 PM
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Originally Posted by jrf View Post
I think I will try thinning the resin (saw that on YouTube) or squeegeeing the resin off the first coat, which has been recommended by several folks.

Jim
A word of caution on thinning, SOME EPOXIES DON'T WORK WELL WHEN THINNED WITH SOLVENTS
As far as thinning FG resins, I haven't tried it but I'd recommend you do some research to determine if solvent thinning will work.
I know West Systems says right in their literature NOT to thin with solvents. They recommend heating the surface and then apply your epoxy as it will open the grain and allow for better penetration with no loss of strength
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Old 02-13-2018, 03:27 PM
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Originally Posted by jrf View Post
I think I will try thinning the resin (saw that on YouTube) or squeegeeing the resin off the first coat, which has been recommended by several folks.
Jim, I would not thin the resin. As mentioned, squeegeeing will be your best bet. I use playing cards, cut in 1/2 to double your money. Wipe off the excess epoxy that the card picks up after each "swipe" onto a paper towel dampened with alcohol. If you travel on airlines you can usually get a deck or two of playing cards free for the asking. Also, sealing the balsa with one coat of sealer helps to prevent excess resin from soaking into the balsa.
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Old 02-13-2018, 05:26 PM
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Tubig:

I am using the fiberglass on the bottom of a set of floats, to strengthen the wood for impact resistance. I want the resin to soak into the wood. That is the reason for the thinning, or heating. Resin impregnated balsa is it's own composite and is far stronger than plain wood with just a thin layer of glass on top.
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Old 02-14-2018, 08:22 AM
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When I fiberglass, I use Z-Poxy Finishing Resin which I cut with Denatured Alcohol without any problems. As an example, I draw 15cc's of part A in a mixing cup, to that I will add another 15cc's of part B, then give it a quick pre-mix. To the cup I will then add 30cc's of Denatured Alcohol, then mix well. You will notice that the mixture will momentarily become cloudy, this is normal and will quickly dissipate as you mix.

This mixture will be very thin, which will allow it to be absorbed into your balsa. I use inexpensive throw away camel hair chip brushes that you normally find in hardware stores to apply the mixture over the glass cloth. I'm sure that your folds will disappear once you brush the resin over the cloth. Let dry, lightly sand, then reapply a second coat (also thinned). No need to spread with an old credit card or to wipe excess resin off. This is a very easy process and need not be complicated. Hope this helps you...

Last edited by VincentJ; 02-14-2018 at 10:10 AM.
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Old 02-14-2018, 04:28 PM
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I get one end stuck down using a 2" cheep brush from Harbor Freight (I use nitrate dope only) and 3" nylon paint brush to smooth the glass out while following with the dope brush. I fill the weave with dope and talcum power or light weight spackle (Ace Hardware) make sure it doesn't have any vinyl or latex in it.
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Old 02-15-2018, 09:40 AM
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Fiberglass 101:

When you buy fiberglass cloth or mat, it will either have a limp feel or a bit of a rigid feel. The more rigid stuff has a sort of sizing in it to help keep the fiberglass strands in place when being cut, handled, etc. Think of this sizing as being much like starch on clothing. This is the material that makes fiberglass have the sharp creases when folded. The sizing is designed to sort of dissolve when wet through with resin or epoxy (I'll just call it resin from her on) though going back to the old days, it dissolves better in polyester resin than it does in epoxy. There are two solutions to the problem. First, buy the raw fiberglass materials from a wholesaler or vendor that cuts the material from a large roll. If they have to ship it to you, have them roll the material and ship in a tube. No creases this way. Supply companies that supply materials to the full scale homebuilders have any fiberglass supplies we might need.

Another solution is just learning how to apply the fiberglass cloth. It's the nature of fiberglass cloth to sort of float up from a surface if excess resin is applied. First, I just lay the cloth in place on the surface. I apply the resin through the cloth by just slopping it thinly in place with a cheap brush. You don't have to be neat with this step. A good modeling brush works better if you're willing to clean it. As we're only interested in having the cloth directly in contact with the surface and smooth when done, we need to remove any excess resin. When the excess resin is removed, the cloth will lay flat on the surface. Resin can be removed in a couple of ways ... squeegee it off or blot it off. I was taught the blot method years ago and though I've tried the squeegee method, I find it time consuming, messy and a general PITA. Blotting is much easier and quicker. I just use cheap toilet paper or paper towels and roll the surface. As the surface of the TP roll gets saturated from the absorbed resin, remove a few turns until you are back to clean material and repeat. When you have removed enough resin the surface will almost look dry and the fiberglass will lay flat, guraranteed! When the resin is hard, lightly scuff sand it and apply another coat, just enough to fill the weave. Sand when hard and you have a paintable surface ready for primer. You know when you have sanded enough when you just start to see the cloth appear. You will also feel it as you touch the cloth.

I use to build a lot of sheeted foam wings for racing and pattern and learned the easy way to fiberglass from the Texas and CA racers. Produced a glass smooth, very light and strong surface every time with minimal elbow grease. Paint / primer in those days was the then very popular SuperPoxy. KlassKote available today works quite well also. These days any number of top coats and primers can be used though I usually stick with KlassKote or automotive urethanes. I'm still trying to learn how to use latex but most of my work looks more suited for a house.

Oh yes, I worked commercially with fibergalss way back when I was going to school some decades ago so I've handled a few yards of it.

Last edited by Truckracer; 02-15-2018 at 09:46 AM.
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Old 02-15-2018, 04:12 PM
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jrf
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Thanks to all of you for the help. Especially to truckracer for all of the useful info. I am doing some experimenting with regular finishing resin or thinned finishing resin, squeegeed or not squeegeed. I'm on the third coat on the thinned. I will report back when the results are in.

Jim
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