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Epoxy / polyester compatibility

Old 01-30-2010, 10:41 AM
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topwinguk
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Default Epoxy / polyester compatibility

I've just managed to damage an ARF sailplane fuselage from a heavy landing. As you will know, most of these models are moulded from one layer of glass cloth and polyester resin. The question I would like an answer to, is whether I can use epoxy resin and glass cloth to repair the damage or must I use polyester resin?


Tony
Old 01-30-2010, 12:21 PM
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qldviking
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Default RE: Epoxy / polyester compatibility

epoxy is the only way to go, I give the area a good clean with acetone first tho. While polyetser is good as made, later repairs or addition with polyester have poor bonding issues. I see this a lot with boats I work on, where repairs done with poly I can just peel of with very little effort
Old 02-03-2010, 02:32 AM
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topwinguk
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Default RE: Epoxy / polyester compatibility

Thanks for that, saved the day.

Tony
Old 02-17-2010, 10:26 PM
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charlieoneseven
 
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Default RE: Epoxy / polyester compatibility

you can repair polyester with either but only epoxy on epoxy.
Old 06-30-2010, 03:05 AM
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teebox11
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Default RE: Epoxy / polyester compatibility

Epoxy on epoxy, POLY ON POLY! You must clean your surface and roughen the surface well, I use 40 grit to score. If you read the label on resins, most are poly. Others are other types to include poly mix. Just make sure the first ingredient is poly and you will be ok. Oh, you don't need to spend you annual earnings on those fancy named resins and epoxy's. I go to Lowes and get Bondo or Elmers resin, or any store that might have something on sale. Both of these are poly. I've been using them on planes for decades. Also, you don't need to spend tons on glass. GO TO THAYERCRAFT.COM. They have millions of yards of every type of glass cloth anyone would ever want. Just make sure you get the general purpose glass that does not require special resin. Have fun!
Old 07-05-2010, 05:35 PM
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Foxman
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Default RE: Epoxy / polyester compatibility

I think using polyester resin on a polyester fuselage would be the best thing and epoxy on epoxy. 5 minute epoxy is a waste of time though and it doesn't seem to stick at all.
Cleaning and roughening up the surface is the only way to go.
Old 10-17-2010, 07:10 PM
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John Sohm
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Default RE: Epoxy / polyester compatibility

Thayercraft.com for fiberglass is the way to go.

Also check out U.S. Composites http://www.uscomposites.com/index.html

They have all sorts of resins at very reasonable prices. You can call either for advice too. I also like AeroMarine Products (JGreer and Associates). They have all type of rtv moldmaking supplies and urethane casting resins along with some really good epoxy finishing resins. http://www.jgreer.com/
Old 12-16-2010, 07:14 AM
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tlar
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Default RE: Epoxy / polyester compatibility

According to several boat repair books you can and should repair poly with epoxy. Never repair epoxy witth poly. Poly laminates well and a lot of boat builders use poly due to the low cost. The problem is that poly melts most foams so you cant use it for core wings or foam parts. BUT if you make wood molds (even plaster) it is a cheap way to build models.
Old 12-16-2010, 08:55 AM
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ARUP
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Default RE: Epoxy / polyester compatibility


ORIGINAL: tlar

According to several boat repair books you can and should repair poly with epoxy. Never repair epoxy witth poly. Poly laminates well and a lot of boat builders use poly due to the low cost. The problem is that poly melts most foams so you cant use it for core wings or foam parts. BUT if you make wood molds (even plaster) it is a cheap way to build models.
Great discussions! If you ever wish to use foam as a base plug just coat it with a few layers of water based wood glue like Elmer's to seal it before applying polyester resin. I carve blue foam to the shape I need, like for a cowl, slightly undersized to account for the glass/ resin build up.
Old 12-17-2010, 04:14 PM
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yachtie2k4
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Default RE: Epoxy / polyester compatibility

use epoxy or vinylester resin, poly isn't the best resin for repairing as qldviking said, epoxy will work the best.
Old 12-19-2010, 06:17 PM
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Default RE: Epoxy / polyester compatibility

I've just managed to damage an ARF sailplane fuselage from a heavy landing. As you will know, most of these models are moulded from one layer of glass cloth and polyester resin. The question I would like an answer to, is whether I can use epoxy resin and glass cloth to repair the damage or must I use polyester resin?
My suggestion would be, with Polyester resin products, use polyester resin for the repair. I try to keep the chemicals the same. I've been doing it this way for 25 years. Polyester glass fuselage? I've installed firewalls with polyester resin and micro baloons. Same with formers.

Sure, I may be wrong with this choice, but it has worked for me perfectly.
Old 12-21-2010, 07:40 AM
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TexasThermalKing
 
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Default RE: Epoxy / polyester compatibility

topwing uk,

I'm sure "gldviking", "tlar", and "yachtie 2k4" got it right...the epoxy will be the strongest bond for a small span area. Where you are bonding to polyester each side of the break , with a narrow area for each side you are trying to get a bond to. The area does need to be sanded, and cleaned with acetone. Sand an area slightly wider than your glass width.

If the fuselage is broke clean in two, it's hard to join, keep it aligned, and glass it. It can be done, it's easier if its mostly round at the break. You need to support the break. Inside is best. I have used the cardboard paper towel roll, split down the length. Taped with a gallon size plastic baggie to one edge of the cut. Roll the plastic around the tube, plastic outside, leave a little long, and trim the excess. Curl it like you would a magazine, with the taped edge (mag bound side, inside the curl) inside the curl. Insert it down the fuselage.

Prop up the front and rear on a table, to hold it just close for now. Then, taking any latex bladder, a glove finger or two, fit to a tube, anything long enough to work with and wrap it tight to the tube where the end will be free to inflate enough, inside the center of the curl, to push the roll apart, and against the fuselage inside. Without it inflated, insert down, to the middle of the break, or close. Lightly inflate. Don't try to use your lungs to inflate...please use a compressed air source. It will stiffen the area of the break. Block it now high enough on each end, so you can wrap glass around it. Set the alignment, wrap with glass that is coated with resin.

Lay a piece of mylar, cut slightly wider than your glass, wrap it around (going same direction as your glass wrap), about one and a half times the diameter of your fuselage. I next use, electrical tape starting in the middle, attached to the free end of the mylar, and draw it tight , wrapping the same direction as the glass, mylar wraps. Have paper towel handy for the ends of the mylar, to wipe the excess resin.

Wrap the electrical tape tightly back and forth over your glassed repair area only. Let it sit for a few minutes...the resin ozzing out will slow...wipe it clean, both sides. Now wrap with the tape, each end. Just the ends. Check the alignment...and leave it alone till cured good. When you unwrap it later, it will be smooth, or lightly humped at the break, but strong and light. The exact weight of glass, and the amount of glass to wrap the break with should be close to what the fuselage was made of. Pull the paper towel roll.
Good luck on your repair...you can do it.

Hope this helps, it worked for me. John Taylor
Old 03-31-2015, 06:16 AM
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teebox11
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POLY ON POLY AS STATED with proper weight of glass. Thayercraft is probably the best place to buy your glass. They have all kinds and the prices are right. I buy mine by three to five hundred yards, two or three styles and weights. You can get your polyester resin at the hardware store, whichever brand is the cheapest. A gallon is generally the price of just a quart of the "other guy's stuff." I use a lot of 1oz glass as well as 2, 3, and 6. I use a 3oz with a special weave that will do compound curves perfectly. Hope this helps!! Oh, btw, I an 70yo and have been glassing since i was 8. I love to glass anything, but especially planes. Good Luck!!
Old 04-08-2015, 05:35 AM
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wyowindworks
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Teebox11, why poly on poly?

Last edited by wyowindworks; 04-08-2015 at 07:52 AM.

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