Do I have this right?

General Composites Discussions Composites Talk
#1

OK so I’ve purchased twill and Silmar 249 plus a hardener for sanding. My thought of process for the interior car parts are:

  1. prep part for wrapping, sand 150 grit wash, dry.
  2. thin coat of 249, lay carbon fiber over part, thin coat 249 and apply little heat for bubbles.
  3. when tacky apply more layers (no sanding) until desired amount of layers for wet sanding. Last layer should include the special hardener for wet sanding.
  4. once completely cured wet sand up to 2000 grit and all done.

I don’t understand how to use the surfacing wax (mod-c)

I also have two parts that are only getting partial wrap. There is a clean molded line on the part and i plan to make the carbon fiber a clean line on the indented part. Any tips for cutting trimming or sanding that area. I can post pics of this if needed, but first i want to get the full wraps done and some practice in with this material.

#2

Will thinner work to clean a nylon brush so i can reuse or are they always throw away?

#3

Throw away. Get the cheapo brushes.
You don’t need wax. That’s for releasing parts from moulds.
After sanding you’ll want a uv protecting clear to stop/slow yellowing

#4

You can use acetone to clean your brushes, though you have to work out if it’s cheaper to just throw them away. If you do use acetone, find a container with a lid so you can just leave the brushes soaking, the lid helps to stop the acetone evaporating.

#5

http://www.uscomposites.com/solvents.html

Idk the tech i talked said to use this so i bought it. I did notice that it hardens fine with out it.

Is it easier to use an epoxy first then the Silmar 249?

Any tips for trying to manipulate the carbon around corners and 90 deg turns?

#6

since you are laying fiber over an existing part try brushing a coat of resin on the part after it’s been keyed when that gets tacky you can use it to hold the fiber around bends and corners

#7

Not sure what “keyed” means but after sanding and cleaning the part i layed a thin layer of the silmar 249 let it get tacky then layed the carbon down. I had to round the sharp edge of corner down because it was separating the weave. I guess more practice is obvious.
Any tips for general wraping parts, i.e. tools you use or anything. i had to take my gloves off because i thought it was easier to lay the fiber that way.

#8

I’m not really a fan of cleaning brushes. When you do, be sure all the solvents are gone, before using them on a mould surface. solvents can effect the release system!
(so I just throw them away, just to be sure.)

#9

This Silmar stuff, is it polyester? If so, then the wax can be incorporated into the polyester, so it cures without being sticky.

Do not mix polyester and epoxy, not even using the same acetone. This can cause very remarkable effects, including not curing resin at all.

#10

Herman can you elaborate on that?

I tossed my air roller in my bucket of acetone replacement biosolv… Historically it has always been tools that are used with epoxy that go in it.

Will hosing off the tools with acetone out of a solvent bottle before use, stop ill effects, or do you need segregated polyester rollers and epoxy rollers?

Thanks,

Zach

#11

Yes its a polyester surfboard resin. The tech said that their epoxy resin (635 thin resin) wouldn’t be recommended for auto use, its too soft?

Anyone with any good tips for wrapping parts? I’ve watched a few vids but they were simple parts. Mine has little 1/4 by 1/4 by 3/4in nub on it that i’n trying to wrap around and struggling a little. the weaves separate easily!!!

#12

I do no thave experience with the technique you describe. I guess with that technique you might be free of trouble. However, I have seen it many times where a brush used in epoxy is cleaned in aceton, and the amines inhibited cure of polyesters, once they were applied with brushes from that bucket.

#13

It might be that their 635 goes soft when it heats up, indicating a low Tg. A high Tg epoxy should be ok.

#14

I don’t mean to thread jack, but a question. In the posters steps. Getting the air bubbles out, heater gun works?

#15

Does anyone know pros and cons of each(Silmar v Epoxy)? I know that the Silmar has UV protection in it, but thats it.

#16

I’m new on here. Just reading through the threads. I use both the Silmar 249 and the 635 epoxy(not together). The 635, being epoxy is stronger, but the Silmar looks much nicer for a cosmetic part. Very clear and less bubbles and much better for a part being exposed to the sun. But it is polyester resin and so is not as strong and can crack pretty easily on the surface if the part is bent. The 635 is not a high temp epoxy so is not good for a hot car interior. And the wax you mix with the silmar floats to the surface and blocks the air, allowing the resin to fully cure. But then you have to sand the wax off. I just spray on PVA to block the air.

#17

Keyed= kicked or reached the point when it starts to rapidly harden.