Here is my latest part. A carbon fiber exhaust heatshield for kitcars. It is ready and trimmed but not clearcoated yet. What do you think?
The surface looks really good. No spray glue in the prep?
No spray glue and no gelcoat. Just high-temp vinylester resin right on the waxed mold.
What type of layup? Infused right?
You know carbon conducts heat right? 
Maybe do 2 different sized tubes, with some dry fiberglass inside the 2 for insulation
Yeah, how was that done? My tubes are always prepreg with heatshrink tape. I never get a perfect surface…always has the ridges from the tape edge.
Could always put copper, aluminum, or gold foil on the side facing the muffler.
Believe it or not it was simple hand layup!
It turned out perfect. That was a great resin too, just a pleasure to work with (Derakane 470-30), just the right viscosity.
Hear conduction is good here, it just helps dissipating the heat more quickly! And the resin can withstand high temperatures up to 150*C.
One was the very nice resin and the other was the perfect plug and mold that helped here!
Thats a remarkable surface for not being bagged. 3oz cloth?
you can get really good surface cosmetics with many parts without bagging it. you do not have a vacuum leaning out the surface and distorting the fibers. a steel roller will help remove any remaining trapped air.
I’ve noticed that also Hojo , vacuum bagging carbon fiber directly onto a mold surface kinda “squashes” the fiber tows.
Open wet lay ups tend to look better from a visual standpoint. Just lose strength by not vacuum bagging, but for some parts that is no big deal.
Speaking of a foil backing on a heat shield… why not silver texalium fiberglass on the inside? Not as good as foil?
p.s. if anyone knows where to buy such heat shield foil with sticky backing let me know! Texalium wouldn’t work for a complex curved part like a couple heat shields i make for motorcycles.
What did you use as a mold for the tube?
I actually need/want to make about a 4" diameter cf tube for an exhaust muffler canister.
Also could you guys help me with tech on what I could use for packing inside the muffler around the baffle tube? I have seen one kit from Vance & Hines Racing but they want $45 plus shipping for some fiberglass muffler packing. One I would rather use metallic packing if possible.
A bunch of steel wool pads LOL. jk
I agree you can get pretty good results in flat areas just with ordinary wet lay up even without using gelcoat but the problem comes when there are curves, corners etc where carbon will not stay without bagging
btw the heatshield looks good!!!
steel wool will rust.
I think I’ve heard of composite people repacking mufflers with some Sglass scraps? Not sure what real packing is, but check out other places, and ebay. might have some cheap kits.
maybe use a vacuum regulator, to pull just enough vacuum to get it to stay? that might work.
Thanks for your good words.
Could you recommend my steps in clearcoating now? Do i need to prep the surface with grit paper prior clearcoating to make a better bond? If yes, what grit paper to use?
I used a shiny stainless steel tube as a plug and then made a mold out of it.
I tried it once, using low vacuum (-5mhg) but the think is that I need to find a way to cool my pump until the part is cured.
Echidna just wet sand with 500grit and then spray 2 coats of clear.
What is the pot life/cure time of your resin? Maybe for small parts, sort out a foambox oven to heat up the part a bit. Or get a new pump
hmm. never tried that way of making tubes. Did it pull right out, or was it a split mold?