any composite guru's out there?

[dcmspikes]

i want to make some carbon fiber parts. i have the cloth, i can make a mold (gel coat or plaster), but im getting interested in this vacuum forming with PETG. this seems like such an easy way to make a mold to lay up the CF in.
this is what i mean by vacuum forming:

http://www.youtube.com/watch?v=PYtvBz7cJ_s

so my question is: does anyone know if polyester or epoxy resins wil attack this PETG plastic? if so, will a grand coat of mold release (wax and/or PVA) do the trick?

i figure i can vacuum form over the part i want to duplicate with 0.030" PETG and then brace the back of the plastic with plaster or whatever it takes so that the mold does not distort when laying up CF. i figure i will start with just doing CF lay up by hand. no vacuum. just to see how it goes. im talking about carb covers and engine side covers. nothing too big to start with

hope i get some replies.

thank you
Josh

 

[conway]

Josh with proper waxing, as well as a proper coat of PVA, that will work just find. This do it your self carbon fiber website, carbonfiberdiy.com has a lot of great info about making composites also well as vacuum molds.
If you have any other questions about composities you can send me a pm.

 

[CCRider]

That's pretty cool. I think you would be OK with epoxy resin. I've laid it up on all sorts of plastics and styrofoams and never had it attack any.

We had the Vac-U-Form toy when I was a kid. I loved that thing. Back when men were men and toys were dangerous.

http://www.spookshows.com/toys/vacuform/vacuform.htm

CC

 

[dcmspikes]

thanks guys. ill read through soe of that website later today. i talked with a suppier and when i find some time i going to get a sample of the PETG and do some tests. let you know in a week how it comes out.

 

[rockcitycafe]

that's really not a great way to make a mold for fiberglass or carbon fiber. in all honesty, it's a lot faster and will give a proper surface finish if you build a composite mold. laying up cf by hand will probably give you plenty of bubbles, if it's a cosmetic part, the proper method is to apply a transparent gelcoat, then lay in the carbon already wetted out, then apply your breather, absorb mat, and vacuum bag.

 

[dcmspikes]

i got some samples of the PETG. so ill throw some resin at it and see what happens.

Rock, i understand the bubbles i will get when laying it up. i would love to vacuum bag, but dont want to pay for all of the materials (vacuum bag, tape, absorb mat...). do you think the plastic mold will yield finish? or just the hand lay up? making the thermo vacuum mod seems so much easier than a proper gelcoat mold. like i said this is all experimental.

i have almost nothing invested in this so far, so im going to give it a shot.

thanks again for any input. let y'all know what happens

 

[CCRider]

I'm looking foward to seeing how this turns out. I think you'll be able to get some acceptable results from a wet lay up.

You can do vacuum bagging pretty cheap though. My vacuum pump is a compressor I ripped out of an old refrigerator in someone's trash. Heavy duty trash bags and visqueen work for bags. I use the cheapest caulk I can find instead of tape to seal the bags. Cheap lightweight polyester lining fabric from the fabric store works just like peel ply and paper towels make good bleeder cloth.

Good Luck, CC

 

[dcmspikes]

CCRider, with some luck and motivation ill make a mold this weekend. dont know if ill be able to get some epoxy resin till next week. would fast set two part epoxy be the same as resin? i have some of that i can put on the plastic.
i knew there had to be a DIY version of vac bagging. i can definitely get my hands on those materials that you listed. i would much rather use a vacuum set-up. thank you for the tips.
ill post as soon as i have something.

 

[CCRider]

The fast set epoxy may be too thick and set up too fast. You want a slower, thin resin to wet out the cloth easily and give you some time to work.

CC

 

[HerrDeacon]

The fast set epoxy may be too thick and set up too fast. You want a slower, thin resin to wet out the cloth easily and give you some time to work.

CC

Also, you don't want it to build up too much heat as it would probably deform that plastic and ruin the mold. Looking forward to seeing how you do with it though, very interesting.

CC, thanks for the econo-version bagging list, really good stuff. I always wanted to try it but cost was a factor. Will have to start looking into this now.

 

[CCRider]

CC, thanks for the econo-version bagging list, really good stuff. I always wanted to try it but cost was a factor. Will have to start looking into this now.

If you want to know how to do things cheap, I'm your man. ;D

CC

 

[dcmspikes]

ok, i made a vacuum box for the thermo form plastic. super easy. made a box with 2x4 sides, plywood bottom and peg board top. caulked all joints between pieces of wood and the inside corners. made a frame out of 1x4 for heating the PETG plastic on. took the starter motor cover off my KZ650 and put a lump of modeling clay under the middle of it so the suction wouldnt distort it under vacuum. did just like the video with PETG in the oven and made a mold. pretty straight forward. had two small webs, but was able to smudge them out afterwards with a heat gun while still on the mold. so now i have a mold.
good point about the exothermic epoxy reaction. i thought about after using the heat gun. if i brace the old or use a thicker plastic it shouldnt be a problem. i only had slow setting epoxy in the small plunger thing. so far it has not reacted negatively with the plastic.
hope to get some epoxy and try laying up a carbon piece this week.
CC what are you using for the vacuum tape? that seems to be one material that is pretty specific. especially when making pleats for the areas with more draw.


here are some pics. kind of hard to see the plastic.

this is the box, plastic, starter cover, and modeling clay

 

[CCRider]

CC what are you using for the vacuum tape? that seems to be one material that is pretty specific. especially when making pleats for the areas with more draw.

Just standard caulking. DAP ALEX acrylic latex painters caulk is about as cheap as ou can get and works well. Lay down a bead where you want to seal the bag and very lightly press the bag together (don't compress the bead too much)

CC

 

[dcmspikes]

ok, here is the first part. mind you, i had severe problems with the epoxy. i started to brush some epoxy in the mold and then it started popping, bubbling, and steaming in the mixing cup. so that was a wash. the next day i tried to get that little bit of resin out of the mold, but no go. i just went over it. you can see it the photo on the flat surface. well CC was right and i really need a vacuum for this mold. i could not get the cloth to conform to the outer flange. most of it is missing. after all of that, i am really happy with the mold itself. the plastic was super easy to form and released with no problem. so im now hunting refrigerators.

CC, will a pump out of a small refrige work? and the idea is to leave the vacuum on until the resin is set? 1hr 2hr?
thank you
Josh

 

[CCRider]

Aside from the obvious problems, the finish of the part looks really good. What type of resin are you using? I'm surprised it went off that quickly.

Compressor from a small frige should work fine.

IF you're very careful making your bag, you SHOULD be able to pinch off the tube to the bag and turn off the compressor once the vacuum is drawn and the bag will hold the vacuum. But that's a mighty big if and should. Honestly, I have not had a whole lot of luck making perfectly air tight bags. You can leave the pump running continuously but they do get hot so be careful. It helps keep the pump somewhat cool to lay a damp rag over it and to keep a fan blowing on it.

Keep at it and good luck, CC