quick help....

General Composites Discussions Composites Talk
#1

I have been racking my brain for a while now trying to come up with a material that will work for the following purpose. Wondering if anyone can help out…

Need a material that will allow me to essentially evenly ‘gap’ a part so that I can make a female mold. The gaping material needs to essentially fill a void equal to the final thickness of the part. The problem is, I need a material that will be pliable (part has 3-d contours) and that I can pull a mold off of. This has been annoying me for a while and anything else you can come up with would be great.

Ideas so far:

Wax - easily damaged resulting in mold being off…hard to maintain position

FG with Epoxy: Expensive and labor intensive for simply gapping a part.

Thermoplastic: Heat molded plastic? Would be perfect but I dont know what I am looking for…opinions?

Any help would be great. let me know if i was not clear enough.

Evan

#2

for heat molded plastics you can use styrene sheets

#3

Don’t use styrene (PS) sheets with PER as it will disslove. Use epoxy resins or:

Use PE either HD or LDPE.

Check out www.kindt-collins.com for beewax sheets as that is what is used normally.

I was thiking of trying out the “bear bond” tapes that Nascar teams use to repair their cars in the pits. You heat it up, apply it, let it cool and it stiff as you know what! :eek:

But too many great ideas and not enough time…

#4

werksberg…that bear bond tape looks exactly like what I want. i would prefer not to use epoxy for making my mold as the cost will be too large. Are the other plastics you mentioned good for heat molding?

#5

http://www.freemansupply.com/SheetWax.htm

#6

good to know!

i tried to search for the bear bond tape you are talking about but couldn’t find anything, do you have any links?

#7

Wax: don’t damage it when working with it :wink:

Maybe silicone molding material?

How about laying up a test part, sand and seal the outter surface, and use that as the spacer. hardwork, but should work.

balsa wood core? They sell conformable types. Might take some work as well however.

#8

www.rubbnrepair.com (866) 341-2744 from my Grassroots Motorsports mag…

#9

Thanks!!! but man is that ever pricey!

#10

I’ve had the same dilema with making some motorcycle swingarm covers.

In then end I waxed the swingarm and then layed over some plain weave fabric (not carbon) then wet it out with PER. I had to make a few cuts in the fabric to allow it to conform but filled these in with more plain weave from the back of the part when I pulled it off. I then covered the cured weave with a very thin layer of bondo (car body filler) and sanded it until the weave just started showing through. The part was then primed, painted, flanged then waxed ready to take a mold from.

Well I say primed and painted but we are at 0 degrees centigrade in the UK at the moment. After I clear coated the part it looked like all it needed was a rub back with 1200 grit wet and dry then a polish. The wet and dry went ok but as soon as I started polishing a whole bunch of surface cracks appeared all over the part. I foolishly used some old clear coat which had been sitting a while so I suspect this was the cause. Any way I’ve rubbed it back to the primer now and its ready for more clear when the weather starts to play ball.

I’ll post some pics if anyone is interested.

Cheers
Andy

#11

I Like the idea. Since I have yet to try the wax and such I think I will go for a method similar that i have used previously but with some heavy fabric rather than the thin plain weave. The issue I have previously had is that using spray wax, if you do not use epoxy the fabric will pull up and distort the shape of the mold. What I think i will do this time is take it a few inches at a time to ensure there is no movement. This should allow me to use gravity to my advantage.

#12

Evan

I’ve detailed my process a bit more and stuck a couple of pictures here

http://www.compositeforum.werksberg.com/showthread.php?t=2663

#13

cool. I think I may end up doing something similar. That is a beautiful piece there. Is that the one you ended up making? My part will have much larger and rounder contours but will use a similar technique…

#14

Those aren’t the pieces I made attached to the bike but I’m expecting similar results. :slight_smile: