Lee,
what you made with the bondo is a plug. Now you need to make a mold off the plug otherwise you will wind up with the rough side of the finished part on the outside. If you don't gelcoat the mold before laying up the part you will end up with a matt finish that is textured like the cf. Most shiney cf finishes have been gel coated, wet sanded and sprayed again with poly-u finish then wet sanded again then polished. Also you can tape off the mold all around the edges and put a black gelcoat strip about 3/8" around the edge, this hides the edges of the cf where you normally would have problems with narly looking weave patterns and adds a nice finished look to the part. another thing you can do to make a nice part is to make an inner mold of the part{use pattern wax to take up space where the part would be } . Then when you lay up the part just add the inner mold and clamp togather and let cure. You might also try the cf material that is called " Pre-preg" , it already has the resin applied and needs heat to cure but it is easier to handle and lay up.
I am not a expert by any means and just picked up some tips from my fabricator . Good luck with your project.
Jerry

JMPRO, Very GOOD Info!

That's the sort of information I need!

The only thing that's confusing me is what you said about my mold. I did make it so the finished side of the CF would face out.

The only way I can really get it right in my head is by thinking of these items (original parts, molds, plugs, etc.) as Positives and negatives.

The outside of the original part is the positive side.

When I made the mold I, in effect, made a "negative" copy.

Now ehn i laid the CF in the mold, I now have a Positive again.


Right??? :)

By the way, can you use polyester gelcoats with the exopy resin?

Soooo.. you take your mold, coat it with gelcoat (black gelcoat around the edges... lay your CF in the mold and clamp it all down.


Sounds simple.

....yeah right... :)

Leland,
If you ever go to selling these rear fuse box covers, count me in for one. I'd also be on the list for a front blower cover panel, in the front trunk (for my RS, of all things).
GeorgeK

Dude - I am so eagerly awaiting pics of the finished product here. CF is cool (I don't care if I am rice in the engine bay).

Your motivation might have been just
 

for fun, but there is a pretty substantial response. I think there is a big market if the cost isn't too high, tho you may not want to exploit that market.

BTW, what is your doctorate in? MD? or PhD in something?

- Randy (PhD in biology)

I have a PhD in Destruction and Domination... which is about the same thing as basket weaving...isn't it?


:)
It's just an inside joke.

Lee,
i'm sorry you are right, i had to go and take the cover off my car and look at it { my fabricator says" think inside out"}. If you were going to make many copies it would be a good idea to make a fiberglass mold anyway because the bondo mold will not last long before it starts to chip at the edges. If you were to make only a few copies you could spray the inside of the mold with a 2 part epoxy primer and wet sand to a very good finish. I don't know about mixing polester and resin, you can just use than same resin you are using as a gelcoat.
A few co. here in ca. already make the door panels. When i see my fab guy again i will ask him about how to mold the filter cover and see if i can pass some ideas along to you. The nice part about these plastic parts is that when they were made they used negetive drafts so none of them have to be redesigned to be copied.
Jerry

Okay, I'll chime in here rather than continuing the PM's with Leland.

For now; FORGET talk about gelcoat and prepreg!

Leland, the two halves pic is just right.
FWIW the factory (roto-mold) tool was 4 pieces to take care of the inside features. . . but that was roto-molded, not a CF lay-up.

So the trick to doing this with the 2-piece mold is to have something on the inside that pushes the CF onto the mold surfaces. . . AND be removable. Some sort of bladder is going to be your best bet. You may be able to do this with a specially made vacuum bag.
But experiment on the simpler parts first.

The other way this *can* be done, is the way composite airplane ducts are made. This is where you make a plaster plug that you would wrap the CF around. You then bag it, let it set, and then knock the plaster out. (there is aslo a water dissolvable version of the plaster. . but, KISS--keep things simple stupid)

Replacing plastic fuse panel covers and FG air shrouds with CF is good for effect, but why not make something that's really useful in the realm of more significant weight savings? Here are a couple of parts to challenge anyone's fab skills:

L and R rear taillight housings or a DIDO muffler in CF. It doesn't have to be shiny, just light.

Just my $.02
Sherwood Lee
http://members.rennlist.org/911pcars

Leland - good skills :)

Hey, I don't wanna sound like your mother here mate, but someone did a posting a month ago on this BBS and said carbon fibre is very nasty stuff to breathe as it has small barbs on each fibre and your body can't flush it out like it can fibreglass.

I just found the thread http://forums.pelicanparts.com/porsche-911-technical-forum/85855-insane-idea-72901-can-carbon-fiber-fabric-used-make-clothing.html?highlight=barbs

taillight housings are fairly complex geometry.

On the muffller, I would think CF would transmit quite a bit of sound. .. like a tight drum skin.

Sherwood... I'm crawling here... not walking yet... :)

Bill, the fibers are dangerous and when i cut it I'll be wearing a respirator.

CF isn't near as bad for you as Carbon Boron, which is used allot in aircraft surfaces. Now THAT stuff is dangerous.

I keep thinking of those kids who were picking up the pieces of the downed F-117 in Kosovo. That thing is almost all Carbon Boron.
They were waving them at the TV cameras... too bad that they didn't now that they'll probably all have cancer in about 10 to 20 years.

Hmmm, Dr. Pate? This wouldn't be a SCWDP plot would it? We all know of your expertise with plastic explosives, explosives that can be moulded. I can see it now...SC guys get carbon fiber, but the early 911 guys? They get.....:eek:

"On the muffller, I would think CF would transmit quite a bit of sound"

Yeah, I know. :)

Here's an example:

I haven't A-B'd metal vs CF versions of these mufflers, but I'd think the noise is controlled just like any other regular muffler - with internal baffling. Bracing inside the shell could counter any affects to transmit noise "like a tight drum skin."

There's no reason why an existing muffler manufacturer (or enterprising DIYer) couldn't adapt metal inlet and outlet sections to a custom CF muffler shell.

Jerry, you now have a new product to develop for pcars.


Sherwood

with internal baffling
 

heh-heh, Sherwood :)

So, pretty much a CF cover. . .bling-bling, C'ching-C'ching ;)

Seriously, I vote for the front trunk blower cover...it and the front trunk fuse cover were both made of cheap pressed cardboard...and in many cars they've simply rotted away...

An easy piece I was going to fab for my car is the plate that goes under the fuel pump and steering rack.

Oh no..... Paul's on to me!!!!!!!!!!

:D

If i could figure out how to make a mold for the front trunk piece, I would... but as it sits right now, I'm not sure how i'd do it. Mine is actually still out of the car from the heater saga so I'll go look at it again and see if I can come up with an idea or two.

Thom, that is a great idea too... and at least half-weay functional to boot!

If only i had a pristine example to make a mold from... mine is all beat up.

"So, pretty much a CF cover. . .bling-bling, C'ching-C'ching"

Island911,
I don't think these Yoshimuras are built like the mufflers one finds in a ricer-mobile (CF jacket over metal muffler shell), just the "C'ching-C'ching" (real thing). But I could be wrong.

Sherwood

Yeah, I'm just say'n; the CF isn't buying you anything in this muffler application. (other than Ooooh:eek: )