Hi Everyone,

I have been working on an intake for my 95 miata. The part routes through a very narrow space near the front of the hood and then through a factory hole in the bumper support. I started the project with an expanding foam pour, 3d scanning, and about a dozen design variations using 3d printed ABS plastic.  Abs has help up well so far but I want to start making versions out of carbon fiber. My current plan is to print two molds for interlocking silicone plugs that have a removable plastic core. I would then do my layup over top, remove the plastic core pieces creating an air space in the center of the silicone plugs. The air space would allow my to deform the silicone enough to remove it from each end.  Is this a reasonable plan? Alternatively, is there an inexpensive soluble casting material I can use that doesn't shrink very much?

Also, I am also planning to redo the aluminum crossover pipe in carbon with an integrated heat shield to reduce sensor heat soak. Is there any issue with doing a wet layup on top of a cured part if I provide a reasonable amount of surface contact area? Would I be better off curing both parts and using a structural epoxy?

I did a test layup over top a prototype print. The part is now over sized but I have a thinner walled ABS print on it's way to me to make a dimensionally correct version.. The results aren't great from a cosmetic standpoint but it is much stronger with a single layer of 15oz carbon sleeve.  I ended up doing a quick sanding pass with 80 and 180 grit to see how easily I could remove the tape wrap marks from the excess epoxy. About 30 minutes of sanding knocked most of it off of the surface and the final part will end up foil wrapped anyway.

I came up with a reliable way to form seamless carbon tubes- For this crossover I will drill a hole for the bung, use structural epoxy to fit it into place, and then layup another layer of carbon fiber overtop.

Dual wall crossover tube with insulation box around the IAT sensor:

This is nice work, I like it. I love the engineering side of composites as much as the practical fabrication side, so this is an interesting project. Thanks for continuing to post despite no responses prior!

I was going to reply earlier but Ruby (my MGF) wouldn't let me!

What is the best way too approach doing the duct part if I don't want to sacrifice a $80 3d print each time? Most split mold techniques I have seen require being able to fit your hand into the part but this is too narrow. I could do it in two pieces and bond them but that seems like it will be difficult to get a clean joint.

Also, has anyone worked with 3d printed molds before? I have been using ABS plastic for everything since it is reasonably resistant to heat, however large prints will almost always warp so it seems like a poor choice for a split mold.

Have you checked out this thread

http://www.talkcomposites.com/10433/4-intake-pipe?PageIndex=1

Lots of stuff here similar to what your doing, 5th post down page 5 might be of special interest.

Thanks for the link, the steel shims sound like a good way to go.