How to Make Carbon Fiber Intake Manifolds by Marinus B. (Ben) Bosma 

I want to make the runners that go from the intake plenum to the  
throttle body.  This requires a 180 degree sweep. Can anyone tell me  
how to approach such a project.  Or recommend a good book on the  subject.     

Jerry Hey


The idea is to create a tool that "disappears" inside a locked shape.  We
use various types of mandrels but the most common technique is to make a
water soluble mandrel.  There really is no limit to the shapes.

Here is a good source for the water soluble plaster.

http://www.acrtucson.com/

Aquacore is about $100/5gal bucket as I recall.  I think it's corn starch
w/plaster... shhhhh 

Another really cool technique is to make the tooling from Z-corp 3D models
and forget to reinforce the model with infiltrant.  Since, they are bound
with a water soluble material you can wash out the tool in a bucket of
water.   We've made tube junctions and high temperature manifolds using this
technique.   Both these methods can withstand the 14.7PSI force of a vacuum
bag and the rigors of autoclaves.

With the 3D printer create an internal geometry that easily washes out like
a lattice work.  That saves in weight and material.

http://zcorp.com

You should've seen the Northrop Grumman quality manager when I pulled a
perfect carbon fiber plenum out of the sink.  The biggest problem with "BIG
AEROSPACE" is that they want to catalog all the tooling and cataloging a
tool that went from 3D model to water soluble part was documenting it.
Where's the tool?  I told him it was that milk in the sink!

I think there is a potential for someone to formulate a moldable water
soluble material.  Something that a ham fist like me can shape into a shape
(play doh?) allow to harden, mold onto and wash away.

The water soluble plaster takes on the same finish as the mold in which it
was created meaning that the INSIDE of the part has a great finish as well.
That's what we want isn't it?  I, too have washed out foam but it left a
very rough finish on the inside that's not conducive to good airflow.

Attached are a couple of pictures of a real part done using this technique.
We have applied for a patent on this "technology" but, I'm not real hopeful
given how mundane it is and the prior art out there.  I'm not showing the
internal structure of this tool because that's the technology we're
struggling to protect.   The tool is about 80% air and can still hold the
forces of the bag.  God developed this a long time ago when He designed
chicken bones.  Great engineering role model.

I don't recommend autoclaving.   We autoclave at 300deg
F and pressurize at 125PSI.   That's very serious composites that are
structural and highly consolidated.  We make microwave components that go
into space and they have to be super light, can't outgas and have to be
strong enough to carry several hundred dollars worth of electronics on a
Delta II ride.

My recommendation is to use a wet lay-up and a simple vacuum bag.

For something like a plenum:

3K twill weave, 3 plys (you don't need to orient them that way).
Huntsman(tm) epoxy resin for infusion (I forget the part number, I'm at
home).  Use the Freekote(tm) release on permanent tooling or a sealer on
soluble tooling (polymer of some kind from Lowe's).   Prime paint (2-part
epoxy like Polane) over the tool.   This is much lighter than gel coat and
gives you a contrasting color on the inside of the part.   I recommend white
because it shows any leaks, drips and other evidence of stuff you don't want
in your part.  The primer becomes the inside layer of your part.  Mix up a
small batch of epoxy by weight and stir in some Cab-o-sil (silica) if you
want a little more viscosity.  Paint the entire tool over the cured primer
and lay-up the 3K like you were putting on a plaster casting.  Strips work
better than big sheets.  Lay-up 3 plys the same way and have a Pepsi(tm).

At this point there are tons of options but for the vacuum bag lay-up put
your peelply over every square inch of the part (it will stick), put
breather (baby blanket) over the peel ply and bag over all that.

Suck out the air with your vacuum pump (Seal-a-meal works great) and leave
the pump on for at least 8 hours.   The Huntsman(tm) infusion resin doesn't
gel for 1:50 which is good if you're infusing since you need it to run for a
long time.   Also, it's very thin.  Silica is a good thickener but it makes
it harder to penetrate the fibers.  With a 1:50 gel time you can start over
a dozen times on a part the size of a manifold and still not have a cure
going.

Having said all that, you can use practically any resin/fiber combination
you are comfy with.  There are numerous grades of carbon fiber and even more
glass.  If you're going for a high temperature application like an intake
manifold the epoxies tend to work better than the polyesters.  We use epoxy
exclusively because all our parts fly into air or space.

I'm a strong believer in creative composite work.  This forum is good for
sharing however, there are as many ways to do something as there are members
who participate in this forum and the those who lurk here.  Try your system
on a flat piece of nylon cutting board first.   Almost nothing sticks to
them.  The idea is to get resin to kiss 360degs of each fiber.   The 3K
stands for 3,000 fibers per tow which is what you'd normally call a thread.
3K fabric is pretty light.  Getting epoxy to wet out into that is a piece of
cake.  When you look at your wet lay-up with your Pepsi in your hand you
will think it's too dry.  When you hookup the vacuum the resin will squeeze
out into the peelply and fill the breather full of excess resin.  You'll
wonder where it came from.  The result however is beautiful.

Here is a great link to a guy who, like us homebuilders, is too cheap to
spend thousands of dollars tooling up a one of a kind part.
http://www.jcrocket.com/kitchenbagging.shtml

While, I've got the floor:

I think there are other creative ways to get a shape into a composite.
We've talked about soluble tooling which is fertile ground for you geniuses
out who still remember Jr. High Chemistry class or home ec.  What are some
other materials that will become rigid yet can easily be removed?
Cardboard?  Biscuits dough?  Play Doh?  Ever consider making a rubber shape,
filling it with sand and sucking the air out of it?  Notice how rigid that
assembly is?  Ref:  coffee bags at the grocery.

What about mixing materials?  Nomex veil + Carbon + epoxy?  What resins cure
up and are able to withstand exhaust temps?  Is there anything?  What
happens when a fully cured composite is torched?  Will the carbonaceous char
still be durable enough for a pipe?

Who says you can't prefabricate a flange and glue it to a soluble tool and
glass around it?  

Well, you get the picture...

Autoclaving is not for the weak at heart.  We use a lot of pressure and a
lot of heat.  Sometimes we even use argon because it has a better heat
coefficient than air and doesn't oxidize parts and tooling under pressure.

Vacuum bagging is sort of a poor middle ground between a wet layup and that
nasty autoclave.

eBay is an excellent resource for vacuum pumps (food sealers).   I purchased
one a couple of years ago on eBay for less than $20 including shipping and
after cleaning the dried veggies and funk off of it was able to draw
28.5inches of vacuum.  That is exactly what we got on our central ($$$$)
vacuum system here.

Do I need to tell you what happened, I mean happens, if you draw resin into
the kitchen pump?  A little resin trap is a good idea.  Again, mason jar
(cans collapse, oops I keep showing my mistakes) with a tube in and a tube
out.

Hobby Lobby is another good source for layup materials.  The polyester
quilting batting works exactly like the breather material you buy from a
composites supplier because it is exactly the same dang thing!

I'm still looking for a poor man's peel ply.  I think there is something at
the fabric store that works.  I just haven't found it yet.   The peel ply we
use is supposedly Teflon(tm) woven into a fabric.   It has to breath some
but won't stick to the resin.  It looks like lingerie material although, I'm
NO EXPERT on lingerie (whew!).

The shiny blue tape you see the pros use to seal to the tool is designed for
high temperatures.  Clear packaging tape from the hardware store works just
as well and is 10% the cost.

We have a room full of bagging films some of which I'll never use again
because they don't work.  The best stuff is nylon but it doesn't stretch so
we use it for flat layups, mostly.  For the kitchen layup use laundry bags,
painting drop cloth.

Now, here's a hot tip.  If you want to make a conformal bag, there is a
product out there that works like a charm.   It's called liquid latex and is
also available from Hobby Lobby as Castin' Craft Mold builder.  It's
designed to be painted, rolled or poured onto something you need to
replicate.  In it's shipped form it's a little heavy but it can be thinned
with a homemade solution of 50/50 ammonia and water.   Use distilled water
because if your tap water is a little hard you'll precipitate that out and
it will cause lumps (ask me how I know that.) Ben

Tom Weber Wrote:
I then went to our local plastic supply house and purchased 2" ID.
clear acrylic tubing.  You can heat the tubbing to form what ever shape
you need,  IE 180, 90 270 what ever,  You have to be diligent and
careful but you can make pretty tight bends without kinking the acrylic.

 Once you have your final shape cut the acrylic tube in half so you can
split it apart length wise.  Coat the inside of the tube with silicon or
mold release. Then I took a 2.25" bicycle inner tube  coated the out
side of the tube with silicon spray for mold release.  I've never tried
the Carbon sleeve but it may work just fine for the next steps.  I took
S glass and epoxy cut to size length wise add a little length.  The
width should be pie times the Diameter so 3.1415 X 2" = 6.2813" times
the number of wraps.  I used three wraps so 18.85" long.  Lay the
material on wax paper, pour the resin on the material, cover with
plastic wrap (like the stuff you use to cover a bowl for the
refrigerator).  Use a rod to roll over the plastic wrap to distribute
the resin and push out any excess. peel the plastic wrap off and wrap it
around the partially inflated tube. Lay the whole mess into your acrylic
mold. Place the top half on and use heavy rubber bands or hose clamps to
keep it together.  Then inflate the tube so you have the material
pushing against the inside of the acrylic mold.  Let the whole thing
cure and split it apart.  clean up the end and viola you now have a
light weight complex intake manifold.  Like I said I think this process
has some merit and I'll work more on it later.  T.W.

Tony LongEZ wrote:
Paul and friends Just some FYI I talked to Acrtucson the web site that Ben 
posted they have a sample pack you can purchase for $30+S&H the woman to 
talk to is Halina Pender very nice lady (520) 434 6342. Apparently they 
have two types they have a pour type for casting and a more solid type 
for machining one is called aquacore and the other is aquapour. Also in 
the sample pack is a quart of both and a filler to make the mold smooth 
and a release agent. I have a kit on the way, it'll take about a week to 
get here.

Tony 

Here is the first design using your technique. The core box
for casting the soluble plaster is on the right. The soluble plaster
core is on the left. You hand lay up around the plaster core and
you have six bell mouths, six runners, a plenum and a 3 inch throttle
body for an RX8. It is designed to be used with the lower
RX8 stock manifold as in this picture. You tig weld a flange
on top of the stock manifold and layup a carbon flange around
the bottom of the runners to form a mating system.

Paul Lamar ...No rotor no motor.