Daniel,
I just got in a little bit ago, so here's my thoughts.
The dense blue foam is polystyrene, and it is sensitive to solvents - hence
the ability to dissolve it out, and the need for epoxy resins - polyester
resins ( like those in the Duro auto fiberglass kits) will attack it.
If you want to get a smooth finish on the blue foam, rough carve, and sand
it as smooth as you can. Then spray or brush on several coats of BIN ( the
stuff for water stains) It is a shellac ( alcohol base) with fillers. It
sands reasonably well when good and dry. After that, you can also use quick
dry spackling compund to fill any dents / pits / goofoos, then top coat with
another coat of BIN. I would avoid the wax, as the resins are exothermic,
meaning that they generate their own heat while curing, which could make
quite a mess.
Use PVA ( polyvinyl alcohol) as a release agent. You can get this cheaply
from the resin supplier. You can brush it on, and it dries to a glossy
film, that is later water soluable. This should give you the smooth inside
your looking for.
As to the nesting of a mounting plate and box, I did a quicky sketch for you
http://home.neo.rr.com/mark2000/airbox_sketch.jpg
If you make the box first, and trim the layup flush with the foam, you can
add another slab of foam on it, and use the first layup as part of the mold
for the second. Liberal use of PVA will help seperate the parts, and it
washes away when you're done.
I know you said C. Fiber & epoxy, but if you've never worked with CF, it can
be a real bitch - doesn't like to drape over corners, and can give you nasty
little stab wounds in the ends of your fingers...... I know it looks cool,
but for the "lost-foam" process you have to figure on surface finishing of
the outside of the part since theres no mold cavity in contact with it to
make it smooth and purty.
For the mounting holes, FG cuts easily with hole-saw, fine tooth saber saw,
drills, etc. - CF not so well, tends to splinter, dull blades....
For the inlet tube, I'd probably make it as a seperate part, then laminate
in. Get a piece of tube ( PVC or metal) that's 1/4 to 3/8" smaller in
diameter than your desired final OD. Stand it up on a smooth base -
hot-melt glue to hold - then PVA the whole thing. Take a piece of aluminum
foil thats long enough to warp around the tube and coat it with PVA and set
aside.
Do the layup by wrapping the tube, so the thickness is 1/8-3/16" thick, and
extending out onto the base to give to a flange to laminate to the box
later - you'll need to make relief slits in the edge of the cloth to get it
fold out onto the base. Then finish off by tightly wrapping the tube with
the PVA'd foil. When its cured, you can peel off the foil, and have a
laminate tube that'll be pretty smooth on the outside. 'Course you could
also shop around for a piece of spiral wound FG tube and save a bunch of
work......
One last tip is to pre-cut and dry test fit all your cloth pieces before mix
any resin.
Whew, kinda got carried away - hope it helps.
Mark Sedlack
/// datsun-roadsters@autox.team.net mailing list
/// Archives at http://www.team.net/archive
|
