boosted94

iTrader: (1)

I trying to make a fiberglass duct and so far I have the duct made out of cardboard. What can I do to transform the cardboard to fiberglass. In other words whats the next step. I've heard of some covering the cardboard with aluminum foil and fiberglassing over that, but does that really prevent the resin and fiberglass from sticking to the aluminum.
Any and all help would be appreciated.

Righty

iTrader: (4)

I would be more worried about it getting the cardboard wet, and then bending or whatnot.
Cover the duct in Tinfoil/plastic wrap, then take some old fabric (bed sheets) and stretch it over the cardboard. I like to add the FG mat after the design is made (to strengthen)

You may even be better to make each piece flat, then assemble like you did the cardboard.
In the end fiberglass looks ugly. Sheet metal FTW!

DMoneyRX-7

iTrader: (2)

I tried making my own fiberglass duct when I had my XS Power SMIC. Putting tin foil on it does stop it from sticking to the cardboard but the tin foil will then stick to the resin. You can put some petroleum jelly on their and that works if you coat is on nicely. I'm sure their is some other kind of gels that you can put on so it wont stick.

How I did mine, I used poster board first and made a template by taping the separate pieces together. Then cut some cardboard in the same shape. Hot glued the pieces together. Wrapped it in tin foil. Then fiberglassed it.

A better way to do it would be to use foam blocks and shape it properly. You will get a better fitting and better looking duct in the end. Their is some stuff though that you can put around foam blocks to make resin not stick to it. I just don't know what it is called.

good luck

boosted94

iTrader: (1)

How much should my intake drop by with the duct in place, because they read about 70C with it on. Outside temp was 90F. Without the duct the temps were 75-80C. Bare in mind that most of my driving is below 40mph city traffic.

Carl

iTrader: (2)

Ihaven't tried it, but read about it and have experience with the individual steps.

Shape the duct or box or whatever using styrofoam blocks (can glue pieces together to get the general shape you need).

Fiberglass over the styrofoam with epoxy resin and fiberglass cloth. The resin has to be epoxy, because polyurethane resin will dissolve the styrofoam.

After the fiberglass coating is done, use acetone to dissolve the styrofoam, leaving the fiberglass shell. I assume that the inside will probably need sanding to smooth it out.

You could also add stiffeners or attachment flanges by glassing them to the shell.

I'm planning on trying this soon on my race car to make so custom shaped air ducts. Just haven't had time yet.

Carl

jgrewe

iTrader: (1)

You can get away with polyester resins over styrofoam if you paint it with EXTERIOR house paint first. It has to be exterior, there is something special in it, I don't remember the name.

I prefer to do a foam shape that is close, paint it with the house paint, use bondo to do the final shape and finish, then paint the plug and make it as smooth as you can. A couple coats of PVA and lay up the mold.

nillahcaz

iTrader: (2)

This thread is getting a little old but if its not too late I will tell you what I have found to work. If you have a good design in cardboard go to a local walmart or hobby store for some air dry modeling clay, I like Crayola Model Magic its cheap, easy to find and work with. Use it to round out the shape, mostly concave edges and seems. Mix some normal Elmers glue with a little water to thin it down to oil paint thickness, apply it to the foil and use a little water as lube and an old credit card to squeegee the foil to the cardboard and DRY clay. Let glue dry. Put a good hazy layer of car paste or liquid *not spray, needs to be hazy after it drys to work best* wax on the foil. Cut standard fiber glass fabric *not mat* into squars *I like about 5"x5" for something duct size* for two layers over all of it. after you have two mostly even layers RIP not cut some mat into workable size pieces, this will bulk it up fast and you may get away with just one layer of this. If you want a smoother finnish to the exposed side apply another layer or two of the cloth applied the same way as the first time. As far as time between layers ALWAYS follow the directions for the resin used.
If you need something easy to get good stretch, use a dark color fleece from a local fabric shop, It gives good contours and fast build at the cost of thickness and some strength.
To apply resin and work air out of part the best thing to use is a paddle roller, If you don't have one or want to get one get the cheep 50cent paint brush and cut the bristles down to be stiff and tap the air bubbles out DO NOT USE STROKES you can use the brush to kinda pull the mat around to even it all out but it really works best if you just tap all the air out.
And after some cure time... Enjoy a strong custom part.
note how he mostly pats with a little stroke thrown in.
Vid on fiber glass lay up
please note this is not my vid and I don't know the guy but shows the basics on layup. he did not cut the bristles down but he ends with a roller.
hope this helps.
pre-edit disclaimer i have been awake for 36 hrs and im a little drunk. sorry for all misspelling or lack of continuity.