# Making Fiberglass CAI Air Box!



## Falco21 (May 11, 2010)

So one of the biggest things I have been dieing to do is make my own air box for my k&n cai. I researched for hours and looked through Svede's thread on making the Intake, which was a lot of help! Thanks Svede!! Anyways, I am going to make the air box mold out of Styrofoam and then apply the fiberglass resin to it. Here are the materials I have listed and the steps to do it. Please make recommendations and post your input on the steps and materials. 

Materials:

Styrofoam
Styrofoam Glue
(Urethane Rubber) Edited
(Polyvinyl Alcohol) Edited
Fiberglass Resin and Hardner
Fiberglass Cloth
Bondo
Sanding Paper

Steps:

1. Measure and shape the Styrofoam to fit the space provided.
2. Apply Urethane Rubber to the Styrofoam, fiberglass resin melts Styrofoam, so this is used to create a boundary. (Thanks Svede!)
3. Spray the polyvinyl alcohol onto the rubber, this will allow the mold to release.
4. Mix fiberglass resin and hardener, and paint the resin onto the fiberglass cloth, which is laid down on the mold.
5. After each coat of resin dries, sand down to smooth. Then apply another layer.
6. After desired amount of layers, apply bondo and sand the bondo. This allows all the holes and unlevel potions to be filled and leveled.
7. Remove the Styrofoam from inside, and prime and paint the final product.

I'm pretty sure this covers everything. Also I would have to attach the Styrofoam in the desired shape so that the measurements are measured correctly to the outer wall. This will allow the resin to harden outside so that when the Styrofoam is removed, the measurements remain correct, and do not end up wider than intended.


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## svede1212 (Nov 1, 2005)

The tape is also to make a barrier so the styrofoam goo isn't stuck all over everything when you melt it. In later intakes I used urethane rubber instead which came in a two part formula. I painted it over the foam and then I sprayed polyvinyl alcohol over that for the mold release. The urethane makes for a smooth interior and was easier. You'll find that the packing tape is hard to form over curved surfaces. Do yourself a favor and get some quality fiberglass cloth and resins. The bondo glass at the auto store isn't very good and is very hard to work with. The resin is also of a poor quality and doesn't hold up well to heat. There's no need to do a lot of sanding between coats if you lay the glass up well. You'll just have to take down any "points" that are there. I got it down so I only had to sand before the finish coat and didn't use any bondo filler atho there's nothing wrong with that. Good luck!


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## Falco21 (May 11, 2010)

Thanks Svede. I will definitely use your points here. Fixed the materials and steps with the products you recommended up top.

I was going to make this air box, and then make a lid for it separately, that way I can access the filter if I need to. Also, where do you recommend I make the opening for the cold air to enter the box? I was thinking about putting it somewhere near the headlight or the front grille, that way the air passing through the engine compartment can enter into the air box. Also how wide do you suggest that opening to be?


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## svede1212 (Nov 1, 2005)

You want it as short and straight as possible. The opening should be at least as big as the area of your TB or larger


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## Falco21 (May 11, 2010)

One more question, sorry to bother you x) 

Do I need to place the fiberglass cloth on the first layer? If I do, how do I get around the corners and details, won't the sheets not allow it to get into the corners of the shape?


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## svede1212 (Nov 1, 2005)

You can't make extremely sharp corners in all three planes (like the corner of a box) but can get very close with slightly rounded corners. That's where the proper type of material is important for wht you're doing. You also don't need the thing to be in one huge piece but make it out of several pieces that you just have to overlap. Look on youtube and there are some demonstrations of composite layup that may help you.


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## Poncho Dan (Jun 30, 2009)

I want to see this when you're done. I'm curious as to what it's going to look like.


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## Falco21 (May 11, 2010)

Well I go back home on May 10th and then I am going to start it. I have always wanted a box to cover the air filter. It keeps getting filthy. The hard part is going to be deciding how I should mold the foam. I'm in between either attaching around 3 inch wide pieces together in the shape and then molding the fiberglass to the outside. Or I might just get a block of Styrofoam and shape it to the desired box and then mold onto that. But I can't seem to find somewhere that sells Styrofoam blocks big enough. Anyone know where I could find them?


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## svede1212 (Nov 1, 2005)

Falco21 said:


> Well I go back home on May 10th and then I am going to start it. I have always wanted a box to cover the air filter. It keeps getting filthy. The hard part is going to be deciding how I should mold the foam. I'm in between either attaching around 3 inch wide pieces together in the shape and then molding the fiberglass to the outside. Or I might just get a block of Styrofoam and shape it to the desired box and then mold onto that. But I can't seem to find somewhere that sells Styrofoam blocks big enough. Anyone know where I could find them?


I used to use 4'x8' sheets of pink foam from Home Depot. You only need 1½"-2" thick board and you cut several pieces and glue them together into whatever thickness you need. I used spray glue from Harbor Freight (It's I think CRC brand in a green can) that doesn't attack the styrofoam much. With that glue I could spray the mating pieces, wait a minute or two, stick the pieces together and start shaping it.


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