Spare Tire well enclosure technique

I thought I'd share the method I always used to make enclosures in the spare tire well. I did them this way to make sure they fit very tightly, captured all available air space and could be built without keeping the customers car. I just build this for my car which has tiny tires almost the size of a donut yet has a spare tire well that could probably fit all 4 OEM tires. Tons of room for a single 12.

I started with a cast of the well. I used plaster cloth that is typically used for model train landscapes.
Attachment 17185
In this case I chose to keep the spare tire so I molded around the tire then removed it.
1. Wax the metal first
2. Rub plaster into cloth, one side will have the powder and that should be the top when placed.
3. Overlap strips, a horizontal and a vertical layer.
4. Let dry or help it along with a heat gun on low. Once water evaporates its hard and easy to clean up.
You can put enough plaster cloth to make it rigid or a thin layer of glass, It won't stick if you got 2 plaster layers.

Attachment 17186
Here is the bottom view of the mold, you can see the detail it picks up. I brush epoxy resin on the bottom if the plaster to seal it. I use West Systems.


I then cut an outer trim approx 2" wide and set the baffle height. Normally this is an inch down from the floor height to allow me to add a 3/4" baffle and have a 1/4" for a grille or trim. this was thoroughly glassed and very rigid much like the sheet metal that has all of those ridges for strength.

I apply 4 layers using cloth first then tearing mat and rolling it down to soak up any excess resin. 4 of these layers and the box can double as a jack stand.

Attachment 17191
In this case I decided to angle the sub and have it sit below floor height so I stretched my fleece from the frame.
Since I kept the spare tire and used the air space inside the rim I made a baffle that mounted over that section. I made uprights that held the baffle in the angle I wanted and used the baffle ring to stretch the fleece further.
I also made a wood panel towards the rear bumper. i didn't need the air space and wanted to create a space for the tools since they could no longer sit inside the rim.
I wanted a gap between the baffle and the rest of the enclosure volume but I'll get more into that later.

4 more layers of glass on top and its ready for filling.
Attachment 17188
Smoothed things out and made a 9" Mitsubishi logo to fill that annoying dead space In hindsight I could have relocated the battery there.
Attachment 17189
Finished product. Added terminal cups to the rear panel and kayak handles to the sides so I could lift it out easy if I needed the spare.

Attachment 17190
OEM masonite tire cover was cut to make a grille so the floor height was consistent.

There is a gap between the tire and baffle that creates a larger common chamber, I want to experiment with using that as a divider to see how it will perform as an AP enclosure. This will be done once warmer weather comes and I get a weekend free to see how it performs.

Great information! Always wondered about using that plaster for molds - especially A-pillars and dash pods. 3M has that medical cast material in a roll that seems easy enough to use also. Wasn't sure about it though.

Basically anytime I'm making something out of fiberglass it allows me to do most of the work outside the car. with a great fit. You can glass in washers for mounting reinforcement, nutserts or other mounting method. It really helps to keep the smell down in the car too when using poly resin. Epoxy resin smells much less/better but is much more expensive. I use it whenever I attach different materials together.

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Originally Posted by chithead

Great information! Always wondered about using that plaster for molds - especially A-pillars and dash pods. 3M has that medical cast material in a roll that seems easy enough to use also. Wasn't sure about it though.

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