SuperTruck: Flat Foam Bed Cover

by Ben N on November 25, 2012

Lately, I was getting a bit down on myself for not having more already accomplished on my Open Source Hybrid Truck project.

When my friend, Tim, was over the other day, he actually reminded me how excited HE was about the project and that I need to keep working on it and keep blogging about it.

Well, today I had a bit of time available to myself, and while still being very cold out, it was sunny. I don’t yet have the motor I’m planning on using for the project, and the engine and transmission are over at a friend’s, but he hasn’t been very available lately to help me, so what could I actually do on the project?

Another thing I’ve been thinking about lately is trying to learn how to fiberglass. I’ve already experimented a bit with fiberglass and foam, with a long-term goal of building an aerodynamic cap for the truck. (The best fiberglass advice I’ve gotten so far is basically “spend lots of money for the fancy expensive materials.) From that experimenting, I know that you can’t put standard fiberglass resin directly on styrofoam or EPS foam. But I’m still pretty confident that I CAN  use that foam, I just have to find the right material to coat it first.

So, without spending more money from a budget I don’t have, how do I keep the project going on a Sunday afternoon?

I thought I would build a FLAT FOAM TRUCK BED COVER. Nope, not a fancy sloping aerodynamic cap, something much simpler. I would still have use for a truck cover. A tonneau cover would keep rain and snow off tools and gear in the back of the truck, and with better sight lines and weight savings than the cap I have on my gas truck right now. It would also be great practice for me for working with foam for when I do actually build the aero-cap.

I also already had the materials. Some time back, I “rescued” a number of sheets of 4″ thick white bead styrofoam from a dumpster. No reason why I couldn’t carve this stuff up to make a truck bed cover. It had been stored outside, and UV light degrades it over time, and it was used material, so it was a bit beat up already.

I measured the truck and found that I would have to use two pieces. A compact, short-bed pickup bed is over four feet wide and a bit over six feet long. The foam is just under 4’x8′. I decided the splice of the two pieces would run transverse, with the splice closer to the cab ind of the bed. That would make for a shorter cut, and opened up the possibility of leaving some open access right behind the cab for a toolbox I sometimes use.

I’d need to clean up the edges of the materials, so I dug out my circular saw and set it to maximum blade depth, which was NOT enough to go all the way through the foam. I would have to make a cut, flip the foam, and cut the back for every complete cut. Oh well, at least the blade cut more than half way deep! I started just by cutting an inch off one edge of a sheet to make my own “factory-edge” that I could measure from and base all the other cuts off of. (Having a 4′ drywall square helped with this as well.)

Once I did that, I flopped the foam up on the bed of the truck, slid it all the way to the back, and made sure it covered the closed tail-gate plus a bit extra. I marked center on the foam. I measured the width of the top outside of the bed, and decided that 64 inches would be more than enough width. I cut a new factory edge on the one side, and cut the opposite side at 64″. I left the original beat up edge hanging off the back of the truck. In the end, that will get curved and sanded and look fresh and new as well. The longest cut edge faced towards the front of the truck, where it will splice into the other piece.

I set several weights on top of the foam with it on the bed to prevent it from moving, and then climbed inside with a marker. Laying on my back, I marked the edge of the inside lip of the truck bed and tailgate. I would then cut a notch there so that the cover sits both over the top of the bed AND sits down into it.

I decided on a 1.5″ depth for that cut. That would leave just over 2″ of material on the top, plenty to smooth and curve for the finish, and a nice thick lip, that’s unlikely to break. I set the circular saw to a 1.5″ blade depth and made the three cuts. Once that was done, I marked the edges of the foam, 1.5″ down on the side. I would then have to cross-cut into the foam, but it was deeper than my circle saw could cut.

By now, I was completely covered with tiny bits of white foam. Head to toe.  I didn’t want to walk right into the house and get styrofoam everywhere, so I knocked on the front door, and my wife opened it. “Yes?” “Could you get me the electric carving knife from the kitchen?” She did, knowing enough now not to bother asking why, as I seem to use more and more garage tools in the kitchen and kitchen tools in the garage. Our two-year-old said “Daddy a snowman!”

I went back to the driveway and proceeded to make cross cuts into the foam with our electric carving knife. Once that was done, I was able to lay the foam in the truck with it properly sunk down that inch and a half.

I did all the same steps with the piece closer to the cab, except that it was only a 31″ length. Cut to size, cut to length. See that it wasn’t a straight cut. Cut it again. Trace from below. Cut out the depth notch on the three sides. Get styrofoam in my eyes. Put on goggles instead of safety glasses. Cut some more.

I about an hour and a half, I managed to become abominable, turn the entire driveway into a snowglobe, and manage to not wreck another kitchen appliance.

The flat bed cover is starting to take shape. At that point, I had to clean up, and head off to something the wife had planned for the afternoon, but at least I got one more little thing done towards the SuperTruck project.

Next time, I’ll start shaping the top of the cover and figure out how I will hold it down to the truck. After that will be assembling the fastening system, then some sort of protective coating over the top of the whole thing (fiberglass? something else?) and in the end, maybe even a coat of paint.

Have you ever built a cover out of foam? Do you have any little car tips or thoughts on my project? Let me know!


{ 2 trackbacks }

Fiberglass basics - Ack! Your tips needed - Page 3 - Fuel Economy, Hypermiling, EcoModding News and Forum -
November 27, 2012 at 8:13 am
“Daddy a Snowman!” Custom Snow Globe
December 25, 2012 at 12:44 pm

{ 1 comment… read it below or add one }

1 Alex August 18, 2021 at 1:55 pm

I’ve never built a cover from foam, but it seems interesting. Your hard work did pay off from the great outcome of your project!

Leave a Comment

You can use these HTML tags and attributes: <a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <s> <strike> <strong>

Previous post:

Next post: