Building a Topper

So I have begun the process of building out the bed of my 2011 Tacoma.
This is what I did.

Modeling

The first steps were the mapping out of the truck bed dimensions and the dimensions that I wanted the topper to be. Because its a home built topper, I wanted to minimize wind resistance, and opted to have the topper be a trapezoid, tucked slightly behind the sides of the cab, and even with the roof of the cab. I drew it out multiple times and used autoCAD to make a 2D scale model.

The frame consists of 2 parts: the aluminum frame, and the wooden base. The base consists of 2x4s that I trimmed with a table saw to get the correct thickness. The front rail of the truck is slightly lower than the side rails so I trimmed the 2x4 that runs the width of the truck down. the total lengths of the wooden base are as follows:

Sides: 2x4 77.5"
Width: 2x4 57"

Assembly

I attached them, using L brackets and flat roofing straps. In the photos, the 1x1 board was added for stability while transporting the base, until the aluminum frame was added, at which point is was removed.

After the base was constructed, I began on the aluminum frame. This was made from 1x1x1/16" square aluminum tube. I got the aluminum from a local supplier, and paid $84 for three 10' pieces. I ended up with minimal left over, however using these plans, you could get away with two 10' pieces and an 8' piece if you don't make any mistakes.

The next step was cutting the aluminum legs. I wanted them to match the cab angles, and also be even with or lower than the roof of the cab. To accomplish this, the legs are at a 67 degree angle, and 19.25" long. The width piece sits on top of the legs, adding another inch in height.

The list of aluminum pieces are as follows:
4: 19.25" pieces cut at 67 Degree angles (parallelogram)
2: 47" pieces cut at 67 Degree angle (MEASURED AT TOP OF BAR) (Trapezoids)
2: 72.75" pieces 90 Degree cut


I decided to cut all of the legs and attach them to the wooden base, prior to cutting any length or width pieces, is the likely case that the lengths would be different than my original plans. All dimensions in this post however, are the real dimensions that I ended up with.

I attached the legs using eye bolts. I drilled through the 2x4 at a slight angle, and drilled a hole completely through the aluminum, about 1" from the base. I put the eye bolt through the 2x4 with the eye up, and fastened it on the bottom with lock washers and a nut. I used and angle grinder to remove any excess bolt sticking out the bottom of the base, and countersunk the nut so the base still lays flat against the bed rail. (I am going to include photos I know this description is wild lol). I then set the aluminum down over the eye, and using the hole drilled in the aluminum, threaded a bolt through the aluminum and the eye inside. I then tightened everything down, and tightened the nut on the eyebolt, which pulled the aluminum very tightly against the wood. I opted to do this process, so as to make the aluminum frame easily removable, and because I have only ever been disappointed by L brackets, and was worried they would be too wobbly, which is also why I used the roofing straps on the base in conjunction with the L brackets.

Once this was complete, I measured the distance between them at the top, 47" and cut my next piece of aluminum. I cut this piece at a 67 Degree angle as well, BUT instead of being a parallelogram like the legs, this one was a trapezoid, the diagonals being mirrored. This allowed a nice, flush connection so the sides eventually fit on smoothly.

Using... L Brackets... and aluminum rivets, I connected the widths to the legs. I had to drill out the brackets a little bit, because I was using 3/16th" rivets which for some reason I took a bunch of photos of. At the time of writing this I have not yet tried brazing them, however I intend to use brazing rod to "weld" the seams, and add a bit more rigidity.

After all the riveting I attached the length pieces using the same method. Now, being fairly inexperienced or completely unexperienced in many of the things I've had to do for this topper, it isn't completely square. One of the legs is at a slightly different angle, and one of the joints is not flush, however by loosening the eye bolts and manipulating the frame a bit, I got the rear of the topper to be square, which is far more important than the front, so the door closes good.

Once it was all adjusted, I measured the dimensions and then cut plywood for the sides. the plywood is about 75.75" x 20.25"

Once the plywood was cut, I placed my windows, 12" from the back, and 6" from the bottom to get them in the desired position, and, using a jigsaw, cut the space out.

I drilled through the aluminum frame surrounding the window and the plywood using a very small drill bit and used very small bolt to attach the window to the wood sides. The windows that I used were from Facebook marketplace, off of a topper from a 1980 el Camino, and are 50" long and 7" tall. I used a thick gasket to make sure that the windows wont leak. After attaching the windows and drilling all the needed holes, I removed them again so I can, sand, prime and paint the walls, and attach any gaskets.

After the windows were removed I placed my walls in position and clamped them with c-clamps, and drilled through the plywood and aluminum frame, every 10" for the length, and 3 times per leg. During final assembly I will use carriage bolts to secure the walls to the frame, and butyl tape in the inside joints, to help seal, and waterproof the topper.

the aluminum frame is pretty minimalist, so I have made "auxiliary" frame pieces out of 1x1 boards, that are attached to the walls on either side of the window, and are not fastened to the aluminum frame. I am also in the process of making 2 intermediate roof supports that do attach to the aluminum frame, also from 1x1 board.

Home Depot also sells a camper gasket, in the weatherstripping section that will go between the bed rails and the wooden base.


Attaching topper to bed

Now this build could probably be used with the clamps for toppers, since the aluminum legs come down toward the outside of the 2x4 base, and there is a ledge inside, however in the effort of saving some money, I will be attaching the topper a different way. My truck has the rails with sliding loops, on the side and front of the bed. In total I just have 4 however I think that will be plenty. I have 4 roof straps that will be bent at 90 Degree angles, and fastened to the 2x4 base, and then hang down over those rails. The sliding pieces come apart, and can be threaded through a hold drilled in the strap and then tightened down on the strap. Because I'm taking the sliding pieces apart to thread them through a hole, instead of cutting a channel in the strap, there will be metal on all sides of the bolt that attaches the slider to the rail. I think that this will be more than sufficient to hold the topper on, and if the topper is experiencing forces that rip the bed rails off, then there is a much bigger problem going on and I think the topper flying off will be the least of my worries haha. Although if anyone has a better idea I would love to hear it!

anyway, this concludes my progress so far. I'll be back at it tomorrow.

 

Also.. the front and rear of the topper will be cut from 3/16" LEXAN polycarbonate sheet. I got it from Polymer Shapers, which has a warehouse very close to my house, and paid $115 for a 48"x 96" sheet, rather than $178 for the 36"x 48" one that Home Depot sells...
Id Highly recommend finding the supplier warehouses, rather than paying retailer prices, even if you have to drive a bit

 

The last few photos

 

Nice job so far. How much do you think this will weigh?

 

It is super light right now, ill try and get a weight tomorrow when i re-assemble it. The aluminum is super light and I used fairly thin plywood. But just guessing i cant imagine it weighs more than 30 lbs? The aluminum weighs ~5lbs and the plywood is lightweight. The only heavy part is the lexan than I have yet to cut down.

 

Ok so i finished it... not light in the slightest probably 50lbs. Not more than that tho.. but it tured out great and looks clean and good. Ill post the 2nd half of the process soon when I dont have work

 

50lbs is nothing. You did good and you also have great craftsmanship.

 

Nice! Looking forward to seeing the final work!

 

I admire your ingenuity, also curious to see how it came out.

 

Looks good. I do have one suggestion. Coat all of the wood with fiberglass resin so seal it completely. It's going to suck in moisture and warp, especially from the ends of the framing lumbar and the edges of the plywood. By coating it with resin it'll basically be encased in plastic.

 

Thank you!

 

Ok part 2:

So after the frame was built i added wall supports on either side of the window made of 2×4s ripped down to about 3/4×3/4. Theyre fixed to the aluminum top beam with an L bracket and to thr bottom rail with deck screws.
For the auxillary top supports, i had to cut a weird angle at the end so they fit on the aluminum. I then drilled through the outside wall, the aluminum top bar and the auxillary roof support and used a carriage bolt. Ill post a picture.

The challenging part was the lexan windows. I got a 4'×8' piece for $120 from the supplier and was able to get both windows out of it with enough to maybe put in a skylight later on. I cut thr lexan using my circular saw, and a jigsaw for a few more small cuts. On the front i just drilled it and the aluminum, used carriage bolts again, with fender washers so it doesnt crack the lexan when tightened down. I used 3/16" thick panes, that are UV treated. The supplier, Polymer Shapes, offers 1/4" and 3/8" but they're much more expensive. I used butyl tape for the seal between the window and front of the frame.


The back gate... this was a challenging part. I was short on time because i needed to finish the topper in time for a trip, and had to change my original plans for the door a lot. I originally planned to have a rectangular window inside a trapezoid plywood. I ended up making the entire gate a lexan piece. Its a trapezoid to the bottom of the 2×4 base, and then has a small lip gping down to bring it flush with the tailgate.

Im sure yall all know, the top of the tailgate is ~1/2" shorter than thrle sides of the bed. So the lip is to account for this. I then attached a plywood strip at the top and bottom of the lexan using bolts, and locking nuts. I cut the extra off so when you are going in and out you dont cut your head open on the sharp bolt sticking down. I used 2 10" piano hinges to attach it to the top. There is a lexan strip mounted to the back width piece of aluminum so the hinge is flat against the back and does not go over the roof.

The door is flush with the tailgate and on the sides I used metal roofing gasket to create a seal. It is super good and the adhesive side is WAY stickier than thr camper seal. I definitely recommend it.

I also bought an RV exaust fan and installed it in the center at the front of the topper.

Once everything was cut and drilled. I painted the plywood with Killz primer and assembled. I used butyl tape inn all joints, where the roof met the top of the frame, where rhe walls met the sides of the frame, around the windows, around the fan. I also put silicone caulk on the ouside if the joints where the walls meet the roof so it looks less like 2 pieces of plywood. The entire thing I then painted in Elastomeric Roof Coating. I used a very thick coat. After the roof coating dried i installed the windows and put the lexan panes on.

The side windows i had just drilled through the aluminum frame of the window and the plywood and bolted them in. Although once the gasket was in , the hole i cut for them was so tight, getting them out would be a challenge.

I wanted to tint the back gate lexan panel But i learned you cant tint lexan on account of its always off-gassing as plastic does and tint does not allow for the gas to escape. And the reaction between the tint adhesive can create a milky fluid that builds up in the bubbles and can create a permanant bond between the lexan and the tint... so i just used static cling from autozone. Gila makes one for like $20. The application solution is just a little bit of mild soap in some water so i mixed it up myself instead of buying the 13$ bottle they sell and it worked great..

To latch the gate i used those RV storage door latches, and put rotating hasps on the inside so if someone is inside they can latch the hasp and it cant be opened from the outside. I dont have a locking tailgate so i jerry rigged a ratchet strap. It just goes around the leg of the cot i built into the back and loops through itself. Someone dedicated could get in but it wouldnt be quick/easy/quiet.


Now i took the little fan propeller off and flipped it around so instead of pulling air out it acts like a mini ceiling fan and blows air in. I also installed an old solar panel on to the middle of the top. I attached a solar panel controller to the inside front and wired in the panel, the fan and one of those Optima car batteries. So the panel charges the battery and then can run the fan/charge phones. Last nigjt was my first night sleeping in it outside of Paducah Kentucky and its was HOT outside but the fan kept me so nice and cool. Furthermore the FL sun charged that battery so much it didnt drop but a tiny bit all night. I used an Optima battery because its totally enclosed (you have to screw the terminals in) and i was told it doesnt vent like regular ones.

Anyway sorry this is rushed im sitting in the topper right now in St Louis on my way to Grand Tetons and then on to Lake Tahoe-> san francisco -> crater lake -> missoula MT and bozeman then back home to orlando FL!
Ill post some some pictures from the journey!

 

thats legit, man, cant believe the low weight too

 

Finished topper in view of the st louis arch

 

Thank yoy! Im so excited about it