Clamping a 2x4 to the bed rails of a 3rd gen

Hey y’all,

I’m preparing to build a diy truck cap but conceptually I can’t wrap my head around safely fastening it to the bed. The base will be a 2x4 but the clamps I got just can’t quite wrap the size. Has anyone found a clamp that will reach this size?

I’ve got options, I suppose I could rip the 2x4s down a half inch or make notches to fit. But would prefer a clamp to just take the full 2x4.

 

angle iron would work better as a base

 

I’m a carpenter and my tools reflect that. Fastening the walls to angle iron would probably require many tools I dont own, drill press/grinder/torch? Jeepers..

 

Wood is heavy, and heavier when wet.

I would recommend aluminum or steel.
Use a “T” shape, that way you can bolt i straight onto the stock bed rails, and that way you can use the other vertical piece to bolt onto your canopy walls.

Alternatively, Angle iron works too, I would thru bolt it onto the bed holes that come from the factory.
Or two Pieces of angle iron thru bolted or welded together.



You can easily drill thru aluminum with a drill bit as a pilot hole and use a Christmas tree bit (stepped drill bit) to make the holes to any size you want.

 

I appreciate your comment and suggestion, I’m However hoping to find a resolution based around my original post. 2 sheets of marine grade plywood and treated 2x4s is a weight I’m comfortable with on my truck.

pulling off the bed rails and bolting through is maybe something worth considering though.

 

Shells have tabs molded into the base that overhang the bed rail with bolts that go through the tab down to a hook that grabs the bed rail track. Easy enough to add tabs (straight or T-strap) to the 2 x 4’s or z-tabs if you want shorter boots. The hooks are just a j-strap with a threaded rod connector bolt welded on(like a long nut).

 

So you have wood clamps, a drill, and a screw?

Clamp the angle iron to a piece of wood.

Figure out where you want the center of the hole to be. Line up the end of a screw there.

Hit it with a hammer. That is your "center punch" to keep the drill from wandering.

After that use your drill bit (or get a step drill $15 bit) and drill your holes.

Cut it to the size you want with a metal saw ($15)

Prime and spray paint it so it won't rust.

You don't need a welder or anything to use angle iron.

 

If you use those clamps I would plow a channel in the 2x so the clamp can’t slip and add a lock nut where the bolt threads into the tapped hook so the bolt can’t loosen.

 

This is good advice thanks. However, my intention is to structurally build this like a house for lack of better words. (I’m sort of thinking out loud) This opens up some design concerns.. if I intended to have studs especially for the frame of a window, I’m competing for fastening real estate. I suppose I could put some kind of bracket or pieces of angle iron to hold the vertical 2x2’s but I’m falling into an area of necessity for a welder and grinder.

 

I don't think you'll necessarily need an angle grinder or anything, you don't really need to nicely round over any edges or make things have a perfect 45, any kind of deeperring you need to do you can accomplish in a few seconds with a belt sander or just using sandpaper with your hands.

I do feel it would be important to incorporate some angle iron around the base though, the reason being is the smaller of a clamp you can use to clamp it to your bed, the less leverage will be acting on that clamp, allowing it to hold your (stupid heavy) frame and timber building to your bed.

Cut some angle iron to length, bolt it to your two by twos, and clamp the flat part of the angle iron to your bed so you're only trying to clamp down like an inch, not 4 inches.

 

stupid heavy is a common misconception. After weight budgeting for design I’m clocked at under 250 pounds. For comparison, fiberglass toppers are at a range of 200-350.

I’m starting to think ripping down a 2x4 a quarter inch and notching might be a better direction.

 

I respect your desire to wood fab a topper. There’s more than a couple unique ones I’ve seen up here. The only ones that seem to last multiple years as a community oddity are the ones fully done out “like a house”, siding of some kind, legit roof; shingle or metal…
I personally don’t think the juice is worth the squeeze since without fully protecting the frame, it will be essentially be just a temporary structure.
+1 for attaching the wooden frame to the truck with metal in some way. The thought of rotten wood failing at the clamp points, at speed, on the highway would have me designing something a little more robust to attach to.

 

I think you have lots of options. If you really want to use clamps, I would notch the 2x4 locally, and add a doubler of aluminum or even steel on the edge of the 2x4 spanning the notched section that’s a few inches longer than the notch. If you notch it 1/2” down you have room for a 1” reinforcement. Aluminum angle recessed into the 2x4 would be even better. Or look at Simpson StrongTie TA staircase angle.
https://www.strongtie.com/decks_decksandfences/ta_angle/p/ta
Use a chisel to remove the steel thickness on the inside and bottom of the 2x4 so it sits flush and that’s plenty beefy. But 1/8-1/4” thick aluminum can be cut with a woodworking blade on a chop saw or miter saw and easily drilled with a cordless drill. No special tools required.

 

I think that notching would be the way to go. Using a piece of aluminum bar to reinforce the notch would help the missing wood material and provide strength.

 

Find a way to use standard c-clamps
They would not distort like the ones you are showing

 

are you saying you've never tied into any structural steel in your entire carpentry experience?

i've had to do that as the electrician...

really not that difficult to use angle iron as a base. a few high speed steel drill bits to drill holes, and then run bolts/lags through that to tie into your wood framing, the same as many steel-reinforcement techniques in deck framing methods with an overly-long span between columns.

i made it over 30 years without a welder, doing all sorts of metal projects, i know there's plenty of ways to manage without one in this case as well!

 

In this case it’s probably easier for him to stick with wood/plywood since he can much more easily rip pieces to other than 90 degrees for the base and top seams if he wants to follow the cab profile. Obviously it not only has to withstand static loads but also has to do it at freeway speeds as well so more than an ordinary fastener spec.

 

Have you considered how much this cap is going to get jostled around on the bed of your truck? I'm not sure wood is a good choice. My dad's first cap back in the mid '70's was a wood frame covered with aluminum, like a camper is built. It practically fell apart in about 2 years. The rear door fell off in about a year. There is a reason that all of the commercial units available are aluminum or fiberglass...they are much more structurally sound.

Good for you trying to do for yourself, I just think you may be going in the wrong direction. Maybe you'll prove me wrong.

 

My house is full of self-designed wood structures ... desks, tables, end-tables, towel-racks ...

Flat clamping wood is not a good idea. Screws are needed to fully secure metal to wood. Better is a channel cut into the long-axis of the wood, the clamp going into that. Even better is a strip of metal embedded in that groove ... provides protection against warping-bending and metal bolts through the wood with nuts clamping onto metal on both sides even better.

You want to get away with two pieces of wood screwed together and clamped on the flat surfaces, long lengths NOT prevented from warping on the long axis. Vibration makes screws loosen, 2x4s warp badly (you worked hard to choose a straight 2x4, correct?).

You could pay attention to the engineers who have spent decades doing this ... or do all of the R&D yourself going through all the failures on your own.

EDIT: And if you think butting 2 long 2x<anythings> on the long axis is automatically a good fit ... forget that. You need a good "planer" (hand-fed big-ass machine, not the hand-operated) to get the matting surfces dead-flat.

 

Just rip down the 2x4. It's fully supported along its length so a full 2 x 4 is overkill and it will save a little weight. As for stiffness that others have questioned, the plywood side will add plenty of strength.