Modified RangeRunner-Style Foamie Build on Harbor Freight Trailer

[heyheyfifi]

Starting my first build! I'll be making a foamie 6'4" x 8' design on a 4x8 harbor freight trailer. The goals of the project are to be low cost, low weight, and simple construction.

The design is heavily influenced by the Runaway RangeRunner design. They have a curvy roof 42" high on the sides and 46" high in the middle. My design has 45.5" headroom on the low side and 51" on the tall side. The RR is 70.5" wide on the inside and mine will be 73" on in the inside. The people in the model are 5'4" and 5'10".

Using 48" foam sheets I'm increasing the headroom using 2x2s on the edges, which also adds to strength. I will be making the doors (wish me luck!) which will span between the 2x2s. There will be 3 doors. The door on the back end will be a little off kilter because I had already purchased a window before finalizing the design. No galley because it seemed really complicated and the way I camp I don't see it being very useful. We'll be making a chuck box. The framing on the trailer will be made with 2x3s with a sheet of plywood on both sides, leaving room for the tires after removing the fenders. There are 2x4s on the corners for strength and to add some D-clamps to tie down a canoe or a few kayak to. The foam on the sides will be 1.5" and the foam on the roof will be 2". I'm estimating the total weight of the empty camper will be around 650 lbs, with about 150lbs of cabinetry (still thinking through), and few hundred pound of our stuff, with a tow vehicle that can pull 1,500 lbs.

I'm hoping to finish this in 2 months or less, we'll see what happens!

 

[Pmullen503]

Consider moving the mattress to the front and swapping the position of your side door and window. You'll have better access to cargo through the rear door and it will be easier to get in and out of bed if you can just swing your legs in and out rather than crawling around.

There's reason most TDs have the door positioned just in front of the wheels.

 

[heyheyfifi]

Thanks for the advice but I’m set on this design.

To start with the bottom will be 1/2” ply then 2x3 then 1/2” ply. This elevated the top floor piece of plywood 3 inches above the frame which is the same height that the metal wheel well was. I looked around tnttt for info about how much clearance you need above a well and found about 3” is good, with some people saying that 2” is close but fine.

On the trailer I took off the wheel wells and started to lay out the 2x3 framing. It’s made of 4 pieces of 6’4”, the sides are 2’3” then 2’ then 3’3”. My trailer seems a bit weird so all the next measurements were done with the trailer rather than measuring. I added 5 cross bars and put them over where they would have a hole to bolt into them. The cross bars are flat to make it easier to bolt in. I got under the trailer and used a bolt with some coffee on it to mark locations of the bolts. I drilled a small hole and hopefully it’ll match again when it’s all done.

 

[heyheyfifi]

Ok I’ve got the frame on the trailer now and have a few lessons learned.

Trailer: I got tractor farm and implement paint for the trailer to go on top of the rust reformer, and I really should have read more about this paint because you need to have the perfect conditions for it, so the paint on the trailer came out terribly but whatever it’s fine enough.

Design: I changed my wood frame design so that there’s a spot for the roof foam to rest on both sides, I had had it on only one. Necessary!

Framing: need to use cross members as stabilizers while setting up all the wooden bits, 2x2 is small as ****.

So we got the trailer painted, the plywood glued and screwed to the bottom of the frame, painted the underside of the plywood with exterior paint, used Pl premium to ask help with some waterproofing on the grain, bolted it down to the trailer. Cut 1.5 in and 1in foam to fill in the cavity, then screwed down with a top layer of 1/2 in plywood. In hindsight I would have left 1 board full and made a 2’4” x 8” board but oh well.

On the roof I’m going to put in some 45 degrees cross bracing at the corners.

It’s all bolted down and ready for foam! At this point I feel like I very much understand why it’s recommended to make the whole structure out of foam only but I hope this will be very strong.