How to attatch wood floor frame to metal trailer frame

[smallcornlife]

Hi there,
I am using the harbor freight foldable trailer frame. The problem I am having is that the trailers cross members sit inside of the side rails. This creates a offset surface between the cross members and the side rails by about 1/8th inch.
I attached a small diagram to explain what is going on.
I plan to bolt the 2x4 frame to the trailer frame, then drill plywood on top of the wood frame. I am using the 2x4 frame so I have something to drill the sides into.
This small gap makes things uneven and not level. I know I do not want to torque the bolts forcing the 2x4 to be level. I may decide to add a shim in the gap under the 2x4 to make it level. Trying to avoid additional weight and material... Maybe there are other options, going to learn a lot of tricks through this build.

What did / would you do?

Thanks,
corny

[KCStudly]

2x4's are more than what is needed, and yes, most people use shims or strips of thin material to make up the difference.

If you are looking for the extra height to get over the fenders, then consider 2x2's. Otherwise 1x's should be all that is needed. Some people don't even use a wood subframe, they just attach the floor directly to the steel and shims, and use a cleat at the floor to wall joint.

Most will say that you can cantilever 6 inches or more w/o a subframe, depending on floor thickness and wall to floor joint style.

[pohukai]

Like you, I used 2x4's and added the shims to the area I wanted contact. I think I have close-up photos in my google page.

https://plus.google.com/photos/109287005282295320233/albums/5746508387867256129/5746512383008153538?banner=pwa&pid=5746512383008153538&oid=109287005282295320233

[smallcornlife]

Okay, good to know.
I am also using the 2x4s to extend the 4x8 frame to 4x10. And using what is free, no 1x1s available... I'm worried using all this reclaimed stuff is going to make for one heavy trailer.. eek.

Great to have some photos to reference, thanks.

[KCStudly]

Got a table saw? Rip 'em down. Just be sure to avoid knots.

[smallcornlife]

Hmm I have a circle saw, maybe I could rip them with some kind of jig

[ctstaas]

Hi Corny,
I have found 1/8" sheet metal strips at most hardware/ building stores and would fill the gaps with those types of things. I would think a 2 foot overhang of your floor attached to your walls would not be excessive without the 2x4 supports.
One thing to consider is your axle placement. Some think your axle should be at 60% to 66% of your cabin length. I'm good with that.
Enjoy, Chris

[bobhenry]

In home construction sill seal is placed between concrete slab and bottom wall plate to conform to small variations in the slab. I had the very problem you are describing when building the barn. I wanted an insulated floor so I placed a layer of 1/2 blue foam and floated a sub floor over the foam. The foam will crush to conform to fill any voids and makes a great water and wind barrier.

[smallcornlife]

I ended up using some pine molding that was labeled as 1/4 in thickness by 1.5 in wide, it was more affordable than aluminum. In reality the molding was 1/8th in thickness and a 4 ft strip was sufficient to cut into smaller pieces.
One thing I noticed is that I believe both my 2x4s and my trailer frame are not straight, but I think the trailer frame is even more off than the wood... I guess that's what china has to offer, I have already gone through a few times and loosened the bolts around the frame to get it as square as I could.
Next step is going to be to apply the ply wood, maybe I'll come back with more questions in a few days, but till then thanks for the help!
corny