Extending the floor space on a HF Superduty

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Extending the floor space on a HF Superduty

Postby ToadSprockett » Fri Jul 10, 2015 10:20 pm

Found an already assembled HF superduty today, they built it and never did anything with it. I got it for less than I would have paid at HF, so I consider that a steal ;)

I stripped off all the lights and wiring, removed the fenders and checked everything out. So far so good, I'm going to put some floor stringers in to give the floorboard a good solid base, I'm planning on using 1/4" OSB, glued to a foam backing.

The one question I'm struggling with is that we want to extend the floor to 5x10, I've seen builds where they use 2x4's glued and bolted to the sides to do this. I can't weld, so this seems like a good solid option, are there any gotcha's to look out for before I commit??

Thanks

-Paul-
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Re: Extending the floor space on a HF Superduty

Postby KCStudly » Sun Jul 12, 2015 10:27 am

I take it you are talking about slabbing wood onto the outside of the trailer frame main rails flush to the existing tops, then building your floor on top. Another option would be to build the wood rails as cleats added onto the floor and then drop the whole assembly onto the trailer frame. So long as the galley and front wall bulkheads cross and are supported by the steel trailer frame, the cabin structure will hold the floor up just fine. Remember, the unity of the cabin will do more to strengthen the steel frame, than the steel frame will do to strengthen the cabin. The cabin is a deep structural box section, whereas the trailer frame is a "floppy" wafer (relatively speaking from an engineering perspective).

All of the usual weather proofing comments need to be inserted here. Seal the wood really well with epoxy, or "the mix" (50/50 poly/mineral spirits) and exterior paint after you drill the holes for your fasteners (soak the holes well with the mix, even to the point of taping one side and filling the holes up and letting it soak for several minutes). (I am not a fan of the black gooey stuff.)

If you do decide to scab on wooden rails, consider using some small standoffs to space the wood off of the steel, maybe well treated squares of 1/2 inch ply, so that moisture is less likely to be trapped between the wood and steel; but then again you will need to look at your overall width to be sure you aren't making a lot of waste when you get to your ceiling and roof panel spans/stock sizes.

Consider using 1x3's or 1x4's instead of 2x4's The strength comes mostly from the installed depth, not the installed width, and you need to keep an eye on tire sidewall clearance.

I am of the school of thought that builds the cabin in the shop and then marries it to the trailer. I like to build as much as I can on the bench and then assemble. I feel it is easier to build this way and am not concerned with skirting or trying to hide the trailer frame (which could still be done). You could do it either way, or mix and match. In order of my preference; incorporating the rails into the floor of the cabin and then placing the assembly (allow a little clearance between wood and steel rails and don't bother fastening them together); scabbing the wooden rails onto the steel and then placing the built cabin on top; or stick building on top of the trailer and having to work around it while climbing in and out building a ship in a bottle. YPYMYTYC (you pays your money, you takes your choice).
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Re: Extending the floor space on a HF Superduty

Postby pohukai » Sun Jul 12, 2015 11:00 am

I used a 2x4 frame and used counter sunk carriage bolts from the top to attach it to the trailer. The only thing I'd do different would be to use carriage bolt washers to prevent the square of the bolt from 'rounding' the hole when it draws up tight. This problem only happened on 2 or 3 of the bolts and solve by glue the bolt head in place. My camper is really solid!
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Re: Extending the floor space on a HF Superduty

Postby Woodbutcher » Sun Jul 12, 2015 11:36 am

This is what I did. All 3/4" exterior plywood on the HF trailer.

TOP...

Image

Bottom....You can see the filler shims that get you above the bolts and keep all the weight on the frame.

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Re: Extending the floor space on a HF Superduty

Postby dales133 » Sun Jul 12, 2015 11:49 am

Nice work, I see you know what your doing
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Re: Extending the floor space on a HF Superduty

Postby ToadSprockett » Tue Jul 14, 2015 8:19 am

Thank you for the information, we laid the cabin out saturday, I was able to pick up some 2x4 lumber for a very cheap price. I spent part of saturday milling it down to about 2-1/4 x 1-1/4, that way it pretty much matched the frame and made it a little lighter. I ended up slabbing the extension to the side of the trailer, bolting that on and using sub flooring adhesive to glue it up, it worked out really well. Tonight I'll start on the back and getting it laid in, I'm going to put 3/8" ply for the floor and nothing else. I'm also adding a dropped floor in the front so we can sit on the bed and watch TV, I'll epoxy the underside and all the joints, and then add a thick coat of car undercoating.

Total width is 63", I'll also add built in fenders for the wheels using the factory ones as a template. The only other addition will be two 2x2 steel tubes under the front part of the frame so I can weld on some steps to each side where the door is (otherwise it will be hard for my wife to get in). So far I'm very happy with the progress, once I box in the frame with the flooring it will strengthen the whole trailer immensely...

I'll post some pictures when I get home tonight..
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