Building a Teardrop Cabin Flush With the Trailer Frame

[mr_trousers]

This might be a naive question, I'm pretty new to this and still working on planning things out. I'm working out of Tony Latham's book, and in that the trailer visibly sits on top of the trailer frame. The Vistabule has the trailer flush to the frame, as in these pictures:

How is this accomplished exactly? And if you're building the exterior from a 4x8 sheet, does it come at the cost of height in the cabin, or would you just build this bottom piece from a separate sheet? And clearly the aluminum siding doesn't extend down past the floor of the trailer - what is the black siding they're using to finish out the bottom?

 

[Tony Latham]

So...

It's much easier to build a cabin that sits on the chassis than one that envelopes the frame. You can build off the chassis – which is a lot easier. If one were to do this, you'll lose 2" of headroom and have to build on the trailer.

Take a look at this video of me loading the cabin:

And this video of me working on it, minus the chassis:

I've built on the trailer, and I'll never do it again. Vistuble pulls the wheels and supports the chassis with jack stands, but they still have to deal with the tongue. What's a bit odd, I think, is that Vistuble adds the black strip that, in a sense, mimics the chassis.

Happy building, and don't be shy with questions.

Tony

 

[mr_trousers]

So...

It's much easier to build a cabin that sits on the chassis than one that envelopes the frame. You can build off the chassis – which is a lot easier. If one were to do this, you'll lose 2" of headroom and have to build on the trailer.

Take a look at this video of me loading the cabin:

And this video of me working on it, minus the chassis:

I've built on the trailer, and I'll never do it again. Vistuble pulls the wheels and supports the chassis with jack stands, but they still have to deal with the tongue. What's a bit odd, I think, is that Vistuble adds the black strip that, in a sense, mimics the chassis.

Happy building, and don't be shy with questions.

Tony

Thanks for the response, Tony. I'm convinced by your argument on building off the chassis, but I don't think it's an option for me. Having no welding experience, were I to practice for some time I would not be comfortable trusting my welds for any core structural parts of the trailer. And as for ordering a custom trailer frame, I've gotten one quote at around $5k, and been given no response from the other five or so companies I messaged...

My best alternative therefore seems to be the Harbor Freight 5x10 trailer, and not having custom mounting brackets like you've indicated, I would have to bolt the floor directly to the frame and then attach the walls on top of those bolts and not be able to build it off the chassis. It introduces some other complications I'm still trying to wrap my head around. For example, the crossbeams are not level with the main trailer frame - so do I build with a gap between floor and crossbeams and add wood spacers to bridge the gap over each beam, or do I build the lower layer of the floor smaller to fit within the frame with a top layer that sits on top of the frame?

But as far as the main question of building flush with the frame on the exterior, I was thinking that to avoid having to sacrifice interior cabin height, I could further the strategy you used to extend horizontally past 8' of connecting another piece via spline joint. Here I would have to add a third piece to my outer wall only, a strip of some 6-12" that would extend the vertical height to cover both the floor as in your model but also the trailer frame. The two issues with this HF frame and that idea are the exterior bolt heads, which I would either have to build wide enough to clear, or drill insets along the inside of the wall to account for; and the fenders which are flush to the frame. But there I think some amateurish welding to attach new fenders would be within my reach, as that's not a major structural area. It looks like the bracket to connect the fenders is on top of the frame anyway, and would be in the way of it the floor lying flat, so the stock fenders might have to go either way.

On the other hand, one small benefit of using this HF trailer is that the tongue actually sits below the rest of the frame, so I could curve the roof around to be flush with the front of the flame without having to contend with the tongue.

I'd love any suggestions you have on any of these dilemmas!

 

[Tony Latham]

It looks like the bracket to connect the fenders is on top of the frame

I now recommend welding the fender brackets underneath the chassis frame instead of butting them.

As for the HF crossmembers not being level with the rest of the frame, you can solve that issue by adding that elevation to the cabin. Just seal the entire floor with epoxy.

Six-bits says you could take the trailer to a welding shop and they'd add attachment points for a reasonable cost.

Tony

 

[mr_trousers]

As for the HF crossmembers not being level with the rest of the frame, you can solve that issue by adding that elevation to the cabin. Just seal the entire floor with epoxy.

Could you elaborate on that? Are you saying to just build the floor within the inset of the frame, and then epoxy over the wood and frame together? Wouldn't that potentially leave the walls on top of the frame with nothing to screw into?

Just having the mounting brackets welded on is very wise. I wish I'd thought of that lol.

I guess then the main problem left with trying to cover the frame would be assembly of the walls onto the floor, with the low-hanging overhangs, but I suppose I could build it on top of a wood frame that keeps the overhangs off the floor.

 

[Tony Latham]

Are you saying to just build the floor within the inset of the frame, and then epoxy over the wood and frame together?

No. Add 1/8" strips (or whatever depth is needed) to the bottom of the floor so it contacts the top of the crossmembers.

Does that make sense?

Tony

 

[Rich796]

You can probably just run a center " beam " ( or a pair of them ) front to back. Supported on the cross braces. To match the height of the top rails. Made from either steel square tube or epoxy sealed wood. Then you can slide the cabin, on and off as needed.

The dimensions shown in the trailer link. Indicate that there is a 3/4" gap, between the outer frame rail, and the fenders.

 

[Pmullen503]

For my last build I used UHWM PE to make "washers" to take up the space between the floor and the cross members. About 2"x4" with a hole in the center for the bolt.

 

[mr_trousers]

No. Add 1/8" strips (or whatever depth is needed) to the bottom of the floor so it contacts the top of the crossmembers.

Does that make sense?

Tony

Yes it does - thanks for the clarification.

You can probably just run a center " beam " ( or a pair of them ) front to back. Supported on the cross braces. To match the height of the top rails. Made from either steel square tube or epoxy sealed wood. Then you can slide the cabin, on and off as needed.

The dimensions shown in the trailer link. Indicate that there is a 3/4" gap, between the outer frame rail, and the fenders.

That's a great idea, but I'll be trying to do subfloor storage/foot wells and I imagine the beams would get in the way, unless perhaps I run the beams on the far outside edges of the floor base...


I'm not sure about the plastic washers, I don't think my floor would be bolted to the crossmembers if I did the mounting brackets as Tony's method suggests, it would just be attached at the brackets, so that may not work.

 

[Pmullen503]

...........
I'm not sure about the plastic washers, I don't think my floor would be bolted to the crossmembers if I did the mounting brackets as Tony's method suggests, it would just be attached at the brackets, so that may not work.

I've used the lighter 4x8 HF trailers which are pretty flimsy. The cabin functions to stiffen up the trailer so I bolted down the center as well as along the rails.

The 5 x10 looks heavier so that may not be necessary.

 

[mr_trousers]

As far as what exactly that bottom strip is made of, am I right to suppose it might be some kind of truck bed liner like Raptor Liner? If so, would it make sense to apply not just to the bottom sixish edges of the wall, but to the underside of the floor as well?

 

[kipa]

Could you elaborate on that? Are you saying to just build the floor within the inset of the frame, and then epoxy over the wood and frame together? Wouldn't that potentially leave the walls on top of the frame with nothing to screw into?

My solution to the floor height was to build an extra 1" layer of XPS into my floor that sits within the outer frame. It also does the job of locating it into the frame, so all the hold down bolts need to do is keep it from lifting up with practically no lateral load placed on them during travel.

It obviously doesn't reclaim any space below the rails, but it made that part simple to deal with.