Safety and durability concerns with design

[rosellem]

Hello all. I'm looking into building my first trailer and I have some questions about whether the design I want to build will be safe and will not be too flimsy/weak.

I'm planning on building something roughly like the Coachmen Clipper ( https://www.trailerlife.com/wp-content/ ... or-web.jpg ) that has the rear pop-up so I can have an area tall enough for me to stand up in. It'll be all wood though, no metal siding or framing (this will be my first trailer build, but I have experience with woodworking) and simpler overall.

I have a 4x8 trailer and would like to build it 5x8, with 6 inches of overhang on either side. I'd also like it to be 5ft tall in the front. Seems like most people go with a 4ft peak height, so I am wondering, will it be too top heavy at 5ft? And will the overhang work?

I am also hoping to make the rear open down to create like a back "patio" and that will create issues with supporting the side walls, but I'm less worried about that.

Thank you for the help!

[airdonut41]

I think you don't have enough information here to make a clear assessment. A few comments that come to mind:
1) Center of mass is critical. If you have a very heavy canvas hatch structure high on your trailer, then you'll lose stability for things like wind and road handling. The higher your CoM is relative to the width of your trailer, the more likely you are to roll it onto its side.
2) Too flimsy/weak is entirely a question of how you build it. For me (and I suspect many people on here), the 4' height made sense because it can be easily built from a continuous piece of standard (4'x8') plywood. That makes cutting the tear shape much easier and makes it easier to build a strong structure.
Given the complexity of what you're thinking about here, I'd strongly recommend making some drawings of how you imagine this might go together. The clearer and more detailed the drawing, the better feedback we'll be able to give!

[tony.latham]

I am also hoping to make the rear open down to create like a back "patio" and that will create issues with supporting the side walls, but I'm less worried about that.

A traditional teardrop has a shearwall fore and aft. The rear shearwall is the bulkhead. It ties the walls together and keeps the structure square. The countertop also ties the walls together almost to the rear of the galley.



The Clipper has two small walls on either side of the door --that I suppose act as shearwalls. I think if you had a drop-down patio, the walls would flex. Flexing members cause failures.



Tony

[JasenC]

As stated the build technique will make or break you.
I'm getting ready to start my build and I'm building outside of the typical 4x8 platform.
Beef up your opening framing, maybe even upgrade to something better then framing lumber in this area like ash, oak, maple to name a few, maybe even a little aluminum angle imbedded.
Some 1/2 lap and other locking joinery will really strengthen things up.
For the hatch I'd go full on torsion box with beefed up load points. Don't think I'd go thinner then a quality 1/4 ply but you could do some tests with 1/8.
I'd also use the same thickness ply on both sides to help keep it balanced against the natural moisture cycles of the wood.
You should be able to keep this no thicker than 1.5" and possibly thinner with the some testing and amount of internal blocking.
Don't see why you can't go with a rear patio, I'd make it swing to the ground and use the BAL stabilizers, all around, no guy wires or chains adding stress to your camper.
The other tricky part is at the hinge, with the top up all the water is going right there. Maybe you could overly the hinge area with a UV stable rubber bounded/covered/sealed to the roof and running long at the ends at the sides of the camper?
Might think about moving the axle back a tad, I'm not super knowledgeable on this as others here are.

[MickinOz]

The Clipper has two small walls on either side of the door --that I suppose act as shearwalls. I think if you had a drop-down patio, the walls would flex. Flexing members cause failures.



Tony

What Tony said. Even the best quality hardwood marine plywood I could get has needed to be tied together by the bulk head and the counter top to remain straight stable.
I think it could be done, but some smart design will be required.