Boat Trailer vs. Utility Trailer

[QueticoBill]

I agree with double cantilever, just need a good connection to center that won't let the "front" rotate. I think you mentioned a short angle iron flange to anchor to.

I wondered if you'd considered leaving side walks attached to roof and box, and hinged in middle. Ends would be removable. Just seemed it would fold better. But I'm sure you have considered and was curious your reasoning.

On the trailer, if wheels, hubs, bearings, and axel are good, and not too hard to be better than a lot of low cost utility trailers, I'd stick with it. I do think a stressed skin floor and well connected sides would just about make any frame mods unnecessary. Need to stiffen rear door opening - maybe a down turned "flange" at rear of deck.

Looking forward to seeing progress!

[Paintsalot]

I wondered if you'd considered leaving side walls attached to roof and box, and hinged in middle. Ends would be removable. Just seemed it would fold better. But I'm sure you have considered and was curious your reasoning.

Thanks QB for your thoughts. About the question above- sounds interesting- it just means I would need a mechanical system of pulleys to lift it. Or a genie in a bottle, haha. Whereas If the top/roof is separate I can lift it by hand. So the main reason is simplicity. The sides could still fold in half, but more joints mean less stability I think.
The second reason is the top of the cabin has angled walls, which means the ends have to fold down last if they fold down. Otherwise they will hit the sides. I hadn’t thought of removing the end though. Although if the ends fold up into roof it might be possible.
It’s worth thinking over.

Celadon shared this link earlier- an accordion box.

https://cdn.shopify.com/s/files/1/0106/4684/7547/products/32L_200S_AMAZON_04_1200x.jpg?v=1634940845

Matthew

[OP827]

I think it is possible to build 5x8 camper substantially under 1000lbs including your boat trailer, if you build light with similar techniques like a wooden airplane or a light boat. I agree with KC, that to keep the boat trailer as is, I would build a light 1inch+ thick sandwich (ply+foam+ply) panel floor (with skins not thicker than 3mm). Baltic birch would be a good choice for that, and it comes in 5'x5' sheets. Place stringers/hardpoints inside the floor so the existing trailer frame can be connected to the floor by U-bolts. Reinforced vinyl roof like in Slidavan could be a good choice too to reduce roof weight and rain noise.

[Paintsalot]

Baltic birch would be a good choice for that, and it comes in 5'x5' sheets. Place stringers/hardpoints inside the floor so the existing trailer frame can be connected to the floor by U-bolts.

Sounds good, thanks.
I can get 3mm Baltic birch ply here in Memphis. In the part that gets walked on I could add floor boards. I have some 1”xps and some 1”thick treated deck boards already.
I may use Havelock 2” sheep’s wool insulation in walls. I want to use natural products where I can. Also, recycling materials from other projects is a goal. Maybe no electric or plumbing, except for some kind of port to outside power. Waxed cotton canvas sides, cedar trim.

[QueticoBill]

On the folding side walls, your roof doesn't need to be more than foam and 1/8 inch ply with very light perimeter frame, as discussed above. I imagined you could just lift the top, one side at a time, and insert, unfold, or otherwise stiffen the wall. You only have to stiffen the center hinge line. Maybe front and back fold in first, and hinge line is wall thickness lower than side walls.

Want more "natural" then foam but (nearly) as light and a lot stronger than sheep's wool? Try cork. Would make a great core for a stressed skin panel roof.

[QueticoBill]

On the folding side walls, your roof doesn't need to be more than foam and 1/8 inch ply with very light perimeter frame, as discussed above. I imagined you could just lift the top, one side at a time, and insert, unfold, or otherwise stiffen the wall. You only have to stiffen the center hinge line. Maybe front and back fold in first, and hinge line is wall thickness lower than side walls.

Want more "natural" then foam but (nearly) as light and a lot stronger than sheep's wool? Try cork. Would make a great core for a stressed skin panel roof.

[OP827]

Baltic birch would be a good choice for that, and it comes in 5'x5' sheets. Place stringers/hardpoints inside the floor so the existing trailer frame can be connected to the floor by U-bolts.

Sounds good, thanks.
I can get 3mm Baltic birch ply here in Memphis. In the part that gets walked on I could add floor boards. I have some 1”xps and some 1”thick treated deck boards already.
I may use Havelock 2” sheep’s wool insulation in walls. I want to use natural products where I can. Also, recycling materials from other projects is a goal. Maybe no electric or plumbing, except for some kind of port to outside power. Waxed cotton canvas sides, cedar trim.

I am not sure you'll need to add floor boards on top of floor the sandwich panel, it should be strong enough to walk on. I have built a dinette table as a panel like that and I can walk and jump on it, it feels solid. Worst case, you could glue another 3mm BB ply layer where there is walking happening. Also if the floor is covered with gym floor foam matts, there is less risk of punching a hole if you drop something like a sludge hammer on it. I agree that for 5x8 floor plan no plumbing makes sense. I am interested to learn your ideas of canvas sides and their insulation.

[Paintsalot]

I am interested to learn your ideas of canvas sides and their insulation.

Thanks. The Havelock sheep’s wool insulation is apparently good at managing moisture. According to their website you don’t need a vapor barrier such as tyvek. I’ve written them and asked for their recommendations if I have a canvas exterior.
I will either paint it, or wax the canvas by brushing on melted beeswax.
I made a little model this morning of this caravan idea. https://youtu.be/W3vUmsK7ga4
I am having some doubts as to whether the folding design will be practical to set up.

I am interested in exploring a natural option for the floor. I don’t need insulation really- so I could just use solid wood with tongue and groove joints or shiplap. My brother is recommending I add some welded steel to trailer to support corners.

[KCStudly]

My floor is 5mm (3/16 inch) Okoume, 1-1/2 inch blue foam, 5mm Okoume with 2x2 (1-1/2x1-1/2 actual) and 1x2 (3/4x1-1/2 actual) on edge clear select cedar frame. I didn't want to have a bunch of waste trimming to use partial large sheets, so my plys are broken into several butted panels and my frame has more cross and longs to support these butt joints. Even so, walking or kneeling directly on the 5mm you can feel a little bit of springiness or give to the floor. I mention the extra frame work because I think the springiness would be even slightly more noticeable with fewer (more typical, lighter construction) subframe members. For walking on a regular basis, I would go 1/4 inch minimum, maybe 3/8 in the traffic areas.

I would be leery about that much cantilever with just a 3/4inch deck, especially in tongue and groove.

When my floor was complete, prebuilt off the trailer, 64 wide x 9ft-8+ inches long, I could pick one corner up and as soon as I did the whole panel lifted up pivoting off of the far diagonal corner without any bow or flex. If it had been 3/4 ply it would have bent/flexed. Doesn't weigh anymore, but by moving the outer fibers further apart (1-1/2 inch in lieu of 3/4 inch) the whole thing became much stiffer. Part of that is that the whole thing is glued together homogeneously. If I had used loose fill insulation it wouldn't be anywhere near as rigid. Same for my walls.

The idea of using natural materials is honorable, so long as you don't expect the same performance as modern materials and techniques.

The thing about adding more steel to a trailer is that it doesn't really do much to make the trailer frame deeper in section, unless you add depth to the section (see Bob Henry's extended tongue open web truss as an example... I think it was on the barn build, IRC). 2x trailer frames are only 2x deep, so just adding more steel doesn't necessarily stiffen the "diaphragm". Adding the (relatively) tall stiff (albeit lightly built) box on top does.

[Paintsalot]

Thanks KC for all the helpful input! Yes I agree, I wouldn’t want to extend just 1x material out to the corner, I was thinking of building a 2 x 4 frame at 16”o.c. with the two by fours turned on the flat and then filling in the middle with 1x material flush with top of 2x. Or overlaying on top. This will add extra depth but it would enable me to keep everything natural. I built some wood doors before and am familiar with making strong corner joints using half laps.

The thing about adding more steel to a trailer is that it doesn't really do much to make the trailer frame deeper in section, unless you add depth to the section (see Bob Henry's extended tongue open web truss as an example... I think it was on the barn build, IRC). 2x trailer frames are only 2x deep, so just adding more steel doesn't necessarily stiffen the "diaphragm". Adding the (relatively) tall stiff (albeit lightly built) box on top does.

By adding steel I was thinking of welding on an angle or something like that to extend out to the corners that aren’t very well supported on each side.

Part of me is beginning to think it may be simpler to purchase a new trailer.
I’ll be visiting my brother in a few days for Thanksgiving, we’ll be talking it over.

Cheers,
Matthew

[tony.latham]

Part of me is beginning to think it may be simpler to purchase a new trailer.

Consider drawing up a custom trailer and getting a bid from a fabricator. Every little welding shop builds trailers.

No sense in letting your foundation drive the structure.



Tony

[Paintsalot]

Consider drawing up a custom trailer and getting a bid from a fabricator. Every little welding shop builds trailers.

No sense in letting your foundation drive the structure.

Thanks Tony- good idea. I’ll check into it. 8ft is pretty short in length for a stand up Vardo inspired wagon.

[S. Heisley]

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This guy successfully built a gypsy caravan on a Harbor Freight trailer chassis and goes into detail on how he did it. It is cantilevered on 3 sides plus you can stand up inside.

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