back hatch

[mikevet]

starting the wall contruction of my flat back off road overland tear drop. question is about the back hatch. i plan on constructing the entire build from 1/8 ply or luon on inside and outside with styofoam core between the sheets. i was not using any wood skeleton. for the back hatch....can i construct it the same way? my build is 6.5 feet wide by 4 foot tall. so the back will be 5.5 feet wide and 3 feet tall. is the door portion to flimsy with just styrofoam and 1/8th ply? the skin will be fiberglass reinforced epox resin (fiberglass).

[JasenC]

That doesn't really work in my mind, although it'll be pretty sturdy I'd want at least a couple vertical pieces of lumber. It's going to take a bit of stress when your closing it, I'm assume your using gas structs to hold it up. If you over stress it and pop your ply/foam bond you're going to be in a bit of trouble.

[fredo]

what are you doing for hinges? have yohttps://www.youtube.com/watch?v=JSTaxhUqtXku seen this?

[QueticoBill]

Holding it in position while forming will be the hardest part. I'm planning very similar with a rib or blocking along edges. The right adhesive and there should be no concern about bond failure. (I'm planning on 3M 30Nf.) And being ultra light, you don't need gas struts to lift it.

[KCStudly]

I have not been too "thrilled" with the holding power of 30NF when laminating thin ply directly to foam. Sure, it will hold two panels together just fine, but when I destructively tested a cutout, or had to cut away some foam for some blocking the ply joints just seemed to pop right apart, quite easily in fact. I think it wants high pressure, such as from a roller... IIRC, something like 100-200 psi, per the instructions... in order to bond well. The foam is generally only good to 25 psi. I did the typical gravity weight thing on some panels, vacuum bag on others, and hand pressed in a third area; none of which gave 100/ct bond. Am I going to go back, tear my camper apart and start over? No, for my usage I'm okay with the sum of the strength developed. But then again I didn't use it in my hatch, and used perimeter frames with wood glue everywhere that I did us it. Just saying, a light weight perimeter frame of select cedar or poplar would add points to attach hinges and latches. If I were ever to do it again I would follow the advice of one of the great ones, Doug Hodder (RIP) and use a loose slurry of thickened epoxy.

[Pmullen503]

starting the wall contruction of my flat back off road overland tear drop. question is about the back hatch. i plan on constructing the entire build from 1/8 ply or luon on inside and outside with styofoam core between the sheets. i was not using any wood skeleton. for the back hatch....can i construct it the same way? my build is 6.5 feet wide by 4 foot tall. so the back will be 5.5 feet wide and 3 feet tall. is the door portion to flimsy with just styrofoam and 1/8th ply? the skin will be fiberglass reinforced epox resin (fiberglass).

If your hatch is flat rather than curved, then yes. I would use a solid wood perimeter for fasteners for hinges, latch and struts.

You should cover BOTH sides with plywood and fiberglass or your panel will bow.

[twisted lines]

Blocking for hinges, door latches, lighting, screws, fenders, ect. You bet
If you don’t block it it will squeeze for one.
I like a couple good polyurethane tubes that cost substantialy more though