Bunk bed question

[stharding1836]

I'm putting bunk beds in my camper. I'm building a hybrid, so I will have 1/4" ply on the outside of the foam walls that will be glued to the foam and screwed into the spars. Then that will be skinned with PMF. The way I'm planning this top bunk is to run the rails through the foam and screw them into the 1/4" ply. Do you think this will be strong enough to support the bunk?

[KennethW]

For bed frames I used regular household bed frames .they are very strong and light. But very hard to drill. (Drill press)

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[tony.latham]

The way I'm planning this top bunk is to run the rails through the foam and screw them into the 1/4" ply.

So you're talking 1/4" ply and 2" foam for your walls?? No matter what thickness of the foam, I don't think 1/4" is going to hold it. Especially if there is foam between the frame and sheathing.

Build some blocking into your wall. But bear in mind, I'm a wood guy, not a foam guy.



T

[KennethW]

For bed frames I used regular household bed frames .they are very strong and light. But very hard to drill. (Drill press)

Also use the bed frames as uprights. Why the 1/4 plywood? Just something to rot. I used no wood in my shell.

[stharding1836]

Also use the bed frames as uprights. Why the 1/4 plywood? Just something to rot. I used no wood in my shell.

Mainly for additional structure. This is my first build, and I've never had any experience with foam, so I'm a little nervous. I also felt like I needed the additional support if I was going to tie the bunk beds into the walls.

[KennethW]

just a little inspiration on foam. Here is my build. viewtopic.php?f=50&t=70181

[stharding1836]

just a little inspiration on foam. Here is my build. viewtopic.php?f=50&t=70181

Thanks, This has given me something to think about.

[stharding1836]

Decided to build the bunk bed from the floor up. The top bunk is 28" high and the bottom is 9" high giving me enough room to put a trundle bed under the bottom bunk. The mattress dimensions are 75"L x 28"W. I layed on the top, so I know it's sturdy enough to hold adults.

[KCStudly]

I realize that this ^ is a slightly older posting, but I have some good hands on experience working with 1-1/2 thk foam board and 1/4 inch ply inner skins (actually 5mm or 3/16 inch). My main reasoning was that I wanted the traditional feel of a wooden interior, and didn’t want to try and install PMF on the inside after building the box, but there are great structural benefits to paneling the foam walls, too.

IMO this is a great and sturdy technique, and would easily support a bunk bed without wall studs or dedicated stanchions in a TD sized camper, however I would definitely add some substantial blocking.

Be aware that adding blocking to a foamie can be a proverbial "rabbit hole". I present to you for your consideration TPCE dinosaur puzzle (a 3D computer model image of my hybrid camper design with all of the foam and interior panels "turned off".


You can see the mostly square 1 inch nominally thick blocks (3/4 x 3-1/2 x 3-1/2 actual size) of mostly pine (some poplar) at each of the cabinet rail and galley counter ends. Larger pieces were used for the fender mounts, side table cleats (not shown), and porch lights (on the lights just because they were so close to the corner of the door frame anyway). Figuring out what was needed for everything ahead of time… and there is a lot of stuff to think about… took quite a while. Light switches, coat hooks, interior lighting, exterior lighting, etc., etc…. the cabinet supports were the easiest because they were pre planned. I mostly used pocket screws in the “backs” of the cabinet frames, screwed through the ply and into the hidden blocking. For some other stuff (axe and shovel mounts, and fenders) I am/will be using threaded inserts or T-nuts imbedded into the blocking.

The inside stuff got blocking on the inside of the foam, the outside stuff was on the outside. The only blocking that goes all the way through (AFAIRCATM) was at the door latch.

At several points in the process of routing the pockets into the foam, gluing the blocks in a few at a time, trimming and fairing the (relatively) hard glue without making a shallow in the adjacent soft foam, and wondering if I was forgetting any potential future needs, I wondered if the weight savings was worth all of the extra effort to go foam and to build it this way. I’m sure my camper would have been completed years ago if I had built more traditionally. I’m not slighting foamies here, but the hybrid methods I chose (and my particular attention to details) really added build time to the process. Everything sounds easy to do, and you don’t expect it to take a lot of time, but it adds up.

Mind you that none of this has gone bouncing down the road under load yet, but you can tell how strong it all is once it all starts coming together.

I would think that you could build a much lighter bed frame, perhaps 1x4 on vertical edge with a 3/8 ply deck dadoed in, and then just screw through the head and toe boards into your wall blocking. What you show above looks like 2x framing lumber and heavier ply, which, IMO, is heavy, defeating one of the big advantages to unitized foamie construction. No offense intended.

[Tyrtill]

Do you have any pictures of the routing wood gluing process? Looks like a very involved build maybe you’ve learned some tricks to share from all this work.

[KCStudly]

It kind of starts here with preparing the router for the guide collar (part way down the post)

Continues here (part way down the post), here, here, and here.

Sorry, my build thread is more of a diary than a tutorial, so there is "some" OT stuff and other tasks intermingled. I'm sure there are more posts including using gravity clamps to counteract the GG, etc., but these are in the general area of the build where I was doing that kind of work. Feel free to look around, or even start at the very beginning (link in signature).

[KCStudly]

Here I have skipped over a few posts with tests and initial attempts, and found improved techniques.

Kind of fun reading thru my old posts again.

[KCStudly]

In this post and the next one following it, I do a test of wood glued to foam using TB2, and estimate the shear load that I tested to.

That was what really convinced me that blocking glued into foam behind plywood would be stronger than the screws holding any framework in place.

[Tyrtill]

Good info. So Guerrilla Glue and Titebond 2 both seem to work really well with wood to foam?

[GPW]

That bunk/trundle combination bed is really pretty COOL , and a great utilization of space … ( did you weigh it with mattresses … ? ) I’d like something like that for my house …