Board strength

[SavannahLion]

It's not arcade related.

I have to build a custom loft bed for my step. Generally, when I built furniture as a bachelor, I really didn't give much of a rats ass as to appearance. Bolt/screw/nail a bunch of 2x4's together into something resembling my functional needs and I was reasonably happy. By the time I moved out of my old pad, I had one bedroom outfitted with wall-to-wall shelving... NOT around the room but throughout.

But now, I've been asked to construct a loft bed... and make it look nice. Due to the requests presented before me by the boss girlfriend, the side rails are to be cut in a water-like pattern. Oikes.

My question. I figure that her bed measures 39" x 78". According to my measurements of loft beds I've spotted at stores like Ikea and the like and examples I've looked up on the internet. 1 1/4" x 8" side panels to make up the bed box should be adequate with a 2"x2" or 2"x~3-4" "lip" should be adequate enough to prevent the wood from bowing as well as provide support for the mattress. But they want a pretty pattern cut into the side board which would necessitate me increasing the width to 12" or even 18" wide planks to ensure I have enough untouched 8" plank to prevent compromising the integrity of the mattress box.

If I elect to use a good 1"+ ply with a nice veneer for the box sides, will that give me the strength I'm looking for? I have never tried to span a minimum distance of 78" without bracing every 18". Bracing of the kind which is not an option here.

I've seen pictures of the Ikea loft beds built like this and Ikea notorious for using engineered wood. I'll have physically go to the showroom and see if it's really engineered wood or natural.

[Neverending Project]

If I understand your question correctly, you are asking about lumber to span the length of the bed without bowing? Most lumber on its side will not bow. Imagine the side 1x lumber you are suggesting using for the rail... if you put it flat it will bow like crazy, but turn it on its side and you could stand in the middle without it flexing. When you add some 2x4 lumber to the inside of the face-frame to support your slats, you should have plenty of strength.

Most beds, lofts included, are just frames with slats spaced across the width. The slats disperse the weight evenly. Often you will find a runner going down the middle (the long way) of the frame to help support the slats. If it is a loft, you would just need to anchor the 4 corners to your posts, and the rest should be the same. The only exception may be that you want some diagonal cross braces to keep the loft from swaying, especially if there is no bed on the bottom to help keep it square.

I know this sounds pretty vague, but there really isn't much of a difference between a regular bed frame and a loft bed frame. Have you considered looking for some plans online, and modifying to your taste? A quick google showed me these plans for $4.

Good luck.

[Edit] Oh, and if it is from Ikea, it is most certainly laminated particle board, or some sort of engineered lumber. Gluing your frame together at the corners will help make it more stable than sides anchored with locking hardware.

[sstorkel]

Don't cut the pretty pattern into the sides. Cut the pretty pattern into 1/4" or 1/2" plywood, then glue it to whatever material you do use for the sides. That will give you some more flexibility with materials.

In my experience, there are two big challenges with a loft bed: 1) making sure the middle of the bed doesn't sag, and 2) making sure the bed doesn't sway back and forth. You'll almost certainly need to add some bracing between the bed and the posts if you don't want the thing swaying all over the place. You may also need to run a board down the center of the bed to help support the slats.

What type of joinery are you planning to use? Butt joints with glue and screws might not be enough to keep your loft bed solid over time. You might want to consider bed bolts, pegged mortise and tenon, or another solid joint.

[fjl]

Show us a drawing of what you want to make.

[Blanka]

A general rule is to use 1/30-1/20 of the span as height for the "beams". The width is about half the height. So With a span of 80 inch, you need about 4x2 inch beams. Strenght increases with the 3rd power of the height. This means that the inner part of a beam does not add much, as it is close to the axe of the beam. If you make holes 2 inch round in a 4 inch beam, you only throw away about 12% of the strength! Thats why trussed beams are so efficient!

Your beams are thinner than the suggested 2 inch, 1 inch, so you need about 5x1 inch (it equals 4x2 inch) for equal support. Add another inch or 2 to the height for some extra strength and room for perforations. There are 2 possible issues remaining:
- Risk of pleat: because your beams are thinner, they can fold or kink. So make sure the beams are tied to the bedframe every 10 inches or so
- This only works for the multiplexes! Chipboard is too weak for this. If the shapes are very rough or sharp edged (or not routed very nice), strange tension can occur which adds more risk of tearing. If the shapes have edges that could tear out easily, increase the height of the continuous material at the bottom/top to 2 inches at least.
- Perforations should not be wider than high. As long as the beam looks like a real trussed beam, there is no problem in perforating:

In this image you see how you can perforate a beam. The black dotted line is an imaginary force line. Do not cut that line and keep these lines 1,5-2 inch solid wood everywhere. 1.5 inch if it is a perfect 45 degree truss, up to 2 inch if it has variation in triangle size. It does not have to be like this exactly. Angles of any section can be anywhere between 30 and 60 degrees without much problems and the different triangles can have different widths. Leave at least 1.5 inch wood between the cut-outs and the edge. You can cut out quite a bunch of shapes out of your suggested 12x40x1 inch multiplex if you follow these guidelines and your panel will hold up your bed easily. 18 inch is totally nuts! If done really smart, you can even cut the height of the panel to 10 or even 8 inch.