Modeling with Foamcore


I’m currently in my very first design class. Our project was to make a box that would hold our future models. It is to be made with foamcore. Our instructor only showed us one way to join foamcores together which was the rabbet joint. I found this wiki page and was wondering whether the miter joint would be more structurally sound for such a box?

I like to think that the miter might just be a little stronger than the rabbet because it seems like the rabbet is hanging on to that small piece of paper whereas the miter rests on the foamcore.


Probably. It depends on how well you cut the miters.

I like the “full radius” edge, done by removing the paper and crushing the foam on the inside of the edge, then bending the wall.

… why don’t you take some scrap and do individual tests of ALL of the joints and see for yourself? You’re already being inquisitive … that’s good thing.

Having said that… I’m with slippy. This technique is sometimes referred to as “groove-folding” ; commonly used in stereo speaker assembly where the “paper” is calendared vinyl (usually wood grain texture), and the “foam” is compressed wood fiber. Two things you would have to be careful with on this joint: a) don’t cut too deep when removing some of the foam (it will bend easier) or it will look like hell, and b) make sure that your “grooves” are square with the edge of the stock so that they will bend accurately.

Hot glue is okay… but will look like crap when it oozes out of the joint. It also cools very quickly and isn’t too forgiving of making adjustments. I think I’d use 5-minute epoxy, and green masking tape to hold it together while the glue cures. Green tape is much less “tacky” than regular masking tape and is less likely to stick to the paper surface of the foamcore (which usually ends up tearing up the surface (not exactly a “designerly” detail to be sure)).

Detail-wise… fitting the bottom using the “rabbet” would give you a nice finish all the way to the edge.

I just finished the base of my box right now and I used rabbet joints. I also tried out miters on my sketch models and wasn’t very successful so I stuck with the rabbets. I’ll try the full radius after I finish my box. Thanks for the tips!

I only used the seamless miter joint in uni. How do you screw it up?

well, using a #11 xacto instead of a mat cutter, for one!