Foamboard Centering Rings

The Rocketry Forum

Help Support The Rocketry Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.


Well-Known Member
Jun 2, 2011
Reaction score
When I say foamboard I'm talking about the "foam sandwhich" which is a layer of foamy stuff laminated in card/paper, the stuff I have is about 4mm thick.

Hopefully you know what I mean, is this stuff suitable to make centering rings out of?

I'm looking to cut a 4 x 24mm (Estes D12's) cluster ring to fit in BT-80 so the material isn't very thick near where the holes are next to the tube and it's got to take F impulse thrust.
I have used foamboard for 29mm in a 6 inch tube. No problem with a G-80.
you could glass the 2 pieces of posterboard to get some strenth, the resin might eat the foam though.
That stuff is cheap anyways. I guess the part that sucks is to build a rocket with it only to find out that it doesn't work. I say go for it. I've used it in some of my 29mm designs. You'll be alright. Just make sure and coat the exposed ends with epoxy or some other flame resistant coat to avoid pitting.
I've found that it's better to use the "cold press" style foam board than "hot press". Hot press is the most common, with the real smooth, shiny white surface. The cold press is usually the foam board that comes in different colors, and has a rough finish. Glue (and epoxy) seems to adhere/soak in better.

And I've never noticed that epoxy resin eats the foam.
I have used a lot of foamboard but it has always been the smooth type. I'll have to check the other out. I mostly avoided the colored boards as I wanted the white color.

Still, I really haven't had any problems with glue coming off. I normally scuff the glued surface up a bit. The normal failure mode is having the paper surface delamiate from the foam. I flew my 24mm cubit on a D12-0 vs the recommended plugged motors. Big mistake. The pressure from the blow through popped the bottom plate off on 2 sides. It wasn't the glue joints that failed it was the internal separation of the foam core sides. The plate was still attached, but only by thin layers of foam ocvered paper.

I have used epoxy and carpenter's glue and have never seen the epoxy eat the foam. I can't say that about spray paint however. :eek:

And yes, if the foam will meet hot exhaust particles, it *must* be protected or it will pit. Soon it may look like swiss cheese.
I have also used polyurethane glue for foamcore with good results.