I am thinking about making my own foam arbors out of gray/blue board concrete insulation foam. It looks like it is more dense than the flex coat arbors I have been using. Then I got to thinking if it would work for that why wouldn't it work also for making foam core grips. Has anybody used this material for those purposes or do I get to be the test subject? The only thing I can see is that maybe the epoxies used would react and eat the foam away. I guess that can be determined by mixing some up and finding out.

Epoxy doesn't contain a solvent so it's doubtful that it would react in any way with that material.

You might be onto a good idea. Let us know how it works out.

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Epoxy will not eat Blueboard. It does make a stiff core material. It does compress more than polyurethane foam.
If you ding it, it will crush and not spring back like polyurethane will.

A layer of carbon sleeve will go a long way to protecting it.

I've made surfboards and small boats out of blueboard covered by epoxy and fiberglass with good results.

I didn't think it would react with epoxies, but I have been wrong before! I think I will have to definetely try making some arbors out of it and see how that goes first. If it works out then proceed to some carbon fiber work. I will post again after I have tried it out.

EPS or XTS(blue Board) will hold up fine with epoxy. It will not hold up up to polyester styrene.

Traditional Surfboard blanks are polyester and will handle anything. Now they are blowing EPS blanks also which can only be coated with epoxy.

I have built two surfboards with foam from building materials. The blue foar, XTR and coated with West Systems epoxy and it did great. That is with triple 6 oz. fiberglass.

EPS foam, liek the stuff for stucco homes, is usually only 1lb. and not durable. Triple 6 oz. laminations still dent.

I have a large sheet of blueboard insulation that blew up into my yard. No idea who it belongs to. About a 5' square. A spare piece that blew in from some construction somewhere I guess. I have been intending for a long time now to build a foam grip out of it. Just haven't done it yet. Looks like someone will beat me to it. I wll be interested in any results. Perhaps I should throw this scrap piece of foam away!
Jim