"The blue foam must be removed chunk by chunk from inside the cured tube."
... I remember an old trick where they used to make parts over styrofoam plugs and after cure you dig out what you can then block off all but one opening and pour in acetone, slosh around and pour out dissolved styromush, repeat till it is clean. I'd be sure the epoxy is very well cured first.
I remember some of the softer styrofoams go away really fast when hit with acetone.

Modern casting technology uses premolded styrofoam cores, these sometimes have to be from several pieces bonded together. Fine sand is packed around the styrofoam and molten metal is poured in. The styrofoam disappears almost instantly and what skin remains against the sand actually enhances the surface finish.

This process revolutionized modern lightweight engine design. It gave the capability to design elaborate and complex intake runners, better cylinder heads and cooling schemes not possible with sand and hard patterns alone.
So all the tooling went into the molds for styrofoam :)
Now if you can find a good way to bond styro to styro with styro you are halfway to the foundry.
...Chrissi

 
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