Rob, et. al.;

Teach me about polyisocyanurate composits.

I have been reading about polyiso and found this.
http://blog.twinsprings.com/wp-content/uploads/2016/06/EA-2.-Cold-Weather-Performance-of-Polyisocyanurate.pdf
Thought it was neat enough to share. It's not boat related, except for, perhaps, Steinar.

I have a local source for it. They do the string cutting like you described, Rob. Mostly for pipes, but will cut sheets. Seems the compressive performance is comparable to 700kpa XPS in the 4#/sq ft (sorry for the units), and close to H100 in the 6#.

They also have a laminate version that has less course bubbles, and slightly less compressive strength.

Which made me wonder if the Divinycell has large bubbles or small fine bubbles like the 700kpa XPS. Rob you have seen both, please advise when you get a chance.