| 96 kg/m3 - Nice. Twice the density of XPS gives it better strength of course. But only half the compressive strength of similar density PVC foam (on paper).

Yep. While I don't think anyone here is a composite engineer, I think having discussions of many possible foam substitutions might make sense for the budget builder. Although, perhaps contra indicated in a discussion on building 10-30m+ boats, which seems a rich mans hobby.

| And the shear strength is only 0.55MPA, which is 1/3 of H100. So on paper it doesn't look ideal. But maybe good enough.

It is kinda funny how there does not seem, to me, to be expected levels of certain types of strength for boat designs, or perhaps my search skills are fail.

Like, it seems, I really don't know how we know how strong a boat needs to be, nor how to stress it, or load it, to PROVE its as strong as it needs to be. Except to go sail it till it breaks and make it stronger. Which suggests individual, case by case experience based knowledge. Which seems so last century.

And so, we do not know if a chosen core is way stronger than needed or too weak. We can only eventually know, perhaps, if it is too weak by its failure, as that fail may have failed in every case because the storms do not come in measured sizes.

It also seems that, given a reasonable array of potential cores, and the relative costs, selection is based on relative criteria of PERCEIVED value, not the objective requirements. Because there is no objective requirements data.

For example Rob has often mentioned H100, because it is about the same price or cheaper for him in AU. Other than cost, and the perceived value of a better material, and reasonable disregard of the small weight gain, H100 is not NEEDED, in that its performance level is not required.

| Would be interesting to compare XPS, PIR, PVC foam in compression, tension and shear. Maybe the cheaper products will not be as inferior as it looks on paper.

We don't even know what the paper is telling us. As pointed out in the boat design threads, perhaps only compressive strength matters in a foam core. And even if we had enough good data from enough of the various cores and layups to get a reasonable statistical expectation of typical or minimum performance, of a home builder, we don't know how to translate that into building a boat.

And IF we had all that, 'a boat' is not a HP, which is an entirely different boat design, mostly, than your typical multihull, or mono, if the words 'typical' can be applied to boats in this case.

Its a rather complicated domain.

| I compared my Finnfoam samples to low density PVC foam in a vice, just like the Trinardo guy, with the same result. But I'm a bit too busy at work, so I haven't played that much with it yet.

Mr. Trinardo did it vs H100, right? Can you specify what "low density PVC" you used?

How does a material with lower compressive strength crush a material with higher compressive strength? Is the paper lying? Do we literally know nothing.

InsaneLaughter.mp3

At this point I need to build a boat and go sailing to get away from the insanity of thinking about how to build a boat.