When you speak of weight versus resiliency with regard to the upper portions of a boat, I don't really think it applies. You don't hit docks and other boats with the coach roof or decks. In some places you want strength and stiffness AND you want light weight. That means a light weight core of greater thickness. If you made up two sandwich pieces of the same weight and dimensions except for the thickness of the core, and the same glass layers, but one had Divinicell H-80 for a core, and the other had XPS which is typically 2 pound per cubic foot versus 5 for H-80, and you tested both pieces in various loadings, the XPS sandwich would be in excess of double the strength in bending at least, and probably also in torsion. Tensile strength would be virtually identical.
I haven't done this, but I've done enough other things that I'm quite confident of it.
XPS that is not part of a sandwich does not bend well, and the thicker it is, the larger will be the radius at which it will fail. In a sandwich, the entire equation is going to change because failure always begins as a tensile failure on the tension side of a bend on bare XPS. With glass bonded to it, it cannot fail in tension before the glass does.
The performance of XPS in a sandwich has been demonstrated again and again. It becomes very resilient in bending
My "local" supplier (hundreds of miles away), carries no densities of marine construction foam less than H-80. Above the hulls themselves, H-80 is probably not the optimal core material. A thicker lower density core has many advantages. Divinicell H-35 might be the preferred choice in these kinds of situations, but in a place where XPS can be made to conform to the shape easily, I suspect that the advantages would be negligible....
H.W.
On 05/10/2018 11:48 AM, mcrawf@nuomo.com [harryproa] wrote:
H.W.,
So you'd say XPS deserves a place in boatbuilding the way balsa core does -- best perhaps for decks and cabintops, and less-than-optimal for hulls and topsides?
That would be a reasonable compromise.
Then, some folks will still go with balsa, or perhaps XPS, for the rest of the boat because weight means more to them than resiliency. Which is, of course, each builder's trade-off to decide upon.
Just out of curiosity, do you know how a sheet of XPS would handle the infusion process with curves? The building process for the Solitarry is pretty wild, at least in terms of what can be done ahead of time:
https://www.youtube.com/watch?v=DfhdRfBTt8o
I've never worked with XPS under 4", so I don't know much about its flexibility.
&nb sp; - Mike
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