Mike:
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