On May 4, 2018 6:48:00 PM UTC, "mcrawf@nuomo.com
[harryproa]" <harryproa@yahoogroups.com.au> wrote:
><<Did you actually read my post.?>>
>
> Yes. Fully.
>
> I think differences come down to two sets of
assumptions.
>
>I'm assuming that the hull will indeed be overstressed
while it's in the water, perhaps in ways that we aren't
aware, so I'd want the most resilient core material
available.
Then why not use a steel core?
One has to compromise. You want a material that meets the
guestimated needs.
My point here is there has not been an assertion of an
engineering reason for choosing such an expensive core
over a less expensive option. Rob has admitted there is a
localized economic reason for his choice if H80. Not an
engineering one.
And, your statement "most resilient core material
available" is factually untrue, with respect, H80 is
simply one grade available. They make higher grade
material that is provably more resilient.
How is H80 better than H60 or H200? Why choose H80?
I mean all the above with diplomacy. If that does not come
through, that is my failing in phrasing. But the points
stand.
>There are significant differences in delamination,
particularly due to impact, between different core
materials. The stress is a given, the amount of damage
from that stress is the variable.
I disagree. Only in the case of an overstress should one
expect delamination. It is obvious that the carbon fiber
and fiberglass anecdotes delaminated due to repeated over
stress of the core, who's properties were not known. To
suggest XPS tends to delaminate based on these anecdotes
is silly.
>I'm also assuming that water will find its way into
the core. XPS may indeed be waterproof (I use it in my
dock float, for example), but that doesn't mean it will
make for a good core material when water gets in between
the sandwich skins, particularly if submerged for long
periods of time and then subjected to thermal cycling.
Rick's experience being a good example.
Again I disagree. Are you saying all the boats made of XPS
are known to delaminate due to thermal cycling? Is
Finnfoam aware of that? Because i think they would laugh
at you. You know, it is known to thermal cycle in their
homeland.
>But I'm a conservative guy. Many others have tested
these materials for compression, tension, shear,
delamination under stress, delamination under impact, and
the effects of water intrusion. Including their
manufacturers. There's a lot of data out there, much of it
that I couldn't reproduce through my own destructive
testing.
That seems strange. These are ASTM standards, right? If
you did not get the same results you probably should
contact them to see how you got your test wrong, right?
Unless you are suggesting there third party testing was
lies. Are you suggesting that?
What grade of XPS did you destructively test?