Re: MDO Strength
Never confuse strength and stiffness. I would be willing to guess that
the coating, having no straight fibers, is relatively floppy stuff and
doesn't get up to any significant stress before the wood reaches its
limits. So it doesn't have to be strong.Kind of like a rubber band
wrapped around a brick. I have a piece of MDO, and the coating is quite
thin.
the coating, having no straight fibers, is relatively floppy stuff and
doesn't get up to any significant stress before the wood reaches its
limits. So it doesn't have to be strong.Kind of like a rubber band
wrapped around a brick. I have a piece of MDO, and the coating is quite
thin.
>Gene T. wrote:
>While grinding through the last weeks message traffic I notice the
>discussion of MDO. Each time this comes up, I wonder about the
>strength of the overlay in tension. I would find it hard to believe
>that the glue particle mixture that makes up the overlay would have
>the tensile strength of an actual wood fiber celular structure. If
>MDO is flexed will the surface on the outside of the curve show small
>cracks or even micro cracks rather than stretch. Will it flex easier
>than plywood of the same thickness. Possibly thicker pieces should
>be used to replace a given piece of hull plywood. I'd see this as
>less of an issue for interior parts. Hull, deck, and seating
>surfaces might require added thickness to supply strength similar to
>that originally specified by the designer.
>
>Gene T.
>
I have found that epoxy soaks through the overlay into the
underlying wood. In my experience it takes more epoxy to wet out
cloth over MDO than over bare plywood. I've tried peeling strips
of fiberglass tape bonded to MDO. Strands of wood fiber came
away with the tape. I would suggest that if you have a concern
about this, you should do your own testing before building with it.
Your MDO might come from a different source than what I had, or
it may have been manufactured to different standards.
Vince
underlying wood. In my experience it takes more epoxy to wet out
cloth over MDO than over bare plywood. I've tried peeling strips
of fiberglass tape bonded to MDO. Strands of wood fiber came
away with the tape. I would suggest that if you have a concern
about this, you should do your own testing before building with it.
Your MDO might come from a different source than what I had, or
it may have been manufactured to different standards.
Vince
The overlay is a thin sheet of phenolic paper bonded to the sanded surface
of the plywood. I have never experienced any cracking nor do I see any need
to increase thickness of the ply. This stuff is way better than the AC stuff
some people use.
Paul
of the plywood. I have never experienced any cracking nor do I see any need
to increase thickness of the ply. This stuff is way better than the AC stuff
some people use.
Paul
While grinding through the last weeks message traffic I notice the
discussion of MDO. Each time this comes up, I wonder about the
strength of the overlay in tension. I would find it hard to believe
that the glue particle mixture that makes up the overlay would have
the tensile strength of an actual wood fiber celular structure. If
MDO is flexed will the surface on the outside of the curve show small
cracks or even micro cracks rather than stretch. Will it flex easier
than plywood of the same thickness. Possibly thicker pieces should
be used to replace a given piece of hull plywood. I'd see this as
less of an issue for interior parts. Hull, deck, and seating
surfaces might require added thickness to supply strength similar to
that originally specified by the designer.
Gene T.
discussion of MDO. Each time this comes up, I wonder about the
strength of the overlay in tension. I would find it hard to believe
that the glue particle mixture that makes up the overlay would have
the tensile strength of an actual wood fiber celular structure. If
MDO is flexed will the surface on the outside of the curve show small
cracks or even micro cracks rather than stretch. Will it flex easier
than plywood of the same thickness. Possibly thicker pieces should
be used to replace a given piece of hull plywood. I'd see this as
less of an issue for interior parts. Hull, deck, and seating
surfaces might require added thickness to supply strength similar to
that originally specified by the designer.
Gene T.