Given the wide variations in quality in construction lumber these days,
does anyone have any insight into how to estimate the voids in a sheet of
ply (say ACX) before cutting into it? (Without breaking down and getting
stuff like marine plywood manufactured to a spec defining no voids, that
is.) I'm thinking of building a little boat this winter, just something a
little more stable than my canoe for fishing small water (knockabout, not
heirloom quality; oars, no motor), and I'd of course prefer to get stuff as
free of voids as possible without spending too much. Any suggestions about
what to get or what to avoid?
I'm sure there are manufacturing standards on the maximum for a given
grade to support the load ratings for span, etc., but I've not looked
for them specifically. I'd start w/ the plywood manufacturers' trade
associations and see what you can find.
But, I don't think it will help very much for construction grade
material as I'm sure it can have a significantly higher void fraction
than you will want and still be suitable for purpose.
Other than that, there's no reason that interior voids (knotholes, small
voids between pieces, etc.) are actually a defect so there's really no
reason to expect it. The one thing that does correlate ime is cost--the
cheap imported stuff is that for a reason. Often, it isn't even stamped
as conforming to trade assoc grades.
I'm not a boat builder but would seem to me that it wouldn't make sense
to put the effort in w/o using something rated for the purpose.
Otherwise, just buy an old knocked-around skiff from somebody else.
Marine plywood is the answer and it would appear that
you knew that. No construction grade plywood is free
of "all" voids.
Your other choice is a solid wood boat made from
from juniper/cypress. That was the choice for
Given that you can buy a fiberglass boat for the
material cost of a wood boat, why go to all that
work and trouble ?
A used jon boat sounds like something you need.
Jim Willemin wrote:
And for a BOAT he definitely needs waterproof glue plywood.
He will want at least a b grade veneer and a "A" or "B" bond. B is
good for about 2 years of exposure to wet - so MIGHT be suitable for a
Anything less than a "B" grade veneer will have voids, which in a "C"
grade may be filled with either wood or wood byproducts. (not good gor
An ACA would be suitable (appearance grade both sides, with a grade c
inner ply structure(no voilds, filled)
The difference in cost between exterior fir ply and marine grade Meranti is
negligible considering the small anount you'll need and the vast effort in
building even a small boat. Note that there are two (at least) grades of
"marine"; you don't need the super dooper one.
Buy a boat.
Don't even think about building one.
You will spend less money buying a finished boat than you will on
materials to build one, not to mention the time spent building it that
could be spent fishing.
Only if your time spent searching for the right thing means nothing.
Personally, I'd rather avoid the whole shopping headache and just build my
own. Several hundred dollars buys a lot of wood, or just one visit to a
If you're quiet, your teeth never touch your ankles.
To email me directly, send a message to puckdropper (at) fastmail.fm
I assume you know that birch plywood wll disintegrae when wet? Marine
plywood isn't so much wet-tolerant wood, but wet-tolerant glue in it.
Also, no voids. Also cost a few bucks. We have used Wolmanized plywood
for rougher boat jobs, and it sems to handle near-constant wetness for
at least a few seasons, but s not as finely finished as true marine ply.
I assume you know that birch plywood will rapidly delaminate when wet?
Marine plywood isn't so much a wet-tolerant wood, but wet-tolerant glue
in it. Also, no voids. Also cost a few bucks. We have used Wolmanized
plywood for rougher boat jobs, and it sems to handle near-constant
wetness (inner floorboards, transom pads, etc.) for at least a few
seasons, but s not as finely finished as true marine ply.
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