marine plywood

[thomas knowles]

Besides the difference in grade (AB vs. CD), what's the difference between
marine grade plywood and exterior grade plywood? And, is the cost justifiable?
In my case, I want to build 16' canoes and am having a hard time spending the
$$$ on marine grade.

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[Hank Metz]

Do an archive search at:
rec.boats.building

This subject has been done to death over there, but the consensus is that if
you can afford it, Marine Ply is the proper choice for boat building in
designs using this material. If you do not anticipate more than a few years
of use, Exterior grade ply will work.

--
Hank Metz,
A Woodworker's Notebook
http://www.ameritech.net/users/hankm/index.htm

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thomas knowles wrote in message
<1999071318312...@www0w.netaddress.usa.net>...

[Rob Weaver]

Typically, but not always (or so I've heard) marine plywood does not
have any voids in the inner plies. You also get more plies per unit
thickness than with regular ply. This means that your curves are
fairer, adn you don't have any concerns about structural integrity of
the plywood. It also means that when you cut it, you won't open up a
big honking hole in the edge of your ply that then needs to be filled.

Is the cost justifiable? What's you time worth, and do you want to
spend it building a perhaps, disposable canoe? OTOH, Dynamite Payson
(Instant Boats guy) builds a lot of boats out of exterior ply, and lots
of people build canoes out of the relatively cheap 1/4" luaun ply from
the Borg.

Jumpo over to news:rec.boats.building for the latest on this. Also do a
search on http://www.deja.com/

[Kim Whitmyre]

> And, is the cost justifiable?
> In my case, I want to build 16' canoes and am having a hard time spending the
> $$$ on marine grade.
>

I'm no expert, but in perusing an expert's book on stitch construction
of boats, he said that if you seal the plywood properly, you don't need
marine grade.

Kim

[Chris K. Moore]

Rob Weaver wrote:
>
> Typically, but not always (or so I've heard) marine plywood does not
> have any voids in the inner plies.

No voids? Then "Marine" plywood must NOT be the kind that leaves you
"looking for a few good _mends_"!!! :-)

[Philip Lewis]

> And, is the cost justifiable?
> > In my case, I want to build 16' canoes and am having a hard time spending the
> > $$$ on marine grade.

You may want to look into using the West
System epoxy coatings for boats and
watercraft. While using a marine
plywood, such as Brunzeel plywood
(approved my Lloyd's of London for
boatbuilding) may be expensive, nice
cedar strip canoes have been built and
sealed with the West System. It is
manufactured by Gougeon Brothers if I
remember correctly.

Best Of Luck
Phil

[GunnyHunny]

>
>I'm no expert, but in perusing an expert's book on stitch construction
>of boats, he said that if you seal the plywood properly, you don't need
>marine grade.
>
>Kim

I think the operative factor is 'How do you intend to use the craft?'

If you're going to use a canoe (like the 6-hour canoe) in very protected inland
waters, I wouldn't hesitate to use a quality exterior grade, epoxy sealed
(which I intend to do in the near future).

However, If I were getting ready to build a stitch-and-tape sea kayak, which I
were going to use in offshore expidition, I'd certainly opt for BS 1088
standard marine-grade plywood.

Keep in mind that exterior grade plywood will require more effort to finish
than marine plywood, and don't even think about finishing it 'bright'!!!

Anthony