Exterior- versus Marine- Ply
Grant
design is called the Pirogue, and I am getting it through Common Sense
Designs. In their homepage they say that use of exterior ply is okay in
the designs they sell, if you can't afford marine. I would like to know
if anyone out there has had any experiences with exterior ply? Is it
okay to use, and do you need to treat it with a fungicide (tbto, etc.)?
I am planning to glass the hull, and am assuming that will take care of
the exterior. Will it protect the ply adequately. Will the use of
fungicide assist in stopping water affecting the wood from the interior?
Thanking you in advance.
Tony Young
Hi Grant,
I've built a few dingys and canoes and only used Marine ply for the first
one.
Reason being that epoxy being what it is, any voids You find during
construction can be filled very easily and voids in the ply is the main
reason Construction ply is not as good as Marine ply. The other reason
Marine ply is better is that as well as it having no or very few internal
voids, it also has more plys for a given thickness, so it's less likely
to fail. If a design is light and specifies Marine ply it's worth
rembering this.
If the boat is going to spend almost all its' life out of the water like
it sounds like this one will, rot wont be a problem if it's kept under
cover, so suit Yourself re rotproofing.
If You're glassing the hull, especially if the plans don't call for it,
there's no doubt Construction ply is good enough.
I'm building a canoe using Construction ply right now. I'll only be
glassing the garboards.
One thing I should mention is that good quality construction ply is
easily available where I am.
Regards Tony
mct...@dct.ac.uk
> I am purchasing plans for a Phil Bolger designed small dinghy/canoe. The
> design is called the Pirogue, and I am getting it through Common Sense
> Designs. In their homepage they say that use of exterior ply is okay in
> the designs they sell, if you can't afford marine. I would like to know
> if anyone out there has had any experiences with exterior ply? Is it
> okay to use, and do you need to treat it with a fungicide (tbto, etc.)?
>
> I am planning to glass the hull, and am assuming that will take care of
> the exterior. Will it protect the ply adequately. Will the use of
> fungicide assist in stopping water affecting the wood from the interior?
>
experience it is fine for boats you don't plan to sell on with any guarantee
of longevity. I used it for Bolger's 13 foot canoe (the one he calls the
'Payson Pirogue' - not to be confused with the Commonsense Designs Pirogue)
and it has lasted well for the past four years with no signs of deterioration
despite being kept outside all year round.
Paint will protect the boat well enough, but coating with epoxy prior to
painting will improve the protection at the risk of spending more on your
coatings than you did on the plywood!
I'd avoid the use of fungicide if the boat is to be coated with epoxy. I'm
not sure it would stick that well to treated wood. It's probably ok with
paint, though, if you give it a chance to dry properly first.
Bill Samson
Pierre Boutet
myself the same question. Finally I came to the conclusion that marine
plywood is better. But not at any price. I found the cheapest
marine-grade plywood is MERANTI. It's only a little bit more expesive
than nice-on-both-sides FIR plywood. But if you want to cover the boat
with epoxy resin, you'll fine that the extra cost for using marine grade
plywood is nothing compared with the cost of epoxy resin! It is worth
spending some time looking for the best deal.
Pat Ford
>I'm planning to build a stich-and-glue plywood kayak, and I've asked
>myself the same question. Finally I came to the conclusion that marine
>plywood is better. But not at any price. I found the cheapest
>marine-grade plywood is MERANTI.
I am informed by a major national wholesaler of boatbuilding plywood that
NO Phillipine mahogany (meranti) plywood meets marine grading criteria.
Something about the adhesive.
Ask your local dealer if this is actually marine grade Phillipine
plywood-they'll start weaseling and then say something like-"well-it's
just as good."
It's hapenned to me.
--------------------------------------------------------------------
Pat Ford-Ford Boat Works-Seattle-206-789-2456
Classic Speedboat Repair for Twenty Years
Pacific Northwest Chapter-Antique and Classic Boat Society web pages:
http://www.halcyon.com/pford/acbsx.htm
Wooden Boat Shop-books and supplies for the wooden boat builder:
http://www.halcyon.com/wbs/wbs1.htm
Mark Finlayson
>I am purchasing plans for a Phil Bolger designed small dinghy/canoe. The
>design is called the Pirogue, and I am getting it through Common Sense
>Designs. In their homepage they say that use of exterior ply is okay in
>the designs they sell, if you can't afford marine. I would like to know
>if anyone out there has had any experiences with exterior ply? Is it
>okay to use, and do you need to treat it with a fungicide (tbto, etc.)?
>
>I am planning to glass the hull, and am assuming that will take care of
>the exterior. Will it protect the ply adequately. Will the use of
>fungicide assist in stopping water affecting the wood from the interior?
I built a Bolger Pirogue a couple of years ago. I used exterior fir plywood,
coated with System 3 epoxy. I covered all the exposed plywood edges with
fiberglass tape. I haven't had any problems with rotting yet, although the
boat is a bit pampered - it's kept indoors, out of the water except when I'm
actually using it - there might be more problems if you kept it in the water
continuously.
Mark Finlayson
finl...@zko.dec.com
Bill Holt
1. The way to get good plywood at a good price was to wait for
the local importer to buy a shipload, then go and look at it,
choosing the sheets myself. I bought in quantity like that, and
got a very good deal. Later I had to get a few additional sheets,
and although they were marked as being to a higher standard, and
cost a lot more, I found that they were poorer quality, had an
offensive smell when cut, and, of course, came out a different
colour when epoxied. Since those heady days of building, I have
always found it pays to take a friend or son to help select
the actual sheets.
2. Everyone writes about voids in the ply. The problems I have
had have mainly been from overlaps in the inner plies. Voids
can be filled with epoxy, but overlaps are invisible until you
slosh the epoxy on, then they swell while it sets.
--
Bill Holt
Thomas Dalzell
>From: Tony Young <tyo...@perth.DIALix.oz.au>
>Subject: Re: Exterior- versus Marine- Ply
>Date: Thu, 12 Oct 1995 20:26:47 +0800
>On 10 Oct 1995, Grant wrote:
>I've built a few dingys and canoes and only used Marine ply for the first
>one.
>Reason being that epoxy being what it is, any voids You find during
>construction can be filled very easily and voids in the ply is the main
>reason Construction ply is not as good as Marine ply. The other reason
>Marine ply is better is that as well as it having no or very few internal
>voids, it also has more plys for a given thickness
This not necesarily so. I have bought BS 1088 plywood in 1/4 inch which was
3 or 5 layer, same rating. Below 1/4 inch it is all 3 ply, as far as I have
seen.
Don Barker
>
> I would like to know
>if anyone out there has had any experiences with exterior ply? Is it
>okay to use, and do you need to treat it with a fungicide (tbto, etc.)?
Bolgers cohort, "Dynamite" Payson, discusses exterior ply in detail
in the intro to one of his "Instant" boat books -- either the first
(Instant Boats?) or "How to build the NEW Instant Boats". Or something
close to that. He recommends (to his surprise) BC and other ext
grades.
Don Barker
dba...@skipjack.bluecrab.org
Bob Davis
decide how long you want your BDG boat to last and select accordingly. Most
home built plywood boats have a low resale value, it may be headed for the
dump in the near future anyway.
BobD
Tim McCrain
thing (maybe the only thing) agreed upon by the majority of the boat pros
I spoke with was this:
The voids in "construction" grade exterior ply collect condensation and
provide the oppurtunity for rot from the inside out, regardless of the
coating applied to the surface of the ply.
--
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Tim McCrain "A dream without action is a fantasy...
twa...@eskimo.com action without a dream is a nightmare."
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Hans Valk
"Another experience from the UK: the marine ply I looked at locally
was rather unimpressive, but the Finnish Birch was enormously
better, and when cut has no voids. I know of one commercial
builder using this - of course, you have to epoxy for long life
as birch is not the most durable of woods."
Yes, this stuff is sold in the netherlands as well. As you said: it
looks good; no voids and thin veneer layers. But I wonder about the glue
quality; is this Water Boil Proof (WBP) ?
Hans Valk (A.J....@bk.tudelft.nl)
Pierre Boutet
>Peter Berrie <ber...@eworld.com> wrote:
>
>>Question, is the Finnish Birch ply WPB? Yes, according to the supplier,
>>but I suppose using it will be the big test....
>
>>Peter
>
>To find out, get a small piece of the wood and boil it. I believe the UK spec.
>recommends boiling for 30 minutes, but I could be wrong on the time.
>
>
It's not the first time I hear about this boiler test. I'm not an expert
in marine plywoods, but why would plywood need to support such a test???
A boat will never be in those extreme conditions. Any clue why the boiler
test seems to be so crucial?
G. Mayner
Thanks for the notes. Here are the results of some destructive testing of
1/4 Luan (spelling?), 1/4 fir AC and 1/4 Marine ply. I checked all three
for obvious external faults. Naturally the Luan and Marine were OK. The
AC had some cracks on one side.
After splitting each sheet into 12in wide strips to fit in my planer I
proceded to plane off the external plies. Fir AC had several voids with
lengths up to 30 inches and width of as much as 3/8in. Luan had some
long narrow voids up to 20in but none wider than about 3/32. The most
amazing part of the test was that the Marine grade had some internal
voids up to 18in and some as wide as 5/32. Overall the Marine was
slightly better than Luan and the Fir AC was pretty disappointing.
If any of this proves anything I hope someone will tell me! :-)
Garry
John McKenzie
> Regarding the testing of plywood glues by boiling and the reasons
> for such tests:
>
> I believe that the elevated temperatures are to substitute for
> exposures of longer times. In other words, by testing the glue
> at 100 deg C (boiling temp.) for 30 minutes, you don't need to test
> at room temperature for 3 to 6 months to learn the same thing.
>
> Dave
>
The boil-swell test is a standard test for hardboard (and I think
particleboard).
And the rationale is exactly as Dave says, except perhaps that the
room temperature test would take years.
Seems a bit "irrational" (boats, or houses, or whatever, are not
boiled) but the results correlate with actual field experience.
John McK
>>To find out, get a small piece of the wood and boil it. I believe the UK spec.
>>recommends boiling for 30 minutes, but I could be wrong on the time.
>>
>>
>
> It's not the first time I hear about this boiler test. I'm not an expert
> in marine plywoods, but why would plywood need to support such a test???
> A boat will never be in those extreme conditions. Any clue why the boiler
> test seems to be so crucial?
>
>
> ---------------------------------167816498861--
James McMullen
>1/4 Luan (spelling?), 1/4 fir AC and 1/4 Marine ply.
ply? You must be! The imported occume marine plywood that I use is an
entirely different sort of thing all together. I have no doubt that the
domestic fir marine plywood was garbage scarcely better than AC fir, but
I think it is important to specify exactly which pluwood it is. The ply
that I now use exclusively for my boats is manufactured by Kelet Afikim
in Israel, meets Lloyd's of London Spec. 1088, and has no voids
whatsoever. The panels are actually MRI'd before they leave the factory
to check for voids. I have planed countless gains and scarfs in this
ply and have never once even had a tearout, let alone a gap or void.
This is the stuff to use if you are going to make a quality boat rather
than a utilitarian quick and dirty one.
--James McMullen
Peter D. Engels
<pbo...@infobahnos.com> wrote:
> cmer...@ix.netcom.com (Chuck Merrell) wrote:
> >Peter Berrie <ber...@eworld.com> wrote:
> It's not the first time I hear about this boiler test. I'm not an expert
> in marine plywoods, but why would plywood need to support such a test???
> A boat will never be in those extreme conditions. Any clue why the boiler
> test seems to be so crucial?
The reason for raising the temperature of the water (which is all that
boiling does) is to accelerate the test, so that you don't have to wait
many days to see whether the glue is really waterproof. Test acceleration
by raising temperature is a standard technique, used on lots of materials.
--
Pete
J R Gahrmann
J R Gahrmann
waterproofness of thier glues? Luan (sp) seems to be very soft wood, will
it hold up?
Pat Ford
I would be reluctant to use it.
I am told (by a major US specialty plywood wholesaler)
that NO luan plywood is graded marine, though dealers will insist that
it is.
Jacques Mertens
>J R Gahrmann <jrg...@dukepower.com> wrote:
>>Have you checked these plywoods for thier durability and the
>>waterproofness of thier glues? Luan (sp) seems to be very soft wood, will
>> it hold up?
>I would be reluctant to use it.
>I am told (by a major US specialty plywood wholesaler)
> that NO luan plywood is graded marine, though dealers will insist that
>it is.
It all depends on the type of boat that you build and on the building
method. If you build or restore those very nice classic boats that I
see on your site, it does not make sense to save on the plywood
considering all the labor invested but, if you build a small and
simple boat in plywood/epoxy (stitch and glue), Lauan us perfect. Your
structure will be totally encapsulated in epoxy and last as long as a
hull built from marine ply.
For a first project, build a simple boat from Lauan, then, if you
liked the experience go for something more complicated and invest in
marine ply.
Jacques Mertens / Mertens-Goossens NA Boat Plans Online!
http://www.bateau.com/
jm...@aol.com