Marine Plywood vs A-B Exterior Plywood
jgubjr
extra cost for fir marine plywood over A-B exterior is not justified today.
Their rationale is that marine plywood is basically exterior plywood with a
lower void content. Several years ago the plywood association that sets
specifications started degrading marine plywood by allowing a higher void
content.
BTW I understand marine plywood is supposed to consist of 7 layers compared
to 5 for exterior.
I intend to build a 20 -22 foot plywood boat and use it for fishing only.
It won't need a yacht type finish but I don't want it to be marred by a lot
of checking either. I will be fiberglassing the bottom, outside and
interior sides.
Does anyone recommend I don't use A-B exterior and the reason ? Also - can
I put two layers of fiberglass on the outside in an attempt to hide checking
? Are there any problems with this that I need to be aware of ?
kr...@socal.rr.com
for anything else, decks, wheel house structure, exterior works just fine.
coat everthing with fiberglass with epoxy.
kevin rea
"jgubjr" <jgu...@nospamworldnet.att.net> wrote in message
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arbarnhart
You left out the "and the reason" part...
<kr...@socal.rr.com> wrote in message
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arbarnhart
You quote a reliable source; if you follow other advice, make sure it is
equally reliable.
Some high end marine ply is guaranteed by Lloyds of London. If it were to
fail, you could possibly get another boat.
It is much more expensive though, so if you use AB exterior instead, you
could spend the savings making the boat better in other areas.
How many sheets are you going to need? One consideration is that you can
just order marine ply and it will all be void free and top quality. You will
want to hand pick the wood if you go with exterior ply.
Number of layers can depend on thichkness, type of wood and manufacturer.
What type of wood do you want to use? Does it need to bend or flex much?
See if there is a lumberyard or home store near you that carries both, go
put one of each in a wood dolly and look them over to see the difference.
Look at the piles to see the variance between boards.
Finally, price it out so you know what the difference really is.
I am not going to tell you what to do, but gather some info and edcide for
yourself. I am cheap, so my opinion is tainted. Yours is the important one
anyway.
-Andy
"jgubjr" <jgu...@nospamworldnet.att.net> wrote in message
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Glenn Ashmore
and a piece of A-B exterior THEN compare prices before you decide.
--
Glenn Ashmore
I'm building a 45' cutter in strip/composite. Watch my progress (or lack there
of) at: http://www.rutuonline.com
NWCedarDecks
ground contact guarantee.
As a carpenter one of my jobs is dryrot repair. The last job was a wheel chair
ramp
that had started to rot. Digging into it I found it was build with some really
good 7/8 ply.
every thing was rotted except the PT sill plates that were on the concrete.
They were still like new so I reused them.
I would say PT never rots but I can't remember seeing one rotting. 15 years as
a carpenter
Now why not use PT plywood
or at least the treatment stuff out of a can.
Good for 20 years. Might have to let the wood redry but that's no big deal.
ED
John McCoy
>System Three's "The Epoxy Book" (2000) recommends, on page 24, that the
>extra cost for fir marine plywood over A-B exterior is not justified today.
I'd agree with them. All the fir plywood I've seen recently is garbage, unless you're
trying to roof a house.
For boatbuilding, tho, you'd probably be better off looking at okoume or meranti
marine plywood, which is still manufactured to marine quality standards.
John
Joe Stafford
but the advantages in weight and ease of use shaping etc. are numerous. Mail
order in bulk you might get a better price.
"John McCoy" <igo...@ix.netcom.com> wrote in message
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Glenn Ashmore
1) It is intended for rough structural work. The veneers are usually the poorest
grade available. The best face geneer you can get is a low B and the interior
plys are about the same as CDX sheathing.
2) It has been impregnated under pressure with a copper compound and usually has a
very high MC when it is sold. As it dries out, it shrinks so it is not
dimensionally stable.
3) The copper perservative interferes with epoxy bond. Not to mention that it
comes with all sorts of cautions on the MSDS.
NWCedarDecks wrote:
--
Glenn Ashmore
$150 per sheet but you can count on half again that for the glass and epoxy
skins.
Joe Stafford wrote:
--
KF4call
this thread. I am using carefully selected B-C Pine (Exterior). The boat is a
12 ft. cat-ketch. By carefully selecting, I have so far been able to "avoid
the void", at least on the edges. On the two sheets used prior to today, no
new voids were revealed when I cut the workpieces out of the full sheet. The
pieces I picked today have second sides which are quite good with only
occasional knots or dutchmen. I hear the pine is better than fir as far as
checking is concerned, for only $10/sheet. However, the advantage of less
checking may not be as prominent as some have claimed, I have heard it both
ways on internet newsgroups. Pine also weighs more.
If economics were not an issue, I would probably use Sapele, which I think
is one of the more beautiful woods. Meranti is also said to be a good choice,
but still quite a bit more than my pine.
Regards,
Warren
pm
<Q9%B6.20678$IJ1.1...@bgtnsc05-news.ops.worldnet.att.net>:
>
>BTW I understand marine plywood is supposed to consist of 7 layers
>compared to 5 for exterior.
Could someone tell me proper name for the "Finland" ply I started building
my interior our of 24 years ago? I counted nine plys in the half-inch pieces
nineteen to the inch) and the faces seemed to be A/A. It only came in 5 x 5
foot or 5 x 10 foot pieces and was so heavy I could only justify its use for
the major bulkheads.
thanks,
pm
Glenn Ashmore
called "Finnish" because 25 or 30 years ago everyone wanted Stoly but nobody
would buy "Soviet Birch".
The proper name is "Baltic Birch".
The earlier product had very fine veneers but the glue was interior only and in
some runs glue quality was variable. Primary use was for Euro style modular
cabinets because it is as stable as MDF and the edges finish so nicely that edge
banding could be eliminated.
They have improved the glue over the years. The standard is a Type 2 interior
hot press. Exterior Type 1 is special order from most distributors.
pm wrote:
--
pm
<3AD99701...@mindspring.com>:
>Finnish or Baltic birch mostly comes from Latvia and Northern Russia.
>It was called "Finnish" because 25 or 30 years ago everyone wanted Stoly
>but nobody would buy "Soviet Birch".
>
>The proper name is "Baltic Birch".
>
>The earlier product had very fine veneers but the glue was interior only
>and in some runs glue quality was variable. Primary use was for Euro
>style modular cabinets because it is as stable as MDF and the edges
>finish so nicely that edge banding could be eliminated.
>
>They have improved the glue over the years. The standard is a Type 2
>interior hot press. Exterior Type 1 is special order from most
>distributors.
>
Thanks Glenn. I must have gotten some of the 'good' glue because when I
originally tried a piece of it I heard it was "boil proof" glue. It was
claimed you could boil a strip of the ply and bend it into a tight arc and
it would take the shape without damaging the laminate. It did. Still I
suppose it could do that without being an exterior product?
pm
ron ginger
>
> You quote a reliable source; if you follow other advice, make sure it is
> equally reliable.
>
> Some high end marine ply is guaranteed by Lloyds of London. If it were to
> fail, you could possibly get another boat.
I dount think this is true. Some is marked as "built to Lloyds
Standards", but that is not at all the same as saying the buyer is
insured for anything.
If the manufacturer claims to be built to a standard, then its likely a
good product, but any claim for its failure would be between the buyer
and the manufactrurer. Note also any warranty Ive ever seen limits the
replacement to the value of the product, so you would not get a new
boat, you would get a new sheet of plywood IF you proved the original
was deffective in manufacture.
There are reasons to buy good quality marine ply, but this is not one of
them
ron giger
Lew Hodgett
> Finnish or Baltic birch mostly comes from Latvia and Northern Russia. It
was
> called "Finnish" because 25 or 30 years ago everyone wanted Stoly but
nobody
> would buy "Soviet Birch".
Don't know about your part of the world but here in SoCal there is a big
difference between "Baltic/Finnish" and "Russian" birch.
My landlord is a gasket house. They use 11 ply (5/8"), for die board.
Tried to laser cut some "Russian", it was a disaster. Seems the glue oozed.
They will only accept "Baltic/Finnish" which they tell me comes out of
Finland.
I do not know that for a fact but have no reason not to believe it.
--
Lew
S/A: Challenge (Under Construction in the Southland)
Visit: <http://home.earthlink.net/~lewhodgett> for pictures
There are no problems, only varying degrees of challenging opportunity
arbarnhart
Is the fir you've been looking at rated AB Exterior?
If so, it would seem that the manufacturer or your supplier is the problem,
because if it really meets the criteria for the rating, it is not garbage.
-Andy
"John McCoy" <igo...@ix.netcom.com> wrote in message
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Glenn Ashmore
shadow of its former self. There is no comparison with Israeli or Belgian 6566
meranti for the 10 or 15 bucks a sheet savings in cost.
arbarnhart wrote:
> Is the fir you've been looking at rated AB Exterior?
> If so, it would seem that the manufacturer or your supplier is the problem,
> because if it really meets the criteria for the rating, it is not garbage.
--
P.C.
Glenn Ashmore skrev i meddelelsen <3ADA0055...@mindspring.com>...
Now I once knew a guy who almost went bancruped with a plywood factory.
Anyway he knew a lot about it ,and what he said was ,that as soon plywood was
fabricated where the wood was, it was cheaper than bringing the lumps to where
the ply shuld be sold ,manufactoring it there.
----------- Now I don't know how it work today ,Ply -- even vorse quality are
water resistance, and if it can expand equally in a construction if structured
reasoble nothing wrong with ply :))
Guess the same count for houses, ------ wonder how much acturly are sold for
boats :))
What about pressed sprokes or crasched woods like the building site sheets that
sometimes substitude ply for things like fences ? ----- Im'e quite sure I could
do a set of ribs for a small boat from that. ------ that's water resistance to.
Have a nice day.
P.C.
John McCoy
>
>Is the fir you've been looking at rated AB Exterior?
>If so, it would seem that the manufacturer or your supplier is the problem,
>because if it really meets the criteria for the rating, it is not garbage.
It's garbage by comparison to the foreign made marine plywood. The
criteria for the rating (for US made fir plywood) have been allowed to
degrade, not to mention a lot of it only marginally meets the spec.
John
arbarnhart
Degrade how?
Voids or surface fills would disqualify it as exterior AB. Glue has to be
"waterproof".
What exactly are you encountering that makes you call the fir exterior AB
ply "garbage"?
Also, if you don't mind sharing the info, what part of the country are you
in, what supplier have you been using?
-Andy
"John McCoy" <igo...@ix.netcom.com> wrote in message
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Pat Ford
wrote:
>
>Degrade how?
>Voids or surface fills would disqualify it as exterior AB. Glue has to be
>"waterproof".
Exterior fir plywood with no voids!!!??? MARINE fir plywood with no
voids????!!!!
>What exactly are you encountering that makes you call the fir exterior AB
>ply "garbage"?
>Also, if you don't mind sharing the info, what part of the country are you
>in, what supplier have you been using?
You evidently do not live in the USA. YOu must live elsewhere, perhaps
an alternate parallel universe where fir plywood is built as it is
supposed to be.
Nobody
and toured their warehouse looking at the various marine plywoods they
carried. They had a huge stock of marine AA and AB douglas fir marine
(PS195) in sizes from 1/4" up to 1-1/2". I looked very closely at several
stacks to see if I could find any edge voids . . . there were none!
The AA and AB fir MARINE plywood carried by Harbor is very high quality.
However they (Harbor) charge a premium price for it, and they get that price
because their customers know that they do not accept "marine fir" with voids
from their supplyer. I can find better prices on everything that Harbor
sells, but their quality control and inspection are absolutely world class.
IMHO, it IS possible to find high quality fir marine plywood . . . but not
at Home Depot or Lowes. Harbor is a specialty supplyer to the boatbuilding
and signmaking industry. They do not market to or compete with the home
building industry.
Use a supplyer that you can trust or buy only what you can inspect and hand
pick yourself.
Buy the imported BS1088 certified stuff.
Live with the risk of using cheaper materials.
Tom Bloomer,
Hartly, DE USA
Jacques Mertens
System Three is correct but in some cases, for some of our boats, we still
specify marine.
The reason is that marine plywood has consistent characteristics and we
don't like to take a chance.
There is more to it than just thickness: a cheap 3/8 exterior will never be
as "strong" as a 3/8 marine ply.
In some cases, we prefer the guaranteed mechanical characteristics of marine
plywood, in other cases, it does not matter but the reason has nothing, or
almost nothing to do with resistance to moisture etc.
--
Jacques Mertens
Boat Plans OnLine
http://www.bateau.com
"jgubjr" <jgu...@nospamworldnet.att.net> wrote in message
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John McCoy
>
>Degrade how?
>Voids or surface fills would disqualify it as exterior AB. Glue has to be
>"waterproof".
Voids used to disqualify it. Not under the current rules. And no matter how
waterproof the glue, if there's not enough of it, the plys will delaminate, which
I've seen happen on "marine" graded fir plywood.
>What exactly are you encountering that makes you call the fir exterior AB
>ply "garbage"?
>Also, if you don't mind sharing the info, what part of the country are you
>in, what supplier have you been using?
South Fla. Don't recall what the manufacturer(s) were for the "marine" fir
ply. If I want marine ply, I'd order okoume from Boulters, I wouldn't even
look at fir now.
John
Rhett A. Davis
> Degrade how?
I spent a half hour this afternoon looking through an entire pile of "#2"
1X4s, I finally found one without knots and/or bark. 20+ years ago, I
remember wood like that to be strictly construction grade and would never be
rated #2. I suspect a widespread right wing conspiracy to hoard all the
finer woods.
> Voids or surface fills would disqualify it as exterior AB. Glue has to be
> "waterproof".
> What exactly are you encountering that makes you call the fir exterior AB
> ply "garbage"?
> Also, if you don't mind sharing the info, what part of the country are you
> in, what supplier have you been using?
I live in coastal Georgia, US. I have checked AB ext. Fir 1/4"ply in 14
building supply stores from Jacksonville to Savannah. The "good" A side
typically contains between 10 to 20 football shaped fills per sheet--the bad
B side between 20 to 30 small knots/knotholes.
I've yet to find any that would qualify by the criteria you describe, but if
I ever do I'm buying all my wallet will allow.
--
Rhett
rave...@bigfoot.com
<
P.C.
Pat Ford skrev i meddelelsen <3ada7922...@news.halcyon.com>...
>On Mon, 16 Apr 2001 02:57:42 GMT, "arbarnhart" <arbar...@aol.com>
>wrote:
>
>>
>>Degrade how?
>>Voids or surface fills would disqualify it as exterior AB. Glue has to be
>>"waterproof".
>Exterior fir plywood with no voids!!!??? MARINE fir plywood with no
>voids????!!!!
>
>>What exactly are you encountering that makes you call the fir exterior AB
>>ply "garbage"?
>>Also, if you don't mind sharing the info, what part of the country are you
>>in, what supplier have you been using?
>
>You evidently do not live in the USA. YOu must live elsewhere, perhaps
>an alternate parallel universe where fir plywood is built as it is
>supposed to be.
Well in a situasion where someone want to _buy_ a ply boat ,it will be strange
if the buyer don't care if the material is pine or mahogony , and what quality.
And I guess that this also mean ,that you can't expect a profesional builder to
use the cheapest quality he can get ,as then it will be quite hard to find
clients ;))
What would you expect ,if you was about to buy a ply boat ; wouldn't you ask for
first class materials, from a profesional builder :))
Wouldn't you say that you don't care if a builder could save a few $.
Migchelsen
quality African trees. That is what you pay for plus the propotional mark up.
Select ordinary plywood of at least A/C quality. AFTER you have cut the parts,
check the edges for the usually small voids. Enlarge the opening a bit.Seal
the bottom edge with tape. Pour in epoxy or a waterproof glue like plastic
resin. Let it dry overnight. The C-side has some plugs. They are mostly
clamped, not glued. Carefully pry them loose and reglue, or fill.
You have earned at least $40 per sheet. Sheers and chines. Barend .
pm
Part of the problem is that while the glue may be waterproof, the wood is
not. If the thinkness of the laminate is not penetrated with the glue the
wood will separate regardless of the glue used. I believe this penetration
problem is the reason the best waterproof plywoods have more laminates per
inch. Also it would contribute as to why more laminates are more expensive.
pm
Jacques Mertens
did not see?
--
Jacques Mertens
Boat Plans OnLine
http://www.bateau.com
"Migchelsen" <migch...@aol.com> wrote in message
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M. Walsh
"Jacques Mertens" <ne...@bateau.com> wrote in message
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