Marine Plywood?
 

My Potter 15 rudder is made of 4 pieces. The top is a solid core about
10"x15", with two pieces of plywood screwed to it on either side measuring
10"x30". The solid blade mounts between the plywood, below the solid top.

One side of the plywood is falling apart, and the other side isn't doing
much better. I went to the lumber yard today to buy some plywood to replace
the bad parts. They have Marine Fir and Marine Okoume. They told me that
neither will be durable; they have to be covered with fiberglass. If that
is true, it certainly explains why the original is falling apart, as it is
not covered in fiberglass.

I bought a piece of fir, which I will cover with spar varnish just to get me
through the end of the year. This winter I will rebuild the whole thing.
(neither the top core nor the rudder blade are looking real good either).

What is the story on plywood? Is nothing suitable for marine use without
being fiberglassed? Would solid wood (3/8") substitute? Any advice on how
I go about doing this so it is durable would be appreciated.

Marine Plywood?
 

What is the story on plywood? Is nothing suitable for marine use without
being fiberglassed? Would solid wood (3/8") substitute? Any advice on
how I go about doing this so it is durable would be appreciated.
Thinking about it, how about making the top core and one side out of one
piece of solid wood, and then using a second piece of solid wood for the
second side? I could partially resaw the core/side to remove most of the
wood (where the rudder blade goes), and rout out the balance. That way it
would all expand evenly, since it is all the same wood oriented the same,
without any pesky plywood.
Would it be strong enough?

Marine Plywood?
 

Toller wrote:
My Potter 15 rudder is made of 4 pieces. The top is a solid core about
10"x15", with two pieces of plywood screwed to it on either side measuring
10"x30". The solid blade mounts between the plywood, below the solid top.

One side of the plywood is falling apart, and the other side isn't doing
much better. I went to the lumber yard today to buy some plywood to replace
the bad parts. They have Marine Fir and Marine Okoume. They told me that
neither will be durable; they have to be covered with fiberglass. If that
is true, it certainly explains why the original is falling apart, as it is
not covered in fiberglass.

I bought a piece of fir, which I will cover with spar varnish just to get me
through the end of the year. This winter I will rebuild the whole thing.
(neither the top core nor the rudder blade are looking real good either).

What is the story on plywood? Is nothing suitable for marine use without
being fiberglassed? Would solid wood (3/8") substitute? Any advice on how
I go about doing this so it is durable would be appreciated.

Thinking about it, how about making the top core and one side out of one
piece of solid wood, and then using a second piece of solid wood for the
second side? I could partially resaw the core/side to remove most of the
wood (where the rudder blade goes), and rout out the balance. That way it
would all expand evenly, since it is all the same wood oriented the same,
without any pesky plywood.
Would it be strong enough?

Toller,
One should very much wonder about the individual that told you that
marine fir would not be durable enough.
The difference between the marine PW and others is 2-fold.
1- PW graded as marine has no voids in the core.
2- The bonding adhesive has very low water permeability (it used to be
better than exterior, but common exterior now usually uses the same process.

Time was all small boats that were not clinker plank (even some that
were) were made from marine plywood, and some are still out there.
I have made rudders and centerboards from marine PW.

Fiberglassing PW will just assure that it never has a chance to dry out
(Oh- sure it is completely encapsulated - with ZERO porosity or
permeability - Right - )

You can make PW cheek pieces and replace those on the rudder. What you
make them from is not of much consequence in actual fact.

The plan you outline in that last paragraph sounds like a whole lot of
work.

Matt Colie
Lifelong Waterman, Licensed Mariner, Congenital Sailor
and Third Generation Boatbuilder

Marine Plywood?
 

Or, you could simply buy a replacement from West Wight...

http://www.westwightpotter.com/

...maybe even upgrade to their 'Kick Up Beaching Rudder'?

The issue with Douglas Fir plywood - marine or otherwise - is that is
'checks' - or cracks along the outer ply layer. Water can ingress
along these cracks, and the rot process begins.

The solution is to cover the plywood with fiberglass (stops the
checking) and epoxy resin (stops the water). The application of these
materials should be considered carefully, meaning that additional
research into 'fiberglass and epoxy plywood encapsulation' should be
undertaken before starting.

Note that any screw / bolt holes in or through the rudder / tiller are
an area of concern.

Common practice (for bolts) is to drill an oversize hole, fill with a
thickened epoxy slurry, allow to cure, then re-drill with the
appropriate sized hole. In this way, water never gets to the wood.
For screws, much the same except allow the crew to penetrate the wood
for about 1/2 its length, i.e. 'drill oversize' for 1/2 the length of
the screw.

Anyway... good luck!

MW

Marine Plywood?
 

A few thoughts:
Ply, since it is laminated, is much more resistant to warping than solid
wood. It's also able to take impact and strain without splitting as solid
wood might. Provided you can keep the water out, it's a very stable
material.
Ply is, pound for pound, really strong. Good marine ply is void-free and
uses waterproof glues. I build stitch and glue kayaks, where the 4mm (3/16")
ply is encapsulated in epoxy resin - about 4 coats on each side. Our 'yaks
take a pounding on our rocky beaches, and I've yet to damage the ply itself.
Provided you epoxy seal both the inside and outside surfaces with multiple
coats of resin, or even fiberglass cloth soaked out with epoxy, making sure
you seal the end grain really well, there's no reason the ply won't outlast
any solid wood, and possibly you
:-))
Make sure you use epoxy, and not polyester resin - the poly doesn't stick to
things or hold them together
nearly as well.
BTW - that Potter is one sweet little craft - used to admire them greatly in
our sailing days, before we downsized and simplified things to kayaks and
canoes.

"Toller" wrote in message
...
My Potter 15 rudder is made of 4 pieces. The top is a solid core about
10"x15", with two pieces of plywood screwed to it on either side measuring
10"x30". The solid blade mounts between the plywood, below the solid top.

One side of the plywood is falling apart, and the other side isn't doing
much better. I went to the lumber yard today to buy some plywood to
replace the bad parts. They have Marine Fir and Marine Okoume. They told
me that neither will be durable; they have to be covered with fiberglass.
If that is true, it certainly explains why the original is falling apart,
as it is not covered in fiberglass.

I bought a piece of fir, which I will cover with spar varnish just to get
me through the end of the year. This winter I will rebuild the whole
thing. (neither the top core nor the rudder blade are looking real good
either).

What is the story on plywood? Is nothing suitable for marine use without
being fiberglassed? Would solid wood (3/8") substitute? Any advice on
how I go about doing this so it is durable would be appreciated.

Marine Plywood?
 

On Sep 10, 12:00 pm, "Toller" wrote:
My Potter 15 rudder is made of 4 pieces. The top is a solid core about
10"x15", with two pieces of plywood screwed to it on either side measuring
10"x30". The solid blade mounts between the plywood, below the solid top.

Those side pieces are called the rudder cheeks. I've replaced mine on
a 21 foot mahogony strip saiboat. They get a lot of stress when
running before the wind with waves comming under the transom and
trying to change your course on you. I just used ordinary fir plywood
without any voids in it. It should be thick and stong. The thickness
might be determined by the hardware used to hang the rudder off the
transom (pintles and gudgeons) although you can rout the plywood to
accept narrow hardware.


One side of the plywood is falling apart, and the other side isn't doing
much better. I went to the lumber yard today to buy some plywood to replace
the bad parts. They have Marine Fir and Marine Okoume. They told me that
neither will be durable; they have to be covered with fiberglass. If that
is true, it certainly explains why the original is falling apart, as it is
not covered in fiberglass.

I bought a piece of fir, which I will cover with spar varnish just to get me
through the end of the year. This winter I will rebuild the whole thing.
(neither the top core nor the rudder blade are looking real good either).

What is the story on plywood? Is nothing suitable for marine use without
being fiberglassed? Would solid wood (3/8") substitute? Any advice on how
I go about doing this so it is durable would be appreciated.

Marine Plywood?
 

"Wm Watt" wrote in message
oups.com...
On Sep 10, 12:00 pm, "Toller" wrote:
My Potter 15 rudder is made of 4 pieces. The top is a solid core about
10"x15", with two pieces of plywood screwed to it on either side
measuring
10"x30". The solid blade mounts between the plywood, below the solid
top.

Those side pieces are called the rudder cheeks. I've replaced mine on
a 21 foot mahogony strip saiboat. They get a lot of stress when
running before the wind with waves comming under the transom and
trying to change your course on you. I just used ordinary fir plywood
without any voids in it. It should be thick and stong. The thickness
might be determined by the hardware used to hang the rudder off the
transom (pintles and gudgeons) although you can rout the plywood to
accept narrow hardware.

Rudder Cheeks eh? What is the piece between the cheeks called?
Mine are 3/8" ply, routed down to 3/16" at the hardware.

What did you put on them to waterproof them?

Marine Plywood?
 

On Sep 12, 1:17 pm, "Toller" wrote:

Rudder Cheeks eh? What is the piece between the cheeks called?
Mine are 3/8" ply, routed down to 3/16" at the hardware.

What did you put on them to waterproof them?-

Paint. For the edges anything you have handy will do. They are not
going to be under water. If I were doing it today I'd spread polyester
resin along the edges where it can soak in to keep moisture from
penetrating. Epoxy, polyurethane varnish, or even linseed oil if
that's what you have at hand.

I'd also smear polyester resin on any places which would chafe, for
example if the tiller is inserted between the cheeks (I don't know
what that's called), or the rudder rotates between the cheeks ("kick
up" rudder) . Polyester is good for abraision resistance. I use it on
my home built boats where parts might rub. I coated the inside of a
dagger board trunk with it. Just the resin, no fibreglass
reinforcement. Or epoxy if that's what you have.

Marine Plywood?
 

"Wm Watt" wrote in message
oups.com...
On Sep 12, 1:17 pm, "Toller" wrote:

Rudder Cheeks eh? What is the piece between the cheeks called?
Mine are 3/8" ply, routed down to 3/16" at the hardware.

What did you put on them to waterproof them?-

Paint. For the edges anything you have handy will do. They are not
going to be under water. If I were doing it today I'd spread polyester
resin along the edges where it can soak in to keep moisture from
penetrating. Epoxy, polyurethane varnish, or even linseed oil if
that's what you have at hand.

I'd also smear polyester resin on any places which would chafe, for
example if the tiller is inserted between the cheeks (I don't know
what that's called), or the rudder rotates between the cheeks ("kick
up" rudder) . Polyester is good for abraision resistance. I use it on
my home built boats where parts might rub. I coated the inside of a
dagger board trunk with it. Just the resin, no fibreglass
reinforcement. Or epoxy if that's what you have.

I have epoxy (and linseed oil and polyurethane varnish) but hesitate to use
it since it is not UV stable.
I have never used polyester, but have heard it doesn't adhear worth a damn.
That is not your experience I take it?

Marine Plywood?
 

Toller wrote:

I have never used polyester, but have heard it doesn't adhear worth
a damn. That is not your experience I take it?

A lot of things - including the 40' ply and fiberglass Newporter
ketch - were made with polyester resin. Does it stick as well as
epoxy? No. But it isn't exactly easy to get off either.

When I had a sizeable sailboat I used it (with fiberglass) on anything
I made of ply - trunk cabin deck, dog house, hatchs, etc. - and never
had any adhesion problem in the 20 years I owned the boat.

Consider the number of cars that have had dings filled with Bondo.
Bondo is polyester resin and talc. Have you seen many chunks of Bondo
along the roadside?


--

dadiOH
____________________________

dadiOH's dandies v3.06...
....a help file of info about MP3s, recording from
LP/cassette and tips & tricks on this and that.
Get it at http://mysite.verizon.net/xico

Marine Plywood?
 

"dadiOH"
Consider the number of cars that have had dings filled with Bondo.
Bondo is polyester resin and talc. Have you seen many chunks of Bondo
along the roadside?

Alas, yes.

Marine Plywood?
 

"Toller"
I have epoxy (and linseed oil and polyurethane varnish) but hesitate to
use it since it is not UV stable.

Almost nothing is UV stable, including paint, wood, epoxy, varnish,
polyurethane, and wood.

However, sealing plywood edges with epoxy, lightweight fiberglass (with the
appropriate weight fabric and a curve that it can take), covered with primer
and paint, is as good as you can plan for. As long as you maintain the paint
for appearance, it will probably serve to preserve the epoxy & fiberglass.
I figure that a decent job of it, aside from direct scrapes and dings,
should be good for 5-10 years of regular use.

If you're looking at the leading edge of a kick-up rudder that meets the
ground routinely, you'll need more than one layer of glass, and regular
touch-ups of paint.

Marine Plywood?
 

"dadiOH"
Consider the number of cars that have had dings filled with Bondo.
Bondo is polyester resin and talc. Have you seen many chunks of Bondo
along the roadside?

More than I can remember.

You can spot a "Bondo Job" from a 100 ft in a snow storm.

Lew

Marine Plywood?
 

On Sep 11, 12:00 am, "Toller" wrote:
My Potter 15 rudder is made of 4 pieces. The top is a solid core about
10"x15", with two pieces ofplywoodscrewed to it on either side measuring
10"x30". The solid blade mounts between theplywood, below the solid top.

One side of theplywoodis falling apart, and the other side isn't doing
much better. I went to the lumber yard today to buy someplywoodto replace
the bad parts. They have Marine Fir and Marine Okoume. They told me that
neither will be durable; they have to be covered with fiberglass. If that
is true, it certainly explains why the original is falling apart, as it is
not covered in fiberglass.

I bought a piece of fir, which I will cover with spar varnish just to get me
through the end of the year. This winter I will rebuild the whole thing.
(neither the top core nor the rudder blade are looking real good either).

What is the story onplywood? Is nothing suitable for marine use without
being fiberglassed? Would solid wood (3/8") substitute? Any advice on how
I go about doing this so it is durable would be appreciated.

You can buy a marine plywood as the following:
Species: hardwood(red hardwood like Okoume is better) or birch
Glue:best Phenolic glue
The core should be void free .

Mason Pan
http://www.plywood.cc/

Marine Plywood?
 

Okume is not hardwood it is softwood, as such it is often covered in
fiberglass. In France we use Moabi plywood with f/g but I'm not sure
if its available in your area.

Mason Pan wrote:
On Sep 11, 12:00 am, "Toller" wrote:

My Potter 15 rudder is made of 4 pieces. The top is a solid core about
10"x15", with two pieces ofplywoodscrewed to it on either side measuring
10"x30". The solid blade mounts between theplywood, below the solid top.

One side of theplywoodis falling apart, and the other side isn't doing
much better. I went to the lumber yard today to buy someplywoodto replace
the bad parts. They have Marine Fir and Marine Okoume. They told me that
neither will be durable; they have to be covered with fiberglass. If that
is true, it certainly explains why the original is falling apart, as it is
not covered in fiberglass.

I bought a piece of fir, which I will cover with spar varnish just to get me
through the end of the year. This winter I will rebuild the whole thing.
(neither the top core nor the rudder blade are looking real good either).

What is the story onplywood? Is nothing suitable for marine use without
being fiberglassed? Would solid wood (3/8") substitute? Any advice on how
I go about doing this so it is durable would be appreciated.


You can buy a marine plywood as the following:
Species: hardwood(red hardwood like Okoume is better) or birch
Glue:best Phenolic glue
The core should be void free .

Mason Pan
http://www.plywood.cc/

Marine Plywood?
 

Go with rotary cut Sapele. It is reasonably rot resistant, much more so
than Occume or Gaboon. It is about as strong as Fir but without the
checking issues.

It costs about 2 times what Occume or Fir costs. If you plan to keep the
boat...go with the best materials and you won't have to do this job again.

Marine Plywood?
 

Okoume is hardwood .
Hardwood means "wood from broad-leaved or deciduous species of trees
(not necessarily hard or dense)" .

Mason Pan
http://www.plywood.cc/

On Sep 23, 3:57 am, Phil wrote:
Okume is not hardwood it is softwood, as such it is often covered in
fiberglass. In France we use Moabi plywood with f/g but I'm not sure
if its available in your area.

Mason Pan wrote:
On Sep 11, 12:00 am, "Toller" wrote:

My Potter 15 rudder is made of 4 pieces. The top is a solid core about
10"x15", with two pieces ofplywoodscrewed to it on either side measuring
10"x30". The solid blade mounts between theplywood, below the solid top.

One side of theplywoodis falling apart, and the other side isn't doing
much better. I went to the lumber yard today to buy someplywoodto replace
the bad parts. They have Marine Fir and Marine Okoume. They told me that
neither will be durable; they have to be covered with fiberglass. If that
is true, it certainly explains why the original is falling apart, as it is
not covered in fiberglass.

I bought a piece of fir, which I will cover with spar varnish just to get me
through the end of the year. This winter I will rebuild the whole thing.
(neither the top core nor the rudder blade are looking real good either).

What is the story onplywood? Is nothing suitable for marine use without
being fiberglassed? Would solid wood (3/8") substitute? Any advice on how
I go about doing this so it is durable would be appreciated.

You can buy a marine plywood as the following:
Species: hardwood(red hardwood like Okoume is better) or birch
Glue:best Phenolic glue
The core should be void free .

Mason Pan
http://www.plywood.cc/

Marine Plywood?
 

On Thu, 11 Oct 2007 01:41:03 -0700, Mason Pan
wrote:

Okoume is hardwood .
Hardwood means "wood from broad-leaved or deciduous species of trees
(not necessarily hard or dense)" .

Balsa is a hardwood. Yellow pine is evergreen and the wood is quite
hard for a pine, of interest if you make tables or floors, and not
meaning jack **** for framing. The confusion begins with the simple
fact that among kinds of lumber pretty much all the hardwoods for sale
are in fact harder than the softwoods for sale. All wood is not
commercial lumber. There is balsa and there is ironwood, which doesn't
float in water.You don't finder either at a lumber yard.

Casady

Marine Plywood?
 

On Sep 10, 10:00 am, "Toller" wrote:
What is the story on plywood? Is nothing suitable for marine use without
being fiberglassed?

As others have pointed out, you have to be careful fiberglassing
plywood.
I build driftboats with marine fir and/or mahogany, covered with
glass.
But only for sides and seats. For the bottoms I use a plastic
honeycomb
core from Nida Core or Plascore. Plywood that stays in contact with
the water will eventually get nicked or dinged. Water will migrate
into
the plywood and then you're toast--well, soggy french toast maybe.
At that point you have to grind off the fiberglass and move to Arizona
for a month or two.

You could make your rudder with 3/4" Plascore, stiffened up with
glass on both sides, with puttied and taped edges. It's a quick and
easy way to
make lightweight, stiff, water proof parts.

Marine Plywood?
 

salmobytes wrote:
Plywood that stays in contact with
the water will eventually get nicked or dinged. Water will migrate
into the plywood and then you're toast--well, soggy french toast maybe.
At that point you have to grind off the fiberglass and move to Arizona
for a month or two.

This must really sound weird to the thousands of plywood sailboats
owners. There are plenty of 30 to 40 years old boats still sailing. Well
painted marine plywood is very durable.

Marine Plywood?
 

On Oct 27, 7:08 am, Jean-Francois Dockes
wrote:
salmobytes wrote:
Plywood that stays in contact with
the water will eventually get nicked or dinged. Water will migrate
into the plywood and then you're toast--well, soggy french toast maybe.
At that point you have to grind off the fiberglass and move to Arizona
for a month or two.

This must really sound weird to the thousands of plywood sailboats
owners. There are plenty of 30 to 40 years old boats still sailing. Well
painted marine plywood is very durable.

I was talking about marine plywood skinned in fiberglass.
The fiberglass will eventually get cut or broken. And then
moisture will migrate in the plywood core. This happens a lot
faster on driftboats than sailboats. But the process is inevitable,
at least for plywood that stays in contact with the water a lot.

Marine Plywood?
 

..........and even then I was talking about hulls
made with plywood that is skinned on *both* sides
with fiberglass. Hull that have fiberglass on the outside
and a paint or oil finish inside can more easily dry out.

I've seen driftboats--with 'encapsulated' epoxy fiberglass bottoms--so
saturated with water their weight was almost double. If you do
build that way you have to keep up with the repairs, adn patch
dinged fiberglass almost right away (not all that hard to do,
but you must do it).

Or you can build with honeycomb core. It's bullet proof and fool
proof,
almost. You can pre-fiberglass honeycomb core while it's still
flat, on top of visqueen covered saw horses, and then treat it
like plywood.

Marine Plywood?
 

On Oct 27, 11:35 am, salmobytes wrote:
..........and even then I was talking about hulls
made with plywood that is skinned on *both* sides
with fiberglass. Hull that have fiberglass on the outside
and a paint or oil finish inside can more easily dry out.

I've seen driftboats--with 'encapsulated' epoxy fiberglass bottoms--so
saturated with water their weight was almost double. If you do
build that way you have to keep up with the repairs, adn patch
dinged fiberglass almost right away (not all that hard to do,
but you must do it).

Or you can build with honeycomb core. It's bullet proof and fool
proof,
almost. You can pre-fiberglass honeycomb core while it's still
flat, on top of visqueen covered saw horses, and then treat it
like plywood.

The encapsulation is the problem. Once water gets in, and it will, it
can't get out. The best way to handle plywood in my opinion is with
paint which is more easily repaired, and allows for some breathing. I
have some plywood boats over a decade old that are fine. One in
particular, a Payson Skimmer has a glass sheathing on the bottom, but
the inside of the ply is paint. I know that about a hundred folks will
come in and slam me here, like every other time I say eposy is not
waterproof in practice, even if it is in theory so I will not argue. I
have built over 60 plywood boats in my life...

Marine Plywood?