"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.

"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.

"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

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/

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/

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.

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/

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

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.

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.