William R. Watt wrote:
Lew Hodgett ) writes:


The above applies ONLY to polyester, mat and roving.

It definitely does not apply to knitted glass and epoxy where the
glass/resin ration is about 50/50.


The above applies ONLY to vacuum bagging. 70% resin is optimistic for a home
builder filling weave by hand.

I don't agree either. 30% glass might be for a weak chopper gun
layup, but it's pretty easy to get up to 40-45% even with mat/roving
combinations. For knitted glass figure 50/50 without vacuum bagging,
maybe 54% if bagged.

Evan

On Sun, 20 Feb 2005 06:54:08 +0800, OldNick
wrote:
So, probably tape chines, inside and out, cover entire boat again
with like a 4 ounce glass and then throw a second layer of 6oz, or a
synthetic, on the bottom, and maybe wrap it a couple of inches up the
sides.

The second layer at 6 0z may be only 4? Watch the weight. You have to
carry this thing. Looking at the canoe as a 2' 6" half tube 5 yards
long, 10 oz of glass + resin = 28 lbs!

Does the strength come from layers or weight? i.e.: would one layer
of 12 oz be as good, better, or worse than two layers at 6 oz? or
three layers of 4 oz, 6 layers of 2oz 24 layers of 1/2 oz....etc....
I know in plywood, the more layers withina givin thickness, the
stronger the plywood. is it the same in fiber/epoxy?



A lot depends on your usage. If you are goping to simply work open
water with the occasional beach landing, then leave it at 1 layer. If
you are going to be really bashing it about, go for 2 layers.

To be honest, I am building this more because I saw the idea in a
magazine and it peaked my intrest. I rarely canoe, and it will
probably only see water a few times a year. In the off time it will
be stored in a shed, out of direct sunlight.

The one that interested me was Syntex, where they showed 2.8 oz cloth
holding up better than 6oz of glass. But I bet it's $$$$. And they
said it was a bitch to cut.

I've heard that about kevlar as well...

I don't have a building jig on this design. It is a simple canoe with
only two "corners"--One chine in the middle of the side, and then a
chine where it hits the bottom. Not sure if that would be considered
one chine or two, but either way it is a simple design.

Ok. Make sure the boat is very straight and true before you tape the
outside seams particularly. That is probably my point.

So noted. Thanks.

dave


email: dallyn_spam at yahoo dot com
please respond in this NG so others
can share your wisdom as well!

Dave Allyn ) writes:

To be honest, I am building this more because I saw the idea in a
magazine and it peaked my intrest. I rarely canoe, and it will
probably only see water a few times a year. In the off time it will
be stored in a shed, out of direct sunlight.

You can save yourself a lot of time and mess by just taping the seams and
painting or varnishing the hull. On my small plywood boats I don't even
tape the seams, just round off smooth the outside of the edges with a
sanding disk on my drill and then apply 2 layers of polyester resin along
the seams to seal and protect the exposed plywood edge. You have to seal
all the exposed plywood edges on the boat anyway to keep moisture from
getting into the edges where the end grain of the wood is open. I mix a
small amount (1 teaspoon) of resin at a time and spread it along the edge
with a toothpick. To each teaspoon of polyester resin you have to add 2
drops of hardener. I touch up the paint each spring and sometimes mid
season as well. (Photos of the boats on my website, see below.) I keep a
boating log which shows I go out about 30 times a season, usually for an
afternoon or evening.

Also seal the gunnel, top and bottom, if the boat is ever going to be
stored outside upside down, especially over the winter. Water will drain
off the bottom of an overturned boat and collect along the gunwale where
it can sit and rot. It will also hang and drip of the top of the gunwale
of an overturned boat. I've had to repair delmainating and rotting plywood
edges along a gunwale after storing a home built boat outside inverted over
the winter. The keel, skids, and bottoms have never been a proboem stored
upside down because water does not collect on them.

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Dave Allyn ) writes:

I almost picked up the luan, mainly for the lighter weight, but the
interior glue threw me. My understanding was I needed to have
exterior glue or the resin could (and probably would) delaminate the
layers. Is that not true? my lumber yard does not carry exterior
glued luan in 1/4" (actually, 5mm)

You need exterior grade plywood. They all use moisture resistant glue
except for the fancy wall panneling. If it's kept inside the store it's
usually not exterior grade. If it's keep outside, even under cover, it
should be exterior grade.

I don't know what kind of meranti or lauan is available in the USA. Here
in Ottawa we just have the underlayment, used to put on floors under
carpteting and vinyl. It has one thick inner ply and two thin outer plys.
You have to look for sheets whith few or no edge voids and few face flaws.
I've seen some poor stuff and some excellent stuff. I have filled voids by
drilling small holes through one face ply and pumping in caulk or adhesive
with a caulking gun. That works well. I got one sheet with worm holes in
one face ply which I filled with little drops of polyester resin before
oiling (I use linseed oil on the interior). If I were covering the hull
with fibreglass and resin I would not have bothered.

As I understand it, the only real need to sheath the hull is to keep the
fir plywood from checking and for that you need a pretty thick layer, from
what I've read.

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It's easier to get good wet out with layers of lighter cloth.
It could make a big difference depending on the skill of the builder.

Does the strength come from layers or weight? i.e.: would one layer
of 12 oz be as good, better, or worse than two layers at 6 oz? or
three layers of 4 oz, 6 layers of 2oz 24 layers of 1/2 oz....etc....
I know in plywood, the more layers withina givin thickness, the
stronger the plywood. is it the same in fiber/epoxy?



A lot depends on your usage. If you are goping to simply work open
water with the occasional beach landing, then leave it at 1 layer. If
you are going to be really bashing it about, go for 2 layers.

To be honest, I am building this more because I saw the idea in a
magazine and it peaked my intrest. I rarely canoe, and it will
probably only see water a few times a year. In the off time it will
be stored in a shed, out of direct sunlight.

The one that interested me was Syntex, where they showed 2.8 oz cloth
holding up better than 6oz of glass. But I bet it's $$$$. And they
said it was a bitch to cut.

I've heard that about kevlar as well...

I don't have a building jig on this design. It is a simple canoe with
only two "corners"--One chine in the middle of the side, and then a
chine where it hits the bottom. Not sure if that would be considered
one chine or two, but either way it is a simple design.

Ok. Make sure the boat is very straight and true before you tape the
outside seams particularly. That is probably my point.

So noted. Thanks.

dave


email: dallyn_spam at yahoo dot com
please respond in this NG so others
can share your wisdom as well!

"William R. Watt" wrote in message
...

Dave Allyn ) writes:

I almost picked up the luan, mainly for the lighter weight, but the
interior glue threw me. My understanding was I needed to have
exterior glue or the resin could (and probably would) delaminate the
layers. Is that not true? my lumber yard does not carry exterior
glued luan in 1/4" (actually, 5mm)

You need exterior grade plywood. They all use moisture resistant glue
except for the fancy wall panneling. If it's kept inside the store it's
usually not exterior grade. If it's keep outside, even under cover, it
should be exterior grade.

If I'm paying good $ for ply I expect it to have been kept dry and at stable
moisture content. INDOORS. My supplier stores everything in the same
warehouse - from marine ply through exterior through formply, chipboard ....

Leave a sheet of ply flat on the concrete floor of the workshop overnight
and it's no longer flat - put it out in the sun for a few hours and it's
bent the other way. And if it's moisture induced curvature, it will try to
go back to being flat when you make it into a boat.
DF


I don't know what kind of meranti or lauan is available in the USA. Here
in Ottawa we just have the underlayment, used to put on floors under
carpteting and vinyl. It has one thick inner ply and two thin outer plys.
You have to look for sheets whith few or no edge voids and few face flaws.
I've seen some poor stuff and some excellent stuff. I have filled voids by
drilling small holes through one face ply and pumping in caulk or adhesive
with a caulking gun. That works well. I got one sheet with worm holes in
one face ply which I filled with little drops of polyester resin before
oiling (I use linseed oil on the interior). If I were covering the hull
with fibreglass and resin I would not have bothered.

As I understand it, the only real need to sheath the hull is to keep the
fir plywood from checking and for that you need a pretty thick layer, from
what I've read.

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Dave,

Neither fiberglass nor fabrics like Dynel® add significant strength and
the checking problem with BCX pine plywood is insignificant. Tape your
joints inside and out and paint with 100% acrylic latex exterior paint
of your preferred gloss. For more on this and other heresies see:
http://www.angelfire.com/nc3/davecarnell/

Dave Carnell

Dave Allyn wrote:

I am building a S&G canoe. I am going to use fiberglass cloth on the
entire outside for extra strength, and to prevent any checking in the
plywood. I'm useing 1/4" BCx plywood.

What weight of cloth would I want to use for this aplication? And the
next question, how would I decide that on future projects? Is there a
general rule of thumb for weight?

One last question, I know I need to tape the inside and outside with
fiberglass tape on the seams, but If I cover the whole outside with
cloth, do I still need the tape on the outside of the seams?

Thanks,

dave


email: dallyn_spam at yahoo dot com
please respond in this NG so others
can share your wisdom as well!

Dave Carnell ) writes:
Dave,


the checking problem with BCX pine plywood is insignificant. Tape your

Oh, I thought he meant BC fir plywood.

Nice to hear from you.



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Dave Allyn wrote:
On Sun, 20 Feb 2005 06:54:08 +0800, OldNick
wrote:

So, probably tape chines, inside and out, cover entire boat again
with like a 4 ounce glass and then throw a second layer of 6oz, or a
synthetic, on the bottom, and maybe wrap it a couple of inches up the
sides.

The second layer at 6 0z may be only 4? Watch the weight. You have to
carry this thing. Looking at the canoe as a 2' 6" half tube 5 yards
long, 10 oz of glass + resin = 28 lbs!


Does the strength come from layers or weight? i.e.: would one layer
of 12 oz be as good, better, or worse than two layers at 6 oz? or
three layers of 4 oz, 6 layers of 2oz 24 layers of 1/2 oz....etc....
I know in plywood, the more layers withina givin thickness, the
stronger the plywood. is it the same in fiber/epoxy?

More layers of thinner cloth will be stronger and more flexible than a
single layer of heavier cloth.

Dave Carnell wrote:
Dave,

Neither fiberglass nor fabrics like Dynel® add significant strength and
the checking problem with BCX pine plywood is insignificant. Tape your
joints inside and out and paint with 100% acrylic latex exterior paint
of your preferred gloss. For more on this and other heresies see:
http://www.angelfire.com/nc3/davecarnell/

Who are you kidding? Perhaps that's true of larger boats with thick wood
skins, but fiberglass adds substantial strength when you're dealing with
light weight, thin skinned boats like canoes and kayaks. This is
especially true with sandwich construction where the core of plywood or
cedar strips is fully encapsulated in fiberglass.