Stitch and glue canoe; scarf or butt?
 

Graduating to my first multi-sheet stitch-n-glue... butt joints with blocks
are ugly, scarfing will throw off my sheet layout. Can I use a plain butt
joint, supported on both sides by glass and epoxy?

Chuck

Stitch and glue canoe; scarf or butt?
 

On Sat, 29 May 2004 15:43:35 GMT, "Chalatso"
wrote:

Graduating to my first multi-sheet stitch-n-glue... butt joints with blocks
are ugly, scarfing will throw off my sheet layout. Can I use a plain butt
joint, supported on both sides by glass and epoxy?

Chuck

Reassure yourself with a test strip say 3 X 12 inches bonded on the
narrow side to another similar piece. Tape both sides.
Then bend to failure.

Did it fail at the joint?
The method is no good.
It failed in the plain ply? Good!

This test is more authoritive than any post you may read here.

Brian W

Stitch and glue canoe; scarf or butt?
 

yes that is the prefered method on many boats. Contact your designer and
ask what material you should use.

--
Matt Langenfeld
JEM Watercraft
http://jem.e-boat.net/

Chalatso wrote:

Graduating to my first multi-sheet stitch-n-glue... butt joints with blocks
are ugly, scarfing will throw off my sheet layout. Can I use a plain butt
joint, supported on both sides by glass and epoxy?

Chuck

Stitch and glue canoe; scarf or butt?
 

"Brian Whatcott" wrote...

Graduating to my first multi-sheet stitch-n-glue... butt joints with
blocks
are ugly, scarfing will throw off my sheet layout. Can I use a plain butt
joint, supported on both sides by glass and epoxy?

Reassure yourself with a test strip say 3 X 12 inches bonded on the
narrow side to another similar piece. Tape both sides.
Then bend to failure.

Did it fail at the joint?
The method is no good.
It failed in the plain ply? Good!

It probably depends also on how the joint will be stressed. If it's in an
area where bending stresses are minimal, it may work just fine. However, if
it is subject to repeated bending loads, it may eventually fail. Also, if
the joint is marginal to begin with, quality control is critical -- make
sure your production pieces are AT LEAST as good as your test pieces.

A compromise may be to use several layers of tape at the joint,
appropriately beveled, to spread the load further. The final layer of cloth
over the hull will add to the strength.

Stitch and glue canoe; scarf or butt?
 

Another consideration is how the boat will be finished. If it's to be bright
(varnished), then a carefully done scarph is the best choice. If painted, a
taped butt, as at http://www.instantboats.com/images/buttjoint700.gif , is
OK. I'd suggest cutting the cloth on the bias, so that all of its threads
cross the joint.
With a little practice, the scarph takes less time.


Chalatso wrote:

Graduating to my first multi-sheet stitch-n-glue... butt joints with blocks
are ugly, scarfing will throw off my sheet layout. Can I use a plain butt
joint, supported on both sides by glass and epoxy?

Chuck

Stitch and glue canoe; scarf or butt?
 

"Jim Conlin" wrote...
Another consideration is how the boat will be finished. If it's to be
bright
(varnished), then a carefully done scarph is the best choice. If painted,
a
taped butt, as at http://www.instantboats.com/images/buttjoint700.gif ,
is
OK. I'd suggest cutting the cloth on the bias, so that all of its
threads
cross the joint.

I taped butt can look good, too. Pygmy uses them on their kayak kits.
Maybe not as elegant as a scarph, but still in character for the boat.

Stitch and glue canoe; scarf or butt?
 

What weight of glass is used? I've found taht its very hard to get glass over
8-10 oz. not to be cloudy.

John R Weiss wrote:

"Jim Conlin" wrote...
Another consideration is how the boat will be finished. If it's to be
bright
(varnished), then a carefully done scarph is the best choice. If painted,
a
taped butt, as at http://www.instantboats.com/images/buttjoint700.gif ,
is
OK. I'd suggest cutting the cloth on the bias, so that all of its
threads
cross the joint.

I taped butt can look good, too. Pygmy uses them on their kayak kits.
Maybe not as elegant as a scarph, but still in character for the boat.

Stitch and glue canoe; scarf or butt?
 

Well, the boat is the bateau.com "cheap canoe," and they suggest a butt
joint, with a block glued over the butt. I think the method suffers a lot
for looks. The joint is right across the fattest part of the canoe, exactly
at the middle. There's added stiffness in the sides from a rubrail, and I
might add a little inwale and a bottom runner, if the taped butt makes me
nervous.

Chuck

It probably depends also on how the joint will be stressed. If it's in an
area where bending stresses are minimal, it may work just fine. However,
if
it is subject to repeated bending loads, it may eventually fail. Also, if
the joint is marginal to begin with, quality control is critical -- make
sure your production pieces are AT LEAST as good as your test pieces.

A compromise may be to use several layers of tape at the joint,
appropriately beveled, to spread the load further. The final layer of
cloth
over the hull will add to the strength.

Stitch and glue canoe; scarf or butt?
 

"Jim Conlin" wrote...
What weight of glass is used? I've found taht its very hard to get glass
over
8-10 oz. not to be cloudy.

Light tape (2 oz?) on the joint, with 6 oz glass over the entire hull. No
clouds after 4 years...

Since the inside of the butt is hidden, a wood block is used on 1 side for
strength. Though it does cause a minor straightening of the curve in the
hull, it is not detectable except under close scrutiny.


John R Weiss wrote:

I taped butt can look good, too. Pygmy uses them on their kayak kits.
Maybe not as elegant as a scarph, but still in character for the boat.

Stitch and glue canoe; scarf or butt?
 

"Chalatso" wrote...
Well, the boat is the bateau.com "cheap canoe," and they suggest a butt
joint, with a block glued over the butt. I think the method suffers a lot
for looks. The joint is right across the fattest part of the canoe,
exactly
at the middle. There's added stiffness in the sides from a rubrail, and I
might add a little inwale and a bottom runner, if the taped butt makes me
nervous.

You might be able to make it a bit more elegant by tapering the block edges.
From the photo of the NC16 on the site, the thwart will draw a lot of
attention away from the blocks. Also, I note they say the blocks may be
made from fiberglass, so a thin strip of tape, followed by a couple layers
of cloth built up with feathered edges may work out just fine.

From the curve of the hull, it appears the tensile stress on the outside of
the hull (where they show no blocks) will predominate over the compressive
stress inboard. Also, if the thwart is glassed in, it will help
considerably in stabilizing the joint. You might also add a fillet or block
under the edge of the thwart, if not already in the plans.

If you're going to paint it, using Kevlar instead of glass may provide more
stiffness with less build-up...

Stitch and glue canoe; scarf or butt?
 

On Sat, 29 May 2004 22:43:44 UTC, Jim Conlin
wrote:

What weight of glass is used? I've found taht its very hard to get glass over
8-10 oz. not to be cloudy.

Why go higher than 4 or 6?? I got multilayers 6oz on my kayak (hull).

Regards
--
steen - menzi.dk
Ready for OpenOffice?
---

Stitch and glue canoe; scarf or butt?
 

"Chalatso" ) writes:
Graduating to my first multi-sheet stitch-n-glue... butt joints with blocks
are ugly, scarfing will throw off my sheet layout. Can I use a plain butt
joint, supported on both sides by glass and epoxy?

yes. however I don't find butt blocks ugly. the ones on my Dogskiff are
beautiful, traditional, functional, and cheap. edges tapered with a sander
before installation. traditional clinched copper nails. lauan underlayment
plywood. a thin line of epoxy applied to the exterior seam with a
toothpick to keep moisture out of the join. interior finished clear with
cheap linseed oil. photos on my website under "Boats".

--
------------------------------------------------------------------------------
William R Watt National Capital FreeNet Ottawa's free community network
homepage: www.ncf.ca/~ag384/top.htm
warning: non-freenet email must have "notspam" in subject or it's returned

Stitch and glue canoe; scarf or butt?
 

I have used a joint that Dynamite Payson developed. It calls for making a
butt joint by scarfing both sides of the stock and using epoxy/glass for the
joint. Lay the pieces on a flat surface in position. Mark the length of
the scarf on both ends. Grind half way through both pieces where they meet
and tapering to nothing at the ends of the scarfs. This results in a
shallow vee spanning both pieces. Fill the vee with glass cloth, roving and
epoxy. When set, grind the epoxy surface flat. Now, carefully turn the
assembly over and make another vee just like before. Fill vee as on the
other side. This makes a very strong joint and if done carefully is not
detectable (if painted). Email me if the method is not clear.
Dave
"Chalatso" wrote in message
. ..
Graduating to my first multi-sheet stitch-n-glue... butt joints with
blocks
are ugly, scarfing will throw off my sheet layout. Can I use a plain butt
joint, supported on both sides by glass and epoxy?

Chuck

Stitch and glue canoe; scarf or butt?
 

"Dave W" wrote in message ...
I have used a joint that Dynamite Payson developed. It calls for making a
butt joint by scarfing both sides of the stock and using epoxy/glass for the
joint. Lay the pieces on a flat surface in position. Mark the length of
the scarf on both ends. Grind half way through both pieces where they meet
and tapering to nothing at the ends of the scarfs.

You don't have to taper it down that far. I just take the pieces
temporarily end to end and belt sand down about 30% of the way through
the pieces (6mm-1/4" material) making a slight trough about 4-5" wide,
lay in a couple of layers of fiberglass tape, say 6 oz, fill with
resin, and cover it with a sheet of wax paper to cure, flip and repeat
on the other side of the board. (note: it is easier to wet the
fiberglass material before laying it on the part, soak the part good
first too. Remember, it is easier to draw goo up through cloth, than
drive goo down into air under cloth ;)I have even used a couple of
layers of 3.5oz tight weave right on the outside of the wood, both
sides, putty in the edges, paint. Although the joint you make has a
"bulge", it will also tend not to bend there. So when you bend the
part around the frames, the flatspot has a nice "bulge" to fair right
in and paint over... Hope that makes sence, it is the easiest of all
but should not be done without the advice of the designer.
Scotty


This results in a
shallow vee spanning both pieces. Fill the vee with glass cloth, roving and
epoxy. When set, grind the epoxy surface flat. Now, carefully turn the
assembly over and make another vee just like before. Fill vee as on the
other side. This makes a very strong joint and if done carefully is not
detectable (if painted). Email me if the method is not clear.
Dave
"Chalatso" wrote in message
. ..
Graduating to my first multi-sheet stitch-n-glue... butt joints with
blocks
are ugly, scarfing will throw off my sheet layout. Can I use a plain butt
joint, supported on both sides by glass and epoxy?

Chuck

Stitch and glue canoe; scarf or butt?
 

Just a thought,
I thought of building a canoe out of 2 layers of 1/8 ply, The joints could
them be staggered there would be no transition, no complicated scarfs and
more strength than butt joints, I was thinking of using contact cement
between the layers, only because I dont have a vacuum to hold the layers at
a uniform tension.
Another idea I am playing with is making two 8' halves with transoms at the
end and joining them together as a single canoe.
Hope this helps

"John R Weiss" wrote in message
news:7t9uc.10769$IB.9176@attbi_s04...
"Chalatso" wrote...
Well, the boat is the bateau.com "cheap canoe," and they suggest a butt
joint, with a block glued over the butt. I think the method suffers a
lot
for looks. The joint is right across the fattest part of the canoe,
exactly
at the middle. There's added stiffness in the sides from a rubrail, and
I
might add a little inwale and a bottom runner, if the taped butt makes
me
nervous.

You might be able to make it a bit more elegant by tapering the block
edges.
From the photo of the NC16 on the site, the thwart will draw a lot of
attention away from the blocks. Also, I note they say the blocks may be
made from fiberglass, so a thin strip of tape, followed by a couple layers
of cloth built up with feathered edges may work out just fine.

From the curve of the hull, it appears the tensile stress on the outside
of
the hull (where they show no blocks) will predominate over the compressive
stress inboard. Also, if the thwart is glassed in, it will help
considerably in stabilizing the joint. You might also add a fillet or
block
under the edge of the thwart, if not already in the plans.

If you're going to paint it, using Kevlar instead of glass may provide
more
stiffness with less build-up...

Stitch and glue canoe; scarf or butt?
 

You can do that. If building on a set of molds, just lay out the first
layer so that the ends of the pieces land on a mold. You can stitch the
wood to the mold or to the other pieces of wood and then use a syringe to
'tack weld' along the edges with epoxy. Pygmy Kayaks are built this way.

Brian

--
http://www.advantagecomposites.com/tongass -- My 22' Tolman Skiff project
http://www.advantagecomposites.com/catalog -- Discounted System Three
Resins products


..
"C" wrote in message
news:%gJwc.687269$Ig.205733@pd7tw2no...
Just a thought,
I thought of building a canoe out of 2 layers of 1/8 ply, The joints could
them be staggered there would be no transition, no complicated scarfs and
more strength than butt joints, I was thinking of using contact cement
between the layers, only because I dont have a vacuum to hold the layers
at
a uniform tension.
Another idea I am playing with is making two 8' halves with transoms at
the
end and joining them together as a single canoe.
Hope this helps

"John R Weiss" wrote in message
news:7t9uc.10769$IB.9176@attbi_s04...
"Chalatso" wrote...
Well, the boat is the bateau.com "cheap canoe," and they suggest a
butt
joint, with a block glued over the butt. I think the method suffers a
lot
for looks. The joint is right across the fattest part of the canoe,
exactly
at the middle. There's added stiffness in the sides from a rubrail,
and
I
might add a little inwale and a bottom runner, if the taped butt makes
me
nervous.

You might be able to make it a bit more elegant by tapering the block
edges.
From the photo of the NC16 on the site, the thwart will draw a lot of
attention away from the blocks. Also, I note they say the blocks may be
made from fiberglass, so a thin strip of tape, followed by a couple
layers
of cloth built up with feathered edges may work out just fine.

From the curve of the hull, it appears the tensile stress on the outside
of
the hull (where they show no blocks) will predominate over the
compressive
stress inboard. Also, if the thwart is glassed in, it will help
considerably in stabilizing the joint. You might also add a fillet or
block
under the edge of the thwart, if not already in the plans.

If you're going to paint it, using Kevlar instead of glass may provide
more
stiffness with less build-up...

Stitch and glue canoe; scarf or butt?
 

"Chalatso" wrote in message ...
Graduating to my first multi-sheet stitch-n-glue... butt joints with blocks
are ugly, scarfing will throw off my sheet layout. Can I use a plain butt
joint, supported on both sides by glass and epoxy?

Chuck

I am the designer of that boat.
Use the butt blocks please.
Do not assume that they are ugly: we work hard on locating the butt
blocks in a strategic spot. Here, the bottom butt block is under the
seat, you can't see it.
The side butt block is right in the middle and looks very appropriate
there. It is a local reinforcement.
Look at the pictures he
http://www.bateau2.com/gallery/NC16/index.htm

Those butt blocks aren;t bad at all.

If you scarf instead of using butt blocks, you will need 2 mores
sheets of plywood because of the width of the scarf . . .

There is another version of that plan that uses fiberglass splices and
produces a longer boat but no scarf version.

Stitch and glue canoe; scarf or butt?
 

About fiberglass splices.
Payson and Carnell miss an important point. They use plain woven glass
in which half of the fibers run paralell to the seam: a complete waste
of glass and resin.
The proper way to build such a seam is with biaxial 45/45. With that
type of glass, all the fibers work and it also adds a little torsional
strength.
I don't know why that point is not understood. I mentioned it for the
1st time here 12 years ago and designers still specify the wrong type
of glass for splices and stitch and glue seams.

Jacques from bateau.com

Stitch and glue canoe; scarf or butt?
 

Jacques,
THANK YOU !!

Not for this particular boat/thread, but just in general for this specific
snippet of info . . .

It 'looked good on paper' and a LOT of 'the experts' recommended it.
However, for some reason I always had a feeling in the 'back of my mind'
{from my Textile Engineering Degree ?? An article I had read ??} that
something didn't quite fit.

Regards,
Ron Magen
Backyard Boatshop

"Jacques" wrote ...
About fiberglass splices. . . .{snip} . . .The proper way to build such a
seam is with biaxial 45/45. {snip}, all the fibers work and it also adds a
little torsional strength.

Stitch and glue canoe; scarf or butt?
 

Stitch and glue canoe; scarf or butt?
 

Stitch and glue canoe; scarf or butt?
 

Small point of information: The original poster was thinking of not using
plywood butted end to end with any kind of joint ...scarf or butt or what
have you. He was thinking more along the lines of a cold-molded approach
where the panels were build from 2 layers of 1/8" skin, staggering the
joints as he went. I can't see how your boat would benefit over this by
using butt block joints, from a strength perspective that is. If I am
wrong, please correct me.

Personally, I am completely happy with butt blocks and don't mind how they
look, especially in a small lighter weight boat or when splicing thin
plywood. They can be a real time saver during construction and are fine for
strength. In larger boats, they can be a PITA if on the decking or anywhere
near the fairbody inside the hull because they tend to disrupt the normal
flow of water and it creates a wet dirty area that's hard to keep clean and
dry ...this is Oregon, not Florida, so things often remain wet and dirty if
not designed for easy drainability.

Brian

PS: In the link below for my current project, you will note that I deviated
from the designer's original plan on the side panels. Because of
order-of-construction versus shop size constraints and the pain level
associated with outdoor structures around here, I chose to build the 24'
side panels out of a forward 16' scarfed section and then used a butt block
to join in the last 8' in the aft section. The designer uses all scarfs.
But in this case, the forward scarf allowed a natural bend in a critical
area, while using a built-in-place butt block for the aft section allowed me
to use panel sections that fit in my cramped shop and were easier to install
in-place than scarfed joints would have been. The butt block is in a
straight section of the hull so there is no issue about curvature and
changing stiffnessnes. Although the designer prefers scarfs, he approved my
butt block approach prior to my using it. Decking and bottom panels are all
scarfed, but are also all short enough to be built in my shop. No drainage
issues will exist.

--
http://www.advantagecomposites.com/tongass -- My 22' Tolman Skiff project
http://www.advantagecomposites.com/catalog -- Discounted System Three
Resins products


..
"Jacques" wrote in message
om...
"Chalatso" wrote in message
...
Graduating to my first multi-sheet stitch-n-glue... butt joints with
blocks
are ugly, scarfing will throw off my sheet layout. Can I use a plain
butt
joint, supported on both sides by glass and epoxy?

Chuck

I am the designer of that boat.
Use the butt blocks please.
Do not assume that they are ugly: we work hard on locating the butt
blocks in a strategic spot. Here, the bottom butt block is under the
seat, you can't see it.
The side butt block is right in the middle and looks very appropriate
there. It is a local reinforcement.
Look at the pictures he
http://www.bateau2.com/gallery/NC16/index.htm

Those butt blocks aren;t bad at all.

If you scarf instead of using butt blocks, you will need 2 mores
sheets of plywood because of the width of the scarf . . .

There is another version of that plan that uses fiberglass splices and
produces a longer boat but no scarf version.

Stitch and glue canoe; scarf or butt?
 

Right on. In addition, the 45/45 biax is built from 2 layers of
unidirectional glass. This is stronger than a normal weave where the yarn
passes over and under other yarn throughout the material ...this naturally
puts a cutting force across the yarn and consequently unidirectional layers
in biax (etc) can take more tension before failing.

Brian D

--
http://www.advantagecomposites.com/tongass -- My 22' Tolman Skiff project
http://www.advantagecomposites.com/catalog -- Discounted System Three
Resins products


..
"Jacques" wrote in message
m...
About fiberglass splices.
Payson and Carnell miss an important point. They use plain woven glass
in which half of the fibers run paralell to the seam: a complete waste
of glass and resin.
The proper way to build such a seam is with biaxial 45/45. With that
type of glass, all the fibers work and it also adds a little torsional
strength.
I don't know why that point is not understood. I mentioned it for the
1st time here 12 years ago and designers still specify the wrong type
of glass for splices and stitch and glue seams.

Jacques from bateau.com

Stitch and glue canoe; scarf or butt?
 

Stitch and glue canoe; scarf or butt?