Can you use chopped strand mat with epoxy?
I read one article that says no and then I read another article that
says it is ok.
I read where mat must always be used between two pieces of woven
roving when using epoxy, and then I read another article that says it
is ok to bond two pieces of woven together if you use a thickened
epoxy between them.
I am confused.
I'm not building a boat. I am repairing one, so I will not be using
polyester, just epoxy.
Thanks,
Dan

First off roving and mat are an extremely inefficient use of epoxy. For
maximum strenght the resin to glass ratio with epoxy should be 50/50 or
less resin. Because of the open weave roving sucks up way to much
resin. The other problem is that most mat is held together with a
styrene based binder. Polyester desolves the binder but epoxy does not
so the bond is to the binder not the glass.

Dan wrote:
Can you use chopped strand mat with epoxy?
I read one article that says no and then I read another article that
says it is ok.
I read where mat must always be used between two pieces of woven
roving when using epoxy, and then I read another article that says it
is ok to bond two pieces of woven together if you use a thickened
epoxy between them.
I am confused.
I'm not building a boat. I am repairing one, so I will not be using
polyester, just epoxy.
Thanks,
Dan

--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

On Sat, 05 Jun 2004 19:08:20 -0400, Glenn Ashmore
wrote:

Thanks Glenn, then what is this E-type mat? This is where I'm getting
confused.
Ebay
This fiberglass is E-type, and is compatible with both polyester and epoxy resins. E-type fiberglass is the most common type of fiberglass. If someone doesn't specify the "type" of fiberglass, then it is most likely E-type.


First off roving and mat are an extremely inefficient use of epoxy. For
maximum strenght the resin to glass ratio with epoxy should be 50/50 or
less resin. Because of the open weave roving sucks up way to much
resin. The other problem is that most mat is held together with a
styrene based binder. Polyester desolves the binder but epoxy does not
so the bond is to the binder not the glass.

Dan wrote:
Can you use chopped strand mat with epoxy?
I read one article that says no and then I read another article that
says it is ok.
I read where mat must always be used between two pieces of woven
roving when using epoxy, and then I read another article that says it
is ok to bond two pieces of woven together if you use a thickened
epoxy between them.
I am confused.
I'm not building a boat. I am repairing one, so I will not be using
polyester, just epoxy.
Thanks,
Dan

Dan wrote:
On Sat, 05 Jun 2004 19:08:20 -0400, Glenn Ashmore
wrote:

Thanks Glenn, then what is this E-type mat? This is where I'm getting
confused.
Ebay

This fiberglass is E-type, and is compatible with both polyester and epoxy resins. E-type fiberglass is the most common type of fiberglass. If someone doesn't specify the "type" of fiberglass, then it is most likely E-type.


The "E" stands for electrical. Fiberglass reinforcing comes in two
types E and S that tell the composition of the glass. E-glass is the
most common and is made from the same mixture of silicon, soda and
aluminum oxide as electrical insulating glass hince the name "E-Glass".
The "S" stands for structural. S-glass has addatives that increase
the ultimate strength about 25% and the modulus about 10%. It is also
about 50% more expensive and is generally used only with epoxy resins on
high performance hulls. Other than that the type of glass however has
little to do with the resins used. More important is the type of sizing
used to treat the fiber and the weave.

As I said, mat is a random pad of fibers glued together with a materail
that desolves in the styrene in polyester resin. It is used to provide
bulk, fill the weave of roving and prevent the weave pattern of roving
from "printing" through to the surface.

Woven roving has thick loosly woven threads made up of many fibers.
Because of the open weave it is normaly used with less expensive resins
like polyester. It is often treated with a sizing that improves the
glass to polyester bond but the sizing is not compatable with epoxy.

Cloth is a tighter weave with thinner threads. Usually unsized so most
is compatible with all resins. It comes in various weave patterns from
plane or square to twills to satins that effect ability to drape over
complex shapes.

Knitted fabrics are primarily used with epoxy. They are straight fiber
bundles tied together with light thread which eliminates the need for
the fibers to straighten out before taking a load the way woven fabrics
do. They come in Uni, Bi and Tri directional bolts that can be aligned
with the expected loads.

--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

I'd go for some biax with the mat already stitched to it. A little more
pricey but much stronger and should not be as resin thirsty. You'll get
more bang for the buck.

Dan wrote:

Can you use chopped strand mat with epoxy?
I read one article that says no and then I read another article that
says it is ok.
I read where mat must always be used between two pieces of woven
roving when using epoxy, and then I read another article that says it
is ok to bond two pieces of woven together if you use a thickened
epoxy between them.
I am confused.
I'm not building a boat. I am repairing one, so I will not be using
polyester, just epoxy.
Thanks,
Dan

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

On Sat, 05 Jun 2004 22:36:49 -0400, Glenn Ashmore
wrote:

Thank You Glenn, that clears it up for me.

Dan wrote:
On Sat, 05 Jun 2004 19:08:20 -0400, Glenn Ashmore
wrote:

Thanks Glenn, then what is this E-type mat? This is where I'm getting
confused.
Ebay

This fiberglass is E-type, and is compatible with both polyester and epoxy resins. E-type fiberglass is the most common type of fiberglass. If someone doesn't specify the "type" of fiberglass, then it is most likely E-type.


The "E" stands for electrical. Fiberglass reinforcing comes in two
types E and S that tell the composition of the glass. E-glass is the
most common and is made from the same mixture of silicon, soda and
aluminum oxide as electrical insulating glass hince the name "E-Glass".
The "S" stands for structural. S-glass has addatives that increase
the ultimate strength about 25% and the modulus about 10%. It is also
about 50% more expensive and is generally used only with epoxy resins on
high performance hulls. Other than that the type of glass however has
little to do with the resins used. More important is the type of sizing
used to treat the fiber and the weave.

As I said, mat is a random pad of fibers glued together with a materail
that desolves in the styrene in polyester resin. It is used to provide
bulk, fill the weave of roving and prevent the weave pattern of roving
from "printing" through to the surface.

Woven roving has thick loosly woven threads made up of many fibers.
Because of the open weave it is normaly used with less expensive resins
like polyester. It is often treated with a sizing that improves the
glass to polyester bond but the sizing is not compatable with epoxy.

Cloth is a tighter weave with thinner threads. Usually unsized so most
is compatible with all resins. It comes in various weave patterns from
plane or square to twills to satins that effect ability to drape over
complex shapes.

Knitted fabrics are primarily used with epoxy. They are straight fiber
bundles tied together with light thread which eliminates the need for
the fibers to straighten out before taking a load the way woven fabrics
do. They come in Uni, Bi and Tri directional bolts that can be aligned
with the expected loads.

You aren't talking about using this with epoxy right?

I'd go for some biax with the mat already stitched to it. A little more
pricey but much stronger and should not be as resin thirsty. You'll get
more bang for the buck.

Dan wrote:

Can you use chopped strand mat with epoxy?
I read one article that says no and then I read another article that
says it is ok.
I read where mat must always be used between two pieces of woven
roving when using epoxy, and then I read another article that says it
is ok to bond two pieces of woven together if you use a thickened
epoxy between them.
I am confused.
I'm not building a boat. I am repairing one, so I will not be using
polyester, just epoxy.
Thanks,
Dan

That is one exception to the rule. 1708 is 17 oz bidirectional knitted
to 8 oz mat. Strong and builds up bulk quickly so it is good for
repairs and tabbing. It can be used with either polyester or epoxy.
The sizing in the mat does not dissolve in epoxy so it will not turn
clear the way plain glass does but the un-sized bi-directional top layer
bonds to the substrate well. A side advantage is that it is easier to
work. Bi-directional has a bad habit of stretching out of shape when
handling after it is wet out. The mat helps it hold together better.

Dan wrote:
You aren't talking about using this with epoxy right?


I'd go for some biax with the mat already stitched to it. A little more
pricey but much stronger and should not be as resin thirsty. You'll get
more bang for the buck.

--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

There is also stitched mat, manufactured specifically for use with epoxy. It
isn't glued together with styrene -- it is stitched instead, so no problems
with "sizing" not dissolving. And since it wets-out clear, the same as
cloth, it's much easier to determine when you are saturated and when you're
not. But it is also entirely possible to use epoxy with plain chopped-strand
mat in many situations. I used it when rebuilding the cabin on my former
CT-41, laying down one layer of CSM between the cloth and plywood to help
prevent delamination (belt and suspenders approach). Regular CSM doesn't
soften much with epoxy, but on flat and gently-curving surfaces that isn't a
problem at all. Still, if stitched mat is available, it is certainly the
better choice.

http://www.westsystem.com/ewmag/21/chopped.html
http://www.shopmaninc.com/mat.html

--
Karin Conover-Lewis
Fair and Balanced since 1959
klc dot lewis at centurytel dot net


"Glenn Ashmore" wrote in message
news:g5Jwc.24171$My6.1770@fed1read05...
That is one exception to the rule. 1708 is 17 oz bidirectional knitted
to 8 oz mat. Strong and builds up bulk quickly so it is good for
repairs and tabbing. It can be used with either polyester or epoxy.
The sizing in the mat does not dissolve in epoxy so it will not turn
clear the way plain glass does but the un-sized bi-directional top layer
bonds to the substrate well. A side advantage is that it is easier to
work. Bi-directional has a bad habit of stretching out of shape when
handling after it is wet out. The mat helps it hold together better.

Dan wrote:
You aren't talking about using this with epoxy right?


I'd go for some biax with the mat already stitched to it. A little more
pricey but much stronger and should not be as resin thirsty. You'll get
more bang for the buck.

--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

Mat is used in polyester laminations to improve the bond between
layers of woven glass. Polyester has poor bonding qualities and that
is why mat is used.Woven on woven in a polyester matrix has poor peel
strength.
Epoxy has greatly superior bonding properties and mat would be a waste
if used for that reason. Mat can weaken an epoxy laminate properties
by increasing the distance between the layers of woven.
(woven includes directional).
The only reason to use mat is to add bulk - thickness - stiffness or
resistance to impact.
For that purpose, mat shoud be used towards the middle of the laminate
stack.
It does not add strength.
This happens in small boats in which the skins are too thin for
adequate stiffnes or resistance to puncture.

Jacques from bateau.com