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

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.