Hi,

Just need a bit of advice about gelcoat, I want to recoat my hull and was
told the only way is a respray. I have two spray units, both High pressure,
but the one is a 1.7mm nozzle. Will this be ok or would it be best to brush
and sand back?

Regards
Alan

Gelcoat is sprayed in the mold before a boat is laminated. It provides
UV protection along with scratch protection. I've never heard of it
being used to protect the glass from the water, since the glass should
also be waterproof (unless it was laminated really dry).

The older gels, such as used in the 70's are polyester based. They
will get brittle with age, and the polyester itself is not necessarily
waterproof. If you take some polyester resin, let it cure, then put it
in some water it will change from clear to foggy colored. This is a
limited amount of water passing through or being absorbed by the
material. It was ok for the 70's, but it is not the material of choice
anymore.

If a boat is 30 years old, and built using polyester, there can
eventually be problems.

The solution is not the re-gel the boat. Gelcoat only cures properly
in an air free environment. When it is sprayed in the mold, the side
against the mold is airtight, and the exposed side is not. The
airtight side cures hard, the inside cures sticky. When the laminate
is installed in the boat, it actually eats into this sticky part to
bond to the gel.

If you just slab some gel on your boat, it will cure sticky (never
really get hard). You do not want this.

The only ways to do surface gel repair are to "seal" the gel away from
the air. If you are filling a crack, this can be done by putting some
Mylar, waxed paper, plastic, or anything airtight over the wet gel (be
careful not to trap air bubbles). The Mylar, plastic wrap, whatever
will work like a mold surface and the gel will cure mostly hard. It is
never perfect.

The other solution is to add a surfacing agent to the gel. Surfacing
agent is a type of wax that will float to the outside of the gel and
help seal it from the air. The downsides are that the agent will
slightly change the color of the gel, and because you just permeated
your repair with wax, in order to do any other repairs in the same
area you will have to rip out all the "waxed gel", because ultimately
nothing will really bond to it.

Application of gel can be by pressure pot or brush, the pressure pot
works better with surfacing agent because you can get a halfway smooth
surface. If you have a regular paint sprayer, you will need to thin
the gel before it will properly spray. I've always used acetone, which
will flash and evaporate before the gel even hits the boat, but I'm
sure there are other options available.

Brushing on the gel, then sanding it down is nasty work. If you use
surfacing agent, and screw up (sand too far), guess what, you have to
redo everything. If you don't use surfacing agent, the gel will be so
sticky it clogs your sandpaper almost instantly.

Best thing to do is fill the cracks, and find a good paint.

Eric

Excellent information and advice. You might look at two part epoxy paints
for a really long lasting finish if you're willing to spend some money.
Applied right they can result in a finish almost as nice as gelcoat. If
you're looking for cheap there is a web site I ran across a while back that
reported pretty good results using house paint above the water line.

"Eric Nyre" wrote in message
om...
Gelcoat is sprayed in the mold before a boat is laminated. It provides
UV protection along with scratch protection. I've never heard of it
being used to protect the glass from the water, since the glass should
also be waterproof (unless it was laminated really dry).

The older gels, such as used in the 70's are polyester based. They
will get brittle with age, and the polyester itself is not necessarily
waterproof. If you take some polyester resin, let it cure, then put it
in some water it will change from clear to foggy colored. This is a
limited amount of water passing through or being absorbed by the
material. It was ok for the 70's, but it is not the material of choice
anymore.

If a boat is 30 years old, and built using polyester, there can
eventually be problems.

The solution is not the re-gel the boat. Gelcoat only cures properly
in an air free environment. When it is sprayed in the mold, the side
against the mold is airtight, and the exposed side is not. The
airtight side cures hard, the inside cures sticky. When the laminate
is installed in the boat, it actually eats into this sticky part to
bond to the gel.

If you just slab some gel on your boat, it will cure sticky (never
really get hard). You do not want this.

The only ways to do surface gel repair are to "seal" the gel away from
the air. If you are filling a crack, this can be done by putting some
Mylar, waxed paper, plastic, or anything airtight over the wet gel (be
careful not to trap air bubbles). The Mylar, plastic wrap, whatever
will work like a mold surface and the gel will cure mostly hard. It is
never perfect.

The other solution is to add a surfacing agent to the gel. Surfacing
agent is a type of wax that will float to the outside of the gel and
help seal it from the air. The downsides are that the agent will
slightly change the color of the gel, and because you just permeated
your repair with wax, in order to do any other repairs in the same
area you will have to rip out all the "waxed gel", because ultimately
nothing will really bond to it.

Application of gel can be by pressure pot or brush, the pressure pot
works better with surfacing agent because you can get a halfway smooth
surface. If you have a regular paint sprayer, you will need to thin
the gel before it will properly spray. I've always used acetone, which
will flash and evaporate before the gel even hits the boat, but I'm
sure there are other options available.

Brushing on the gel, then sanding it down is nasty work. If you use
surfacing agent, and screw up (sand too far), guess what, you have to
redo everything. If you don't use surfacing agent, the gel will be so
sticky it clogs your sandpaper almost instantly.

Best thing to do is fill the cracks, and find a good paint.

Eric

Hi Eric,

Thanks for the info, At this stage I have sealed all possible dings etc with
resin. Gelcoated over that. I found that if I leave the gelcoat for a few
days and then put the boat in the water the gelcoat hardens sufficiently to
smooth with wet paper. I am not that great a sprayer, but I do believe that
a two pack paint would be the way to go. I was also told that this will set
the gelcoat rock hard.

Regards
Alan



"Eric Nyre" wrote in message
om...
Gelcoat is sprayed in the mold before a boat is laminated. It provides
UV protection along with scratch protection. I've never heard of it
being used to protect the glass from the water, since the glass should
also be waterproof (unless it was laminated really dry).

The older gels, such as used in the 70's are polyester based. They
will get brittle with age, and the polyester itself is not necessarily
waterproof. If you take some polyester resin, let it cure, then put it
in some water it will change from clear to foggy colored. This is a
limited amount of water passing through or being absorbed by the
material. It was ok for the 70's, but it is not the material of choice
anymore.

If a boat is 30 years old, and built using polyester, there can
eventually be problems.

The solution is not the re-gel the boat. Gelcoat only cures properly
in an air free environment. When it is sprayed in the mold, the side
against the mold is airtight, and the exposed side is not. The
airtight side cures hard, the inside cures sticky. When the laminate
is installed in the boat, it actually eats into this sticky part to
bond to the gel.

If you just slab some gel on your boat, it will cure sticky (never
really get hard). You do not want this.

The only ways to do surface gel repair are to "seal" the gel away from
the air. If you are filling a crack, this can be done by putting some
Mylar, waxed paper, plastic, or anything airtight over the wet gel (be
careful not to trap air bubbles). The Mylar, plastic wrap, whatever
will work like a mold surface and the gel will cure mostly hard. It is
never perfect.

The other solution is to add a surfacing agent to the gel. Surfacing
agent is a type of wax that will float to the outside of the gel and
help seal it from the air. The downsides are that the agent will
slightly change the color of the gel, and because you just permeated
your repair with wax, in order to do any other repairs in the same
area you will have to rip out all the "waxed gel", because ultimately
nothing will really bond to it.

Application of gel can be by pressure pot or brush, the pressure pot
works better with surfacing agent because you can get a halfway smooth
surface. If you have a regular paint sprayer, you will need to thin
the gel before it will properly spray. I've always used acetone, which
will flash and evaporate before the gel even hits the boat, but I'm
sure there are other options available.

Brushing on the gel, then sanding it down is nasty work. If you use
surfacing agent, and screw up (sand too far), guess what, you have to
redo everything. If you don't use surfacing agent, the gel will be so
sticky it clogs your sandpaper almost instantly.

Best thing to do is fill the cracks, and find a good paint.

Eric

Try posting on the Allcoast board. Some of those guys have re gelcoated.
http://www.allcoastsportfishing.com/...&conf=mainconf
Bill

"Grumpy" wrote in message
u...
Hi Eric,

Thanks for the info, At this stage I have sealed all possible dings etc
with
resin. Gelcoated over that. I found that if I leave the gelcoat for a few
days and then put the boat in the water the gelcoat hardens sufficiently
to
smooth with wet paper. I am not that great a sprayer, but I do believe
that
a two pack paint would be the way to go. I was also told that this will
set
the gelcoat rock hard.

Regards
Alan



"Eric Nyre" wrote in message
om...
Gelcoat is sprayed in the mold before a boat is laminated. It provides
UV protection along with scratch protection. I've never heard of it
being used to protect the glass from the water, since the glass should
also be waterproof (unless it was laminated really dry).

The older gels, such as used in the 70's are polyester based. They
will get brittle with age, and the polyester itself is not necessarily
waterproof. If you take some polyester resin, let it cure, then put it
in some water it will change from clear to foggy colored. This is a
limited amount of water passing through or being absorbed by the
material. It was ok for the 70's, but it is not the material of choice
anymore.

If a boat is 30 years old, and built using polyester, there can
eventually be problems.

The solution is not the re-gel the boat. Gelcoat only cures properly
in an air free environment. When it is sprayed in the mold, the side
against the mold is airtight, and the exposed side is not. The
airtight side cures hard, the inside cures sticky. When the laminate
is installed in the boat, it actually eats into this sticky part to
bond to the gel.

If you just slab some gel on your boat, it will cure sticky (never
really get hard). You do not want this.

The only ways to do surface gel repair are to "seal" the gel away from
the air. If you are filling a crack, this can be done by putting some
Mylar, waxed paper, plastic, or anything airtight over the wet gel (be
careful not to trap air bubbles). The Mylar, plastic wrap, whatever
will work like a mold surface and the gel will cure mostly hard. It is
never perfect.

The other solution is to add a surfacing agent to the gel. Surfacing
agent is a type of wax that will float to the outside of the gel and
help seal it from the air. The downsides are that the agent will
slightly change the color of the gel, and because you just permeated
your repair with wax, in order to do any other repairs in the same
area you will have to rip out all the "waxed gel", because ultimately
nothing will really bond to it.

Application of gel can be by pressure pot or brush, the pressure pot
works better with surfacing agent because you can get a halfway smooth
surface. If you have a regular paint sprayer, you will need to thin
the gel before it will properly spray. I've always used acetone, which
will flash and evaporate before the gel even hits the boat, but I'm
sure there are other options available.

Brushing on the gel, then sanding it down is nasty work. If you use
surfacing agent, and screw up (sand too far), guess what, you have to
redo everything. If you don't use surfacing agent, the gel will be so
sticky it clogs your sandpaper almost instantly.

Best thing to do is fill the cracks, and find a good paint.

Eric