JIMinFL wrote:
My thinking is backward from yours, Chuck. I think of the gel coat as the
layer that is supposed to be waterproof. The laminate may or may not be
waterproof depending on how well the layers are saturated with resin. I'm
sure if you scrape the gelcoat off something like a BayRay or other mass
produced boat, you will have a leak.
JIMinFL

I don't always agree with David Pascoe on some issues, but I think he
has written one of the most informative and easily understood essays on
blisters and how they affect a boat.
If you check out the illustrations and explanation at this link, you
might amend your opinion about gelcoat preventing leaks in a fiberglass
hull


http://www.yachtsurvey.com/BuyingBlisterBoat.htm

wrote in message
oups.com...

JIMinFL wrote:
My thinking is backward from yours, Chuck. I think of the gel coat as the
layer that is supposed to be waterproof. The laminate may or may not be
waterproof depending on how well the layers are saturated with resin. I'm
sure if you scrape the gelcoat off something like a BayRay or other mass
produced boat, you will have a leak.
JIMinFL

I don't always agree with David Pascoe on some issues, but I think he
has written one of the most informative and easily understood essays on
blisters and how they affect a boat.
If you check out the illustrations and explanation at this link, you
might amend your opinion about gelcoat preventing leaks in a fiberglass
hull


http://www.yachtsurvey.com/BuyingBlisterBoat.htm

I read his essay and I don't think that I said anything that needs to be
amended.
Pascoe did say that both the gelcoat and roving/mat are porous. I don't know
if this is true of modern resins but the older boats made of polyester resin
were somewhat porous. But not to the point that you would notice significant
accumulation of sea water in the bilge. I had an old Reinell once that
leaked about 2 quarts a day. It wasn't coming from the engine room nor way
forward. It had to be coming from under the cabin sole. I cut an inspection
port into the sole and found a spot where water was oozing in drop by drop
right at the center of the keel. I didn't see any cracking so I decided to
leave it as is until haulout time. After removing several coats of bottom
paint I found that the gel coat had been worn off . Probably from repeated
beachings at one time. My fix for that was a few layers of cloth and epoxy.

I would not let any crack or gouge in gelcoat go unrepaired. Particularly
under the water line.

JIMinFL wrote:


I would not let any crack or gouge in gelcoat go unrepaired. Particularly
under the water line.

I think we would agree on that. Particularly since it's almost
impossible to crack or gouge *only* the gel coat. :-)

Your experience with the leaking keel is a good example. After several
groundings, you noticed some water seeping into the bilge through the
keelson. The couple of layers and cloth you applied for a fix went well
beyond a simple gelcoat repair.

I think you could strip all the gelcoat entirely off a boat and it
would still float. If the fibers were adequately wetted out with resin,
the hull wouldn't even absorb water (or "wick" it around). That seems
to be where we disagree.

As you know, there are some premium manufacturers who don't even use
gelcoat on their fiberglass boats. If the mold is perfect enough, one
can get by with paint rather than gelcoat. Gelcoat is an easy
workaround for imperfectly finished molds, as it tends to hide various
sins while paint tends to magnify them.

wrote in message
oups.com...
Your experience with the leaking keel is a good example. After several
groundings, you noticed some water seeping into the bilge through the
keelson. The couple of layers and cloth you applied for a fix went well
beyond a simple gelcoat repair.

That isn't exactly what I said, but after removing the bottom paint, the
area sans gel coat was smooth and I didn't know if any of the laminations
had worn off. Being a belt and suspenders kind of guy, I chose to build the
area up a little. I probably could have gotten by painting the spot with
epoxy.





I think you could strip all the gelcoat entirely off a boat and it
would still float. If the fibers were adequately wetted out with resin,
the hull wouldn't even absorb water (or "wick" it around). That seems
to be where we disagree.

Now you are qualifing with "adequately wetted out with resin". Sure some
better hulls will be more resistant to water penetration. The cheaper hulls
still depend on the gel coat to keep the water out.

30. JIMinFL



I think you could strip all the gelcoat entirely off a boat and it
would still float. If the fibers were adequately wetted out with resin,
the hull wouldn't even absorb water (or "wick" it around). That seems
to be where we disagree.



Now you are qualifing with "adequately wetted out with resin". Sure
some
better hulls will be more resistant to water penetration. The cheaper
hulls
still depend on the gel coat to keep the water out

******

:-)

When one states that water is going to leak through the frp laminate
and into the boat unless it is somehow stopped by the gelcoat- and if
one means "if the hull is defective.......", then it would be best to
so state. When talking about general functions of gelcoat, laminate,
etc it would be customary to assume one is talking about a standard
hull rather than a defective one.

No builder depends on gelcoat to keep water from leaking into the
bilge.

wrote:
30. JIMinFL




I think you could strip all the gelcoat entirely off a boat and it
would still float. If the fibers were adequately wetted out with resin,
the hull wouldn't even absorb water (or "wick" it around). That seems
to be where we disagree.




Now you are qualifing with "adequately wetted out with resin". Sure
some
better hulls will be more resistant to water penetration. The cheaper
hulls
still depend on the gel coat to keep the water out

******

:-)

When one states that water is going to leak through the frp laminate
and into the boat unless it is somehow stopped by the gelcoat- and if
one means "if the hull is defective.......", then it would be best to
so state. When talking about general functions of gelcoat, laminate,
etc it would be customary to assume one is talking about a standard
hull rather than a defective one.

No builder depends on gelcoat to keep water from leaking into the
bilge.


Gee Chuck I think that's a bit of a statement. Most fibreglass
laminates are pretty porous if there are no barriers.

I'm not saying water would "flow" as such, but certainly it will seep
into the glass & definitely damage it over time.

On the other side if anyone did actually wet the layup enough that it
was truly water "proof" then it would be a very weakened laminate,
overly heavy & expensive waste of resin.

The best fix thus far is a good outer barrier usually of vinyl ester
resins in conjunction with a tissue tie layer. Even inside you need
flowcoat or such to stop the laminate being too porous from that direction.

K

K. Smith wrote:
wrote:
30. JIMinFL




I think you could strip all the gelcoat entirely off a boat and it
would still float. If the fibers were adequately wetted out with resin,
the hull wouldn't even absorb water (or "wick" it around). That seems
to be where we disagree.




Now you are qualifing with "adequately wetted out with resin". Sure
some
better hulls will be more resistant to water penetration. The cheaper
hulls
still depend on the gel coat to keep the water out

******

:-)

When one states that water is going to leak through the frp laminate
and into the boat unless it is somehow stopped by the gelcoat- and if
one means "if the hull is defective.......", then it would be best to
so state. When talking about general functions of gelcoat, laminate,
etc it would be customary to assume one is talking about a standard
hull rather than a defective one.

No builder depends on gelcoat to keep water from leaking into the
bilge.


Gee Chuck I think that's a bit of a statement. Most fibreglass
laminates are pretty porous if there are no barriers.

I'm not saying water would "flow" as such, but certainly it will seep
into the glass & definitely damage it over time.

On the other side if anyone did actually wet the layup enough that it
was truly water "proof" then it would be a very weakened laminate,
overly heavy & expensive waste of resin.

The best fix thus far is a good outer barrier usually of vinyl ester
resins in conjunction with a tissue tie layer. Even inside you need
flowcoat or such to stop the laminate being too porous from that direction.

K

I agree that fiberglass can allow water molecules to penetrate through.

There was an often referenced demonstration where somebody built a
fiberglass box, filled it with water, and bonded an air-tight top. It
sat in a classroom under daily observation, and no water was ever seen
leaking out. When the box was opened, several months later,
it was bone dry. I can't honestly say whether the box in the experiment
was covered with
gelcoat, paint, or consisted of exosed glass cloth

That's far different from a theory that gelcoat.... (which is more
porous than the laminate itself, causing the water that penetrates it
to stop or slow down when it reaches the
laminate below and hang around long enough to foster chemical reactions
that produce the gas that creates blisters)... waterproofs the laminate
to prevent leaking.

According to this observation from Pascoe's essay on blisters:

"Blistering involves only the gel coat and surface mat in 99% of the
cases. This is due to the fact that the structural fabrics, such as
roving, get saturated better. Its also because the water is less likely
to penetrate beyond the mat and, even if it does, woven fabrics do not
have the weak gel coat factor and are much too strong to allow whatever
pressure may develop within a void to cause a separation. The incidence
of blisters occurring within structural laminates is extremely small."

It would make more sense to use the structural laminate to "waterproof"
the gelcoat than to say that the gelcoat somehow seals or waterproofs
the laminate.

A vinylester barrier has proven to be extremely effective in reducing,
and in many cases eliminating, the tendency for FRP hulls to blister.

wrote in message
oups.com...
:-)

When one states that water is going to leak through the frp laminate
and into the boat unless it is somehow stopped by the gelcoat- and if
one means "if the hull is defective.......", then it would be best to
so state. When talking about general functions of gelcoat, laminate,
etc it would be customary to assume one is talking about a standard
hull rather than a defective one.

No builder depends on gelcoat to keep water from leaking into the
bilge.

I can't argue this point with you. I don't know what the hell you are
talking about.

JIMinFL wrote:
wrote in message
oups.com...
:-)

When one states that water is going to leak through the frp laminate
and into the boat unless it is somehow stopped by the gelcoat- and if
one means "if the hull is defective.......", then it would be best to
so state. When talking about general functions of gelcoat, laminate,
etc it would be customary to assume one is talking about a standard
hull rather than a defective one.

No builder depends on gelcoat to keep water from leaking into the
bilge.

I can't argue this point with you. I don't know what the hell you are
talking about.

I'm talking about your position that damaged gel coat will cause a
fiberglass hull to leak,
(based upon the premise that the function of gelcoat is to "waterproof"
the fiberglass).