We had dinner with a buddy boat tonight. They commented that the barrier
coat they used had a brochure in it which described exactly what we are
doing as particularly important to THEIR system, which they guarantee for
some length of time (years). When I have the actual brochure in my hands
I'll repeat it verbatim - along with the name (Interlux, I think) and
product number - here in a followup. However, at least one manufacturer,
and in particular, one which offers a guarantee, agrees that the only hope
one has for a successful barrier coat is to do exactly what we're doing.

The continued research we've been doing suggests that if the fiberglass
isn't perfect in layup (materials, humidity, application techniques, etc.),
once you START having blisters, you're going to continue to have blisters,
no matter what you do about it.

HOWEVER - the best you CAN do, apparently, is, indeed, to wet the hull and
then pressure wash it, several times.

Yesterday we wet it thoroughly. Today, new areas were visible (encouraging
the now-liquid-ized stuff to come to the surface), albeit all still VERY
small. The new cheapo pressure washer was applied to the surface next. Any
blisters with the slightest amount of open area allowed water in under
pressure, further lifting any non-perfectly bound glass, and, further, for
the most part, causing it to depart the skin of the boat as, once the
process started, the light stuff blew off, allowing access to more of it,
and so on.

So....

Not only does it work, but it's going to save me a lot of grinding to get
the same areas removed for "packing" prior to the barrier coat. Those areas
I'd already identified were, of course, the worst (if you can call an area
of less than a dime in size "worst"), and were more prone to opening with
the puny 1600PSI sprayer we have. However, a few more of these treatements,
and I expect we'll have a VERY good remediation of the tiny blisters we
have. Sure is fun to see the hull getting lighter as we wash off that tiny
film of hydrolized compounds which have been making their way to the surface
and darkening it slightly!

L8R

Skip, who MAY get some more pix up some time soon, after I get some of the
PW series yet to be taken in and out of the camera...

--
Morgan 461 #2
SV Flying Pig KI4MPC
See our galleries at www.justpickone.org/skip/gallery !
Follow us at http://groups.yahoo.com/group/TheFlyingPigLog
and/or http://groups.google.com/group/flyingpiglog

"Believe me, my young friend, there is *nothing*-absolutely nothing-half so
much worth doing as simply messing, messing-about-in-boats; messing about in
boats-or *with* boats.

In or out of 'em, it doesn't matter. Nothing seems really to matter, that's
the charm of it.

Whether you get away, or whether you don't; whether you arrive at your
destination or whether you reach somewhere else, or whether you never get
anywhere at all, you're always busy, and you never do anything in
particular; and when you've done it there's always something else to do, and
you can do it if you like, but you'd much better not."

"Flying Pig" wrote in message
...
We had dinner with a buddy boat tonight. They commented that the barrier
coat they used had a brochure in it which described exactly what we are
doing as particularly important to THEIR system, which they guarantee for
some length of time (years). When I have the actual brochure in my hands
I'll repeat it verbatim - along with the name (Interlux, I think) and
product number - here in a followup. However, at least one manufacturer,
and in particular, one which offers a guarantee, agrees that the only hope
one has for a successful barrier coat is to do exactly what we're doing.

The continued research we've been doing suggests that if the fiberglass
isn't perfect in layup (materials, humidity, application techniques,
etc.), once you START having blisters, you're going to continue to have
blisters, no matter what you do about it.

HOWEVER - the best you CAN do, apparently, is, indeed, to wet the hull and
then pressure wash it, several times.

Yesterday we wet it thoroughly. Today, new areas were visible
(encouraging the now-liquid-ized stuff to come to the surface), albeit all
still VERY small. The new cheapo pressure washer was applied to the
surface next. Any blisters with the slightest amount of open area allowed
water in under pressure, further lifting any non-perfectly bound glass,
and, further, for the most part, causing it to depart the skin of the boat
as, once the process started, the light stuff blew off, allowing access to
more of it, and so on.

So....

Not only does it work, but it's going to save me a lot of grinding to get
the same areas removed for "packing" prior to the barrier coat. Those
areas I'd already identified were, of course, the worst (if you can call
an area of less than a dime in size "worst"), and were more prone to
opening with the puny 1600PSI sprayer we have. However, a few more of
these treatements, and I expect we'll have a VERY good remediation of the
tiny blisters we have. Sure is fun to see the hull getting lighter as we
wash off that tiny film of hydrolized compounds which have been making
their way to the surface and darkening it slightly!

L8R

Skip, who MAY get some more pix up some time soon, after I get some of the
PW series yet to be taken in and out of the camera...

--
Morgan 461 #2
SV Flying Pig KI4MPC
See our galleries at www.justpickone.org/skip/gallery !
Follow us at http://groups.yahoo.com/group/TheFlyingPigLog
and/or http://groups.google.com/group/flyingpiglog

"Believe me, my young friend, there is *nothing*-absolutely nothing-half
so
much worth doing as simply messing, messing-about-in-boats; messing about
in
boats-or *with* boats.

In or out of 'em, it doesn't matter. Nothing seems really to matter,
that's
the charm of it.

Whether you get away, or whether you don't; whether you arrive at your
destination or whether you reach somewhere else, or whether you never get
anywhere at all, you're always busy, and you never do anything in
particular; and when you've done it there's always something else to do,
and
you can do it if you like, but you'd much better not."





Skippy, you are myopic if you think spraying the hull with water is going to
remove all the osmotic fluid from inside the laminate. The BEST your
spraying technique is going to do is to wash off the fluid that has managed
to migrate to the surface by oozing out of cracks and small holes in the
laminate. In those areas not cracked or holed, the the osmotic fluid will
remain inside the laminate and, even if you do barrier coat the works,
unless you barrier coat BOTH inside and outside the osmosis will continue
and so will the blisters.

I'll say it again. To eliminate blisters completely the ONLY foolproof
method that will work every time is extensive drying of the hull to diffuse
and evaporate all the moisture that is causing the pressure that causes the
blisters. This needs to be done in a very low humidity environment and might
well take two years or more depending upon how soggy the laminate is.

After the hull is dried, both the inside and outside of the laminate needs
to be barrier coated.

End of problem and the ONLY way to end the problem. What you are doing now
is just a waste of time because blisters will return. GUARANTEED!


Wilbur Hubbard

Skip,

I guess you are on the hard at that marina just south of the bridge.
Does the City marina south of you still exist? I put in there for a few
months just before the big hurricane which took Ft. Pierce apart. I
heard the City marina was hard hit. Can you confirm or deny? Thanks.

On Thu, 28 Apr 2011 09:05:08 -0400, "Wilbur Hubbard"
wrote:

"Flying Pig" wrote in message
...
We had dinner with a buddy boat tonight. They commented that the barrier
coat they used had a brochure in it which described exactly what we are
doing as particularly important to THEIR system, which they guarantee for
some length of time (years). When I have the actual brochure in my hands
I'll repeat it verbatim - along with the name (Interlux, I think) and
product number - here in a followup. However, at least one manufacturer,
and in particular, one which offers a guarantee, agrees that the only hope
one has for a successful barrier coat is to do exactly what we're doing.

The continued research we've been doing suggests that if the fiberglass
isn't perfect in layup (materials, humidity, application techniques,
etc.), once you START having blisters, you're going to continue to have
blisters, no matter what you do about it.

HOWEVER - the best you CAN do, apparently, is, indeed, to wet the hull and
then pressure wash it, several times.

Yesterday we wet it thoroughly. Today, new areas were visible
(encouraging the now-liquid-ized stuff to come to the surface), albeit all
still VERY small. The new cheapo pressure washer was applied to the
surface next. Any blisters with the slightest amount of open area allowed
water in under pressure, further lifting any non-perfectly bound glass,
and, further, for the most part, causing it to depart the skin of the boat
as, once the process started, the light stuff blew off, allowing access to
more of it, and so on.

So....

Not only does it work, but it's going to save me a lot of grinding to get
the same areas removed for "packing" prior to the barrier coat. Those
areas I'd already identified were, of course, the worst (if you can call
an area of less than a dime in size "worst"), and were more prone to
opening with the puny 1600PSI sprayer we have. However, a few more of
these treatements, and I expect we'll have a VERY good remediation of the
tiny blisters we have. Sure is fun to see the hull getting lighter as we
wash off that tiny film of hydrolized compounds which have been making
their way to the surface and darkening it slightly!

L8R

Skip, who MAY get some more pix up some time soon, after I get some of the
PW series yet to be taken in and out of the camera...

--
Morgan 461 #2
SV Flying Pig KI4MPC
See our galleries at www.justpickone.org/skip/gallery !
Follow us at http://groups.yahoo.com/group/TheFlyingPigLog
and/or http://groups.google.com/group/flyingpiglog

"Believe me, my young friend, there is *nothing*-absolutely nothing-half
so
much worth doing as simply messing, messing-about-in-boats; messing about
in
boats-or *with* boats.

In or out of 'em, it doesn't matter. Nothing seems really to matter,
that's
the charm of it.

Whether you get away, or whether you don't; whether you arrive at your
destination or whether you reach somewhere else, or whether you never get
anywhere at all, you're always busy, and you never do anything in
particular; and when you've done it there's always something else to do,
and
you can do it if you like, but you'd much better not."





Skippy, you are myopic if you think spraying the hull with water is going to
remove all the osmotic fluid from inside the laminate. The BEST your
spraying technique is going to do is to wash off the fluid that has managed
to migrate to the surface by oozing out of cracks and small holes in the
laminate. In those areas not cracked or holed, the the osmotic fluid will
remain inside the laminate and, even if you do barrier coat the works,
unless you barrier coat BOTH inside and outside the osmosis will continue
and so will the blisters.

I'll say it again. To eliminate blisters completely the ONLY foolproof
method that will work every time is extensive drying of the hull to diffuse
and evaporate all the moisture that is causing the pressure that causes the
blisters. This needs to be done in a very low humidity environment and might
well take two years or more depending upon how soggy the laminate is.

After the hull is dried, both the inside and outside of the laminate needs
to be barrier coated.

End of problem and the ONLY way to end the problem. What you are doing now
is just a waste of time because blisters will return. GUARANTEED!


Wilbur Hubbard

And here's Willie-boy spouting his usual idiotic blather. Willie-boy I
keep telling you to keep your mouth closed and people might think that
you are a fool but then you open your mouth the while world knows it.

I went to the trouble of giving you several references regarding
osmosis which it is obvious that you didn't read, or can't comprehend.
I can only assume that as they demonstrated that your antiquated ideas
are totally incorrect you ignored them.

Willie-boy. you can argue that the world is flat 'cause if it were a
ball we'd all fall off', but that doesn't make you right.

Cheers,

Bruce
(bruceinbangkokatgmaildotcom)

On Wed, 27 Apr 2011 21:43:57 -0400, "Flying Pig"
wrote:

We had dinner with a buddy boat tonight. They commented that the barrier
coat they used had a brochure in it which described exactly what we are
doing as particularly important to THEIR system, which they guarantee for
some length of time (years). When I have the actual brochure in my hands
I'll repeat it verbatim - along with the name (Interlux, I think) and
product number - here in a followup. However, at least one manufacturer,
and in particular, one which offers a guarantee, agrees that the only hope
one has for a successful barrier coat is to do exactly what we're doing.

The continued research we've been doing suggests that if the fiberglass
isn't perfect in layup (materials, humidity, application techniques, etc.),
once you START having blisters, you're going to continue to have blisters,
no matter what you do about it.

Actually polyester composites are not waterproof and as the uncured
chemicals are present in all layups, in some amounts, osmosis will
occur in all polyester based laminates, in some degree, in time.

The modern "treatment" is to initially lay up hull with an external
layer of vinylester resin which is more waterproof then polyester and
cheaper then epoxy.

Your "barrier Coat" by the way, is simply epoxy and the important
factor is to apply it in the thickness recommended. Probably two coats
totaling about 12 - 16 mils.


HOWEVER - the best you CAN do, apparently, is, indeed, to wet the hull and
then pressure wash it, several times.

Yesterday we wet it thoroughly. Today, new areas were visible (encouraging
the now-liquid-ized stuff to come to the surface), albeit all still VERY
small. The new cheapo pressure washer was applied to the surface next. Any
blisters with the slightest amount of open area allowed water in under
pressure, further lifting any non-perfectly bound glass, and, further, for
the most part, causing it to depart the skin of the boat as, once the
process started, the light stuff blew off, allowing access to more of it,
and so on.

So....

Not only does it work, but it's going to save me a lot of grinding to get
the same areas removed for "packing" prior to the barrier coat. Those areas
I'd already identified were, of course, the worst (if you can call an area
of less than a dime in size "worst"), and were more prone to opening with
the puny 1600PSI sprayer we have. However, a few more of these treatements,
and I expect we'll have a VERY good remediation of the tiny blisters we
have. Sure is fun to see the hull getting lighter as we wash off that tiny
film of hydrolized compounds which have been making their way to the surface
and darkening it slightly!

L8R

Skip, who MAY get some more pix up some time soon, after I get some of the
PW series yet to be taken in and out of the camera...
Cheers,

Bruce
(bruceinbangkokatgmaildotcom)

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



Wilbur, Read down to ***!



Let's face it, an awful lot of boats have blisters, so that finding one that
doesn't (or won't get them) can be a difficult proposition. The short answer is
that if at all possible, you should try to avoid that, if for no other reason
than the potential expense you may face in the future. That expense may not
result from the absolute necessity to repair the blisters, but the position you
may find yourself in when it comes time to sell the boat. Particularly with
newer model boats, say 1 - 3 years old, it is not unusual for buyers demand a
reduction in price, or that the blisters be repaired.

For older boats, its usually much less of a problem, for the fact is that
moderate blistering on an older boat rarely impedes the sale. Unfortunately,
another fact of boating life is that there is a great deal of misinformation on
this much talked-about subject. One common misconception is that blisters
seriously weaken and/or damage boat hulls. In 30 years of surveying and
examining around 4000 hulls, I have seen less than 10 cases where blisters have
resulted in serious structural degradation of a hull where it was weakened to a
point where some type of failure was immanent.

What is a blister? First, let's understand that all fiberglass hulls absorb
water to some degree because both the gel coat finish on the exterior, and the
fiberglass reinforced plastic is porous. Since water is a solvent, it will react
with the plastic resulting in the water and solvents in the plastic mixing to
create a weak solvent solution, usually with styrene. This then softens the gel
coat somewhat and, combined with a bit of gas or fluid pressure, results in the
blister.

Are blisters harmful? Yes, but. This is a question of how much harm. Blisters
form at the interface between the gel coat and what is called the skinout mat,
which is a layer of chopped, short-strand fiberglass that is used to prevent the
coarser weave pattern of heavier fiberglass cloth from telegraphing through to
the finish surface. You've probably seen boats with a checkerboard pattern
showing on the surface, and this is the reason why. Now, fiberglass fabric,
being made of bundles of very fine glass fibers, is very porous also, most
especially the outer layer of mat. Once the gel coat absorbs water, the fibers
in the mat that are unsaturated with resin then spread the water around via the
capillary effect.

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.

Boat hull blisters
If the resin used to make the hull is of a lower quality that will react with
water, a process known as hydrolysis, which means nothing more than becoming
saturated with water and dissolving, then the hull is poised to develop
blisters. Many other factors also come into play here, such as how well the mat
layer is bonded to the gel coat.

Since the vast majority of blisters occur between the mat and gel coat (depicted
in illustration above), this bond has to be fairly weak for the blistering
process to occur. If the bond is strong, then blisters will not occur, even
though there is a lot of water absorption. This is a very general, even generic,
description of the blistering process. There are frequently numerous other
factors involved which I will not address here.

Aside from the damage it causes to the surface, most of the damage done by the
blister is to the gel coat and the skin out mat, which is not a structural part
of the hull laminate. Remember, the mat is only there to prevent the fabric
pattern from showing through to the surface. The obvious question is now, "But
isn't the water dissolving the rest of the plastic resin in the laminate?" The
answer to that is "No, its not." At least not to any considerable degree.


***
You may have noticed that I have not used the word "osmosis" that we hear so
much these days. Technically, water passing through the porous gel coat is not
osmosis; its just water passing through a porous material.



However, the blistering process may involve osmosis, a process which
concentrates solvents within the space formed by the blister void. This
concentration of solvents does indeed dissolve the plastic, but fortunately the
amount of fluid involved is so small that it does not seriously threaten the
laminate.

Of course, the larger the blister, the more concentrated solvent is present, the
more damage it will cause. Therefore the amount of damage, and therefore
structural weakening caused by blistering, is directly proportional to size and
number of blisters. This explains why only boats with very large blisters can
end up with serious structural weakness problems.

We're just NORTH of the bridge.

I have no local knowledge of damages recent - but just happened to be
talking with one of the owners who was speaking of what they had done when
they built, and that other marinas hadn't.

During a long-ago hurricane, those marinas were very badly hit. So far as I
know, all are in operation again...

L8R

Skip

--
Morgan 461 #2
SV Flying Pig KI4MPC
See our galleries at www.justpickone.org/skip/gallery !
Follow us at http://groups.yahoo.com/group/TheFlyingPigLog
and/or http://groups.google.com/group/flyingpiglog

"Believe me, my young friend, there is *nothing*-absolutely nothing-half so
much worth doing as simply messing, messing-about-in-boats; messing about in
boats-or *with* boats.

In or out of 'em, it doesn't matter. Nothing seems really to matter, that's
the charm of it.

Whether you get away, or whether you don't; whether you arrive at your
destination or whether you reach somewhere else, or whether you never get
anywhere at all, you're always busy, and you never do anything in
particular; and when you've done it there's always something else to do, and
you can do it if you like, but you'd much better not."

"slide" wrote in message
...
Skip,

I guess you are on the hard at that marina just south of the bridge. Does
the City marina south of you still exist? I put in there for a few months
just before the big hurricane which took Ft. Pierce apart. I heard the
City marina was hard hit. Can you confirm or deny? Thanks.

"CaveLamb" wrote in message
m...
http://www.yachtsurvey.com/BuyingBlisterBoat.htm



Wilbur, Read down to ***!



Let's face it, an awful lot of boats have blisters, so that finding one
that doesn't (or won't get them) can be a difficult proposition. The short
answer is that if at all possible, you should try to avoid that, if for no
other reason than the potential expense you may face in the future. That
expense may not result from the absolute necessity to repair the blisters,
but the position you may find yourself in when it comes time to sell the
boat. Particularly with newer model boats, say 1 - 3 years old, it is not
unusual for buyers demand a reduction in price, or that the blisters be
repaired.

For older boats, its usually much less of a problem, for the fact is that
moderate blistering on an older boat rarely impedes the sale.
Unfortunately, another fact of boating life is that there is a great deal
of misinformation on this much talked-about subject. One common
misconception is that blisters seriously weaken and/or damage boat hulls.
In 30 years of surveying and examining around 4000 hulls, I have seen less
than 10 cases where blisters have resulted in serious structural
degradation of a hull where it was weakened to a point where some type of
failure was immanent.

What is a blister? First, let's understand that all fiberglass hulls
absorb water to some degree because both the gel coat finish on the
exterior, and the fiberglass reinforced plastic is porous. Since water is
a solvent, it will react with the plastic resulting in the water and
solvents in the plastic mixing to create a weak solvent solution, usually
with styrene. This then softens the gel coat somewhat and, combined with a
bit of gas or fluid pressure, results in the blister.

Are blisters harmful? Yes, but. This is a question of how much harm.
Blisters form at the interface between the gel coat and what is called the
skinout mat, which is a layer of chopped, short-strand fiberglass that is
used to prevent the coarser weave pattern of heavier fiberglass cloth from
telegraphing through to the finish surface. You've probably seen boats
with a checkerboard pattern showing on the surface, and this is the reason
why. Now, fiberglass fabric, being made of bundles of very fine glass
fibers, is very porous also, most especially the outer layer of mat. Once
the gel coat absorbs water, the fibers in the mat that are unsaturated
with resin then spread the water around via the capillary effect.

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.

Boat hull blisters
If the resin used to make the hull is of a lower quality that will react
with water, a process known as hydrolysis, which means nothing more than
becoming saturated with water and dissolving, then the hull is poised to
develop blisters. Many other factors also come into play here, such as how
well the mat layer is bonded to the gel coat.

Since the vast majority of blisters occur between the mat and gel coat
(depicted in illustration above), this bond has to be fairly weak for the
blistering process to occur. If the bond is strong, then blisters will not
occur, even though there is a lot of water absorption. This is a very
general, even generic, description of the blistering process. There are
frequently numerous other factors involved which I will not address here.

Aside from the damage it causes to the surface, most of the damage done by
the blister is to the gel coat and the skin out mat, which is not a
structural part of the hull laminate. Remember, the mat is only there to
prevent the fabric pattern from showing through to the surface. The
obvious question is now, "But isn't the water dissolving the rest of the
plastic resin in the laminate?" The answer to that is "No, its not." At
least not to any considerable degree.


***
You may have noticed that I have not used the word "osmosis" that we hear
so much these days. Technically, water passing through the porous gel coat
is not osmosis; its just water passing through a porous material.



However, the blistering process may involve osmosis, a process which
concentrates solvents within the space formed by the blister void. This
concentration of solvents does indeed dissolve the plastic, but
fortunately the amount of fluid involved is so small that it does not
seriously threaten the laminate.

Of course, the larger the blister, the more concentrated solvent is
present, the more damage it will cause. Therefore the amount of damage,
and therefore structural weakening caused by blistering, is directly
proportional to size and number of blisters. This explains why only boats
with very large blisters can end up with serious structural weakness
problems.



But, the very next paragraph after the asterisks mentions osmosis.

Put it this way. You've heard of reverse osmosis, right?

That is where you force salt water through a membrane where it would not
normally go by using lots of pressure. The salt is too big to pass through
the membrane and only fresh water passes because water molecules are quite
tiny.

Osmosis without the 'reverse' operates the other way. Water migrates through
membrane because on one side there is a denser substance (laminate chemicals
that attract water) and continues to do so until an equilibrium is reached
between the densities inside and out. This migration at the molecular level
is what pushes up the blisters. Once the water gets inside the laminate it
will NOT migrate back out when the boat remains in the water. It will
diffuse and evaporate out when the boat is stored on the hard in a
low-humidity environment. Cold = low humidity so cold storage is a faster
way to dry out the laminate that is pressurized by osmotic action.

Spraying the hull with water will do nothing to release the trapped osmotic
fluids that push out the blisters. Only in areas where the laminate is
compromised will the osmotic fluid ooze out to be washed off. In areas where
the laminate is intact there is also osmotic fluid under pressure which does
not ooze out. So, Skippy is fixing about half the problem given the
assumption that bout half his hull laminate is structurally compromised as
in cracks, fractures, holes, splits, etc.

Wilbur Hubbard

On Fri, 29 Apr 2011 09:46:32 -0400, "Wilbur Hubbard"
wrote:

"CaveLamb" wrote in message
om...
http://www.yachtsurvey.com/BuyingBlisterBoat.htm



Wilbur, Read down to ***!



Let's face it, an awful lot of boats have blisters, so that finding one
that doesn't (or won't get them) can be a difficult proposition. The short
answer is that if at all possible, you should try to avoid that, if for no
other reason than the potential expense you may face in the future. That
expense may not result from the absolute necessity to repair the blisters,
but the position you may find yourself in when it comes time to sell the
boat. Particularly with newer model boats, say 1 - 3 years old, it is not
unusual for buyers demand a reduction in price, or that the blisters be
repaired.

For older boats, its usually much less of a problem, for the fact is that
moderate blistering on an older boat rarely impedes the sale.
Unfortunately, another fact of boating life is that there is a great deal
of misinformation on this much talked-about subject. One common
misconception is that blisters seriously weaken and/or damage boat hulls.
In 30 years of surveying and examining around 4000 hulls, I have seen less
than 10 cases where blisters have resulted in serious structural
degradation of a hull where it was weakened to a point where some type of
failure was immanent.

What is a blister? First, let's understand that all fiberglass hulls
absorb water to some degree because both the gel coat finish on the
exterior, and the fiberglass reinforced plastic is porous. Since water is
a solvent, it will react with the plastic resulting in the water and
solvents in the plastic mixing to create a weak solvent solution, usually
with styrene. This then softens the gel coat somewhat and, combined with a
bit of gas or fluid pressure, results in the blister.

Are blisters harmful? Yes, but. This is a question of how much harm.
Blisters form at the interface between the gel coat and what is called the
skinout mat, which is a layer of chopped, short-strand fiberglass that is
used to prevent the coarser weave pattern of heavier fiberglass cloth from
telegraphing through to the finish surface. You've probably seen boats
with a checkerboard pattern showing on the surface, and this is the reason
why. Now, fiberglass fabric, being made of bundles of very fine glass
fibers, is very porous also, most especially the outer layer of mat. Once
the gel coat absorbs water, the fibers in the mat that are unsaturated
with resin then spread the water around via the capillary effect.

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.

Boat hull blisters
If the resin used to make the hull is of a lower quality that will react
with water, a process known as hydrolysis, which means nothing more than
becoming saturated with water and dissolving, then the hull is poised to
develop blisters. Many other factors also come into play here, such as how
well the mat layer is bonded to the gel coat.

Since the vast majority of blisters occur between the mat and gel coat
(depicted in illustration above), this bond has to be fairly weak for the
blistering process to occur. If the bond is strong, then blisters will not
occur, even though there is a lot of water absorption. This is a very
general, even generic, description of the blistering process. There are
frequently numerous other factors involved which I will not address here.

Aside from the damage it causes to the surface, most of the damage done by
the blister is to the gel coat and the skin out mat, which is not a
structural part of the hull laminate. Remember, the mat is only there to
prevent the fabric pattern from showing through to the surface. The
obvious question is now, "But isn't the water dissolving the rest of the
plastic resin in the laminate?" The answer to that is "No, its not." At
least not to any considerable degree.


***
You may have noticed that I have not used the word "osmosis" that we hear
so much these days. Technically, water passing through the porous gel coat
is not osmosis; its just water passing through a porous material.



However, the blistering process may involve osmosis, a process which
concentrates solvents within the space formed by the blister void. This
concentration of solvents does indeed dissolve the plastic, but
fortunately the amount of fluid involved is so small that it does not
seriously threaten the laminate.

Of course, the larger the blister, the more concentrated solvent is
present, the more damage it will cause. Therefore the amount of damage,
and therefore structural weakening caused by blistering, is directly
proportional to size and number of blisters. This explains why only boats
with very large blisters can end up with serious structural weakness
problems.



But, the very next paragraph after the asterisks mentions osmosis.

Put it this way. You've heard of reverse osmosis, right?

That is where you force salt water through a membrane where it would not
normally go by using lots of pressure. The salt is too big to pass through
the membrane and only fresh water passes because water molecules are quite
tiny.

Osmosis without the 'reverse' operates the other way. Water migrates through
membrane because on one side there is a denser substance (laminate chemicals
that attract water) and continues to do so until an equilibrium is reached
between the densities inside and out. This migration at the molecular level
is what pushes up the blisters. Once the water gets inside the laminate it
will NOT migrate back out when the boat remains in the water. It will
diffuse and evaporate out when the boat is stored on the hard in a
low-humidity environment. Cold = low humidity so cold storage is a faster
way to dry out the laminate that is pressurized by osmotic action.


You really don't get it, do you.

Water doesn't migrate through any membrane into a polyester laminate,
the laminate absorbs water, just as a sponge does. The water reacts
with resident chemicals in the laminate to form new substances which
have a larger molecular size and thus do not flow through the laminate
as easily as water.

When you take a boat out of the water whatever water has been absorbed
by the hull will slowly dry out and blisters, which contain a mixture
of water and osmosis liquid will usually become less visible. However,
"drying the boat" removes only water content and will never remove all
of the "osmosis liquid", and thus cannot remove the root of the
problem.

The only method, to date, for getting rid of the osmosis liquid is to
let the boat set and some of the osmosis liquid may slowly defuse
outwards where it can be washed off.

Or alternatively, to strip the outer layers of the hull until you
remove the portion of the laminate containing the majority of the
osmosis, which is very costly as it involves both removing laminate
and replacing the removed laminate with new, if the hull is to be
returned to its original strength.

And finally, if you place an object containing water in an arctic
climate the water will freeze and in the case of a boat might well
explode the hull. Living trees in the arctic occasionally exploded due
to freezing of the sap.

Spraying the hull with water will do nothing to release the trapped osmotic
fluids that push out the blisters. Only in areas where the laminate is
compromised will the osmotic fluid ooze out to be washed off. In areas where
the laminate is intact there is also osmotic fluid under pressure which does
not ooze out. So, Skippy is fixing about half the problem given the
assumption that bout half his hull laminate is structurally compromised as
in cracks, fractures, holes, splits, etc.

Wilbur Hubbard


Sorry Willie-boy but you are wrong again, the osmosis liquid is not
wholly contained in discrete bubbles it is pretty well defused in the
hull material and the waiting and washing is intended to remove this
liquid from the surface of the hull so that the barrier coat will
adhere to the hull.

While one might applaud your valiant, but futile, attempts to prove
that you understand osmosis you are hampered by your inability to
realize that your preconceived notions are not facts and not correct
and you are thus unable to realize that you "don't know what you are
talking about". Since you can never realize that you are wrong you are
unable to ever learn.

In short Willie, your antiquated notion that osmosis can be cured by
drying is about as logical as the argument that the earth is flat else
we'd all fall off, and arguing your preconceived "fact" just
demonstrates your stupidity.

Cheers,

Bruce
(bruceinbangkokatgmaildotcom)

On Thu, 28 Apr 2011 20:33:15 -0500, CaveLamb
wrote:

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



Wilbur, Read down to ***!



Let's face it, an awful lot of boats have blisters, so that finding one that
doesn't (or won't get them) can be a difficult proposition. The short answer is
that if at all possible, you should try to avoid that, if for no other reason
than the potential expense you may face in the future. That expense may not
result from the absolute necessity to repair the blisters, but the position you
may find yourself in when it comes time to sell the boat. Particularly with
newer model boats, say 1 - 3 years old, it is not unusual for buyers demand a
reduction in price, or that the blisters be repaired.

For older boats, its usually much less of a problem, for the fact is that
moderate blistering on an older boat rarely impedes the sale. Unfortunately,
another fact of boating life is that there is a great deal of misinformation on
this much talked-about subject. One common misconception is that blisters
seriously weaken and/or damage boat hulls. In 30 years of surveying and
examining around 4000 hulls, I have seen less than 10 cases where blisters have
resulted in serious structural degradation of a hull where it was weakened to a
point where some type of failure was immanent.

What is a blister? First, let's understand that all fiberglass hulls absorb
water to some degree because both the gel coat finish on the exterior, and the
fiberglass reinforced plastic is porous. Since water is a solvent, it will react
with the plastic resulting in the water and solvents in the plastic mixing to
create a weak solvent solution, usually with styrene. This then softens the gel
coat somewhat and, combined with a bit of gas or fluid pressure, results in the
blister.

Are blisters harmful? Yes, but. This is a question of how much harm. Blisters
form at the interface between the gel coat and what is called the skinout mat,
which is a layer of chopped, short-strand fiberglass that is used to prevent the
coarser weave pattern of heavier fiberglass cloth from telegraphing through to
the finish surface. You've probably seen boats with a checkerboard pattern
showing on the surface, and this is the reason why. Now, fiberglass fabric,
being made of bundles of very fine glass fibers, is very porous also, most
especially the outer layer of mat. Once the gel coat absorbs water, the fibers
in the mat that are unsaturated with resin then spread the water around via the
capillary effect.

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.

Boat hull blisters
If the resin used to make the hull is of a lower quality that will react with
water, a process known as hydrolysis, which means nothing more than becoming
saturated with water and dissolving, then the hull is poised to develop
blisters. Many other factors also come into play here, such as how well the mat
layer is bonded to the gel coat.

Since the vast majority of blisters occur between the mat and gel coat (depicted
in illustration above), this bond has to be fairly weak for the blistering
process to occur. If the bond is strong, then blisters will not occur, even
though there is a lot of water absorption. This is a very general, even generic,
description of the blistering process. There are frequently numerous other
factors involved which I will not address here.

Aside from the damage it causes to the surface, most of the damage done by the
blister is to the gel coat and the skin out mat, which is not a structural part
of the hull laminate. Remember, the mat is only there to prevent the fabric
pattern from showing through to the surface. The obvious question is now, "But
isn't the water dissolving the rest of the plastic resin in the laminate?" The
answer to that is "No, its not." At least not to any considerable degree.


***
You may have noticed that I have not used the word "osmosis" that we hear so
much these days. Technically, water passing through the porous gel coat is not
osmosis; its just water passing through a porous material.



However, the blistering process may involve osmosis, a process which
concentrates solvents within the space formed by the blister void. This
concentration of solvents does indeed dissolve the plastic, but fortunately the
amount of fluid involved is so small that it does not seriously threaten the
laminate.

Of course, the larger the blister, the more concentrated solvent is present, the
more damage it will cause. Therefore the amount of damage, and therefore
structural weakening caused by blistering, is directly proportional to size and
number of blisters. This explains why only boats with very large blisters can
end up with serious structural weakness problems.


Or, as somebody once said, "You can lead a horse to water, but you
can't make it drink".
Cheers,

Bruce
(bruceinbangkokatgmaildotcom)