Refinishing: Who has tried a shortcut?

Paul Gaines wrote in message ...


Dry out your ship, slick it up, use WX block system once, preferably =
twice a year, NEVER tie it out, and store it in your trailer inside a =
basement or hanger, etc..

P. Gaines


Why *NEVER tie it out*. Is your concern UV, moisture, or something
else? My ship is based in Phoenix, AZ where the humidity is usually
very low. Most of my fellow club pilots tie down for the duration of
a contest.

When I go to New Mexico or Texas I see dew on the wings in the
morning. Why should I be concerned about a little moisture on the
wings if I put 30 gallons inside them for 6 or more hours each contest
day?


Andy (GY)

Moisture will also settle around fittings and migrate into areas where it
really should not be. I think it is always better practice not to leave a
ship outside. Wider temp swings, etc...

Paul
----- Original Message -----
From: "Glider Pilot Network"
To: "Paul Gaines"
Sent: Tuesday, December 23, 2003 9:40 AM
Subject: [r.a.s] Refinishing: Who has tried a shortcut?-U out there JJ?


------------------------------------------------------------
Newsgroup: rec.aviation.soaring
Subject: Refinishing: Who has tried a shortcut?-U out there JJ?
Author: Andy Durbin
Date/Time: 14:30 23 December 2003
------------------------------------------------------------
Paul Gaines wrote in message news:...


Dry out your ship, slick it up, use WX block system once, preferably
=
twice a year, NEVER tie it out, and store it in your trailer inside a
=
basement or hanger, etc..

P. Gaines


Why *NEVER tie it out*. Is your concern UV, moisture, or something
else? My ship is based in Phoenix, AZ where the humidity is usually
very low. Most of my fellow club pilots tie down for the duration of
a contest.

When I go to New Mexico or Texas I see dew on the wings in the
morning. Why should I be concerned about a little moisture on the
wings if I put 30 gallons inside them for 6 or more hours each contest
day?


Andy (GY)

------------------------------------------------------------

A couple more data points for you *do-it-yourself* aficionados:

1. Re-establishing the original airfoil can be done by making some *quick &
dirty* templates, before starting. Wax and PVA (mold release) several locations
along the leading edge, say every 24 inches. Now make cardboard templates for
these locations, nothing fancy, just roughly the shape. With the L/E up, lay on
about 3 strands of glass rovings around the template locations. Next, pile on
some epoxy flox and shove your cardboard templates into the goo. Pop them off,
when cured and you have some exact replicas of your original leading edge
shape. I carry my templated back about 3 inches, as this is the most critical
area. Everything else is contouring to keep a smooth shape, both spsn-wise and
cord-wise.

2. You will need a good water trap in your feed line coming from the
compressor. I have used the *toilet paper* trap for years. It employs a roll of
toilet paper as the filter element. Just replace the roll before each major
operation (each wing) Some red-neck repairmen have even been known to dry out
the used rolls and then employ them again, for their original purpose. If you
don't have a good moisture trap, your spray gun will spit out little water
drops and they will show up as little craters on the product.
Have fun and remember, Everybody's got to be doing something. You have just
chosen to sand for the rest of your life.
JJ Sinclair

The wings I am preparing to refinish will be done in urethane and I
will be removing all the gelcoat that can be removed safely. I am
addicted to gelcoat though. Must be the smell.

Reuben

Stewart Kissel wrote in message ...
This thread is what makes ras work. Reuben I have
a 17 year
old ship with some cracking on the wings. From your
experience
with composites, should I go poly or gel? And should
I have all
the old gel taken off, even if this will be more money?

I believe that Vegas are painted rather than gelled,
I have seen poor paintwork on Vegas though.

John

This thread has become very interesting…. there is considerable technical
discussion orbiting some of the comments. It would be nice if we were all in
the same room, where we could exchange a mass of information, rather than
simple RAS sound bites.

In too brief a sound bite fashion let me address a few of the comments:

The difference between boat gel coat and glider gel coat - It is a given that
boat gel coat holds up better than glider gel coat… many boat companies offer
a 10 year gel coat warranty! Boats are built with polyester gel coat and a
polyester (or vinyl ester variant) laminating resin substrate. The resulting
bond is a *COHESIVE* in nature. A previous comment was correct, that
essentially when boats come out of the mold they are finished (from a gel coat
cosmetic perspective - no sanding). The boats built today are using 4th and 5th
generation gel coat formulations that are fairly sophisticated. One small boat
company in the U.S. will use more gel coat than the entire glider industry.

Gliders, on the other hand, use polyester gel coat and an epoxy laminating
resin substrate. The resulting bond is an *ADHESIVE* force. The state-of-cure
of the gel coat applied in the mold at the time of laminate application is
critical to the bond. This is a complex interplay involving initiator level,
temperature, time, gel coat thickness, and other factors. There is an optimal
cure-state window for development of maximum bonding between the cured gel coat
and the laminate. At best, the adhesive bond between polyester and epoxy will
not produce as much energy as a polyester to polyester cohesive bond. The gel
coat typically used on gliders is the same basic 2nd or 3rd generation
technology as used on boats in the '70's and '80's. Also, there is
considerably more surface movement on a thin skinned glider laminate as
compared to a much thicker boat laminate.

Addressing a few of Ruben's comments - When gel coat is applied wet-on-wet, as
in the mold, it does cure as a uniform molecular matrix. When gel coat or a
paint coating is post-applied (as in repairs or refinishing leading edges out
of the mold) there is little, if any, crosslink bonding that occurs. This
scenario relies for the most part on a simple mechanical bond as Ruben
correctly stated.

Ah, the moisture issue….. It is correctly stated that gel coat and
composites laminates have the properties of a semi-permeable membrane. However
the discussion leaves the tracks with the idea of liquid water penetration and
surface porosity. *Water vapor*, that is individual molecules of H2O, will
continually seek to equilibrate on the inner and outer skins of a laminate in a
very slow process. Water in the liquid state will *not* penetrate gel coat.
The surface pores and voids in the 3-D molecular matrix are too small for
liquid phase water to penetrate. This has to do with the inherent surface
tension of liquid H2O. The surface does not wet enough for liquid to flow into
the normal porosity.

You *do not* have to be concerned about washing your glider with water, or
leaving it out in the rain for that matter. It will not have a negative effect
on the gel coat. Wax does not seal in water. Vapor phase H2O will freely
equilibrate with no noticeable retardation of transmission through a wax film.
Additionally, since liquid water is not present within the gel coat or laminate
matrix, (under normal circumstances - let's not talk osmotic blisters), there
is no issue with freezing and causing cracks. This could become an issue with
giant cracks, but not with typical gel coat effects. Freezing water is simply
not an issue.

Again, hope this helps…. After 38 rounds this thread has stayed coherent….
has to be a record for RAS!

Bob Lacovara

This thread has become very interesting…. there is considerable technical
discussion orbiting some of the comments. It would be nice if we were all in
the same room, where we could exchange a mass of information, rather than
simple RAS sound bites.

In too brief a sound bite fashion let me address a few of the comments:

The difference between boat gel coat and glider gel coat - It is a given that
boat gel coat holds up better than glider gel coat… many boat companies offer
a 10 year gel coat warranty! Boats are built with polyester gel coat and a
polyester (or vinyl ester variant) laminating resin substrate. The resulting
bond is a *COHESIVE* in nature. A previous comment was correct, that
essentially when boats come out of the mold they are finished (from a gel coat
cosmetic perspective - no sanding). The boats built today are using 4th and 5th
generation gel coat formulations that are fairly sophisticated. One small boat
company in the U.S. will use more gel coat than the entire glider industry.

Gliders, on the other hand, use polyester gel coat and an epoxy laminating
resin substrate. The resulting bond is an *ADHESIVE* force. The state-of-cure
of the gel coat applied in the mold at the time of laminate application is
critical to the bond. This is a complex interplay involving initiator level,
temperature, time, gel coat thickness, and other factors. There is an optimal
cure-state window for development of maximum bonding between the cured gel coat
and the laminate. At best, the adhesive bond between polyester and epoxy will
not produce as much energy as a polyester to polyester cohesive bond. The gel
coat typically used on gliders is the same basic 2nd or 3rd generation
technology as used on boats in the '70's and '80's. Also, there is
considerably more surface movement on a thin skinned glider laminate as
compared to a much thicker boat laminate.

Addressing a few of Ruben's comments - When gel coat is applied wet-on-wet, as
in the mold, it does cure as a uniform molecular matrix. When gel coat or a
paint coating is post-applied (as in repairs or refinishing leading edges out
of the mold) there is little, if any, crosslinking that occurs. This scenario
relies for the most part on a simple mechanical bond as Ruben correctly stated.

Ah, the moisture issue….. It is correctly stated that gel coat and
composites laminates have the properties of a semi-permeable membrane. However
the discussion leaves the tracks with the idea of liquid water penetration and
surface porosity. *Water vapor*, that is individual molecules of H2O, will
continually seek to equilibrate on the inner and outer skins of a laminate in a
very slow process. Water in the liquid state will *not* penetrate gel coat.
The surface pores and voids in the 3-D molecular matrix are too small for
liquid phase water to penetrate. This has to do with the inherent surface
tension of liquid H2O. The surface does not wet enough for liquid to flow into
the normal porosity.

You *do not* have to be concerned about washing your glider with water, or
leaving it out in the rain for that matter. It will not have a negative effect
on the gel coat. Wax does not seal in water. Vapor phase H2O will freely
equilibrate with no noticeable retardation of transmission through a wax film.
Additionally, since liquid water is not present within the gel coat or laminate
matrix, (under normal circumstances - let's not talk osmotic blisters), there
is no issue with freezing and causing cracks. This could become an issue with
giant cracks, but not with typical gel coat effects. Freezing water is simply
not an issue.

Again, hope this helps…. After 38 rounds this thread has stayed coherent….
has to be a record for RAS!

Bob Lacovara

This thread has become very interesting…. there is considerable technical
discussion orbiting some of the comments. It would be nice if we were all in
the same room, where we could exchange a mass of information, rather than
simple RAS sound bites.

In too brief a sound bite fashion let me address a few of the comments:

The difference between boat gel coat and glider gel coat - It is a given that
boat gel coat holds up better than glider gel coat… many boat companies offer
a 10 year gel coat warranty! Boats are built with polyester gel coat and a
polyester (or vinyl ester variant) laminating resin substrate. The resulting
bond is a *COHESIVE* in nature. A previous comment was correct, that
essentially when boats come out of the mold they are finished (from a gel coat
cosmetic perspective - no sanding). The boats built today are using 4th and 5th
generation gel coat formulations that are fairly sophisticated. One small boat
company in the U.S. will use more gel coat than the entire glider industry.

Gliders, on the other hand, use polyester gel coat and an epoxy laminating
resin substrate. The resulting bond is an *ADHESIVE* force. The state-of-cure
of the gel coat applied in the mold at the time of laminate application is
critical to the bond. This is a complex interplay involving initiator level,
temperature, time, gel coat thickness, and other factors. There is an optimal
cure-state window for development of maximum bonding between the cured gel coat
and the laminate. At best, the adhesive bond between polyester and epoxy will
not produce as much energy as a polyester to polyester cohesive bond. The gel
coat typically used on gliders is the same basic 2nd or 3rd generation
technology as used on boats in the '70's and '80's. Also, there is
considerably more surface movement on a thin skinned glider laminate as
compared to a much thicker boat laminate.

Addressing a few of Ruben's comments - When gel coat is applied wet-on-wet, as
in the mold, it does cure as a uniform molecular matrix. When gel coat or a
paint coating is post-applied (as in repairs or refinishing leading edges out
of the mold) there is little, if any, crosslinking that occurs. This scenario
relies for the most part on a simple mechanical bond as Ruben correctly stated.

Ah, the moisture issue….. It is correctly stated that gel coat and
composites laminates have the properties of a semi-permeable membrane. However
the discussion leaves the tracks with the idea of liquid water penetration and
surface porosity. *Water vapor*, that is individual molecules of H2O, will
continually seek to equilibrate on the inner and outer skins of a laminate in a
very slow process. Water in the liquid state will *not* penetrate gel coat.
The surface pores and voids in the 3-D molecular matrix are too small for
liquid phase water to penetrate. This has to do with the inherent surface
tension of liquid H2O. The surface does not wet enough for liquid to flow into
the normal porosity.

You *do not* have to be concerned about washing your glider with water, or
leaving it out in the rain for that matter. It will not have a negative effect
on the gel coat. Wax does not seal in water. Vapor phase H2O will freely
equilibrate with no noticeable retardation of transmission through a wax film.
Additionally, since liquid water is not present within the gel coat or laminate
matrix, (under normal circumstances - let's not talk osmotic blisters), there
is no issue with freezing and causing cracks. This could become an issue with
giant cracks, but not with typical gel coat effects. Freezing water is simply
not an issue.

Again, hope this helps…. After 38 rounds this thread has stayed coherent….
has to be a record for RAS!

Bob Lacovara

Bob



If what you say about the 2nd or 3rd generation gel coat used in the boat of
the 70s and 80s is true and the assumption that moisture is not a problem
with gel coat how do you account for the horrible blister problems below the
waterline of many of the boats of the 70 and 80s. I experience this with
sailboat in the early 80s. The blister were full of liquid. A large number
of boats in the area where I sailed had this problem. It was not boat
manufacture specific.



Richard Pfiffner





"B Lacovara" wrote in message
...
This thread has become very interesting.. there is considerable technical
discussion orbiting some of the comments. It would be nice if we were all
in
the same room, where we could exchange a mass of information, rather than
simple RAS sound bites.

In too brief a sound bite fashion let me address a few of the comments:

The difference between boat gel coat and glider gel coat - It is a given
that
boat gel coat holds up better than glider gel coat. many boat companies
offer
a 10 year gel coat warranty! Boats are built with polyester gel coat and
a
polyester (or vinyl ester variant) laminating resin substrate. The
resulting
bond is a *COHESIVE* in nature. A previous comment was correct, that
essentially when boats come out of the mold they are finished (from a gel
coat
cosmetic perspective - no sanding). The boats built today are using 4th
and 5th
generation gel coat formulations that are fairly sophisticated. One small
boat
company in the U.S. will use more gel coat than the entire glider
industry.

Gliders, on the other hand, use polyester gel coat and an epoxy laminating
resin substrate. The resulting bond is an *ADHESIVE* force. The
state-of-cure
of the gel coat applied in the mold at the time of laminate application is
critical to the bond. This is a complex interplay involving initiator
level,
temperature, time, gel coat thickness, and other factors. There is an
optimal
cure-state window for development of maximum bonding between the cured gel
coat
and the laminate. At best, the adhesive bond between polyester and epoxy
will
not produce as much energy as a polyester to polyester cohesive bond. The
gel
coat typically used on gliders is the same basic 2nd or 3rd generation
technology as used on boats in the '70's and '80's. Also, there is
considerably more surface movement on a thin skinned glider laminate as
compared to a much thicker boat laminate.

Addressing a few of Ruben's comments - When gel coat is applied
wet-on-wet, as
in the mold, it does cure as a uniform molecular matrix. When gel coat or
a
paint coating is post-applied (as in repairs or refinishing leading edges
out
of the mold) there is little, if any, crosslinking that occurs. This
scenario
relies for the most part on a simple mechanical bond as Ruben correctly
stated.

Ah, the moisture issue... It is correctly stated that gel coat and
composites laminates have the properties of a semi-permeable membrane.
However
the discussion leaves the tracks with the idea of liquid water penetration
and
surface porosity. *Water vapor*, that is individual molecules of H2O,
will
continually seek to equilibrate on the inner and outer skins of a laminate
in a
very slow process. Water in the liquid state will *not* penetrate gel
coat.
The surface pores and voids in the 3-D molecular matrix are too small for
liquid phase water to penetrate. This has to do with the inherent surface
tension of liquid H2O. The surface does not wet enough for liquid to flow
into
the normal porosity.

You *do not* have to be concerned about washing your glider with water, or
leaving it out in the rain for that matter. It will not have a negative
effect
on the gel coat. Wax does not seal in water. Vapor phase H2O will freely
equilibrate with no noticeable retardation of transmission through a wax
film.
Additionally, since liquid water is not present within the gel coat or
laminate
matrix, (under normal circumstances - let's not talk osmotic blisters),
there
is no issue with freezing and causing cracks. This could become an issue
with
giant cracks, but not with typical gel coat effects. Freezing water is
simply
not an issue.

Again, hope this helps.. After 38 rounds this thread has stayed coherent..
has to be a record for RAS!

Bob Lacovara

I was actually trying to avoid this part of the discussion, but here goes…..
Interestingly enough, boat hull blistering is not a gel coat problem, but
rather a laminate problem. Considering the laminate as a semi-permeable
membrane the potential for osmosis can take place. Osmosis is the tendency of a
fluid of lower concentration to pass through a semi-permeable membrane into a
solution of higher concentration. In the case of boat hulls, water vapor (lower
concentration) passes from the inside of the hull to the outside of the hull
(higher concentration). The gel coat matrix is denser than the laminate matrix
and the transmitted water vapor will eventually collect in what are known as
seed sites. These are voids at the gel coat/laminate interface. Eventually, the
liquid in the seed sites will become denser that the outside water and the
process reverses pulling water in from the opposite direction…. This is where
the big nasty boat hull blisters appear. Blistering problems have been solved
by the boat or swimming pool industries, because they now use vinyl ester skin
coats behind the gel coat. The point is that the problem was solved with a
laminate modification, rather than a gel coat modification.

The reason I was trying to avoid this discussion, is that this mechanism is not
in play in relation to gel coat cracks. Sailplane gel coat, or more likely
urethane paint, can blister from osmosis. Just put a glider in a wet fuselage
cradle! However, until the seed site is saturated and dense there is no
transport of *liquid water*. All the moving H20 is vapor phase. This only
happens under very specific conditions. So unless you are going to ride it
hard and put it away wet there is absolutely issue with washing a gel coat
finish. But even when blistering takes place, there is no relation to typical
gel coat cracking.

Bob Lacovara