Gelcoat and Lacquer/Acetone
Nolaminar
on Gelcoat.
I have completed an unscientific test on an old Gelcoated wing tip. It has
been soaking for weeks and there has been no degrading of the surface.
I wonder if this is one of the old folklore stories.... Urban legend.
RE Gaines,
USA
OscarCharlie
Gelcoat care and cautions to never, never use acetone (among other solvents)
on your gelcoat covered glider. Schempp-Hirth recommends the same in the
literature that accompanies their new gliders. Now that you've bathed the
piece, put it out in the sun for a while next to a piece untouched by
solvents, then watch what happens. From experience I can tell you that
acetone will shorten the life of the gelcoat by half (at least).
"Nolaminar" <nola...@aol.com> wrote in message
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B Lacovara
certification programs to gel coat manufacturers and composites molders.
Here are the technical facts: Aromatic solvents, such as acetone and lacquer
thinner, or petroleum distillates, such as mineral spirits, have little or no
affect on gel coat. In fact it is possible to store acetone in a gel coat lined
vessel. There is absolutely no problem wiping down gel coat with either one.
There is no documented association between wiping a cured gel coat with acetone
and discoloration. (There is an issue with thinning liquid gel coat with
acetone during application, that produces a known set of performance problems).
I think the glider pilot folklore comes from wiping lacquer-based paint stripes
with either acetone or lacquer thinner. People see the "paint" coming off and
assume it could affect the gel coat in the same way.
In terms of solvents the only really bad actors with gel coat are methylene
chloride, dibasic ester (DBE), and propylene carbonate (PC). Methylene chloride
or DBE are the base products in most paint removers, and PC is an industrial
solvent not readily available to the general public. Occasionally some of the
tape residue removers use these solvents.
The composites industry in general routinely uses acetone for gel coat surface
clean-up. I use acetone or lacquer thinner as needed on my glider.
Bob Lacovara - 2BT
Doug Haluza
uses kerosene to remove mylar seals and tape residue. It works well, as long
as you are patient. I assume that kerosene falls into the petroleum
distilates category and is also safe?
"B Lacovara" <blac...@aol.com> wrote in message
news:20020916163614...@mb-cb.aol.com...
OscarCharlie
The producer of my sailplane (Schmepp) and DG both warn specifically against
the use of acetone. Per DG's website (the emphasis is DG's):
"A further enemy of polyester gelcoats are chlorinated hydrocarbon cleaning
solvents. NEVER clean the gelcoat with MEK, Trichloroethylene, Acetone or
similar products. The use of any of these will cause permanent damage to the
gelcoat. While ethyl alcohol (iso propyl alcohol) or petrol can be used
sparingly to clean tape marks from the gelcoat, it is much better to use a
'green' solvent such as De-Solvit or a good silicone free polish such as Car
lack or Lesonal. If used regularly, these latter polishes will also provide
some protection against UV. Avoid the use of any polish containing silicones
as it makes it very difficult to re-finish a scarfed repair on the structure
should it ever be necessary."
Am I misreading this warning?
As for paint, the reason we used acetone in the past was to save ourselves
the trouble of sanding it off. It softened the paint (and tape residue, and
particularly stalwart bugs, etc.) without affecting the gelcoat. But at
least two major manufacturers have taken the position that it be kept far
away from the surfaces of their gliders. As an expert, can you tell me why
they would take this position?
Many people still use acetone to clean gelcoat surfaces prior to repair. Are
we seeing practice outweighing common sense? Or convenience over long term
effects? The crazing on my ASW 20 started in those places that were exposed
to acetone (leading edge, wing root, ailerons... wherever I had difficult
cleaning chores). I used to use the stuff pretty liberally because that was
what I was told to do. When I began to suspect that it wasn't such a good
idea, I started looking at other gliders that had seen repeated exposure...
and they appeared to have fared less well than other gliders that didn't
receive the same degree of attention. Hardly scientific. But who do I trust?
My own hunch and the recommendations of the manufacturer? Or an industry
expert? Tough call.
Folklore? Doesn't appear so. Not since people used to bathe their gliders in
it. And many repair shops still do.
"B Lacovara" <blac...@aol.com> wrote in message
news:20020916163614...@mb-cb.aol.com...
Doug Haluza
are areas where there is a lot of filler, and the ailerons are an area where
gellcoat seems to craze on most ships. So your crazing may be related to
solvents, or may be due to other factors.
As I recall, the european gel coats used on sailplanes were more prone to
crazing than the american gel coats used on boats. Perhaps there is a
difference in their solvent resistance. Or, perhaps the sailplane
manufacturers are looking for an excuse....
"OscarCharlie" <fiveni...@yahoo.com> wrote in message
news:3d865...@corp-goliath.newsgroups.com...
Doug Easton
you quoted and also this... "By the way, if you put the seal on yourself, be
careful that the surface to be taped to is sparkling clean and free of oil.
The best thing to clean it with is acetone and then be sure not to touch it
with your fingers!" So even the manufacturers aren't giving us a consistent
story.
Doug
"OscarCharlie" <fiveni...@yahoo.com> wrote in message
news:3d865...@corp-goliath.newsgroups.com...
B Lacovara
of gel coat is chlorinated hydrocarbon cleaning solvents." Earlier I referred
to methylene chloride and being a no-no with gel coat. So is trichlor, but to a
lesser extent.
However, the misinformation in the DG statement is including the ketone
solvents, (i.e. acetone and MEK) in a true statement about chlorinated
solvents. There are several possibilities to consider: 1) any solvent a
manufacturer recommends *will* be abused by someone and they will complain that
they damaged their finish; 2) they consider a solvent a solvent and are not
technically discriminating the properties.
Bob
Tom and Jane Gilbert
areas that get some extra treatment at the factory's finishing shop. When
this work is first carried out it blends well with the general gelcoat
finish. However in time it shows discoloration or cracking long before
other areas. The reason (I believe) is that the gelcoat is over catalysed
and excess thinner is used to help speed up the process. Other areas
include the top of the fuselage and the leading edge of the vertical
stabiliser.
I run a repair shop and see this type of failure quite often. I also see
the same failure on old repairs (and some not so old repairs) where the
gelcoat was mixed incorrectly.
In the workshop we use acetone on a regular basis to clean adhesive residue
and around areas to be repaired. No bad effects have ever been observed and
some of the ships have been coming to us for many years.
Tom Gilbert
Robert Ehrlich
>
> The areas you mention as being the first to show signs of failure are the
> areas that get some extra treatment at the factory's finishing shop. When
> this work is first carried out it blends well with the general gelcoat
> finish. However in time it shows discoloration or cracking long before
> other areas. The reason (I believe) is that the gelcoat is over catalysed
> and excess thinner is used to help speed up the process. Other areas
> include the top of the fuselage and the leading edge of the vertical
> stabiliser.
On the gliders in my club, it is very obvious that cracks and discoloaration
start on leading edges. My personnal hypothesis about that was that every
day cleaning of bugs with water, even if dried after that, may cause water
penetration in the gel coat, which then freezes during the winter and so
causes micro cracks due to the increase of volume during freezing.
B Lacovara
boats would have a bit of a problem, wouldn't they?
The issue with common cracks and discoloration on the leading edges is that is
where the wings are bonded. The leading edge is filled with a patching compound
and gel coat is applied and hand finished.
The patching compound has a greater tendency to crack than the surrounding gel
coat applied in the mold. The most likely cause of the yellowing on the leading
edge is the glider manufacturers improper thinning or under-catayzation of the
gel coat when hand finishing the leading edge area.
Bob
Ronald
The gelcoat was normally polyester-based and hardenes pretty quickly.
You don't want this when you built a wing or fuselgae halve in a mold.
During the lay-up process of the GRP/CRP you want the gelcoat to be
'tacky'so they slow down the hardening process. The gelcoat will
harden together with the Epoxy-resin.
When the fuselage and wing halves are bonded together during asembly
of the glider, there is no gelcoat at these 'bonding lines'.
The area's were sanded and sprayed over with a gelcoat of different
composition (more/other catalyst) to speed up the process of
hardening.
Also area's that were damaged or needed refinishing of the gelcoat
were sprayed over with this faster hardening gelcoat.
It was not expected that in several years of time the 'faster'gelcoat
would discolour more quickly than the 'slow' one.
You will find yellow patches on older gliders mainly at the
leading-edges, top of the fuselage, rim of the cockpit and sometimes
patches on the wing or fin.
No way to prevent this except keeping it from sunlight.
OscarCharlie
my delivery paperwork that recommended agains the use of acetone due to long
term damage, and warned that petrol product could be used, but should be
removed as quickly as possible.
I think I'll stick to my safe position and be wary of solvents in general...
convenience should always be suspect. But I'll do some experimenting of my
own. Bob, I want to simulate long term effects in a relatively short time;
is it appropriate to take identical pieces of gelcoated fiberglass, expose
them to sunlight for a prolonged period (months), wiping one down with
acetone each morning while cleaning the other with a water-dampened cloth?
"B Lacovara" <blac...@aol.com> wrote in message
news:20020916230220...@mb-fz.aol.com...
John Cochrane
> is it appropriate to take identical pieces of gelcoated fiberglass, expose
> them to sunlight for a prolonged period (months), wiping one down with
> acetone each morning while cleaning the other with a water-dampened cloth?
The acetone will pull off wax, inclding any UV protector in the wax, while
the water will not. Maybe rewax after each try? Just trying to get a good
controlled experiment here!
I use the 3m adhesive remover for most uses covered here. Any comments from
the experts about this product?
John Cochrane
OscarCharlie
At some point, the gelcoat will fail.
Bob notes that water shouldn't be a problem... after all, boats sit in the
water. I heard the same argument for leaving gliders out.... after all,
boats sit out. I guess so long as you sell your glider before it gets too
old, it will always be someone else's problem. Here's where we need some
expertise. What is the difference between the boat and glider manufacturing
processes? Materials? They operate in very different environments. I suspect
that if I tied my floating glider up to a salt-water dock for the summer, it
would fare decidedly less well than a cabin cruiser. Why? After all, they're
both just resin and gelcoat.
"Ronald" <all...@zonnet.nl> wrote in message
news:6a070d2a.02091...@posting.google.com...
OscarCharlie
also a glue joint. Cupping came sooner to those spots as well. The crazes in
areas less exposed to acetone were long lines, appearing later, whereas the
leading edge and ailerons (where tape was overlayed, showed short
cross-checking, then cupping).
I've long had a hunch for a while that solvents have a long-term insidious
effect. We all agree water is not good for the finish. I have to believe
that acetone is even more aggressive in finding its way into the gel coat.
And while it may not soften it in the short term, I suspect it produces the
same degree of damaging effects in the long term.
We've often wondered in the past why one ASW 19 can have such a good finish,
while another is literally sloughing off its gelcoat. We attribute
differences to manufature, climate, storage, exposure, altitude... I watched
the gelcoat on my 20 deteriorate over the course of 17 years, and took every
opportunity to compare it with other ships of like age, because I wanted to
understand why mine seemed to age so much less gracefully. Acetone became a
prime suspect long before anyone started warning us off of it. And when I
banned all solvents from my kit, the process slowed.
"Doug Haluza" <dhaluza...@pipeline.com> wrote in message
news:8rth9.86229$e44.2...@news4.srv.hcvlny.cv.net...
Robert Ehrlich
>
> I doubt water would have anything to do with the gel coat cracking... otherwise
> boats would have a bit of a problem, wouldn't they?
>
But this is a known problem on boats ! However, as long as they remain in water
the water does not freeze.
Doug Haluza
below?
"OscarCharlie" <fiveni...@yahoo.com> wrote in message
news:3d875...@corp-goliath.newsgroups.com...
JJ Sinclair
>There is an issue with thinning liquid gel coat with
>acetone during application
I've been told by an engineer at Simtec to use acetone because it was so
volatile that it would evaporate after leaving the gun and probably before it
hit the work. Also, what are the known performance problems?
> that produces a known set of performance problems).
Wondering in Placerville,
JJ Sinclair
R. Wubben
What about taking the yellowish old tape residue off of wood and
fabric. Specifically at the wing root of a K-6?
Any recommendations for getting this stuff off safely?
Ryan Wubben
Chapel Hill, NC