Gelcoat question
 

About 3 months ago, I bought 1 quart of clear gelcoat. Didn't get
around to using it for about a month. When I went to open it up, it
was pretty hard and unuseable.

I bought another quart from the same seller about 2 weeks ago, and
opened it up within a week. This time, the consistency was about that
of grape jelly. At no time was any of this liquid.

I've worked with surfboard fiberglass resin and thought gelcoat would
be similar liquid consistency.

Am I wrong or:

a) Was unlucky, got two bad batches and need to take it up with the
seller?

b) Waited too long to use it? I don't see how it can harden up like
that within a week.

c) Need to add something else to liquify it or thin it, like acetone.
I tried acetone, but it doesn't take out clumping.

d) Leave gel-coat repair to a professional. I've done plenty of
fiberglass repair and didn't think gelcoat would be that different.

A little advice is much appreciated.

L.

Gelcoat question
 

Hi, your first batch was too old. The shelf life for polyester resins is
maybe 6 months although it may harden to the point of uselessness before
that. And your retailer may have given you pretty old stuff. But it sounds
like the second batch was fine. There are two types of gel coat; brushing
gel coat and spray gel coat. What you bought is probably brush gel coat.
Spray gel coat is much thinner. Its essentially the same formulation but
they use silica and other additives to thicken it. Usually, I just buy the
one I need. Adding acetone will not work; it flashes off (evaporates) too
soon. You can try adding neat resin but it may not be worth while; just buy
the right stuff and use it with confidence.
Gel coat repairs are not that hard and one can usually achieve a 100% repair
ie invisible! But you do need to match the color first. The concept is the
same as Bondo repairs.

Arnold

Gelcoat question
 

You might be able to recover the 2nd batch
by adding some styrene. It's probably too late,
but I've done it.

Bill


"LouiSurfer" wrote in message
ups.com...
About 3 months ago, I bought 1 quart of clear gelcoat. Didn't get
around to using it for about a month. When I went to open it up, it
was pretty hard and unuseable.

I bought another quart from the same seller about 2 weeks ago, and
opened it up within a week. This time, the consistency was about that
of grape jelly. At no time was any of this liquid.

I've worked with surfboard fiberglass resin and thought gelcoat would
be similar liquid consistency.

Am I wrong or:

a) Was unlucky, got two bad batches and need to take it up with the
seller?

b) Waited too long to use it? I don't see how it can harden up like
that within a week.

c) Need to add something else to liquify it or thin it, like acetone.
I tried acetone, but it doesn't take out clumping.

d) Leave gel-coat repair to a professional. I've done plenty of
fiberglass repair and didn't think gelcoat would be that different.

A little advice is much appreciated.

L.

Gelcoat question
 

Another gelcoat / flowcoat question...

How thick can gel coat / flowcoat be applied before it becomes a problem?
I have a bubble at the deck/hull join area where evidently a bubble existed
under the gelcoat.
If I fill it with gelcoat it will be approx 2-3 mm thick. Will this
thickness cause a problem?

Gelcoat question
 

Can you get good looking results using a brush? Is there a problem with
streaking
lines? My buddy did his boat and possibly screwed up the brush work because it
is very obvious it was brushed on. I think brushing would be a lot easier for
the
boat owner to do themselves, as opposed to spraying.

Sherwin D.

Ystay wrote:

Hi, your first batch was too old. The shelf life for polyester resins is
maybe 6 months although it may harden to the point of uselessness before
that. And your retailer may have given you pretty old stuff. But it sounds
like the second batch was fine. There are two types of gel coat; brushing
gel coat and spray gel coat. What you bought is probably brush gel coat.
Spray gel coat is much thinner. Its essentially the same formulation but
they use silica and other additives to thicken it. Usually, I just buy the
one I need. Adding acetone will not work; it flashes off (evaporates) too
soon. You can try adding neat resin but it may not be worth while; just buy
the right stuff and use it with confidence.
Gel coat repairs are not that hard and one can usually achieve a 100% repair
ie invisible! But you do need to match the color first. The concept is the
same as Bondo repairs.

Arnold

Gelcoat question
 

Hi Sherwin,
Generally, you can't escape brush marks when flowcoating. FYI, flowcoating
is where you apply gel coat (usually with a brush) hoping that it will
"flow" out like paint. Gel coat does not do this because it is too thick.
Spray grade gel coat is better for flowcoating with a brush but still does
not leave a pleasing surface. However, if the area is small like say a toe
rail or hull to deck joint then you may have luck using the softest brush
you can find. Most kayaks have their hull-to-deck joints flow coated.
Otherwise, its sanding time! Spraying is not much better; you get orange
peel (looks like the skin of an orange as opposed to the skin of an apple)
also because gel coat is too thick to go on smooth.

Arnold


"sherwindu" wrote in message
...
Can you get good looking results using a brush? Is there a problem with
streaking
lines? My buddy did his boat and possibly screwed up the brush work
because it
is very obvious it was brushed on. I think brushing would be a lot easier
for
the
boat owner to do themselves, as opposed to spraying.

Sherwin D.

Gelcoat question
 

Hi Hobbs,
a thick layer of gel coat is not really a good thing because it has no
fiberglass reinforcement. This can cause it to crack at a very slight
knock. The guru's will tell you that the ideal thickness for gel coat is
about 1 to1.5 mm. But in reality, you will find that many GRP parts have
gel coat in excess of that, sometimes up to 4 mm in certain areas. This is
one of the draw backs of brush applied gel coat. But anyway, your repair
should hold fine. Just make sure you catalize the gel coat to cure real
slow otherwise it'll shrink too much and wouldn't bond properly.

Arnold


"Hobbs" wrote in message
...
Another gelcoat / flowcoat question...

How thick can gel coat / flowcoat be applied before it becomes a problem?
I have a bubble at the deck/hull join area where evidently a bubble
existed under the gelcoat.
If I fill it with gelcoat it will be approx 2-3 mm thick. Will this
thickness cause a problem?

Gelcoat question
 

Thanks Arnold - I'll give it a go.

One other thing - it's winter here in Australia and the daytime temp is
between 9-15 deg C.
Will the gelcoat properly cure at this low temperature?

"Ystay" wrote in message
...
Hi Hobbs,
a thick layer of gel coat is not really a good thing because it has no
fiberglass reinforcement. This can cause it to crack at a very slight
knock. The guru's will tell you that the ideal thickness for gel coat is
about 1 to1.5 mm. But in reality, you will find that many GRP parts have
gel coat in excess of that, sometimes up to 4 mm in certain areas. This
is one of the draw backs of brush applied gel coat. But anyway, your
repair should hold fine. Just make sure you catalize the gel coat to cure
real slow otherwise it'll shrink too much and wouldn't bond properly.

Arnold


"Hobbs" wrote in message
...
Another gelcoat / flowcoat question...

How thick can gel coat / flowcoat be applied before it becomes a problem?
I have a bubble at the deck/hull join area where evidently a bubble
existed under the gelcoat.
If I fill it with gelcoat it will be approx 2-3 mm thick. Will this
thickness cause a problem?

Gelcoat question
 

"Hobbs" wrote in message
...
Thanks Arnold - I'll give it a go.

One other thing - it's winter here in Australia and the daytime temp is
between 9-15 deg C.
Will the gelcoat properly cure at this low temperature?

Hi Hobbs,
no experience in that kind of temperature. But the cure depends a fair bit
on ambient temperature so you may want to catalyse the resin a little more.

Arnold

Gelcoat question
 

Hi Arnold,

How would you compare the looks of a painted boat to one sprayed with gel coat?

Sherwin

Ystay wrote:

Hi Sherwin,
Generally, you can't escape brush marks when flowcoating. FYI, flowcoating
is where you apply gel coat (usually with a brush) hoping that it will
"flow" out like paint. Gel coat does not do this because it is too thick.
Spray grade gel coat is better for flowcoating with a brush but still does
not leave a pleasing surface. However, if the area is small like say a toe
rail or hull to deck joint then you may have luck using the softest brush
you can find. Most kayaks have their hull-to-deck joints flow coated.
Otherwise, its sanding time! Spraying is not much better; you get orange
peel (looks like the skin of an orange as opposed to the skin of an apple)
also because gel coat is too thick to go on smooth.

Arnold

"sherwindu" wrote in message
...
Can you get good looking results using a brush? Is there a problem with
streaking
lines? My buddy did his boat and possibly screwed up the brush work
because it
is very obvious it was brushed on. I think brushing would be a lot easier
for
the
boat owner to do themselves, as opposed to spraying.

Sherwin D.

Gelcoat question
 

On Sat, 16 Jun 2007 16:39:25 -0700, LouiSurfer
wrote stuff
and I replied:

As has been said, the first batch was too old. Don't feel too sorry; I
have had 200 litres of resin go hard on me....once G!

The trouble with Gelcoat is that it's really designed for working
inside a mould, and not for brushing. It has additives that make it
flow more the longer you work it, but also make it stop flowing almost
as soon as you stop. The beauty of this for inside moulding is that it
will not run or sag, and of course the mould's surface gives a smooth
exterior appearance.

Wall plaster has the same tendency.

If you are really worried about finish then either very finely (600+
grit) sand and polish the area (practice on something that does not
matter first! You will also have to affect the surrounding gelcoat),
or I would ask around and find a basecoat and (pref 2 part) paint that
will do a better job if brushed, and are meant to go on
polyester/gelcoat. The 2-part urethanes are good.

About 3 months ago, I bought 1 quart of clear gelcoat. Didn't get
around to using it for about a month. When I went to open it up, it
was pretty hard and unuseable.

I bought another quart from the same seller about 2 weeks ago, and
opened it up within a week. This time, the consistency was about that
of grape jelly. At no time was any of this liquid.

I've worked with surfboard fiberglass resin and thought gelcoat would
be similar liquid consistency.

Am I wrong or:

a) Was unlucky, got two bad batches and need to take it up with the
seller?

b) Waited too long to use it? I don't see how it can harden up like
that within a week.

c) Need to add something else to liquify it or thin it, like acetone.
I tried acetone, but it doesn't take out clumping.

d) Leave gel-coat repair to a professional. I've done plenty of
fiberglass repair and didn't think gelcoat would be that different.

A little advice is much appreciated.

L.

Human bevaviour: Bestiality with a brain

Gelcoat question
 

Put the open container in a pan of water on the stove and warm it up.
Old dry hard crystallized polyester resin will liquify and can be used
when heated.
Not sure about gelcoat but worth a try.
Also worth a try is hacking some out of the container and warming in a
microwave oven on low heat. Gotta move with the times.

Gelcoat question
 

"sherwindu" wrote in message
...
Hi Arnold,

How would you compare the looks of a painted boat to one sprayed with gel
coat?

Sherwin

Hi Sherwin,
absolutely no comparison. A gel coat sprayed boat will look like awful.
See Oldnick's post below. Good info there. But I am about to spray gel
coat on a small boat. I expect to spend many hours sanding and fairing and
polishing it after. I make a lot of GRP plugs so all that sanding is no big
deal - kinda used to it. But I won't want to do it on anything more than 10
feet or so.

Arnold

Gelcoat question
 

"sherwindu" wrote in message
...
Hi Arnold,

How would you compare the looks of a painted boat to one sprayed with gel
coat?

Sherwin

Also, if you intend to use gel coat this way. make sure you add wax to the
gel coat. You can buy liquid wax from a grp supplier or you can use any
kerosene based wax (I use floor wax frequently). This is to inhibit air
from getting to the gel coat. The wax rises to the surface and blocks out
the air thereby alowing a full cure. If you omit this step, your gel coat
will remain tacky for a LONG time. But you can also wax the part liberally
after the gel coat has cured. This will also keep the air out but its an
extra step.

Arnold

Gelcoat question
 

Arnold,

I think you missed my drift. I was thinking about regular paint vs. gelcoat. I
suppose
that gelcoat is used for repairs or when the original gelcoat has worn through.
In my
case, the gel coat is probably still intact, but there are numerous tiny crazing
and the
original white color has faded to a dull yellow. I guess regular paint is the
way to go,
but can it be applied with a brush and still come out streak free? Any special
tricks
to make this happen?

Sherwin

Ystay wrote:

"sherwindu" wrote in message
...
Hi Arnold,

How would you compare the looks of a painted boat to one sprayed with gel
coat?

Sherwin

Also, if you intend to use gel coat this way. make sure you add wax to the
gel coat. You can buy liquid wax from a grp supplier or you can use any
kerosene based wax (I use floor wax frequently). This is to inhibit air
from getting to the gel coat. The wax rises to the surface and blocks out
the air thereby alowing a full cure. If you omit this step, your gel coat
will remain tacky for a LONG time. But you can also wax the part liberally
after the gel coat has cured. This will also keep the air out but its an
extra step.

Arnold

Gelcoat question
 

"sherwindu" wrote in message
...
Arnold,

I think you missed my drift. I was thinking about regular paint vs.
gelcoat. I
suppose
that gelcoat is used for repairs or when the original gelcoat has worn
through.
In my
case, the gel coat is probably still intact, but there are numerous tiny
crazing
and the
original white color has faded to a dull yellow. I guess regular paint is
the
way to go,
but can it be applied with a brush and still come out streak free? Any
special
tricks
to make this happen?

Sherwin
Hi Sherwin,
you're opening up a can of worms learning to paint! I'm guessing you know
about surface prep etc. Here's a tip when prepping - use as fine a grit
paper as you can stand. 300 plus grit will be ok but your paint will flow
better if you go higher, say 600. Custom car guys will sometimes go to 800
but we don't need to aim so high. Some people are happy with 220 grit. The
finish will be ok, just not stunning. Your prepped surface has to be near
perfect because paint will not cover up any surface imperfections; that's
what a hi-build primer is for. So any crazing, nicks etc will have to be
filled first.

Now to the painting! The most important thing you can do is to thin your
paint properly. The manufacturer will have a recommendation but I've found
that they are almost always cautious. You need to buy or make a vicosity
measuring device like a Ford cup or a Dean cup. You fill this up and time
how long it takes to empty. Write this figure down! Roughly you can expect
a Dean cup to empty in about 18 secs (very big +- ). I like the roller
brush method (lots on Google). But use the softest brush you can find and
treat it to some hair conditioner (really!).

The theory behind getting a flawless finish is like this - You need to apply
enough paint such that it almost wants to sag and /or run but doesn't. If
you have enough paint on there, the brush marks will "flow" and even out.
This is how you get a mirror finish. Too much paint and you get runs. Too
little and it won't flow out. Fun, huh? Don't forget that vertical
surfaces will flow out much easier! So how do you aid flow out? Thinning!
But that's not all, you need to know how viscous to keep your paint at
different temperatures. You need to know how much time you have before the
thinner flashes off. Once the thinner has mostly evaporated (flashed),
you're out of luck - the paint will be too tacky to flow. If using
polyurethanes, buy the slowest harderner they have. Good quality paints
flow better than cheaper ones. Matt and semi-gloss paints show fewer flaws.
Might be something on youtube to further confuse you!

Feel free to mail me directly if you have other questions.

Arnold