another gelcoat story

[Brad[_2_]]

When we made my fuselage, it was winter and we were heating the shop
with a propane heater. Propane releases moisture during combustion.

So........molds are waxed multiple times, gelcoat (shurfab polyester
product) is sprayed into the mold, we leave the heater on and go home
for the night............gelcoat cures.

Next day come back to the shop, make up a batch of epoxy and a bit of
micro as the first layer against the gelcoat and then start laying in
the carbon, no veil cloth, the idea was the epoxy/micro slurry would
help reduce print thru.

Fast forward 2 years.............fuselage is now in my shop where I
have been working on the interior bits this spring/summer. I am bored
and decide to sand the fuselage with 220 then down to 320 to get ready
for top coating with Prestec. Wow.............it looks great.

I blow off the dust with a compressor and then wipe the fuselage with
a damp rag and go watch TV for a bit. A few hours later I go into the
shop and am horrified to see large areas of blisters have formed under
the gelcoat...........I am able to peel the gelcoat off in places with
my fingernail! Further investigation with a sanding block and 70 grit
paper confirm there is no secure bond between the gelcoat and the
epxoy slurry in enough areas that I resign myself to remove the
gelcoat off the entire fuselage, down to the carbon.

1/2 is already done and I'll start today on the other
half...................ugh........

so.....my theory: the gelcoat had moisture on it when we started
brushing in the epoxy...........and probably there was a temperature
issue as well that may have prevented a full cure of the epoxy/gelcoat
interface.

Anyways.............a lot of work for sure.

Next step...................get some Prestec 2481 and brush it on and
start sanding again. Gotta do this before the WX turns here in
Washington and we start the rainy season.

Brad

[JJ Sinclair]

> Next step...................get some Prestec 2481 and brush it on and
> start sanding again. Gotta do this before the WX turns here in
> Washington and we start the rainy season.
>
> Brad


Bad luck with the gelcoat Brad, I would sand everything down with 80
grit, Prime with PCL Polyprimer (907 white), then sand with 220 and
spray on acrylic urethane (PPG concept super white), 4 flow coats then
block sand after 18 to 24 hrs with 600w, then 800w use dye-coat, then
let it cure for 3 days before buffing it out with liquid buffing
compound and a wool pad turning at about 1700 rpm. Gel coat was never
intended for airplanes, urethane was/is!
JJ
PS, do it before you need propane heat!

[[email protected]]

A buddy of mine had this problem while painting his Skyhawk one
winter. Our theory was that the diesel powered heater was
contaminating the air with some greasy byproduct of combustion. Two
days after painting the paint was flaking off like a bad sunburn.
Since then I have kept heaters away from paint projects.

[RL]

Brad – There are several issues that are potential problems: As has
been pointed out there could be a moisture issue, or a moisture +
combustion by-product contamination problem. Another contributor to
gel coat adhesion is the timing of the cure and laminate application.
It is not recommended to allow gel coat to cure overnight before
applying the laminate. The window for maximum adhesion (with properly
cured gel coat) is 45-minutes to 3-hours. If the temp was high enough
during the overnight period, the advanced state-of-cure of the gel
coat may have resulted in a less than optimum interface bond. The last
potential concern is the use of micro (or any other filler) in the
resin. This reduces the wetting capability of the resin and again
reduces the interface bond strength. I’m guessing you had all these
factors leaning in the wrong direction.

Bob

[Brad[_2_]]

thanks for the comments and suggestions guys. as to the amount of gas
we burned that night, Bob K might know, it was in his shop where we
layed up the skins.............

I am leaning now towards JJ's suggestion and not go with the Prestec.
I have pretty crude painting facilities at my shop (read none) so I
hope the PPG products can tolerate a less than ideal spraying
environment.

when I sanded down the second fuselage half, I noticed that the
gelcoat on that side was a bit more tenacious that the first side,
sorta had me wondering if I could leave some on and just prime over
it, but despite have sore arms, I bit the bullet and sanded it all
off..............well, that's the plan, there is still alittle bit
left to do.

my hat is off to all those brave folks who have done
this..............it is not fun!

Brad

PS............Bob L..........we are going to make some wings in the
next month or so at Bob's shop...........what can we do to prevent
another disaster like this!!!

On Aug 24, 5:30*pm, RL > wrote:
> Brad – There are several issues that are potential problems: *As has
> been pointed out there could be a moisture issue, or a moisture +
> combustion by-product contamination problem. Another contributor to
> gel coat adhesion is the timing of the cure and laminate application.
> It is not recommended to allow gel coat to cure overnight before
> applying the laminate. The window for maximum adhesion (with properly
> cured gel coat) is 45-minutes to 3-hours. If the temp was high enough
> during the overnight period, the advanced state-of-cure of the gel
> coat may have resulted in a less than optimum interface bond. The last
> potential concern is the use of micro (or any other filler) in the
> resin. This reduces the wetting capability of the resin and again
> reduces the interface bond strength. I’m guessing you had all these
> factors leaning in the wrong direction.
>
> Bob

[Brian Bange[_2_]]

I'm a newbie at painting and refinishing. I used the products mentioned
and got a good job in my garage. The biggest problem I had was sanding
through the edges while polishing it out. Put LOTS of paint on the leading
edges and any corners or sharp compound curves and sand very, very lightly
there. The PPG products are vary easy to deal with and seem to hold up
well. While you are at the paint store, ask them about 3M "Guide Coat".
This product is a real time saver and one $25 container can do several
ships.

Brian
At 02:20 25 August 2008, Brad wrote:
>thanks for the comments and suggestions guys. as to the amount of gas
>we burned that night, Bob K might know, it was in his shop where we
>layed up the skins.............
>
>I am leaning now towards JJ's suggestion and not go with the Prestec.
>I have pretty crude painting facilities at my shop (read none) so I
>hope the PPG products can tolerate a less than ideal spraying
>environment.
>
>when I sanded down the second fuselage half, I noticed that the
>gelcoat on that side was a bit more tenacious that the first side,
>sorta had me wondering if I could leave some on and just prime over
>it, but despite have sore arms, I bit the bullet and sanded it all
>off..............well, that's the plan, there is still alittle bit
>left to do.
>
>my hat is off to all those brave folks who have done
>this..............it is not fun!
>
>Brad
>

[Fred Blair]

When you say 'less than ideal', the main thing is air flow to get the fumes
out and keeping the outside dust from getting in. I have sprayed in very
humid weather here in the Houston area. We used Ful-Thane 2K Urethane with
their primer.

"Brian Bange" > wrote in message
...
> I'm a newbie at painting and refinishing. I used the products mentioned
> and got a good job in my garage. The biggest problem I had was sanding
> through the edges while polishing it out. Put LOTS of paint on the leading
> edges and any corners or sharp compound curves and sand very, very lightly
> there. The PPG products are vary easy to deal with and seem to hold up
> well. While you are at the paint store, ask them about 3M "Guide Coat".
> This product is a real time saver and one $25 container can do several
> ships.
>
> Brian
> At 02:20 25 August 2008, Brad wrote:
>>thanks for the comments and suggestions guys. as to the amount of gas
>>we burned that night, Bob K might know, it was in his shop where we
>>layed up the skins.............
>>
>>I am leaning now towards JJ's suggestion and not go with the Prestec.
>>I have pretty crude painting facilities at my shop (read none) so I
>>hope the PPG products can tolerate a less than ideal spraying
>>environment.
>>
>>when I sanded down the second fuselage half, I noticed that the
>>gelcoat on that side was a bit more tenacious that the first side,
>>sorta had me wondering if I could leave some on and just prime over
>>it, but despite have sore arms, I bit the bullet and sanded it all
>>off..............well, that's the plan, there is still alittle bit
>>left to do.
>>
>>my hat is off to all those brave folks who have done
>>this..............it is not fun!
>>
>>Brad
>>
>

[JJ Sinclair]

Brad, I wouldn't brush on the primer, half your sanding will be to
just remove the brush marks. You can get a cheap gun and compressor
for this. It is usually best to use the primer that is recommended by
the paint you are using, but most are gray in color and this will
start to show through if (when) you get a little to heavy handed with
the wet sanding during the finishing process. That is why I use PCL
Polyprimer, because it is pure white and believe me white is the way
to go. You do need good ventilation any time your spraying anything,
not only to prevent trapping unwanted by-products in the paint, but
you don't want to be trapping any of this stuff in your lungs, either!
That is REALLY true when using uretahne, we had a mechanic here who
recovered a Cub in the dead of winter with propane heaters running
inside the shop. He didn't want to ventilate because he would lose all
his heat. Then he sprayed urethane in the same environment (probably
with just a dust mask)........................anyway, he is no longer
with us!
From personal experience, I was spraying uerthane one evening and
started to lose my peripheral vision, then I tightened up the mask and
got it back! Scary stuff, I could have passed out, alone inside a
paint booth full of stuff that can kill you. I use a resporator now,
not too expensive, $300'ish from Spruce and Specialty.
Oh, my how I have carried on and we haven't even touched on the
biggest proplem you will face. Pumping water droplets out of your
spray gun. Got to go wet sand yesterdays paint.............
JJ

[PMSC Member]

On Aug 25, 10:24 am, JJ Sinclair > wrote:
> Brad, I wouldn't brush on the primer, half your sanding will be to
> just remove the brush marks. You can get a cheap gun and compressor
> for this. It is usually best to use the primer that is recommended by
> the paint you are using, but most are gray in color and this will
> start to show through if (when) you get a little to heavy handed with
> the wet sanding during the finishing process. That is why I use PCL
> Polyprimer, because it is pure white and believe me white is the way
> to go. You do need good ventilation any time your spraying anything,
> not only to prevent trapping unwanted by-products in the paint, but
> you don't want to be trapping any of this stuff in your lungs, either!
> That is REALLY true when using uretahne, we had a mechanic here who
> recovered a Cub in the dead of winter with propane heaters running
> inside the shop. He didn't want to ventilate because he would lose all
> his heat. Then he sprayed urethane in the same environment (probably
> with just a dust mask)........................anyway, he is no longer
> with us!
> From personal experience, I was spraying uerthane one evening and
> started to lose my peripheral vision, then I tightened up the mask and
> got it back! Scary stuff, I could have passed out, alone inside a
> paint booth full of stuff that can kill you. I use a resporator now,
> not too expensive, $300'ish from Spruce and Specialty.
> Oh, my how I have carried on and we haven't even touched on the
> biggest proplem you will face. Pumping water droplets out of your
> spray gun. Got to go wet sand yesterdays paint.............
> JJ

My $0.02 on iso-cyanates and urethane paint:

Back around 1990 I painted a ship with Deltron Acrylic Urethane (PPG).
The results were great... However, I will not be doing that again.
Urethanes are simply too toxic for this amateur. Iso-cyanates are
incredibly bad news. How bad? To give an idea: I walked back into my
"booth" without protection about an hour after spraying the fill coat
(K-201 iirc) on one wing and almost instantly had bronchial
constriction and a really nasty head buzz. No more than 60 seconds
exposure an hour after spraying.... Scared the hell out of me. If
you must do this... at least be aware of who is down wind and how
far. If you decide to cheap out and forge ahead with a carbon filter
mask instead of a proper air-supply system, change the filters
frequently and don't wait for odor to become noticeable through the
mask, cause you'll be sorry. Furthermore, wear the mask any -- I mean
*any* -- time the paint is open including mixing.

Take the warnings seriously.

Today's mad hatter is more likely to be an auto body guy. Doubt me?
Go hang at the local body shop and see what you see. There's no way
to do this stuff with zero exposure.

[Nyal Williams[_2_]]

I have a very lightly used Graco HVLP spray system that I'd be willing to
sell. It eliminates oils and moisture introduced by a compressor. It is
complete with mask to deliver fresh, outside air under positive pressure
to the wearer. Write privately for details.


At 15:13 25 August 2008, PMSC Member wrote:
>On Aug 25, 10:24 am, JJ Sinclair wrote:
>> Brad, I wouldn't brush on the primer, half your sanding will be to
>> just remove the brush marks. You can get a cheap gun and compressor
>> for this. It is usually best to use the primer that is recommended by
>> the paint you are using, but most are gray in color and this will
>> start to show through if (when) you get a little to heavy handed with
>> the wet sanding during the finishing process. That is why I use PCL
>> Polyprimer, because it is pure white and believe me white is the way
>> to go. You do need good ventilation any time your spraying anything,
>> not only to prevent trapping unwanted by-products in the paint, but
>> you don't want to be trapping any of this stuff in your lungs,
either!
>> That is REALLY true when using uretahne, we had a mechanic here who
>> recovered a Cub in the dead of winter with propane heaters running
>> inside the shop. He didn't want to ventilate because he would lose
all
>> his heat. Then he sprayed urethane in the same environment (probably
>> with just a dust mask)........................anyway, he is no longer
>> with us!
>> From personal experience, I was spraying uerthane one evening and
>> started to lose my peripheral vision, then I tightened up the mask and
>> got it back! Scary stuff, I could have passed out, alone inside a
>> paint booth full of stuff that can kill you. I use a resporator now,
>> not too expensive, $300'ish from Spruce and Specialty.
>> Oh, my how I have carried on and we haven't even touched on the
>> biggest proplem you will face. Pumping water droplets out of your
>> spray gun. Got to go wet sand yesterdays paint.............
>> JJ
>
>My $0.02 on iso-cyanates and urethane paint:
>
>Back around 1990 I painted a ship with Deltron Acrylic Urethane (PPG).
>The results were great... However, I will not be doing that again.
>Urethanes are simply too toxic for this amateur. Iso-cyanates are
>incredibly bad news. How bad? To give an idea: I walked back into my
>"booth" without protection about an hour after spraying the fill coat
>(K-201 iirc) on one wing and almost instantly had bronchial
>constriction and a really nasty head buzz. No more than 60 seconds
>exposure an hour after spraying.... Scared the hell out of me. If
>you must do this... at least be aware of who is down wind and how
>far. If you decide to cheap out and forge ahead with a carbon filter
>mask instead of a proper air-supply system, change the filters
>frequently and don't wait for odor to become noticeable through the
>mask, cause you'll be sorry. Furthermore, wear the mask any -- I mean
>*any* -- time the paint is open including mixing.
>
>Take the warnings seriously.
>
>Today's mad hatter is more likely to be an auto body guy. Doubt me?
>Go hang at the local body shop and see what you see. There's no way
>to do this stuff with zero exposure.
>
>

[Gary Emerson]

JJ Sinclair wrote:
> Brad, I wouldn't brush on the primer, half your sanding will be to
> just remove the brush marks. You can get a cheap gun and compressor
> for this. It is usually best to use the primer that is recommended by
> the paint you are using, but most are gray in color and this will
> start to show through if (when) you get a little to heavy handed with
> the wet sanding during the finishing process. That is why I use PCL
> Polyprimer, because it is pure white and believe me white is the way
> to go. You do need good ventilation any time your spraying anything,
> not only to prevent trapping unwanted by-products in the paint, but
> you don't want to be trapping any of this stuff in your lungs, either!
> That is REALLY true when using uretahne, we had a mechanic here who
> recovered a Cub in the dead of winter with propane heaters running
> inside the shop. He didn't want to ventilate because he would lose all
> his heat. Then he sprayed urethane in the same environment (probably
> with just a dust mask)........................anyway, he is no longer
> with us!
> From personal experience, I was spraying uerthane one evening and
> started to lose my peripheral vision, then I tightened up the mask and
> got it back! Scary stuff, I could have passed out, alone inside a
> paint booth full of stuff that can kill you. I use a resporator now,
> not too expensive, $300'ish from Spruce and Specialty.
> Oh, my how I have carried on and we haven't even touched on the
> biggest proplem you will face. Pumping water droplets out of your
> spray gun. Got to go wet sand yesterdays paint.............
> JJ

JJ, you mean supplied air system, right?

The box w/ a fan that sits where the clean air is and the fan pumps the
clean air through a hose to your mask.

[Craig[_2_]]

On Aug 25, 10:09*am, Nyal Williams > wrote:
> I have a very lightly used Graco HVLP spray system that I'd be willing to
> sell. *It eliminates oils and moisture introduced by a compressor. *It is
> complete with mask to deliver fresh, outside air under positive *pressure
> to the wearer. *Write privately for details.
>
> At 15:13 25 August 2008, PMSC Member wrote:
>
> >On Aug 25, 10:24 am, JJ Sinclair *wrote:
> >> Brad, I wouldn't brush on the primer, half your sanding will be to
> >> just remove the brush marks. You can get a cheap gun and compressor
> >> for this. It is usually best to use the primer that is recommended by
> >> the paint you are using, but most *are gray in color and this will
> >> start to show through if (when) you get a little to heavy handed with
> >> the wet sanding during the finishing process. That is why I use PCL
> >> Polyprimer, because it is pure white and believe me white is the way
> >> to go. You do need good ventilation any time your spraying anything,
> >> not only to prevent trapping unwanted by-products in the paint, but
> >> you don't want to be trapping any of this stuff in your lungs,
> either!
> >> That is REALLY true when using uretahne, we had a mechanic here who
> >> recovered a Cub in the dead of winter with propane heaters running
> >> inside the shop. He didn't want to ventilate because he would lose
> all
> >> his heat. Then he sprayed urethane in the same environment (probably
> >> with just a dust mask)........................anyway, he is no longer
> >> with us!
> >> From personal experience, I was spraying uerthane one evening and
> >> started to lose my peripheral vision, then I tightened up the mask and
> >> got it back! Scary stuff, I could have passed out, alone inside a
> >> paint booth full of stuff that can kill you. I use a resporator now,
> >> not too expensive, $300'ish from Spruce and Specialty.
> >> Oh, my how I have carried on and we haven't even touched on the
> >> biggest proplem you will face. Pumping water droplets out of your
> >> spray gun. Got to go wet sand yesterdays paint.............
> >> JJ
>
> >My $0.02 on iso-cyanates and urethane paint:
>
> >Back around 1990 I painted a ship with Deltron Acrylic Urethane (PPG).
> >The results were great... However, I will not be doing that again.
> >Urethanes are simply too toxic for this amateur. *Iso-cyanates are
> >incredibly bad news. *How bad? *To give an idea: I walked back into my
> >"booth" without protection about an hour after spraying the fill coat
> >(K-201 iirc) on one wing and almost instantly had bronchial
> >constriction and a really nasty head buzz. No more than 60 seconds
> >exposure an hour after spraying.... *Scared the hell out of me. *If
> >you must do this... at least be aware of who is down wind and how
> >far. *If you decide to cheap out and forge ahead with a carbon filter
> >mask instead of a proper air-supply system, change the filters
> >frequently and don't wait for odor to become noticeable through the
> >mask, cause you'll be sorry. *Furthermore, wear the mask any -- I mean
> >*any* -- time the paint is open including mixing.
>
> >Take the warnings seriously.
>
> >Today's mad hatter is more likely to be an auto body guy. *Doubt me?
> >Go hang at the local body shop and see what you see. *There's no way
> >to do this stuff with zero exposure.

I've sprayed Imron and Deltron with just a chemical filter mask, but
wouldn't do it again. Interestingly enough methyl isocynate is what
was released in the Bhopal disaster. Nasty stuff.
http://www.ncbi.nlm.nih.gov/pubmed/8277516
Craig

[Capt. Geoffrey Thorpe]

"Brad" > wrote in message
...
>thanks for the comments and suggestions guys. as to the amount of gas
>we burned that night, Bob K might know, it was in his shop where we
>layed up the skins.............
>
>I am leaning now towards JJ's suggestion and not go with the Prestec.
>I have pretty crude painting facilities at my shop (read none) so I
>hope the PPG products can tolerate a less than ideal spraying
>environment.

FWIW

I sprayed a 26' boat a few years ago with AwlGrip under rather primitive
conditions - came out great.

I had a "tent" with a tarp for the floor, another tarp for the roof and
sheet plastic walls out in the middle of a gravel boat yard. I did it in
the spring when the days were warm enough, but I ran a propane heater
overnight to keep the temperature up to allow the paint to cure (lots of
moisture).

It turned out to be real easy to spray (I last painted cars back in the
'70s) - went on nice, flowed out nice. I ended up with one sag in the
finish coat (my face shield was so fogged up with overspray at the end I
really couldn't see good enough). No problems with adhesion and the boat
has been outside in the weather ever since.

Do yourself a favor and use outside air. Per the data sheets the
iso-cyanawhatever has "poor warning properties" - by the time you realize
it is coming through your mask, it is too late...

--
Geoff
The Sea Hawk at Wow Way d0t Com
remove spaces and make the obvious substitutions to reply by mail
When immigration is outlawed, only outlaws will immigrate.

[JJ Sinclair]

> JJ, you mean supplied air system, right?

Yes, I have a spray booth with florescent lights, but find I need a
drop cord light also (old eyes), so I'm dragging 2 air hoses and a
drop cord. This can end up in a gigantic tangeled mess, so I have
taken to taping them all together every 3 feet or so. Works well.
Right now, I'm doing a little repair to a 26 rudder which involves
color matching old gelcoat. Gelcoat ages (oxidizes) and turnes yellow,
but when I sand out the edges of my repair I sand out the yellow and
therefor must do a color match in this 'sanded' area. I find it works
best to extend the 220 sanding a good 4 inches beyond the repair area
and then scrub down another 4 inches with abrasive cloth beyond this
area before masking off the rest of the rudder. I then spray on 3
coats, extending the paint edge an inch each pass, so that the final
paint line is at the end of the 220 sanding. The overspray is on the
scrubbed area and my masked line isn't covered with paint. 18 hours
later the overspray area can be knocked down with a few passes of 600w
up to, but not over the mask line. Then I go over the mask line with
the 800w and blend in (remove yellow) on down the rudder so as to show
a gradual blending of sanded white into non-sanded yellowish white. If
you bury the mask line with paint, it is too easy to go through the
old paint and show primer...........ugh!
I hate painting,
JJ

[bumper]

JJ,

You may hate painting, but I am very glad an artist like you is repairing my
ASH26E rudder . . . thanks!

bumper


"JJ Sinclair" > wrote in message
...
>
>> JJ, you mean supplied air system, right?
>
> Yes, I have a spray booth with florescent lights, but find I need a
> drop cord light also (old eyes), so I'm dragging 2 air hoses and a
> drop cord. This can end up in a gigantic tangeled mess, so I have
> taken to taping them all together every 3 feet or so. Works well.
> Right now, I'm doing a little repair to a 26 rudder which involves
> color matching old gelcoat. Gelcoat ages (oxidizes) and turnes yellow,
> but when I sand out the edges of my repair I sand out the yellow and
> therefor must do a color match in this 'sanded' area. I find it works
> best to extend the 220 sanding a good 4 inches beyond the repair area
> and then scrub down another 4 inches with abrasive cloth beyond this
> area before masking off the rest of the rudder. I then spray on 3
> coats, extending the paint edge an inch each pass, so that the final
> paint line is at the end of the 220 sanding. The overspray is on the
> scrubbed area and my masked line isn't covered with paint. 18 hours
> later the overspray area can be knocked down with a few passes of 600w
> up to, but not over the mask line. Then I go over the mask line with
> the 800w and blend in (remove yellow) on down the rudder so as to show
> a gradual blending of sanded white into non-sanded yellowish white. If
> you bury the mask line with paint, it is too easy to go through the
> old paint and show primer...........ugh!
> I hate painting,
> JJ

[Dan[_6_]]

On Aug 26, 11:43*am, "bumper" > wrote:
> JJ,
>
> You may hate painting, but I am very glad an artist like you is repairing my
> ASH26E rudder . . . thanks!
>
> bumper
>
> "JJ Sinclair" > wrote in message
>
> ...
>
>
>
>
>
> >> JJ, you mean supplied air system, right?
>
> > Yes, I have a spray booth with florescent lights, but find I need a
> > drop cord light also (old eyes), so I'm dragging 2 air hoses and a
> > drop cord. This can end up in a gigantic tangeled mess, so I have
> > taken to taping them all together every 3 feet or so. Works well.
> > Right now, I'm doing a little repair to a 26 rudder which involves
> > color matching old gelcoat. Gelcoat ages (oxidizes) and turnes yellow,
> > but when I sand out the edges of my repair I sand out the yellow and
> > therefor must do a color match in this 'sanded' area. I find it works
> > best to extend the 220 sanding a good 4 inches beyond the repair area
> > and then scrub down another 4 inches with abrasive cloth beyond this
> > area before masking off the rest of the rudder. I then spray on 3
> > coats, extending the paint edge an inch each pass, so that the final
> > paint line is at the end of the 220 sanding. The overspray is on the
> > scrubbed area and my masked line isn't covered with paint. 18 hours
> > later the overspray area can be knocked down with a few passes of 600w
> > up to, but not over the mask line. Then I go over the mask line with
> > the 800w and blend in (remove yellow) on down the rudder so as to show
> > a gradual blending of sanded white into non-sanded yellowish white. If
> > you bury the mask line with paint, it is too easy to go through the
> > old paint and show primer...........ugh!
> > I hate painting,
> > JJ- Hide quoted text -
>
> - Show quoted text -

AMEN....
JJ's the man!
Dan Rihn
WO

[Bob Kuykendall]

On Aug 24, 9:28*am, Brad > wrote:
> Propane releases moisture during combustion...

Correct me if I'm wrong, but I'd expect that oxidizing propane would
only release moisture into the exhaust gasses. My heater setup vents
all of the combustion exhaust gasses outside the building. I figure
it'd have to, or else we'd all have died from CO poisioning by now.

Thanks, Bob K.

[Uncle Fuzzy]

On Aug 26, 2:09*pm, Bob Kuykendall > wrote:
> On Aug 24, 9:28*am, Brad > wrote:
>
> > Propane releases moisture during combustion...
>
> Correct me if I'm wrong, but I'd expect that oxidizing propane would
> only release moisture into the exhaust gasses. My heater setup vents
> all of the combustion exhaust gasses outside the building. I figure
> it'd have to, or else we'd all have died from CO poisioning by now.
>
> Thanks, Bob K.

Was Brad using a Space Heater, or a forced air gas furnace like you
have? I wouldn't think your heater would be a problem.

[Bob Kuykendall]

On Aug 26, 4:18*pm, Uncle Fuzzy > wrote:

> Was Brad using a Space Heater, or a forced air gas furnace like you
> have? I wouldn't think your heater would be a problem.

Brad laid up his fuselage shells at my shop, using my shop heater, not
a space heater. It's a Modine Hot Dawg 75 kbtu unit I put up several
years ago.

In the past I've used kerosene and propane space heaters, but mostly
just with quickie polyester/glass layups. Those things give me the
willies, I'm always worried about carbon monoxide poisoning.

Thanks, Bob K.

[Uncle Fuzzy]

On Aug 26, 5:07*pm, Bob Kuykendall > wrote:
> On Aug 26, 4:18*pm, Uncle Fuzzy > wrote:
>
> > Was Brad using a Space Heater, or a forced air gas furnace like you
> > have? I wouldn't think your heater would be a problem.
>
> Brad laid up his fuselage shells at my shop, using my shop heater, not
> a space heater. It's a Modine Hot Dawg 75 kbtu unit I put up several
> years ago.
>
> In the past I've used kerosene and propane space heaters, but mostly
> just with quickie polyester/glass layups. Those things give me the
> willies, I'm always worried about carbon monoxide poisoning.
>
> Thanks, Bob K.

That's what I thought. Unfortunately, that kinda' decreases the
chances that excess moisture in the air caused the epoxy not to bond
to the gelcoat.

[HL Falbaum]

"Bob Kuykendall" > wrote in message
...
On Aug 26, 4:18 pm, Uncle Fuzzy > wrote:

Those things give me the
willies, I'm always worried about carbon monoxide poisoning.

Thanks, Bob K.


As well you should be!

Carbon Monoxide detectors are available and inexpensive. They look like
smoke detectors.
Pilot shops sell CO detectors for the cockpit.


Insidious and deadly. Use extreme caution.

Hartley Falbaum

[[email protected]]

On Aug 26, 9:02*pm, Uncle Fuzzy > wrote:
> On Aug 26, 5:07*pm, Bob Kuykendall > wrote:
>
> > On Aug 26, 4:18*pm, Uncle Fuzzy > wrote:
>
> > > Was Brad using a Space Heater, or a forced air gas furnace like you
> > > have? I wouldn't think your heater would be a problem.
>
> > Brad laid up his fuselage shells at my shop, using my shop heater, not
> > a space heater. It's a Modine Hot Dawg 75 kbtu unit I put up several
> > years ago.
>
> > In the past I've used kerosene and propane space heaters, but mostly
> > just with quickie polyester/glass layups. Those things give me the
> > willies, I'm always worried about carbon monoxide poisoning.
>
> > Thanks, Bob K.
>
> That's what I thought. *Unfortunately, that kinda' decreases the
> chances that excess moisture in the air caused the epoxy not to bond
> to the gelcoat.

The process the factories use has developed over quite some time.
Important factors include:
1) The exact chemistries of the gelcoat and epoxy being used. These
are chemically disimilar materials being asked to form a "permanent"
bond during curing.
2) The timing of the process. The time from when gelcoat is sprayed
and has gelled- but not cured- to when the first application of epoxy
is important to getting whatever "bond" you get between materials .

Using a developmental process with different materials will obviously
require a good bit of testing.

Another option could be to skip the whole gelcoat thing and do the
lamination of epoxy/glass/carbon directly in the mold and accept that
it will need pinhole/prime/fill and then paint. You would avoid the
time delay failure mode that gelcoat finishes have inherent to them.
They all fail- its only a matter of time till the gelcoat comes off in
sheets or chips.

FWIW
UH

[Eric Greenwell]

wrote:

>
> Another option could be to skip the whole gelcoat thing and do the
> lamination of epoxy/glass/carbon directly in the mold and accept that
> it will need pinhole/prime/fill and then paint. You would avoid the
> time delay failure mode that gelcoat finishes have inherent to them.
> They all fail- its only a matter of time till the gelcoat comes off in
> sheets or chips.

It's all about the duration, though:

Time = 5 years = angry owner
Time = 50 years = happy owner(s)

Do the factories offering polyurethane paint as an option to gel coat
still use a thin layer gel coat? How much does that method extend the
life of the gel coat?

--
Eric Greenwell - Washington State, USA
* Change "netto" to "net" to email me directly

* Updated! "Transponders in Sailplanes" http://tinyurl.com/y739x4
* New Jan '08 - sections on Mode S, TPAS, ADS-B, Flarm, more

* "A Guide to Self-launching Sailplane Operation" at www.motorglider.org

[[email protected]]

On Aug 27, 1:37*pm, Eric Greenwell > wrote:
> wrote:
>
> > Another option could be to skip the whole gelcoat thing and do the
> > lamination of epoxy/glass/carbon directly in the mold and accept that
> > it will need pinhole/prime/fill and then paint. You would avoid the
> > time delay failure mode that gelcoat finishes have inherent to them.
> > They all fail- its only a matter of time till the gelcoat comes off in
> > sheets or chips.
>
> It's all about the duration, though:
>
> Time = 5 years = angry owner
> Time = 50 years = happy owner(s)
>
> Do the factories offering polyurethane paint as an option to gel coat
> still use a thin layer gel coat? How much does that method extend the
> life of the gel coat?
>
> --
> Eric Greenwell - Washington State, USA
> * Change "netto" to "net" to email me directly
>
> * Updated! "Transponders in Sailplanes"http://tinyurl.com/y739x4
> * * * New Jan '08 - sections on Mode S, TPAS, ADS-B, Flarm, more
>
> * "A Guide to Self-launching Sailplane Operation" atwww.motorglider.org

The painted gliders still come out of the mold with gelcoat. It gives
them something to sand and provide basis for finish.
Life isn't known yet because the aren't that many out there with
original PU finishes. It has only been commonly available, as far as I
know, for maybe 5 yrs. If you can keep moisture and UV away from it, I
would expect gelcoat to last quite a while, certainly longer than
"natural" gelcoat.
All this said, we have a Std Libelle in our club which is over 35 yr
old and the finish on the wings(original) is still excellent.
We also have an ASK-21 which is about 25 yr old which I expect we will
be able to take the gelcoat off with a chisel(don't ask) in chunks.

[RL]

> Do the factories offering polyurethane paint as an option to gel coat
> still use a thin layer gel coat? How much does that method extend the
> life of the gel coat?

Yes, it is necessary to use gel coat or an in-mold primer gel coat. As
Hank mentioned it is not practical to laminate directly on the mold
surface. The laminate will be full of pinholes and require extensive
post-mold priming and sanding before a finish coating can be applied.
Now here's a catch 22 - It is not feasible to apply a "thin" layer of
polyester gel coat. The normally recommended wet film thickness ranges
from a low of 14 mils (mil =.001") to 18+ mils. With anything thinner
than 14 mils the proportional amount of styrene lost through
evaporation becomes so high that there is not enough styrene left for
complete crosslinking. Bottomline - overly thin gel coat will be
permanently under-cured regardless of catalyst level or curing
temperature.

A linear urethane topcoat will extend the life of a well applied gel
coat substrate condsiderably.

Bob

[Craig[_2_]]

On Aug 27, 1:31*pm, RL > wrote:
> > Do the factories offering polyurethane paint as an option to gel coat
> > still use a thin layer gel coat? How much does that method extend the
> > life of the gel coat?
>
> Yes, it is necessary to use gel coat or an in-mold primer gel coat. As
> Hank mentioned it is not practical to laminate directly on the mold
> surface. The laminate will be full of pinholes and require extensive
> post-mold priming and sanding before a finish coating can be applied.
> Now here's a catch 22 - It is not feasible to apply a "thin" layer of
> polyester gel coat. The normally recommended wet film thickness ranges
> from a low of 14 mils (mil =.001") to 18+ mils. With anything thinner
> than 14 mils the proportional amount of styrene lost through
> evaporation becomes so high that there is not enough styrene left for
> complete crosslinking. Bottomline - overly thin gel coat will be
> permanently under-cured regardless of catalyst level or curing
> temperature.
>
> A linear urethane topcoat will extend the life of a well applied gel
> coat substrate condsiderably.
>
> Bob


http://www.dg-flugzeugbau.de/gelcoat-e.html
http://www.dg-flugzeugbau.de/pur-lack-e.html

[Peter Thomas[_2_]]

At 19:24 27 August 2008, wrote:
>On Aug 27, 1:37=A0pm, Eric Greenwell wrote:
>> wrote:
>>
>> > Another option could be to skip the whole gelcoat thing and do the
>> > lamination of epoxy/glass/carbon directly in the mold and accept
that
>> > it will need pinhole/prime/fill and then paint. You would avoid the
>> > time delay failure mode that gelcoat finishes have inherent to them.
>> > They all fail- its only a matter of time till the gelcoat comes off
in
>> > sheets or chips.
>>
>> It's all about the duration, though:
>>
>> Time =3D 5 years =3D angry owner
>> Time =3D 50 years =3D happy owner(s)
>>
>> Do the factories offering polyurethane paint as an option to gel coat
>> still use a thin layer gel coat? How much does that method extend the
>> life of the gel coat?
>>
>> --
>> Eric Greenwell - Washington State, USA
>> * Change "netto" to "net" to email me directly
>>
>> * Updated! "Transponders in Sailplanes"http://tinyurl.com/y739x4
>> =A0 =A0 * New Jan '08 - sections on Mode S, TPAS, ADS-B, Flarm, more
>>
>> * "A Guide to Self-launching Sailplane Operation"
atwww.motorglider.org
>
>The painted gliders still come out of the mold with gelcoat. It gives
>them something to sand and provide basis for finish.
>Life isn't known yet because the aren't that many out there with
>original PU finishes. It has only been commonly available, as far as I
>know, for maybe 5 yrs. If you can keep moisture and UV away from it, I
>would expect gelcoat to last quite a while, certainly longer than
>"natural" gelcoat.
>All this said, we have a Std Libelle in our club which is over 35 yr
>old and the finish on the wings(original) is still excellent.
>We also have an ASK-21 which is about 25 yr old which I expect we will
>be able to take the gelcoat off with a chisel(don't ask) in chunks.
>That's because the first is schwabellack gel an the second is
vorgelat(undecoat) or T35. I have 1974 Club Libelle with good original
gel. the trouble with Schwabellack is it gets very hard very quickly so is
a pain to finish. "gel coat" means that, epoxy goes on once it has gelled
, not cured. Normally epoxy and polyester are not considered compatible

having refinished more than one glider in gelcoat, i am not convinced it
bonds to cured epoxy very well, automotive paint systems may well be more
reliable.

there is some useful info on the DG website in the glider manufacturing
and optional paint finish articles. they seem to use gel as an undercoat
even if painting.

[Brad[_2_]]

>With anything thinner
> than 14 mils the proportional amount of styrene lost through
> evaporation becomes so high that there is not enough styrene left for
> complete crosslinking. Bottomline - overly thin gel coat will be
> permanently under-cured regardless of catalyst level or curing
> temperature.
>

Bob,

You just solved my gelcoat problem. The layer was to thin. In the
areas where it was thicker, I had to use a DA to get it off,
everywhere else, it flaked off with the sandpaper or by sliding a
putty knife under the paint and removing "leaves" of it.

I have had ISP problems the last several days, hence my dissapearance
on this thread!

Will give you a call tonight Bob.

Brad

[John Scott[_2_]]

I believe AMS-Fligth in Slovenia is building gliders with only PU. They
have developed a method for spraying the PU in the mold prior to layup so
that the pieces comeout with a PU finish. This is the way my APIS was
built. The finish is all PU, no gelcoat that I am aware of.

http://www.ams-flight.si/ abour 1/3 of the way down the
page "AMS Sets The Standard In Glider Finishes".

John Scott

[Brad[_2_]]

On Aug 27, 4:33*pm, "John Scott" > wrote:
> I believe AMS-Fligth in Slovenia is building gliders with only PU. *They
> have developed a method for spraying the PU in the mold prior to layup so
> that the pieces comeout with a PU finish. *This is the way my APIS was
> built. *The finish is all PU, no gelcoat that I am aware of.
>
> * * * * * *http://www.ams-flight.si/* * * *abour 1/3 of the way down the
> page "AMS Sets The Standard In Glider Finishes".
>
> John Scott

My Apis was built by Albastar, not sure what they used as a mold coat.
Whatever it was, it was really thin, and I used it as a primer coat
for Prestec 2781.

Brad