Gel coat spraying problem
John Bojack
What does one do to prevent the "fisheye" phenomenon?
The newly sprayed gelcoat forms "divots" where no new gelcoat covers
the old surface.
I am sure the surface is clean, (I used acetone), and has been sanded
with 80 grit to provide a rough surface to adhere to.
Is there something that can be added to the spray mixture?
Thanks in advance ,
John
Bert Willing
John Bojack wrote:
Did you dilute the spray mixture by acetone? 10-30% vol are needed.
--
Bert Willing
Caproni Calif D-6600
Visit the airfield of La Motte du Caire in the French Alps:
http://www.decollage.org/la_motte/
Marco Haakmeester
knowledge gained in the automotive field.
Fisheyes can be caused by a number of reasons, such as the use of
silicon wax on the old surface. Most waxes contain silicon. This is
very hard to remove. Therefore use a silicon remover before sprayer.
With a automotive supplier you'll find specialised products). Also
possibble is oil in the air of your spraygun (compressor OK?).
Finally the use of silicon-containing products (such as most waxes) in
the same envorinment of the area in which you're spraying. This may
even have been in the past if for instance the polishing cloth is
still around. To sum-up make sure that everything is really clean and
use specialised products.
I hope these idea's will give a an idea where to look for the cause of
your problem.
Marco
On Wed, 26 May 1999 12:57:19 GMT, pat...@DONTSPAMME.worldnet.att.net
(Todd Pattist) wrote:
>jbo...@mindspring.com (John Bojack) wrote:
>
>>What does one do to prevent the "fisheye" phenomenon?
>>The newly sprayed gelcoat forms "divots" where no new gelcoat covers
>>the old surface.
>
>What brand/type of gelcoat are you spraying?
>---
>
>Todd Pattist Ventus C - WH
>Fly safely, fly often.
>(remove "DONTSPAMME." from my e-mail address to contact me)
>---
>
Willows
It could be due to the glass fibre ends poking through, I had a similar
problem with a glass filled moulding. This can be overcome with a good
primer and ensuring that it's applied as a fine mist coat.
We managed but not without our paint companies chemist getting involved with
advise on the primer for our materials.
But check for silicon's first, get them out of your work area they migrate
everywhere. Release agents, dry lub's etc;
Good luck
Bill Griffiths.
John Bojack wrote in message <374b4e7c...@news.mindspring.com>...
>
>What does one do to prevent the "fisheye" phenomenon?
>
>The newly sprayed gelcoat forms "divots" where no new gelcoat covers
>the old surface.
>
>I am sure the surface is clean, (I used acetone), and has been sanded
>with 80 grit to provide a rough surface to adhere to.
>
>Is there something that can be added to the spray mixture?
>
>
>
>
Rex & Noelle Mayes
sells one. Use up to 2%. I have good sucess. It is most likely a problem of
contamination no matter how well you have wiped with acetone. Also you may
want to consider not spraying over 80 grit scratches. As the gelcoat
shrinks it will fail along the heaviest scratch. I reccommend spraying over
240 scratches. I have had much better results. You are also less likely to
ghost through during the sanding polishing steps.
good luck.
Rex Mayes
Williams Soaring Center
**** Posted from RemarQ - http://www.remarq.com - Discussions Start Here (tm) ****
Juha Kettunen
>
>What does one do to prevent the "fisheye" phenomenon?
>
>I am sure the surface is clean, (I used acetone), and has been sanded
>with 80 grit to provide a rough surface to adhere to.
>
>Is there something that can be added to the spray mixture?
I am not aware of any additives, they should not be necessary.
Fisheyes are caused by impurities on the surface or/and in the spray.
I suggest you spray some test surface - if you have fisheyes on any
surface, your spray air is contaminated. Many air compressors leak
oil into the pressure line. Generally in spray work you will need best
water trap you can get as near the spray gun as possible.
Then there is a possibility, that the plane has been waxed with a
silicone containig wax. In this case you have a serious problem.
Hope this helps
Juha Kettunen
Donald Ingraham
I've only refinished one ship so I'm no expert...but...
I used a gel-coat made by PolyLux at George Applebay's
recommendation. PolyLux provided a fish-eye "reducer" with
my order, which I used. I also cut the mix down with acetone
to get a good shooting consistency (milky) and since my ship
(Jantar Std) was over 20 years old I mixed in talc with the
gel-coat for the base coats. Talc thickens the coat, fills the
flaws, is light and cuts easily (you remove about 70-80% of it)
with sanding. The finish came out great (thanks to much advice
from George Applebay), but I did battle fish-eyes on one of the
wings, while the other pieces had only 30-50.
I don't know why...the surface was freshly sanded (120 grit),
blown clean, no water in the line...
But you MUST take care of them before applying another coat.
They won't fill in, and if it appears that they did, there
will be tiny air-pockets awaiting your fine sanding! Go around
with a nail and tap each fish eye with a drop of gel coat while
the coat is still wet. It's frustrating because you want to shoot
the next coat as soon as the first one gets tacky...and if you have
a lot of fisheyes you don't get much rest! The bump will easily
sand out later with with a few strokes. I've even heard of shops
using a squeegy to put on the first "coat" to avoid this problem!
Sorry, that's all I got :-) Hope it helps.
Let us know if you find the cause.
Good luck,
Don
_______________________________________________________
Don Ingraham
SGI Friends help you move.
d...@sgi.com Real friends help you move bodies.
Shane Neitzey
John Bojack wrote:
>
> What does one do to prevent the "fisheye" phenomenon?
>
> The newly sprayed gelcoat forms "divots" where no new gelcoat covers
> the old surface.
>
> I am sure the surface is clean, (I used acetone), and has been sanded
> with 80 grit to provide a rough surface to adhere to.
>
> Is there something that can be added to the spray mixture?
>
> Thanks in advance ,
>
> John
Call the paint manufacturer and ask if they sell or recommend a
compatible "fish eye eliminator". They usually have Techs you may consult
with. They can tell you what to use i.e., primer/filler, sealer,
additives, etc..
Read and follow all directions on the label. Including using a
viscosity cup.
Personally, the coarsest sand paper I would use is wet-or-dry #320.
Block sanding method.
Good Luck,
Shane Neitzey
P.S. Try a test piece or area before doing to whole job. Use a inline
pre-filter/moisture trap to capture any particles of oil and water.
Tom Seim
to spraying.
Tom Seim, 2G
Shane Neitzey wrote in message <374E9487...@gslink.com>...
B Lacovara
Although I am sure well meaning, just about all of the advice you have recieved
so far is incorrect. First, you have to understand that gel coat is NOT paint,
and should not be handled as such. Gel coat should not be thinned with
solvents, and fish eye eliminators desgined for paints do not work in gel coat.
I have authored several study courses for composites manufacturers, instructing
proper gel coat application techniques. We work very closely with the gel coat
formulators, and they use our educational materials for training their
customers. Please contact the Composites Fabricators Association web site, and
look through the technical section for several articles relation to gel coat
application. [ cfa-hq.org ]
Please feel free to contact me if you would like to discuss the specifics of
your problem.
Bob Lacovara "2BT"
Tech. Dir.
Composites Fabricators Association