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Fiberglass Cowl/Pin *****s

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Fiberglass Cowl/Pin *****s

Old 12-24-2003, 10:28 PM
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Default Fiberglass Cowl/Pin *****s

Thoroughly washed the cowl with soap and water,dried it.The next day two coats of primer (Pacta) with sanding between coats and cleaned with alcohol.Still looks like pin *****s on the side.Looks like the primer isn't covering or sticking to or filling up the *****s.Don't want to put a coat of paint (Lustrecoat black) on this cowl till it looks rite.

What's causing these pin looking *****s.Why isn't the primer covering them up.

Help is appreciated
Old 12-24-2003, 11:09 PM
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Default RE: Fiberglass Cowl/Pin *****s

Sounds like a condition called "fish-eyes" ------ simply because that is what they look like.

I have had the same experience. The cause------you wont want to believe this------is surface contamination, probably oil or silicone based----or some of that pesky release agent from the molding process.

You can go to an automotive paint supplier and they have silicone removal agents, probably more advanced stuff than I am familiar with, as one small can lasts a LONG time with model A/C.

Next you can do the perfectionist's routine, and strip away all your primer so that you can clean and shoot again. (been there, done that)

Or, after you reconsider, wet sand the areas with the silicone removal fluid as the wetting agent and spot prime until you are satisfied . Then fog a complete coat of primer on the cowl or since you are using black for the color coat just shoot it with black.

Unfortunately this is a rather common occurence.

Having done it both ways, the wet sand and spot prime is definitely the way to go !!

Have a Merry Christmas.
Old 12-25-2003, 01:23 PM
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Default RE: Fiberglass Cowl/Pin *****s

Trick I found with black is to change its color a bit to a lighter shade, or fog on a coat of flat before the final finish. That way scuffs won't show as bad. It also helps you to see if you have complete coverage. I'm inclined to agree with onewasp that the underlying problem is the release agent. Used to find the same problem on full scale boat hulls. Tough to have to remove the primer you already applied but we build for fun and to pass the time. This will help in the time passing department but only delay your first flight for one day.
Old 12-26-2003, 12:47 PM
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Default RE: Fiberglass Cowl/Pin *****s

A lot of people use liquid dishwashing soap which can be bad news. Use a real degreaser such as Tri-Sodium Phosphate (TSP) to degrease before painting. Dishwashing soap (depending on the brand) will cause fisheyes.

Also, if you're having problems with the filler sinking in then you're probably not giving it enough time to dry before sanding. A lot of folks are impatient and sand it as soon as it feels dry. It can take literally days or weeks for this stuff to dry so if you sand it 20 minutes after applying it then often it will shrink more as time passes and leave indents in your finish.

The number 1 most important thing to a finish is sandpaper. The second most important thing is letting each application of whatever dry as long as possible.

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