gelcoat and fiberglass question?

[betayv]

Hi guys I made a new engine cover and I used math and cloth, I want to painted with gelcoat the box dry and looks very good but is not smooth my question is I need to sand and leave it smooth before painting?. thanks.

 

[gm280]

Well there are two ways to look at this. If you are wanting a really nice smooth finish, then yes you either need to sand down the ripple in the cloth, OR use a high build epoxy sandable primer or do a little of both things. I have used such a primer and you can easily fill in the cloth effect fairly easy to get that totally smooth finish. On the other hand, if that cloth look doesn't bother you, then spray a primer, and paint. It is totally up to your idea and wants. One thing I will add, if you go for the sleek smooth glossy finish, anything you can see or feel in the primer WILL show up in the final finish. Prep IS the number one thing to a quality great looking finish... JMHO!

 

[DeepBlue2010]

As it has been said, if you are after the factory glossy finish type, then yes. You need to sand and fill and then sand and fill and sand then fill and ..................
Then you shoot the gelcoat and after it cures you will wet sand, compound and polish. If you don't mind rough look or you want it to be anti skid, you can knock down any high spots, clean with acetone and then use Ondarvr trick (spread a thin layer of gel on the surface with squeegee to fill out any low spot or pen holes) and then you can spray or even roll the gel on.