Primer, Undercoat, Final

[tengals123]

I am painting over old gelcoat sanded and preped. Do I really need a porimer then an undercoat then a final coat?<br /><br />Cheers and sorry about all the paint questions

 

[Dunaruna]

Re: Primer, Undercoat, Final

Depends, if the gelcoat is abraded and cleaned - you should be good to go as far as adhesion is concerned. Visually you may need an undercoat though, some topcoats will show any and all imperfections, a good undercoat will provide a nice new canvas to paint your masterpiece on. <br /><br />Aldo

 

[tengals123]

Re: Primer, Undercoat, Final

thanks dunaruna, I am going to undercoat definatly, but wanted to know about the primer?<br />The guy at whitworths told me I need the primer 'interprotect', the undercoat 'perfection undercoat' and the final 'perfection 2 pack.

 

[Dunaruna]

Re: Primer, Undercoat, Final

The main concern is giving the paint a surface to stick to, I don't think a primer will do that any better than an undercoat, the gelcoat preperation is the key. <br /><br />Personally, I wouldn't use a primer BUT I bow to the whitworth reps knowledge - unless he's just trying to extract more green ones from your wallet?? Interprotect ain't cheap - is it?<br /><br />Aldo

 

[tengals123]

Re: Primer, Undercoat, Final

You got that right! It's pricey as! I think I should be ok with good sanding and surface prep, even if the gelcoat is still there as long as it has 'bite' and is clean, the undercoat should stick ok. true?<br /><br />cheers

 

[Dunaruna]

Re: Primer, Undercoat, Final

Originally posted by tengals123:<br /> the undercoat should stick ok. true?<br /><br />cheers

Depends, there are so many undercoats/primers on the market these days. Most of them do both jobs. In fact most 2 pack epoxy's don't require a primer just a good abrade (roughing up) but the gelcoat isn't an ideal surface to gain 'bite' so I'm hesitant to say yes or no. <br /><br />Assuming you don't have any osmosis I would probably use an good epoxy based undercoat (flat dulux comes to mind - about $20 litre at bunnings) and then the 2 pack. The dulux epoxy also is available in an etch primer but I don't see how an etch primer is going to 'bite' into gelcoat, it's designed for bare steel or alloy.<br /><br />Aldo

 

[tengals123]

Re: Primer, Undercoat, Final

I'm going to use the international 'perfection undercoat', I'm sure I don't need the primer.<br /><br />cheers

 

[tengals123]

Re: Primer, Undercoat, Final

Now Im even more confused. The link below is a part thread on an awesome paint job. He did'nt even use undercoat. Just the topcoat over the primer? I've put so much effort into this boat, I just want to make sure I do it right. Everyone seems unclear as to the correct proceedure. Anyone have a take on this?<br /><br />cheers<br /> http://www.iboats.com/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic;f=26;t=001448#000015

 

[tengals123]

Re: Primer, Undercoat, Final

ok, now im getting somewhere. The 'interprotect' is a primer/undercoat. So I clean, sand etc, clean, slap a few coats of 'interprotect', then sand, clean and begin my final coats of 'perfection'. No need for another 'undercoat'. I think this is right.<br /><br />cheers

 

[ondarvr]

Re: Primer, Undercoat, Final

Are you painting the deck or the hull? On the deck there is no need for a primer unless you need to fill very small scratches and/or pits, the bond will be very good without primer. For the hull it depends on how long you plan to leave the boat in the water at one time. If tied to the dock all summer you need very a good primer and paint, if it's only in the water every other Saturday afternoon for a few hours, the paint choice isn't as important, most will work fine.

 

[tengals123]

Re: Primer, Undercoat, Final

it will not be left in the water for more than a day at a time. So, I guess it's settled then. Primer and topcoat. At least I know where i'm heading now.<br />cheers

 

[BillP]

Re: Primer, Undercoat, Final

There are generally two types of "primer". One is more a filler for sanding and the other a thinner surface prep. Paint over either one. <br /><br />If the surface is smooth and ready for paint, use the thin primer to make sure of paint compatability. If going over glass it usually isn't necessary. If going over old paint it MAY be necessary for a good bond. You just need to know what the other paint was.

 

[tengals123]

Re: Primer, Undercoat, Final

thanks for the post BillP. I've ordered Interprotect primer and 'perfection' topcoat. Im hitting it with 3 coats of primer and 3 coats of topcoat. Sanding and cleaning in between all coats. Should leave me with a nice smooth, glossy white boat when im finished. I start painting on the 17th of May, when the boat goes into a garage. Can't wait.<br />cheers

 

[Tinkerer II]

Re: Primer, Undercoat, Final

tengals, <br /><br />Here's a good source of info on repainting http://www.norglass.com.au/PDF/Fibreglass_Info.PDF

 

[Buttanic]

Re: Primer, Undercoat, Final

One problem you might run into is tiny pin holes or porosity in old jell coat. I had this problem on two boats I painted. The paint wouldn't cover the pin holes and would pull back from them like a fish eye. Even primer had a hard time covering them. In some areas I had to use my fingers and rub the primer to force it into the holes and then sand and put another coat of primer. Somestimes the jell coat looks OK but as soon as you put the paint on the holes show up.

 

[LubeDude]

Re: Primer, Undercoat, Final

Originally posted by tengals123:<br /> Sanding and cleaning in between all coats. cheers

This is completly unnecesary.<br /><br />Wipe the boat with a wax and grease remover before sanding, this will make sure you dont sand wax into the gell coat. Prime the boat with three coats one after the other. Then sand the primer with a bit of contrasting color dusting of rattle can primer. (This is a very light dusting), This is called a guide coat and will show you any imperfections. 320 grit would be fine. Then put on your color, all three coats. If you want you can then wet sand the final coat of color when it is dry with 1200 grit and polish. (Only if the paint you are using is a catylized product though).

 

[tengals123]

Re: Primer, Undercoat, Final

thanks for the replys guys.<br />LubeDude- Thankyou for your reply, but, after reading many, many posts and informative books and sites, I think I will still sand between coats. It helps smoth out any dimples etc, before one last final coat. Also, maybe I forgot to mention, I'll be 'roll and tip' ing this project.<br /><br />cheers

 

[BillP]

Re: Primer, Undercoat, Final

I've noticed in recent years some of the marine paints are instructing to sand between every coat. They used to say do a second coat after the first tacks off.