How do I prep an old hull for new gelcoat?

LQT420

Member
Hi,

After a long layoff from Sunfish sailing I have once again gotten the itch. I would like to restore my old 1971 hull into a racing condition boat. The hull has been laying upside down on a lake in my hometown, idle for the last 15 years. I saw it this past weekend and it'd be a great and worthwhile winter project for me.

I would like to have the deck and hull completely resprayed with new gelcoat. What surface preparations need to be made before I can have this done? Has anyone ever had this done? Any help and advice is much appreciated.

Regards,

- leon
 
Leon, a few costs other than the gelcoat to make the boat competative.
Pricing is as of the last time I checked.

Racing sail $325
Plastic dagger board $169
Retrofit of the old style rudder system $350
Harken mainsheet ratchet block and hardware $40
Ajustable gooseneck fitting $12-$20
Boom cleats for adjustable outhaul and cunningham plus line $25-$40
There's more you can do but that's what comes immediately to mind.
 
Thanks for your replies guys. I already have most of those parts for a really nice '78 hull that I also currently own. The winter project is because I'll be bored for the winter and will be more of a challenge / reward thing for me. I want the satisfaction of restoring and racing the first boat that i ever owned. Does anyone out there have any experience or advice on complete gelcoat restoration?
 
I've only used it for fairly small repairs (one square foot or less) and that has made me decide I'd never attempt to do an entire hull...LOL
The link shutterman gave is good, but remember gelcoat is primarily used on the inside of a mold, where the mold forms the finished surface. Rather than you forming the surface after applying the gelcoat. It will give you something to do ALL winter long...again LOL
 
I plan to have a professional boat repair place spray the hull and deck for me. I'm just looking for the initial hull prep advice and finishing / sanding advice.
 
If your getting a shop to do the gel coat spraying you might consider Awlgrip two part paint instead, it is much harder than gel coat and more fade resistant (if you are going for a colour). There are also linear polyurethane paints you can apply yourself, they are supposed to be self levelling. (theoretically). Light colours will be more forgiving with regard to a less than perfectly prepared surface, whereas black will magnify all your preparation oversights.
 
I have re-gel coated two hulls, in each case the shop that sprayed the gel coat for me asked that I rough sand the entire hull (60 grit) just to remove the shine and then wipe down with acetone. In addition they suggested that any deep cracks in the existing gel coat be sanded down to the fiberglass (stop when you see green). You want to feather these spots so that they aren't visable later. FYI ... this is the easy step it's the sanding after the gel coat is applied that really counts. There is a lot more sanding in your future but the results can be very rewarding. Good Luck!
 
I'd go down to #180 on the sanding. #60 grit marks are alot to fill. And let the guys spraying do the scrub with the tone. Buy lots of 800 1000 1200 + compound to finish it off. Don't leave any stress cracks unrepaired. they will come back in a few months. Air tools can make this go alot faster. Have fun.
 
Hey guys, I really appreciate all the replies. Bbryant321, what do you mean by feather?

Thanks again,

- Leon
 
By "feather" I mean sand the cracks etc down so that it's a smooth transition from the sanded area to the orginal gel coat. As for the paper to remove the shine, I stand corrected, I used 120 grit (NOT 60) as the shop suggested. Removing the shine is something that will only take you 10 minutes for the bottom of the hull. If you already have a shop lined up to spray the gelcoat I am sure they will tell you exactly how the want the boat delivered. In my case they just shot the gelcoat for $200. I did all the rest. FYI, if you are going to do the sanding after the getcoat is applied you will likely need Acetone. I am not a gelcoat expert but in my case I had to rub the hull after the fact with Acetone in order to sand the finish. Be sure to buy sandpaper good for wet sanding. I think I probably spent 20 hours on the 2nd hull. You can see pictures on this site on the photo gallery page. It was a great winter project.
 
Why would you want to put acetone on a fresh gelcoat job? I seem think iit stains it yellowish. your not thinking of PVA are you?
I As another poster said Awlgrip can work as well. But you can't buff out a scratch or blend in a small repair as easy. + in the prep you need to sand to #220 for the primer. #320 or #400 for the top coat. Gel repairs can be done with a pre-val grip repairs for the most part can't. Even slow painters take 30 minutes to clean a gun $$
jm2c
 
Why don't you order some duratec and spray it yourself? Lots cheaper than having a glass shop spray and less finishing work too.
 
Congressman,

What is Duratec? I'm not familiar with it and I am definitely open to suggestions.

Thanks,

- Leon
 
jsdeimel,

In order for the gel cote to cure properly it needs to be protected from air. The makers put wax in the resin that comes to the surface to form this protective barrier allowing the gel cote to cure. This is the slightly sticky surface everyone mentions when reparing or spraying gel cote. The acetone is used to remove this wax layer in order to sand everything smooth with out clogging up the sandpaper (wipe on , wipe off, don't let it sit). By the time you are done sanding, any "yellowing" will be gone. Most PVAs, a mold release, wash off with water (at least the ones I am familar with).
 
Duratec Hi-Gloss Additive, add 50/50 to gel-kote and spray. Glosses out to a very smooth surface. I spray a lot of gel-kote, so I get a really nice finish when I use it, but even an amature with a pre-val sprayer can get a good finish. At worst you might have to sand with 800 and buff. I get it from Minicraft - www.minicraft.com - 50 bucks a quart, 100 for a gallon, something like that. Very easy to use and a lot cheaper than hiring somebody like me to do it for you. Got a buddy who's a cheap sob and uses Laquer thinner, it works, but you have to sand an buff after. Personally I don't think you get as good a depth in the finish after buffing. It doesn't reflect a true image back at you, kinda fuzzy - sort of like reading without your glasses, but then again I do this stuff all day long and am very critical about the quality of my finish. I do alot of metal - flake work.
 

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