Gel coat repair necessary?

[MaryEllaRose]

In the process of sanding the Rose's bottom in preparation of new bottom paint I exposed some of the fiber glass. Not a lot, just a few places where the surface was irregular. What's the best way to repair this? I'm going to use Interlux followed by VC 17. Can I just paint over it or is some kind of repair / export in order?

Thanx,

Tom G

 

[Megaro76]

Same question here...I'm watching this thread

 

[Gene Neill]

I'm following in both your footsteps.

From what I've read, a layer of Interlux Interprotect 2000 eliminates the need for any gelcoat repair. But let someone more knowledgeable confirm this.

 

[MaryEllaRose]

That's the stuff I'm going to use. Does anyone know how much it takes?

 

[LakeShark]

I will give this a shot! One of my first jobs was working at a Boat Yard in San Diego Ca. With a new boat or one that has never had bottom paint applied you must remove the shiny portion of the gelcoat. If you do not your paint will eventually flake off no matter what primer you use and it makes for a much messier job the 2nd time around. At times when sanding (even a new 65 foot boat) you could accidentally gouge or sand too deep into the gelcoat exposing the fiberglass. If this happened it was treated the same as a blister repair. You simply added some filler (I forget which type) and sanded it smooth before applying the primer and painting the bottom. Fiberglass is clear so it is possible to even see light through a shallow gouge or bad blister spot and still be ok without laying new glass so long as the sanding spot is not too deep. I guess that it the long way of saying that the goal is a smooth finish that won't chip, crack, or blister so if the hole is deep fill it before primer etc.. If it's just scuffed where the gelcoat was thin then don't sweat it and paint away. Hopefully this helps. PS: many manufactures of larger yachts did not even spray a shiny finish gelcoat on the bottom of where paint was to be applied.

 

[MaryEllaRose]

Well, there's certainly no shine left on this old girl's bottom. My concern is that water doesn't work it's way into the fiber glass if for some reason the paint fails.

Will two coats of Interprotect be sufficient? How much paint will that require ?

Thanx,

Tom G

 

[CloudDiver]

No, gelcoat repair on the bottom not required. The purpose of Interlux Interprotect (or similar epoxy barrier coats) is a waterproof barrier. Epoxy is actually waterproof where polyester gelcoat is not. It takes 2 gallons of Interprotect to effectively coat the bottom of a C22 including the keel and rudder bottom. Use a 1/4" nap roller, not foam rollers which are too fine and breakdown.

 

[MaryEllaRose]

Wow! I had no idea it would take that much! How many costs does that work out to be?

I'm planning on topping the Interpritect with VC 17. Should I plan on 2 gallons of that as well ?

 

[CloudDiver]

If you use a 1/4 nap roller you should get 4 coats. Foam rollers will give you more coats, probably 8, but obviously much thinner ones. It does not matter as long as the film thickness builds up and you use the entire 2 gallons. I tried the foam rollers because they produce a smoother finish, but I noticed the epoxy paint causes the foam roller to break down and it eventually gets squishy and comes off the roller. I quickly switched to 1/4" nap for the second gallon.
Prior to painting the barrier coat, if you want to repair gouges or fair out any un-even parts of the hull where you sanded (and this is a good idea) use epoxy and the 405 light fairing filler, the red powder. It is easy to apply like bondo, but much easier to sand than other fillers. You can also use Interlux Watertite, this is an easy to use 1 to 1 mix filler. It is good for scratches, gouges and chips but not as easy to sand. It is much cheaper to buy than epoxy, but don't count on fairing large areas with it. There are premix fairing compounds available if you don't want to invest in a gallon or quart of epoxy plus fairing filler powder, just make sure its an epoxy based compound. After sanding bottom paint and preparing to apply the fairing filler, make sure the hull is clean... Blow or vacuum the dust off and wipe with acetone.
You should only need 1 gallon of VC17... Bottom paint is usually much thinner viscosity than the epoxy barrier coat. I used Interlux Micron CF and I got 3 coats with a 1/4" nap roller and still have just less than 1/2 gallon left. I need to bottom paint my mooring buoy and I will probably use up the rest on a final coat to the bottom before launch.

 

[vhoisington]

On my H28, I did a complete bottom job several years ago. Here was the process

Random orbit sand off all of the "old" bottom paint and barrier coat to gel-coat using 80 grit. Of course I removed gel-coat in a few places by accident to bare fiberglass, I didn't bother to fill any of the gouges since they were all minor.. Regardless, final wipe down with Acetone. 4 coats Interlux 2k, I used a foam roller, I had no issues with breakdown of the foam roller however, the recommendation of a 1/4" nap roller would get you to the desired thickness sooner. As mentioned it doesn't really matter how many coats as much as getting to the recommended thickness of coating. Because I was in cool freshwater, I chose hard bottom paint for a smoother finish, and applied it as soon as I could over the Interlux to achieve a chemical rather than a mechanical bond between the two materials.

When we pulled the boat this year (year 4) other than a mild power wash and a few flakes off the lead keel, everything was perfect with only a slime film but certainly no growth of anything.

Take all of the recommendations from this group and any others you can get, read the manufacturers recommendations, prep and then prep again and you'll end up with a perfect job.

Good luck,

Victor

 

[vhoisington]

Oh and my buddy doings his Catalina 28 besides me used VC-17, it took about a quart (it is very thin) he did 2 coats and hasn't touched his in the same time. His came out this year with even less slime than mine. He didn't even require a power wash other than at the boot stripe where the muddy water left a line.

 

[MaryEllaRose]

I've got two coats of Interprotect on. Should I be sanding between coats?

 

[CloudDiver]

As long as you apply the coats within 6 months you don't have to sand Interprotect between coats. You get a good chemical bond with epoxy based paints. If they are two coats with a 1/4" nap roller you should be good to go. Use up all the paint you have mixed, epoxy paints cure in the can like mixed epoxy will.

 

[MaryEllaRose]

How many coats of VC 17?

 

[mfourn20]

Oh and my buddy doings his Catalina 28 besides me used VC-17, it took about a quart (it is very thin) he did 2 coats and hasn't touched his in the same time. His came out this year with even less slime than mine. He didn't even require a power wash other than at the boot stripe where the muddy water left a line.

In my opinion, and what I heard around the yacht club is thinner is better. I used a foam roller, and did two coats of bottom paint. I sanded off about 8 layers when I bought the boat. I NEVER want to do that again.

The directions on the can are really meant as a worst case scenario. If you've got a nice smooth clean bottom paint free hull 2 coats with a foam roller should be plenty.

Also best to do 2 different color layers...as it wears the initial color is exposed and you know what needs to be touched up.

 

[CaptDon01]

Just a little helpful hint from someone who's done a few C-22 bottom jobs over the years.......

Foam rollers will work with most bottom paints, but the Interlux barrier coating will melt them.

Prior to applying the bottom paint, don't wipe the barrier coating surface with acetone or lacquer thinner. Every year I had horrible adhesion problems when power washing the bottom surface, so I finally read the Interlux directions where they specified using Interlux 333 to wipe down the hull, which when I read the can, said it was xylene. Afler a light sanding and wipe down with xylene, no more adhesion problems, don't ask me why, but for whatever reason, it solved the problem.

Don

 

[Barnacle Bill]

2 coats of VC 17 is recommended. Interlux makes a newer Interprotect product called HS which has the same desired results with fewer coats. Gelcoat gives the boat its color, but is not very water proof unless it is a vinylester type, which is more expensive and some manufactures use that below the waterline only to help prevent blisters. It is a modified epoxy resin. And for those who are doing gelcoat repairs elsewhere, it isn't very compatible with epoxy resins for a few reasons - one is the amine blush. So, use polyester resins instead. It doesn't matter on the hull or deck anyway.

 

[MaryEllaRose]

Well, I've got three coats of Interprotect on. That worked out to be just shy of two gallons. I did the keel and the rudder. Tomorrow I'll put the last of two coats of VC17 on the back end of the hull where the support was. After that, I've got to do the boot stripe. After that I don't want see any sand paper, roller pans, masking tape, rollers or the bottom of any boats for a long long time..