New Gelcoat on bottom of Sunfish

[AJC6882]

I'm gonna gelcoat the entire bottom of one of my sunfish. It's a 1986. the gelcoat isnt worn out but its getting there. The previous owner kept her covered on a beach and the motion of water occasionally hitting it has worn some good abrasions over the whole bottom. I have wet sanded most of them out but the bottom gelcoat is still not up to par. Also there are a few spots that I suspect are absorbing water due to some small cracks in the gelcoat.

Here's my plan... I will remove aluminum trim around bottom and tape off the hull number and rudder bracket sand the entire bottom of the boat with 100 grit paper getting any areas where fine cracks have formed sanded completely down. I will thin the gelcoat with styrene thinner and color match to the off white existing gelcoat. Then I will apply two -three thin coats of gelcoat. The first two coats without wax and the last with wax additive. Since I want to make this a easy gelcoat job I'm attempting to do this with a foam roller and after cured I will wet-sand and buff.

Im gonna take pictures of my progress. If anyone has anything im missing or suggestions please let me know. Im ordering a gallon of white gelcoat. Is that enough? I want to make it about 20mils I think.

 

[Trueke]

Don't know much about gelcoat (I'm actually painting mine), but a gallon seems a bit much just for the bottom....anyone?

 

[PBA]

Supposedly, there is a specific Sunfish gelcoat "white", which will match up with the Sunfish deck white, etc.. Maybe this makes a difference here, maybe it does not.

Removing the aluminum trim raises a big flag, so perhaps you may want to wait until Wayne or some other really knowledgeable source from the board chimes in. Did you (slightly) dig out any hairline cracks in the gelcoat with a Dremel bit before all of this? How bad were the "spider cracks" - every old fish has them, to varying degrees.

 

[AJC6882]

I dont think two quarts are enough. So 1 gallon would be less money than three quarts. If the bottom comes out good Im gonna do my other boat. also I havent done work to it yet. Removeing the trim is not that big of deal. Just drill out the rivets. Ive done it already i can remove all the trim and reinstall it in less than an hour.

Like I said before I will sand down any stress cracks. But my main concern is the worn out gelcoat on the underside of the boat. It is very thin in some places. I'm gonna try to make it new again. I'm gonna start next week I think.

But please feel free to make any comments on any suggestions.

 

[Webfoot]

See previous threads on Gel Coating. I recommend making you first attempt on something other than you boat, like a scrap of fiberglass. Gel coating is like trying to get a dozen ducks lined up, one bad duck screws up the whole thing. Things I've learned are make sure the raw Gel Coat material is less than a year old. Also, use a new foam brush every time you try to rethin the Gel Coat. I would recommend trying to use a Preval Sprayer. Practice on scrap material, I think the desired thickness was .016/.018? Make sure you have a good professional paint mask and ventilation, this stuff is nasty.

 

[Wayne]

I'm gonna gelcoat the entire bottom of one of my sunfish.
Here's my plan... I will remove aluminum trim around bottom and tape off the hull number and rudder bracket

Sounds good, but why leave the gudgeon bracket on. For your year boat the backing is a metal plate and the screws are tapped right into the backing. There’s a very low probability the plate has come loose from the transom like a wood backing in earlier years was prone to do if it got wet and rotted.

2¢ … Fill all the rivet holes with polyester resin and re drill them when you re-install the trim. That way the rivets will have new, tight holes to grip.

. . . sand the entire bottom of the boat with 100 grit paper getting any areas where fine cracks have formed sanded completely down.

I think you want to fill out the cracks before you do your fairing/prep sanding so the surface can be smoothed all-in-one.

My thought would be to use gelcoat paste as a filler to maintain consistency so you don’t have any special case issues when you begin top coating.

I will thin the gelcoat with styrene thinner and color match to the off white existing gelcoat. Then I will apply two -three thin coats of gelcoat. The first two coats without wax and the last with wax additive. …I want to make it about 20mils, I think.

Since I want to make this a easy gelcoat job I'm attempting to do this with a foam roller and after cured. I will wet-sand and buff.

You may want to reserve your thoughts about thinning until you do a little practice. Humidity, ambient temperature, how you charge the catalyst will all be contributing factors to choosing the viscosity most easily worked with.

20 mils is about right for loosing ~2 mils to finish sanding and compounding. How are you going to measure? You can buy a gauge just for this job ($10)

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I don’t see a need to color match, since the old gelcoat is faded anyway and the new will cover the entire bottom, leaving nothing to be judged next to.

. . . or do you have friends who come around with a color chart in their pocket to inspect the exact shade of white.

You're 1 shade off ... now sand it all off and do - it - again
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Did you (slightly) dig out any hairline cracks in the gelcoat with a Dremel bit before all of this? How bad were the "spider cracks" - every old fish has them, to varying degrees.

I concur, if any of the old gelcoat is being left it needs to be (a) solid and (b) any cracks properly filled.

See previous threads on Gel Coating. I recommend making you first attempt on something other than you boat, like a scrap of fiberglass. Gel coating is like trying to get a dozen ducks lined up, one bad duck screws up the whole thing. Things I've learned are make sure the raw Gel Coat material is less than a year old. Also, use a new foam brush every time you try to rethin the Gel Coat. I would recommend trying to use a Preval Sprayer. Practice on scrap material, I think the desired thickness was .016/.018? Make sure you have a good professional paint mask and ventilation, this stuff is nasty.

It’s all nasty in raw form … and some even worse in the dust form, like epoxy. Use the safety equipment per the instructions.

Choose your sanding grit and cleaning solvents recommended in the particular gelcoat brand’s guidelines. You may be able to ascertain generic equivalents to their branded products, but that isn’t always a given so read everything you can (on the can, in the pamphlet, and on-line) from the manufacturer you select.

A couple of suppliers even provide video overviews.

(example of a quickie overview from TAP Plastics)
these videos lack much in detail ... don't rely on them alone

[ame="http://www.youtube.com/watch?v=en-8SbhdF_k"]YouTube- How to repair Gelcoat Part 2[/ame]
​

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[chau8238]

I'm definantly following this thread. I still have plans to repaint or gelcoat my boat.

 

[BadProductions]

I'm a little confused about the technique used for a simple gelcoat repair and that used for the re-paint of the entire hull.

I understand that the best practice is to remove all the old gelcoat daown to the fibre glass, re-paint the entire surface with appropriate tools (rolled without thinning being the best choice but the most labour to get an even thickness and smooth finish) and then vacumn bag the entire hull to cure the product. A far different process from a simple ding repair...

...with that in mind, Ben & I have vigorously sanded the gelgoat on our sunfish, repaired as needed with Devoe epoxy (142 for the curious) & West epoxy and sprayed the entire hull with several coats of Devoe epoxy (4508 white) using a borrowed HVLP system. Tough as nails, smooth & even application, 5 days full cure before hitting the water . Seems far easier and less expensive than the gelcoat option (granted, I work for Devoe).

We are working on the Sunfish & a Chrysler C-15 at the same time using this technique... Ben will upload some pictures as we progress.

cheers
Bill & Benjamin @ BAD Productions
Freddy Beach NB

 

[Wayne]

I'm a little confused about the technique used for a simple gelcoat repair and that used for the re-paint of the entire hull.

I understand that the best practice is to remove all the old gelcoat down to the fiber glass, re-paint

Be careful with the perception of "paint". With gelcoat you are applying a new cosmetic finish, but it's a layer of resin..., the same basic resin the structural part of the boat is built with, only gelcoat is formulated with pigment and extra UV resistance and no glass fiber reinforcement.

. . . the entire surface with appropriate tools (rolled without thinning being the best choice but the most labor to get an even thickness and smooth finish) and then vacuum bag the entire hull to cure the product. A far different process from a simple ding repair...

I don't know about the vacuum bagging part of that last statement. Bagging is a technique I know for pulling out trapped air bubbles, getting resin to penetrate reinforcing fabric more deeply, and tightly pulling the layers of reinforcement together. I have not seen it used for gelcoat re-application. Where did you hear of bagging used in this way?

...with that in mind, Ben & I have vigorously sanded the gelcoat on our sunfish, repaired as needed with Devoe epoxy (142 for the curious) & West epoxy and sprayed the entire hull with several coats of Devoe epoxy (4508 white) using a borrowed HVLP system. Tough as nails, smooth & even application, 5 days full cure before hitting the water . Seems far easier and less expensive than the gelcoat option (granted, I work for Devoe).

So you took the classic epoxy paint approach. That's one alternative to re-gelcoating and also works.

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