Advice on gel coat to centerboard

[stickinthemud57]

I have stripped the VC17 off my centerboard and plan to re-do the gel coat. I know that spraying will give the best finish, but the current surface has lots of rough spots, so I am thinking that maybe I will apply and sand a brush-on, non-wax product, then take it to a local shop to apply the final coat using a sprayer.

Any helpful hints would be appreciated.

Thanks!

 

[sail sfbay]

You are on the right track............use a small foam roller to apply the gelcoat, sand and wax.

 

[dlochner]

Gelcoat is probably not the right product. When you say "rough spots" are you talking about rust?

How is the centerboard constructed? some are mostly fiberglass with a lead weight in the bottom, others are steel or cast iron.

Gelcoat does not have good adhesive properties and it is not particularly hard. A better product will be an epoxy based primer or barrier coat. Roll and tip several coats and then sand and polish to a very smooth finish.

 

[stickinthemud57]

Gelcoat is probably not the right product. When you say "rough spots" are you talking about rust?

How is the centerboard constructed? some are mostly fiberglass with a lead weight in the bottom, others are steel or cast iron.

Gelcoat does not have good adhesive properties and it is not particularly hard. A better product will be an epoxy based primer or barrier coat. Roll and tip several coats and then sand and polish to a very smooth finish.

Sorry, should have mentioned construction. It is a partially hollow fiberglass centerboard. No metal.

Thanks for the advice!

 

[dlochner]

If you spray gelcoat, you or someone will spend a lot of time sanding and polishing. If you brush gelcoat on, you or somebody will spend a lot of time sanding and polishing.

Sand and fair the CB with a compound good for underwater use. Then apply several thin coats of gelcoat with a brush. Use waxes aka laminating gelcoat. Laminating gel coat does not fully cure in the presence of air. Once you have enough gelcoat on the board, spray with PVA or a good spray wax. This will block the air and the gelcoat will finish curing. Once fully cured remove the wax and start sanding. If the surface is fairly smooth you can start with a fine grit 220 or higher, if less even start with a a coarser grade. Keep working your way up to 1000 grit and then use a rubbing or polishing compound for the final gloss.

Alternatively use the same process with an epoxy based paint, like VC Performance. VC Performance will form a very hard polishable surface. Its main drawback is the fairly narrow window to sand and polish the surface. After a couple of days the surface is extremely hard.

You might find this video helpful. Andy has other videos on painting and working with gelcoat too.

 

[thinwater]

I have stripped the VC17 off my centerboard and plan to re-do the gel coat. I know that spraying will give the best finish, but the current surface has lots of rough spots, so I am thinking that maybe I will apply and sand a brush-on, non-wax product, then take it to a local shop to apply the final coat using a sprayer.

Any helpful hints would be appreciated.

Thanks!

It is NEVER going to see the sun or be visible. There is no reason for gel coat. Why not just sand, fair, epoxy, and VC17, or some other freshwater antifoul again? You are making this more complicated for no reason I can understand. Epoxy will be more waterproof than gelcoat. It was gel coated in the factory because it was sprayed in the mold and that was the cheapest and easiest finish, not the best finish. Gelcoat is not a particularly good underwater hull finish material.

I would never gel coat my centerboard, not if it were free.

 

[stickinthemud57]

Thanks all for getting me straight on the gel coat. I am used to seeing it as the smoothest finish, but can see the advantage of going with a tougher finish.

Turns out I have plenty of Interprotect 2000e left over from when I did the bottom back in the Spring of 2021. I am in the process of filling and sanding the CB, will apply the Interprotect, sand, repeat until I have enough built up to buff down to a smooth finish. 3 coats I am thinking. Does this sound like a viable plan or no?

I am not quite sold on re-applying the VC17 like before. Comments pro or con?

 

[thinwater]

Thanks all for getting me straight on the gel coat. I am used to seeing it as the smoothest finish, but can see the advantage of going with a tougher finish.

Turns out I have plenty of Interprotect 2000e left over from when I did the bottom back in the Spring of 2021. I am in the process of filling and sanding the CB, will apply the Interprotect, sand, repeat until I have enough built up to buff down to a smooth finish. 3 coats I am thinking. Does this sound like a viable plan or no?

I am not quite sold on re-applying the VC17 like before. Comments pro or con?

Saltwater sailor. No experience, no opinion.

Well, several thoughts.

• I've done number of anti-fouling tests (panels) and never been at all impressed with slick coatings.
• Anti-foulings last a LOT longer in CB cases because the water is in constrained area and there is no sunlight.
• You want to limit build-up because it can make the board stiff.

Obviously, it depends a lot on how much you keep the boat in the water.

 

[dlochner]

Thanks all for getting me straight on the gel coat. I am used to seeing it as the smoothest finish, but can see the advantage of going with a tougher finish.

Turns out I have plenty of Interprotect 2000e left over from when I did the bottom back in the Spring of 2021. I am in the process of filling and sanding the CB, will apply the Interprotect, sand, repeat until I have enough built up to buff down to a smooth finish. 3 coats I am thinking. Does this sound like a viable plan or no?

I am not quite sold on re-applying the VC17 like before. Comments pro or con?

When I rebuilt a centerboard on a Flying Scot, I used Interprotect for the same reason, I had some. It worked fine. 3 coats will probably be thick enough.

If the boat is going to be left in the water, then do apply antifouling especially if the Lake has Zebra mussels. If it will be dry sailed or trailered, there's no need.

 

[stickinthemud57]

When I rebuilt a centerboard on a Flying Scot, I used Interprotect for the same reason, I had some. It worked fine. 3 coats will probably be thick enough.

If the boat is going to be left in the water, then do apply antifouling especially if the Lake has Zebra mussels. If it will be dry sailed or trailered, there's no need.

Zebra mussels, yes (unfortunately). I was appalled that they had managed to set up housekeeping at the drain holes of the CB. I guess this will be just like before, except that I will be working harder to get a smooth finish than last time.

I have a bit of VC17 leftover as well. It is my understanding that Black Widow can be burnished smooth. Anyone with any experience or recommendations for that product?

 

[dlochner]

We've been dealing with Zebra Mussels for decades, they are a pain, but manageable. Fortunately their ability to adhere to stuff is pretty weak so they are easily scraped off.

I have no experience with Black Widow, but I have not heard rave reviews. VC 17 can be burnished too. Get it rolled on as smooth as possible. When dry take a crumpled up newspaper and burnish it. VC17 is inherently slippery, so burnishing won't add much.

In the past my boat was in a marina with some hardcore racers, they did not burnish VC 17.

 

[Crazy Dave Condon]

@stickinthemud57

which boat do you have and a photo of the centerboard would help for me to chime in

 

[stickinthemud57]

@stickinthemud57

which boat do you have and a photo of the centerboard would help for me to chime in

MacGregor 26S. Centerboard is about 6' long and 1' wide with corners rounded at both ends about 1.5 to 2" at leading edge. Tapers to about .75" at the trailing edge. Mostly solid fiberglass with a hollow section with drain holes near the bottom.

 

[Crazy Dave Condon]

@stickinthemud57
You have the power sailor hull. What size engine do you have? Will you be able to get the photo of the centerboard and post it here. Use to be a MacGregor dealer as well

 

[stickinthemud57]

@stickinthemud57
You have the power sailor hull. What size engine do you have? Will you be able to get the photo of the centerboard and post it here. Use to be a MacGregor dealer as well

Not sure what you mean by power sailor hull. The 26X and 26M have the planing hull for use with larger motors. The 26S is a displacement hull with a hull speed of around 6.5 knots.

My kicker is an 8 HP Tohatsu 2-stroke.

Attached is a picture of the centerboard. I am in the process of filling in the uneven areas. I am surprised how rough it was overall.

 

[Crazy Dave Condon]

@stickinthemud57
My goof on the designations as you are correct but it is the board I think is still the same. Sent you a PM. Can you call me?

crazy dave

 

[thinwater]

MacGregor 26S. Centerboard is about 6' long and 1' wide with corners rounded at both ends about 1.5 to 2" at leading edge. Tapers to about .75" at the trailing edge. Mostly solid fiberglass with a hollow section with drain holes near the bottom.

If the CB is 3/4-inch wide at the trailing edge, I'd start there (unless there is a class restriction). Reshaping could make a difference pointing. As other 26S sailors. Ideally, the trailing edge should be ~ 1/8-inch and square. No more than 1/4-inch.

Google the topic (daggerboard foil shape naca).

 

[stickinthemud57]

If the CB is 3/4-inch wide at the trailing edge, I'd start there (unless there is a class restriction). Reshaping could make a difference pointing. As other 26S sailors. Ideally, the trailing edge should be ~ 1/8-inch and square. No more than 1/4-inch.

Google the topic (daggerboard foil shape naca).

I have thought about grinding the CB to improve hydrodynamics, but I fear that doing so would lighten it and exacerbate the existing problem (CB riding up at higher speeds).