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Catalina/Capri 25/250 Sailor's Forums

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Cement Residue on Cabin Top

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JJM
Navigator

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USA
170 Posts

Initially Posted - 04/08/2005 : 17:58:22

My sailing partner (my wife) felt a bit under the weather last weekend, so Sunday was a wax the boat day.

A little History: Late last year our marina had repaired some of the cement dock immediately next to my boat. After they were done I found cement chips inside my cockpit on the floor.

So when I was waxing the cabintop on the same side that the cement repair occurred, I noticed that I could not get the finish smooth - it felt 'gritty'. My guess is that this is some cement overspray from that event.

The other cabintop side was perfect, but not this one.

Does anyone have a suggestion regarding what to use to smooth out the finish and getting that slick wax finish back without damaging the gelcoat?

Thanks!

John
"Enchanted Becuma"
C250 '04 WK #746

Edited by - on

Ericson33
Admiral

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USA
892 Posts

Response Posted - 04/08/2005 : 20:25:05

First I would decide how thick the cement is on the cabin top. to take gelcoat to a fine polish and get the cement off is going to take some work. 1 I wold get a sanding block with some 200 grit paper and lightly sand the top of the hatch that has the material on it. Next switch to a 400 grit paper and start wet sanding the area wash this off and meke sure all of the cement is off. be carefull not to sand in one place too long and never go over any corners or edges, the gelcoat in these spots are very thin and it only takes a little pressure to remove it. Next take 600 wet and dry and wet sand the area and a little bit over onto the shiny gelcoat. next get some rubbing compound and a buffer and lightly go over the entire hatch or area. next a polishing compound and then wax. This method is also usefull to restoring chalked gelcoat to a deep shine. It should take you a couple of hours to do this area no more, And let me just say again gelcoat is only about 20 mills thick so do it very lightly. with out looking at the damaged area it is hard to invision what is exactly there, is it all over the top in a fine mist, or in small clumps all over the area? you might even try a green 3M pad first the compound and they also sell the small square cleaning pads (for cleaning up grills) you cut them in half and they will fit right below the green pads, I would also take a small rag and fold it up wet to have something to hold on to. Keep it flat and even.

Edited by - on

Leon Sisson
Master Marine Consultant

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USA
1893 Posts

Response Posted - 04/08/2005 : 20:45:52

John,

I'd suggest being very careful using abrasives to attack this problem. I tried very wet #220 sandpaper on some badly chalked gelcoat, and regreted it. If you've got just a barely visible light dusting of cement powder on smooth gelcoat, I'd start with a fine kitchen scrubby pad. If that doesn't work, maybe consider #400 wet sandpaper, then #600, rubbing compound, polish, wax, etc.

If the cement is in the nonskid and not real conspicuous I'd leave it alone. If that's the case, let us know how well it improves traction, and how long it lasts! On these older boats, we're always interested to hear of cheap and easy ways to renew the nonskid!

Whatever you use to get it off of smooth gelcoat, flood the area with lots of clean running water to carry away all abrasive particles, and to lubricate whatever you're rubbing it with.

What about using a mild acid? Isn't cement extremely alkaline?

-- Leon Sisson

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Steve Milby
Past Commodore

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USA
5896 Posts

Response Posted - 04/09/2005 : 07:17:54

I think Leon is right on. The impression I get from reading your question is that it doesn't look bad. It just feels gritty. Heck, that's good. It improves your non-skid. It'll probably come off pretty quickly when you walk on it. Unless it looks bad or causes a problem, I wouldn't worry about it. With normal wear, rain and a winter freeze-thaw cycle, it'll probably be mostly gone within a year. If you don't want to wait for nature to take it's course, then I'ld wipe it with a diluted muriatic acid. I'd try a 1:10 mix. It shouldn't have to be very strong to get off a very fine overspray of cement.

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frogger
Navigator

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USA
184 Posts

Response Posted - 04/09/2005 : 08:27:36

I'd try vinegar (5% acetic acid) first using a sponge. Let soak a few minutes, rinse, and wipe dry. Repeat as necessary. It's what is commonly used to clean tile, glass, etc. in homes. Muriatic acid is a commercial version of hydrochloric acid.

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lcharlot
Master Marine Consultant

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Antigua and Barbuda
1301 Posts

Response Posted - 04/09/2005 : 11:01:25

For dirt (or cement powder?) in the non-skid, I have found that a commercial pressure washer is most effective. These are the gas engine powered 3500psi units that you can rent. The electric pressure washers like you can buy at Home Depot are only about 1800psi and while they do work, they take a lot longer to clean something as large as a boat, and they don't seem to have nearly as long a service life as the gas engine ones. Anyway, I would try a pressure washer first, then scrubbing with a Scotchbrite pad and mild acid, before you attempt cleaning with abrasives. Even 1000 grit wet sandpaper will go through gelcoat pretty fast.

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JJM
Navigator

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USA
170 Posts

Response Posted - 04/11/2005 : 13:41:14

Thanks everyone for your replies. I don't think I want to sand it because of the potential of going through the gelcoat. The area is, as Leon you have correctly remarked, very inconspicuous. I think I will continue with normal maintenance, and as Steve has recommended - let nature take it's course. If down the road it remains a real bother to me - I may attempt to pressure wash.

Right now it is hardly noticeable (except to me!!).

Edited by - on

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