New Boat: Annapolis/Baltimore area: Sanding?

[Charrob]

Hi,

we are new to boating and just purchased a 1978 Catalina 27 sailboat. Currently the bottom shows rings where barnacles were, the keel has barnacles on it as does the prop and the metal tubing that goes into the boat from the prop. Also there is paint peeling on various areas of the bottom. The previous owner stated that the current paint on the bottom is a "hard" paint, not an "ablative" paint.

Question1: we would like the bottom to have an ablative paint. The owner of the marina who has worked on boats for 22 years stated that we should not put an ablative paint over a hard paint-- that mixing paints is not good. Is this true?

Question2: Being new to boats, I am unclear how much sanding the bottom should get before applying the paint. One person told us we'd need to sand to the point where there is only a very thin layer of the current hard paint left. Question: how can you tell how "thick" the layer of paint you are working on is? I just don't have a grasp of how much of the current paint needs to come off before applying the ablative paint.

Question3: How does one go about hiring someone to do this work? What do you look under in the yellow pages to find a person such as this?

[TakeFive]

As a general rule, ablative paint can go over hard paint with modest surface prep. Where you get into problems is putting hard paint over ablative. Consult the websites of paint manufacturers (Pettit, Interlux) for specific compatibility charts and recommendations for the amount of sanding. If would help a lot if the prior owner could tell you exactly what paint is on the top layer.

Get recommendations for a good boat yard if you want this work done for you. However, based on the marina owner's questionable advice about ablative over hard paint, I would not work with that marina.

There are others with much more experience than me in this area - hopefully they'll have more advice.

[BarryL]

Hello,

The 'best' thing would be for you to sand off ALL the paint. Since I / you don't know how much paint is on the bottom, that may not be practical. What I would do is sand until the bottom is smooth, with no barnacles or loose or flaking or chipping paint. Use 40 or 60 grit for this. When all the old paint is gone, go over the bottom with 80 grit. Wipe down with a solvent and then repaint.

There are instructions for this on the major paint vendors (Interlux, Pettitt, etc.) web sites.

Good luck,
Barry

[TakeFive]

Originally Posted by BarryL

...The 'best' thing would be for you to sand off ALL the paint....

Many people give this advice, and it does make some sense. However I'll throw out some contrarian thinking here. When I went to paint my boat for the first time this year I scraped the bottom, and came to realize that MOST of the paint was adhered to the hull very well. There were three identifiable coats on my hull, and in the few spots where there were chips they went all the way to bare fiberglass (vinyl ester, thus no epoxy barrier coat needed). There were no cases of adhesion failure between coats of paint, but several cases of adhesion failure with the fiberglass.

Given this observation, I think it makes sense to leave the existing paint on the hull if the existing paint build is not too thick. If you have paint that is already sticking well to the fiberglass, keep it there. If you remove it and go back to bare fiberglass, it's a crap-shoot whether the new paint will stick. So focus your efforts on de-waxing the bare spots where prior coats came off, and sand to reduce orange peel in the areas where the paint is adhered well and to feather the edges of the chips. Then, after a good wipedown with solvent, apply a compatible paint over top the existing paint.

Obviously racers and those who want to use exotic freshwater paints like VC-17 may want to go to bare fiberglass. But for the rest of us, I'd advise thinking twice before going back to bare fiberglass.

[T37Chef]

Congrats on the new boat! Where are you going to keep it?

If you have flaking, you may consider having the bottom soda blasted, then take care of any blister problems if needed, then barrier coat, then coat of hard paint, followed by two coats of ablative paint (I would suggest Pettit Ultima SR40) of a different color.

Around Pasadena/Baltimore, the guy who does the sida/snad blasting is called the Sandman, sorry I cant find his number. You can barrier coat and paint yourself, not much harder than dry wall and painting in your house IMO.

But for this year if you wanna just get sailing, slap on a coat of the cheapest ablative you can find and have fun, wait to do it right over the winter

Read here on what I did the first Spring on our boat: http://www.sailnet.com/forums/322678-post.html

[HPLou]

Congratulations on your new boat.

As previously stated, you can use an ablative paint over a hard paint with just a light sanding. As for any areas where there is flaking, you can use a disk sander to feather the edges to the good paint. Apply a good coat of bottom paint and you're ready to go. You can also check the paint manufacturer's web site for any recommendations they may have using their product.

As for the prop, you can use a wire brush attachment on an electric drill to get all the paint off in preparation of whatever anti-fouling works best in your area. Check with other boaters in your area for what works best on your prop. Don't forget to install a new zinc and then you are ready to go.

You can check with your fellow boaters in the area for recommendations on where to go or who to use to do the bottom work. Note that some marinas may not allow outside contractors do work in their yard or they may have a list of outside contractors that they may allow to do work in their yard.

Good luck and enjoy your new boat.

[Charrob]

Thank you all so much for your advice and recommendations. This forum is great!

[pdqaltair]

I see a lot of scraping in the spring--hard work--but not really needed, IMHO.

My last boat had ~ 4 coats of hard paint on it when I bought it. I sanded lightly and used a 2-year soft paint. Subsequent years, I power washed it and generally skipped the sanding (perhaps few spots).

I sold the boat on it's 30th birthday, never having scraped the bottom. She went 14 knots (without surfing) in a 12 knot breeze during sea trials--not a slow boat at all. Because of occasional in-water scrubbing and using the paint to exhaustion, build-up was zero.

Read my blog, if you like; a lot of local stuff.