Freshwater Bottom Paint

[Jeff Benagh]

What do people recommend for freshwater bottom paint in northern US (MA)? The lake does not suffer from much growth -- after the whole summer I had just a thin, black scum on the boat.

Last summer, I left my Shellback (plywood lapstrake) on a mooring and suffered blistering on and near the skeg. I had not closely read the posts about bottom paint since its first year it lived on the beach. It is painted with Kirby's which was perfect above the waterline and pretty good below (not that there is much below on a Shellback). I would like to leave it on the mooring again as it provides some protection against theft and vandalism but will not if I can't keep the paint in good order.

When using bottom paint, is a primer used? Or just a thinned coat of the bottom paint?

[mwybo]

I am finishing up a Pooduck that I will launch this year and asked myself the same question. I am on Lake Champlain so in similar conditions. My plans are to use VC17 since it does not rub off like some of the ablative paints. Many boats here use either VC17 or some ablative paint like Micron or Petit Horizons. I have had good luck with both on fiberglass sailboats.

I have used Petit Easypoxy top and bottom on the Pooduck so the VC-17 will go over that (which is over the Petit primer).

[Peter Malcolm Jardine]

Most bottom paints have an active ingredient, combined with paint. The active ingredient is usually cuprous oxide, although the USA also allows Biolux, which is a anti slime component. Most low priced bottom paints are ablative in that they are suspended in water, and release cuprous oxide until it is exhausted. When that happens the bottom paint is no longer effective in preventing growth on the boat bottom, yet some of the paint remains. After several seasons of buildup, adhesion problems may result, and flaking takes place. Removing a heavy buildup of bottom paint residue is a nasty job.

VC17 is a harder finish bottom paint with biolux available in the USA, and it also has teflon. It is recommended for boats looking for a smoother, faster surface, such as racing sailboats and performance powerboats.

I'd consider using MICRON CSC, which is a self polishing bottom paint. It gradual wears off the boat, eventually exposing the original bottom, whether it be gelcoat or a painted wood bottom. As it wears, new cuprous oxide is exposed, continuing to protect the boat. If there is still CSC on the bottom, wet or drysailed, the boat is protected. It also assures that no heavy buildup collects. Interlux will specify application, but as far as I know, a light sanding is all that would be required. There are a few colors.;)

Your paint flaking or lifting is only a factor of the boat being in the water, it is not likely that bottom paint would have prevented that. A finished bottom could still be used, and a good cleaning each fall would take most of the guck off if your lake is as clean as you say.

[curmudgeon]

Investigate Pettit product 1959 ... Hard Racing Copper Bronze.
This a non antifouling bottom paint with a traditional look.

[Todd Bradshaw]

Mwybo, you probably should do some testing before putting VC-17 over Easypoxy. The solvents in VC are very strong and will peel some enamels and other traditional paints. It also will not form a complete water barrier to keep moisture out of the enamel, so if the boat is left in the water the paint will probably eventually fail, just as a plain Easypoxy or Brightside coated hull will.

[curmudgeon]

I agree with Mr Bradshaw. If your boat is now coated with a topside paint then remove it before applying any bottom paint.

[michigangeorge]

I agree with Curmudgeon- good old copper/bronze. I've used it on sail and power; racing or cruising with equal success. And be certain to get rid of the topside paint. I once had problems with a F/G Dyer Dink I had done in awlgrip- left it in 80 degree Florida salt water and it (the awlgrip) blistered on me.

[Bob Smalser]

First, consider the body of water your boat resides in.

http://pic3.picturetrail.com/VOL12/1104763/9745605/138775808.jpg

As my ponds and most others around here are all nurseries for the Coho (Silver) Salmon fry that spend their first year in fresh water before making their run back to the sea, along with the sea-run Cutthroat Trout that accompany them, there's no way in hades I'll ever use a poisonous paint not thoroughly topcoated by a non-poisonous paint.

Boat slime washes off...those harmful metal ions contaminating sensitive bodies of water do not. What may not cause serious harm to a large, tidal body of water could be disastrous in a small freshwater lake with no water flow at all in the warm, dry season when the paint ablates the most.

[Paul Silverman]

I sail on Flathead Lake in Montana- cold freshwater that usually produces some scum on the hull after a season in the water. I use a cheap ablative bottom paint cut about 50% with a oil-based housepaint of similar color. Seems to work fine. Needs touch-up every season and repainting every two seasons or so. She's out of the water 7 or 8 months of the year.

[John Bell]

My in-fresh-water-year-round aluminum boat has got quite a beard on her after sitting unused most of the winter. I think the only anti-fouling that can be used on Al is TBT based, and there's no way I'm putting that in the lake. The good news is that I can swim around her with a wire brush and a scotchbrite pad and get her clean as a whistle. The bad news is that I have to swim around underneath her with wire brush and a scotchbrite pad to get her clean as a whistle. ;) But with gas over $3.00/gallon at the marina, a clean bottom is worth the effort.

[Jeff Benagh]

Thanks for all the advice! I think I will heed Bob Smalser's advice and try to forgo the bottom paint.

My big concern is the blisters and if it is possible to avoid them. I will try a post with a better title.

[Peter Malcolm Jardine]

Copper Bronze is effective for only one season, and after the boat is out of the water for more than a few days, the paint no longer functions when it is put back in the water. I use it on my CC because it is the traditional finish, but the technology is old.

[curmudgeon]

The original question refered to a paint suitable for use in fresh water where fouling is not an issue. Pettit # 1959 in not an antifouling paint. It is the only botom paint that I am aware of that is not antifouling although Interlux probably make a companion product. As I mentioned in a previous post, it is essential that if the surface to be coated, was previously painted with a topside paint, then this must be removed before applying any bottom paint.
The copper bronze paint refered to by Mr Jardine is not the same product. Copper bronze is also available in an antifouling formulation and does last only one season. It is old technology, I recall using it in the 1950's.

[mwybo]

OK, so there is something I clearly do not understand here. In traditional construction one expects the wood to absorb some moisture and to swell up tight. Is this also the case when building with marine ply? My assumption is that I do not want the plywood to absorb any moisture. If this is the case what is the best bottom treatment for a marine plywood boat? The boat is in fresh water, will be beached when not in use but will also be in use for extended periods (one month) in the water. I am using it as the tender for my fiberglass sailboat.

Thanks

Mike

[Peter Malcolm Jardine]

My mistake.... I didn't know Pettit made a copper bronze without cuprous oxide...:eek:

Pettit 1933 is the equivalent to Interlux 999 ... both have cuprous oxide.

I see that Pettit #1959 needs to be clear coated to prevent it from going green in some instances.

Add one more piece of boat info to the database. Thanks Curmudgeon.

[Audasea]

You appear to be looking for a paint solution that will survive imersion in fresh water for months at a time. Topsides paints and varnish are not rated for that. Water gets under them, lifts the paint and it blisters.

As you are in colder, freshwater, you don't have much of a problem with growth, so really don't need an anti-fouling paint.

You could leave the bottom as bare epoxy coating, but what about UV? Again, anti-fouling paints will protect it, but if you are trying to avoid bottom paints and all that comes with that, then what?

Fiberglass boats have gelcoat for this, so you need something that simulates gelcoat. That product is two part epoxy paint. It will survive constant imersion and is a tough, durable bottom coat. It will resemble gelcoat when applied over epoxy covered glass. Most versions of it will chalk if exposed to sunlight, but if it's on the bottom under water, that is not your problem.

Try these guys as a source:

http://www.epoxyproducts.com/4_epoxypaint.html#EPOXY%20PRIMER%20COAT