Dear Auntie Fouling
Spring is here and
my bottom is a disaster! There is so
much advice out there about how to get it in shape - how do I know what’s right
for me and my bottom?
More specifically, I
have just bought a 25-year old Catalina 25 lifting keel with, I would say, 25
years of bottom paint still clinging to the hull, judging by the layers of
colors I’ve found so far.
I know I have to scrape
until I get all of the old paint off, but how do I know when to stop? And then what? Do I need to prep the surface or can I just
slap the paint on? And which
paint?! I’m tending towards the really
expensive stuff because I want to do it right, but I’m just not sure what’s
right for me. I also read that these bottom paints are toxic and that I should
suit up for the Apocalypse. What’s up with THAT? And how many coats of paint
should I use? And do I need to do something in between coats?
Signed,
Bummed about my bottom
Dear Bummed,
If you ask 3 different people how they clean their
bottom and apply bottom paint, you’ll get 5 different answers. Confusion is
just part of the fun of being a boat owner and you must learn to embrace it.
Scraping your bottom: yes and no.
(See how much fun this is going to be?)
Ideally, you should try to get as much of the old paint off as possible,
but you must keep in mind that your goal is to have a smooth bottom. If you’ve got pits and rough spots, those
need to go. Usually your epoxy layer is
a white or cream color, and as far as I know, no one makes bottom paint that
color, so stop when you strike white (or white-ish). If getting down to the epoxy layer is a
massive job, just aim for smooth. Buy a
quality scraper with replaceable cartridge blades. These babies cut through old
paint like a hot knife through butter.
When you’ve got things as good as you can with the scraper, pull out
your orbital sander and have a go at any uneven spots.
A note about safety: Bottom paints are toxic to aquatic scum, and
very bad for any of your soft tissues, specifically skin, eyes, lungs, etc. One of the biggest dangers is from the fine
dust while you’re sanding the old paint off the bottom. Before we learned how to suit up properly, we
suffered lung infections and eye infections from bottom paint dust and we hope
you’ll learn from our mistakes. Tales abound of reckless people eschewing masks
who ended up in the hospital for months with severe lung damage, so please take
the warnings seriously.
![]() |
| What's hot in boat-yard apparel for 2016. |
When scraping and especially while sanding, cover your
eyes, nose and mouth. Those little
filter-type masks with the metal nose clip and elastic bands are, in my humble
opinion, good for NOTHING. They’re hot
and sweaty and have gaps in them and make you itchy and miserable. The best method we’ve found is to take an old
tee-shirt and pull it down over your head until it stops on the bridge of your
nose and on your ears. If the sleeves
are long enough, tie them behind your head.
Bonus points if you take a magic marker and draw a big smile around the
mouth area. Friendly suggestion: brush your teeth well before putting on any
mask. You’ll be mouth-breathing in close
proximity to your own nose. Trust me on
this one. For the eyes, use wrap-around
eye protection that you can get from a hardware or garden store, not sun
glasses with open sides. When it comes
time to paint, cover your skin to minimize contact with the fresh paint
(plastic gloves, long sleeves, pants).
Don’t forget a bandana or cap for your hair. If you have a choice, it’s good to do the
painting on a breezy day when the fumes will be whisked away. See also “Clean Up” below.
Preparing to paint: Now you have a smooth bottom and are ready to
paint. Wipe the bottom down with a damp
rag to get rid of the dust. Tape off the zone to be painted around the water
line. Do NOT use masking tape. Once it bakes in the sun it’s very difficult
to get off. Use the plasticky pvc-type
tapes for this job found at any boat store.
Bottom paints need to be stirred well before you use them. Use a stirring stick or paint mixer
attachment for a drill and mix for several minutes. You may need to remix every hour or so if you
see any separation occurring. Read the
can for instructions for your particular paint.
Most paints will lose their anti-fouling properties if they are exposed
to air for more than 3 weeks, so you should only start painting when you know
the boat will go in the water within the time delay.
But wait !
Which paint ??: This all
depends on your bottom, what kind of sailing you do, where your boat is
berthed, what kind of water it is in, what the last type of paint applied was,
how well you removed (or didn’t) the last coat of paint, and how much money you
have. In general, if you are taking your
boat out of the water and re-applying bottom paint every year (as you should),
you do not need to do anything fancy.
There are two basic flavours:
hard matrix (modified epoxy paint) and ablative. The biocide in the hard matrix gets leached
out over time but the paint layer stays more or less intact. It dries to a hard smooth(ish) surface that
doesn’t wear off. The ablative paint slowly
wears away, exposing fresh biocide at a regular interval and the paint itself
erodes with time as well. If you sail a
lot of miles or if your boat is berthed in an area with a strong current, an
ablative paint will wear away quickly, but the advantage is that it’s easier to
remove for the next season’s paint job.
The hard matrix will provide continual protection but eventually the
biocide will be gone and you’ll just be left with paint and algae, and a bigger
mess for the next season.
We have always used hard matrix. For the way we sail, it lasts longer, it’s
cheaper, and we scrape and repaint every year.
This year, however, we’re doing something different. We’re heading into the Med and we’re not sure
we’ll pull the boat out of the water or not for 18-24 months. We need long-lasting protection. The Jeanneau boatyard guys suggested the
following one-two punch: hard matrix as
a first layer, then ablative as a second layer in a different color. The ablative will slowly wear away to expose
the hard matrix, which will then take over as the ablative fades. With the color differences, we’ll be able to
see the “wear” zones and can judge how quickly the ablative is ablating.
![]() |
| 1st coat, hard matrix in grey. Note red pvc tape at the water line. |
![]() |
| Final coat, black ablative. |
For you, Dear Bummed, I would suggest 1 good layer of
hard matrix. Your boat is berthed in brackish
water in a river exposed to current, and you tend to haul out at least once per
year anyway, so no need to go overboard (so to speak…) with fancy high-copper
content paints. Go for plain hard
matrix.
Painting: We like
small rollers for applying an even layer.
Use cross-hatched passes to cover an area. If you want to impress, you can finish the
last pass of the roller in the direction of the water flow, which, in
principle, may give you an additional 0.1 knot of speed. It’s a long boring job
and you may as well amuse yourself.
Start painting the keel and the underside, then paint your way up and
out to avoid getting paint on your hat or bandana when (not if) you bang your
head. (Hey, you already look pretty silly with that tee-shirt pulled half-way
down over your face – why not add an old bicycle helmet to the costume?)
If you choose to do a 2nd coat, read the can
for instructions about drying times. If
you put the 2nd coat on straight away, you can just put it on
directly over the 1st coat after it’s dry. If you have to wait for a few weeks between
coats, you will no longer have a chemical bond with the 1st coat and
will have to make a physical bond for the 2nd coat, which simply
means a quick pass with fine-grained sandpaper (HAZMAT clothes and mask
again…). You want to have a little bit
of paint left over to cover the patches under the cradle or trailer that you
can’t reach. Do this just before the
boat goes in the water – it doesn’t need much drying time. If you’ve got quite a lot left over, take
another pass along the water line, which is where most of the algae will build
up.
Note: this should go without saying, but I’ve seen it
happen. Do NOT paint your anodes,
folks. Think about it.
![]() |
| Change anode. Do NOT paint it ! |
Clean up: Take
the tape off as soon as you finish your last coat. Don’t let it stay on until the paint dries or
you risk pulling off flakes. Dispose of
everything as directed on the can. For
any spills on the skin, you can use paint thinner (or gasoline) to wash it off,
but hop in the shower as soon as possible and scrub down well (loofa, sponge) a
couple of times to “detox”. Don’t forget
the inside of your ears. That fine dust
can find its way into the darndest places.
Rinse eyes as needed with water or a saline solution. For your nose, netty pot, netty pot, netty pot.
And now the most important part: no matter how careful
you were with the mask, etc., your nasal passages and throat have probably been
assaulted. The best thing for you to do
is to pour yourself a large icy gin and tonic.
The ice soothes, the bubbles dislodge any lingering particles, and the
lime and gin disinfect. You may need several applications of this phase, but
your health is no place to cut corners.







































