Older Aluminum Boats (2006)
Question:
What
advice and cautions would you have
regarding buying older aluminum boats?
I have been told to pay particular
attention to the area under the heads
and engine and around the
through-hulls. Is there anything else
you might be wary about in an older
aluminum boat?
Answer: All the areas you mention are
important. The good thing is that with
aluminum any structural problem is
usually fairly obvious, unlike
fiberglass, and can be easily fixed to
be as strong as new, again unlike
fiberglass. I would add one other area
to check carefully: the shaft tube.
Many aluminum boats have experienced
corrosion problems in this area due to
the dead water that sits in the tube
together with the stainless steel
shaft. Properly inspecting this area
is non-trivial since the propeller
shaft must be removed, which often
requires removing the rudder—no bad
idea in itself.
There is no fundamental reason why a
15 to 25 year old aluminum boat should
not be sound, but a good survey is
essential. Also the surveyor should
have a lot of experience with
aluminum. I would suggest Tony Knowles
of Newport Marine Survey. I think
buying a boat 30 to 40 years old might be
pushing your luck, particularly since
the heyday of aluminum yacht
construction did not start until the
late seventies. Look for a boat from a
reputable boat yard with plenty of
aluminum boats under their belts
before they built yours.
A more fundamental question is whether
such a boat is a good buy. (Morgan’s
Cloud was only six years old when
we bought her.) The key is whether the
boat has been consistently upgraded to
modern standards (like Morgan's
Cloud); if so, you may get a great
deal. If not, you could be looking at
a refit that will cost more than a new
boat if you pay someone else to do it,
or that will take several years if you
do it yourself and still cost a lot of
money.
I understand your reluctance to blow
too much of the cruising kitty on a
boat, but I would still look carefully
at either a new production aluminum
boat (probably from France or Holland)
or a bare aluminum hull and finish it
out yourself. Either option could, in
the end, be less costly than an older
boat. If you go the latter route,
allow at least two years of full time
work to finish out a 40’ hull; much
more if you are trying to hold down a
job at the same time. Another benefit
of new construction is that you stand
a better chance of getting the deck
salon/wheelhouse you’re interested in,
which was an unusual feature until
comparatively recently. (Incidentally,
I would not even think about
home-building a hull; way too much
work for the rewards.)
Installing
Treadmaster (02/2008)
Question: When you were installing your
Treadmaster, did you grind back to clean metal and glue
it down, or did you, as I was advised, paint with epoxy
first?
Answer: Our boat was already covered in epoxy
putty, which still had a good bond, so we glued to that
with
West System epoxy. If I were putting Treadmaster on
bare aluminum, I would use the West System two part
aluminum etch (we have had great luck getting a good
bond after treating bare aluminum with this stuff) and
then glue it down with West System epoxy slightly
thickened with colloidal silicate. Note that we have
friends that did not acid etch the aluminum and the
Treadmaster peeled off on them despite aggressive wire
brushing and cleaning prior to putting it down.
Bronze Sea Cocks (2006)
Question:
Do you have bronze sea cocks in your
aluminum hull and if so what level of
corrosive activity have you seen?
Answer:
We have bronze sea cocks insulated from
the hull with fiber spacers. The
through hulls are plastic. There is
no sign of any corrosion around most
of the sea cocks, which are located in
the engine room. The only exception
are the head sea cocks located forward.
Here the hull plate under them is
showing some light pitting from copper
salts dripping off the sea cocks over
the last 20 years. I think the reason
that the engine room sea cocks don't
have this problem is that the heat
from the engine and generator keep
them and the surrounding area pretty
dry, whereas up forward the area is
often wet from condensation,
particularly when we are in cold water
areas (most of the time).
Depth Sounder with Bronze Transducer
(2006)
Question: We
want to replace the current inoperable
depth sounder on our aluminum boat
with a forward looking type (EchoPilot
or Interphase), but we have run into
the dilemma that the transducers
suitable for our hull have bronze
stems. We have been advised that
bronze stems can be installed in
aluminum hulls if the stem is well
isolated from the hull and an aluminum
donut is installed as well.
We would appreciate any information
you could provide us and what your
experience has been, especially if you
did install a bronze stemmed
transducer on Morgan's Cloud.
Answer:
I would not recommend installing a
bronze through hull on an aluminum
boat, even if it is isolated from the
aluminum; there is just too much risk
of electrolysis. Also, if there is any
dampness, and there will be, copper
salts will form on the bronze and drip
into the bilge...not good.
When we bought our EchoPilot FLS II,
EchoPilot (see
Stuff
that works for more information on
the EchoPilot) provided a custom
aluminum through-hull at additional
cost. This is not a cheap solution,
but definitely the way to go. Once we
had the aluminum through-hull we had
an aluminum donut machined that
compensated for the angle of the hull
since it is vital that the transducer
be installed absolutely vertical.
The next challenge is to get all this
installed and safely watertight. You
could weld the donut in, but this is
messy and it is very difficult to get
everything lined up perfectly when
welding, due to heat distortion of the
surrounding plate. To get around this
we used Plexus adhesive to glue the
donut down before drilling the hole
(see
Stuff that works for more
information on Plexus).
The cool thing is that Plexus sticks
to aluminum brilliantly, particularly
if you use the Plexus aluminum primer,
and it will gap fill up to ½” so you
can use it to make any small
adjustments to the leveling of the
donut. Once the Plexus is dry, drill
the hole through the donut and the
outside plate making sure it is
absolutely vertical.
Before starting this project make sure
the boat is level on the ground, both
fore and aft and side to side.
Remember, you are trying to level the
actual water line (scum line) since
you want the beam from the sounder to
be parallel to it. If you want to get
really anal retentive about it you
could rent a self leveling laser that
surveyors use to line up buildings. We
rented one for a recent project for
about US$100 and it was great,
although it is probably overkill for
this. This process will drive your
travel lift operator crazy, but is the
only way to get things right.
Your next issue is to fair-in the
transducer through-hull on the
outside, since it won’t lie flush. The
answer here is to cover it in mold
release wax and then install it onto a
pile of epoxy putty on the outside of
the hull (we make our own putty from
WEST system resin and micro-balloons).
Tool the putty to a fair shape while
wet. Once dry, remove the transducer
through-hull, clean off the mold
release wax with acetone, sand the
epoxy putty to a final smooth and fair
shape and make the final installation
with a good underwater sealant.
It’s a lot of work, but well worth it;
once you have a forward scan sounder
you won’t be able to imagine how you
got along with out it.
For the high latitudes, I would
recommend the new EchoPilot Platinum
model which replaced the FLS II that
we have
and, as I understand it, fixes most of
our criticisms of the older model. I
would also recommend having a spare
transducer aboard since they seem to
lose their sensitivity after a few
years and can die suddenly.
Treadmaster Gluing Problems (2005)
Question:
We are
having trouble getting our Treadmaster
deck covering to stay stuck to our
bare aluminum deck. What can you tell
me about getting epoxy to stick to
aluminum reliably?
Answer:
We did not have to stick our
Treadmaster to bare aluminum, but
rather to the filler that covers the
entire boat. However, we do have some
experience with getting WEST System
epoxy to stick to aluminum since that
is what we use, thickened with
microlight powder, to repair any dings
or corrosion problems on the hull
fairing.
Here is what I know:
-
You only have about an hour after
grinding aluminum to get the epoxy on
it before the aluminum oxide re-forms.
Once this happens you will not get a
good bond.
-
For the very best adhesion, we use the
WEST System two part acid wash
treatment first and then make sure we
get the resin on within one hour. This
is about the only way we have found to
make absolutely sure that the resin
stays bonded to the aluminum. The down
side is that the chemicals involved
are really nasty.
-
If you don't wish to use the nasty
chemicals in the above, a useful trick
is to "wet sand" the aluminum using 80
grit wet or dry paper and the
un-thickened WEST System resin. This
keys the resin right into the aluminum
and does not allow any oxide to form
because the wet resin keeps the air
off.
-
When bonding, WEST System resin works
a lot better if thickened with the
appropriate powder. We used colloidal
silicate on the Treadmaster job,
available from WEST. You get much
better void filling this way.
New
Aluminum Boats: What to Paint and What Not to Paint?
(02/2008)
Question: You say you would not paint aluminum.
Ok, it is hideously expensive (I have been quoted
£10,000 just for materials), it is difficult to key, and
we have been advised to sand blast and paint the same
day (tricky!). So, if you were to start all over again
with a newly built boat, what parts would you paint?
Answer: You are right, painting an aluminum boat
is incredibly expensive and if you get someone else to
do it the materials price you were quoted will be less
than half of the final cost. Yes, you must key the
aluminum, but there is much more to it than that. You
also need to acid wash and get a good zinc chromate
primer on that day (this goes under the normal high
build primer). Don’t believe anyone who tells you that
acid etching and metal primers are not necessary. Even
some professional painters will try and tell you this
because they don’t want to deal with these nasty
chemicals. If you don’t etch and prime properly, all
your expensive paint will start bubbling in a couple of
years. By the way, the same applies to painting aluminum
spars.
Question: Should we paint the hull under the
waterline?
Answer: Yes, you need to paint the bottom.
Starting with a primer as discussed above, followed by a
good barrier coat (we use InterProtect from Interlux)
and topped off with an aluminum-friendly anti-fouling
(we use E-Paint ZO).
Question: Should we paint the bilge?
Answer: No, don’t paint the bilge. You will never
get the paint to stick properly and you will then have
to live with loose paint chips in the bilge with the
potential to block bilge pumps, block limber holes and
gather in wet clumps with any dirt. This will actually
promote corrosion rather than prevent it.
Question: Should we paint the cockpit?
Answer: If I was doing a new boat in aluminum I
would not paint anything other than the hull below the
waterline.
Question: Where do your main problems with the
paint on Morgan’s Cloud lie: with the paint
becoming chipped from wear and tear, or from inadequate
preparation, or from salt water working under the paint
edge?
Answer: All of the above, but any inadequate
preparation will result in a bubble sooner or later and
it is almost impossible to perfectly prepare an entire
boat, particularly on deck.
Question: We are planning to insulate the
interior of our new aluminum boat with spray foam, any
comments? Is your hull foamed? Was it primed with paint
before or sprayed directly onto the metal?
Answer: Our hull was primed first and then
sprayed, but I’m not sure this is really required. Talk
to the manufacturer of the foam system. Also, you may
want to look at self adhesive foam sheet systems rather
than spray on.
Whether to Apply Antifouling Paint
or Not (2007)
Question: I’m thinking of
leaving the bottom of my aluminum boat
unpainted since I’m afraid of
electrolysis caused, or at least made
worse, by antifouling paint,
particularly if the bottom is
scratched. The boat is in fresh water,
so she will not foul much.
Answer:
There is no reason why properly
applied antifouling paint that is
intended for aluminum boats should
cause or aggravate electrolysis. The
key to preventing electrolysis is an
isolated ground electrical system,
good zinc anodes (or magnesium in
fresh water) and an isolation
transformer to prevent damage from
other boats that are improperly wired
when plugged into shore power. (See
below for more information on bottom
paints for aluminum boats.)
Coppercoat Antifouling Paint (2007)
Question: We are considering applying Coppercoat
to our aluminum boat and would be
interested in your thoughts. I have
attached some correspondence that I
had with the makers of Coppercoat that
may help:
Question
to Coppercoat [edited for brevity]:
I'm seriously considering Coppercoat
for my aluminum cutter. I am confused
by one group of advisors that strongly
advise me to stay away from copper
(other than copper thiocyanate) and
another group that says an insulating
barrier between hull-bottom and
Coppercoat suffices to be safe.
Could you please explain to me how
Coppercoat manages to be safe on an
aluminum hull, even when the hull is
scratched by a rock and bare aluminum
is showing under water?
Answer from Coppercoat [edited for
brevity]:
Unlike many paint companies, we do not
manufacture different types of
anti-fouling for different sorts of
boats and particular locations.
Instead, Coppercoat is only available
in a full strength, hard wearing
version. The epoxy carrier is filled
with the maximum amount of copper
allowed by law, and consequently this
coating will keep fouling at bay in
virtually all conditions (including
warm and cold, fresh and salt waters).
Please note that Coppercoat only uses
pure copper, and not the weaker and
less effective alloys such as
copper-nickel. Furthermore, while the
non-eroding epoxy can easily withstand
use by high powered motor-boats and
racing yachts, this coating is equally
effective on less frequently used
leisure vessels.
Over the years we have supplied
Coppercoat to numerous aluminum boats.
You must remember that Coppercoat is
not a copper anti-foul in the
traditional sense, in that it is not a
water miscible paint. Instead,
Coppercoat has all the copper bound
within a waterproof epoxy. Coppercoat
is non-conductive and does not cause
or promote electrolysis or cathodic
decay. However, when treating aluminum
it is important to
prime the hull thoroughly with a good
layer of pure epoxy primer before
over-coating with the Coppercoat. This
distances the copper rich epoxy from
the aluminum hull, and, to all intents
and purposes changes the hull from
being aluminum to being plastic (as
far as our anti-fouling is concerned).
I understand that you have
reservations concerning a potential
breach of this epoxy primer (if
scratched by a rock), thereby exposing
fresh aluminum to the sea which is
also in contact with the Coppercoat.
However, the relatively poor
conductivity of the sea-water and the
incredibly weak field emitted from the
tiny amount of exposed copper powder
combines to mean that this is not a
problem. Remember that although
Coppercoat contains a large amount of
copper, at any given time only a very
small percentage of this is actually
exposed as the vast majority is held
within (and each individual copper
sphere encapsulated by) two-pack epoxy
resin.
Answer:
I can't really advise you on what to
do on your boat since I'm not an
expert, or even close, on
electrolysis. Also, we all have
different levels of comfort with such
things. What I can say is that after
giving it quite a bit of thought I
would not apply Coppercoat to
Morgan's Cloud, or at least not
without a great deal more research,
for the following reasons:
-
I'm just plain uncomfortable about
mixing more noble metals with aluminum
on our boat. I'm sure Coppercoat are
correct in everything they say, but
suppose there is something strange
about my boat, or suppose the problems
only manifest after 10 years? If
Morgan's Cloud was damaged by the
paint, we would never be able to afford
to repair or replace her; it’s just
not worth the risk to us, no matter
how small.
-
There is one part of aluminum boats
that can't be coated and is always in
contact with the water and that is the
inside of the propeller shaft tube.
I'm advised by Tony Knowles, a very
experienced surveyor of aluminum
boats, that it is relatively common
for the tube to corrode out on older
aluminum boats, resulting in a complex
and expensive repair. Would Coppercoat
make this worse? I don't know, but I
don't want to find out the hard way.
The tube on Morgan's Cloud is
still in good shape after nearly 20
years. I don't know for sure why that
is, but I don't want to change
anything. If it's not broken, don't fix
it.
-
Although we have no experience with
Coppercoat, we have had poor results
from hard antifouling finishes over
the years. I think they can work well
for high speed motor boats or boats
that are underway all the time, like
commercial crew boats, but for the
average yacht—even one like ours that
is underway a relatively high amount
of the time for a yacht—soft ablative
finishes seem to do better. We use the
zink-based antifouling from e-paint
and have tried both their hard and
soft products and found that the soft
works a great deal better in our
application. (See below for more on
bottom paints.)
Which
Antifouling Paint? (2006)
Question: I bought an aluminum
40ft Roberts from the original owner
and am in the process of many changes.
One area which seems very gray these
days is what bottom paint to use. An
epoxy barrier coat is there but I do
not want any copper impregnated paint
anywhere near my boat. Could you
please let me know what you've found
that works.
Answer:
Antifouling paint for aluminum boats
has been a problem ever since tin
based paints were banned. For some ten
years we have used the ZO and SN-1
products from epaint,
www.epaint.net. However,
performance has been inconsistent;
some years it has worked well lasting
up to a year with almost no slime and
some years it has grown slime in just
a few months. On two occasions it
failed completely after just four
months, and this in cold water with
the boat constantly on the move. The
first time this happened epaint
replaced the paint but did not cover
the cost of recoating. The second time
was last year and we did not approach them about it.
As it happens, as I write this we are
removing all the paint off the bottom
of the boat down to the barrier coat
and so are faced with the same
difficult decision you are.
The only other option I know of is
Trilux® 33 from Interlux, see
www.yachtpaint.com. This is a
copper based paint but it is copper
thiocyanate, which Interlux say is
safe for properly barrier coated
aluminum boats. We tried the original
Trilux product before switching to
epaint and found it pretty poor. Interlux
say that they have substantially
improved Trilux from the original
product that we tried.
The plot gets even more ambiguous:
Interlux sells Trilux® 33 in the USA
but not in Canada and Trilux II in
Canada but not in the USA. Practical
Sailor’s tests would seem to
indicate that the Canadian product is
better than the US product, but when I
asked the Interlux technical
department, they said the opposite.
(I’m a bit skeptical about the
Practical Sailor tests since their
test rig does not move, which I think
may change everything.) At least you
can overcoat Trilux® 33 with Trilux II,
according to Interlux technical
support.
Update,
September, 2006: Steve Dashew (www.setsail.com) reports that they've had really
good luck with an industrial system
supplied by Ameron, both primers and
copper bottom paint. It is possible
that you have to start with bare
metal, but Steve reports that the
bottom paint is better than anything
they've ever used. Apparently this
system has been used on aluminum crew
boats for years without problems.
Update,
October, 2006: In the end,
after a long and informative
telephone conversation with the people
at epaint, we
applied epaint ZO. It turns out that
the SN-1 product, that we had poor
results with, is too hard for a
sailboat and is really designed for
fast moving motor boat hulls. The ZO
product ablates better at sailboat
speeds. This difference between the
products is not made clear on the
epaint web site, which seems to imply
that the SN-1 is a more powerful
industrial strength product, when
compared to the ZO.
Painting the Hull (2006)
Question: You call painting an
aluminum hull a mug's game yet you
painted your hull?
Answer:
The problem is that Morgan’s Cloud
was built before computerized plate
cutting and bending and like all boats
of the time has a lot of fairing
compound on her to cover small dips
and hollows induced in the plate
fitting process. To have her unpainted
we would have to blast all the fairing
compound off. There would be no
structural problem in doing this; it’s
just that the combination of Jim
McCurdy’s lines and her builders’
execution are so aesthetically
pleasing that we can’t bring ourselves
to take this drastic step.
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