Andre,
Yes, it does, with caviats. Aluminum is very reactive in salt water. The
5000 AISI series is specifically intended for marine use. Do not use other
aluminum alloys. Do not electrically connect any other metal above or below
the waterline. Do use a cromate based primer. Do not believe any paint
company's assurances of performance from cromate free paints without making
tests yourself. I have seen many, many failures. In fact I have only seen
one truly successful aluminum yacht. It was built by an Australian Navel
Architect. It was 35' in length. He was so anal about mixing metals,
everything was aluminum, including the prop and shaft. I was there when he
took it out of the water on the Isle of Wight after 3 continuous years of
cruising. He had 10' long grass growing from the hull and absolutely NO
corrosion. So it is possible to be successful, but you will not acheive it
with out of the box components.
Steve

"André Langevin" wrote in message
...
Very good comment indeed Steve. I'll also keep for later usage. Would
your recommandations also stand for an aluminum hull ? I know it has to
be insulated but i remember to have read that in order for adherence to
the aluminum, this later has to be etched and primed.

André

"Steve Lusardi" wrote in message
...
Michael,
I am a builder and owner of a large steel boat. Insulation is absolutely
necessary in a steel hull. Corrosion is no problem on the outside, but
can be a nightmare on the inside. Condensation is the culprit. The
solution is to seal the interior metal surfaces from exposure to air.
This is especially true for those surfaces that are hard to get to. That
requirement is best met by sprayed urethane foam on top of a quality
paint scheme. It has incredible adhesion qualities. It is fast to apply,
but extensive masking is required. It has some disadvantages, it is
expensive. It is not a closed cell foam, so it can absorb liquids over
time, which are not removable without gutting the foam. It outgases for a
long time, some of which can be harmful. When exposed to fire, the gasses
created are deadly. Once sprayed and cured, it should be painted with a
waterbased flame retardant paint. This will seal the foam countering the
disadvantages somewhat. Polystyrene foam is another choice. It is of the
closed cell variety, it is less expensive, it is not as messy as urethane
and it has a better R rating. It is harder to use because the adhesives
are slow curing. Volatile adhesives will dissolve the foam. Because of
this, it is slower to apply, as clamping is required. It does NOT seal
the steel from exposure to air, so the foam must be additionally sealed
with plastic sheet and outgassing in fire is also a problem as with
urethane. Another choice worth considering is rock wool. It is less
expensive than styrene, faster to install than styrene and can be
purchased in a roll with one side bonded with a plasticized aluminum foil
which will aid in sealing the metal surfaces from air as well as having a
much better R rating and an infra-red reflector. Probably the most
endearing quality Rockwool has is ease of maintenance and accessibility.
It is easy to remove and replace if it gets wet, as well as being fast to
remove in an emergency. One last point that is related is bilge
protection, which is also critical in steel hulls. Your insulation must
not go much lower than the waterline, typically only to the cabin sole.
So where water congregates requires special attention. There, you want to
derust at well as possible. then use a rust converter like a weak
solution of phosphoric acid or a commercial equivalent like Fertan, wash
out well with water. then an etching two part epoxy primer followed by a
compatible bilge paint. But, where water can sit, additionally spray that
area with a special marine paraffin based wax similar to Ziebart for
cars. This material never quite hardens and continually seals against
water. Completing these steps with just occasional maintenance will allow
the hull to remain viable for well over 100 years. One last note,
commercial ships and super yachts use Rockwool and the paraffin wax
solutions almost universally.
Steve



"Michael Prewett" wrote in message
...
I'm considering purchasing a small steel-hulled yacht, but she does not
have any insulation. I would imagine that the immediate problems in a
European summer will be excessive heat,condensation, and to a lesser
extent, noise. Retro-fitting insulation is an option, possibly in
stages, and I'm wondering whether anyone would have some views on this.
My initial thoughts tend toward the use of foam board, room permitting.
(I know that Alubat offer foam insulation as an option on their
aluminium boats, fitting boards between frames, but I don't know what
material they use - I would imagine that it is some form of
polyurethane).

Michael Prewett