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Michael Prewett · Guest

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

Steve Lusardi · Guest

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" <prewett@tiscali.co.uk> wrote in message
news:45531bff$1_1@mk-nntp-2.news.uk.tiscali.com...

Michael Prewett · Guest

Thanks for that very comprehensive reply; there's a lot of food for
thought there. I'm going to have a first sight of the boat tomorrow, and
I'll be taking printout of your comments with me.

Michael Prewett.

Steve Lusardi wrote:

André Langevin · Guest

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" <stevenospam@lusardi.de> wrote in message
news:eivfls$kve$03$1@news.t-online.com...

Steve Lusardi · Guest

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" <Andre.Langevin_@_mediom.com> wrote in message
news:ej29qn$t54$1@utornnr1pp.grouptelecom.net...

André Langevin · Guest

Hi Steve,

Thanks for your insight ! Altough my cruising ground is fresh water, i do
have an aluminum boat which turns 40 years old next year and it has no sign
of external or internal corrosion whatsoever. It was built from 5032-H34
alloy. I agree from my studies in chemistry that in salt water any
contact with another metal would create a cell and Al has very low
electronegativity. This is why i have 2 magnesium anodes instead of zinc.

The boat can be seen here; www.langevin.biz/marinette34

I am currently budgeting the cost for building a 45 feet aluminum sailboat.
Thus i have to take account into my budget that the aluminum hull has to be
primed inside. But your "rock wool" idea is very interesting also. It
could save me for priming the inside of the hull. Do you have any idea the
basis for comparing wool versus foam or another ? Is it a matter of price
or sound insulation ?

André

"Steve Lusardi" <stevenospam@lusardi.de> wrote in message
news:ej2nr5$cro$02$1@news.t-online.com...

Michael Porter · Guest

Well, each to his own, but I have experienced burning urethane foam
once and was lucky to survive it. Before I put _any_ foam in a boat I
would want to see rigorous test data fromsomeone besides the salesman.

As to other chemicals, consider frayed insulation on a wire behind a
bulkhead that eventually sparks enough against the hull or another
wire to get things going. I've seen it happen,both in boats and in
houses.

Not for me, thanks.

"CS" <colinstone@hotmail.com> wrote: