Stainless Steel Yacht ?

[noelex 77]

Originally Posted by Ctrich

a short list of pro's and con's.?

I had dinner on a SS yacht a few years ago. It was a large Ketch
The yacht had replaced all the deck because of corrosion under the teak, but from what I understood (there was some language difficulty) this was not due to crevice corrosion, but caused because the deck was mild steel and only the hull was SS.
The only other thing I remember was that he said it was nightmare getting antifouling paint to stay on.
Unfortunately I have not seen the Yacht for several years and they did not have email.

[delmarrey]

Originally Posted by Boracay

and some would need to be painted.

Painting SS is not an option. It will not stick. Paint trucks for road striping use all SS parts just for that reason!!!! The same with monel.

[estarzinger]

Originally Posted by delmarrey

Painting SS is not an option. It will not stick. . . .!!!! The same with monel.

Geeze, why the yelling. Our friends with SS boats all have epoxy barrier coats with anti-fouling over on the hull bottoms (And also all have boot stripes painted on and deck paint), and we ourselves painted a stainless centerboard trunk we had custom made in NZ (for our old boat). If you do it carefully it works just fine, like with aluminum.

Interlux's instruction for painting stainless:

http://www.yachtpaint.com/Literature...ar_usa_eng.pdf

Jotun primer recommended for stainless:

http://www.jotun.com/jotun/paints/20...26.11.2010.pdf

[delmarrey]

OK, I toned it down a bit. But I can guarantee that if it gets a good smack or scratch, that the spot will start a peeling process.

The reason SS was made in the first place was as a STAINLESS steel, which means nothing will stick to it. It's the teflon of steels.

It's surface would have to be abraded like micro stones so that paints and other coating have something to grab. Rubber would make a better bonding agent because it would be able to take a hit w/o delaminating. But a scrape would still pull it off.

If you notice in the painting instructions it has to be blasted and treated with a dry solvent to a perfectly clean surface and then painted w/in a couple hours. It would have to be sprayed on in order to get it all on in that time.

The chromium in the steel combines with oxygen in the atmosphere to form a thin, invisible layer of chrome-containing oxide, called the passive film. The sizes of chromium atoms and their oxides are similar, so they pack neatly together on the surface of the metal, forming a stable layer only a few atoms thick. If the metal is cut or scratched and the passive film is disrupted, more oxide will quickly form and recover the exposed surface, protecting it from oxidative corrosion.

If I were to build a boat of SS I would use an A-20 material for the bottom and not worry about the paint. >>> Alloy 20 Stainless Steel | A20 Stainless Steel - Warren Alloy
This is what we use in the valve industry for chemical valves, which commonly have to be oxygen washed for the same reason (sanitary).

BTW- The passive film requires oxygen to self-repair, so stainless steels have poor corrosion resistance in low-oxygen and poor circulation environments. In seawater, chlorides from the salt will attack and destroy the passive film more quickly than it can be repaired in a low oxygen environment.
SS needs to breathe!

[Capt.Fred]

Just build your boat out of epoxy, matt and cloth. Squeejee out the bubbles, do not rolled them out. Over the gel coat in the mold apply a coat of black resin to block U-V's. Install at least 3/4" closed cell fexible foam insulation between inner and outer hull....Now you will have a boat that will survive reefs and last several hundred years worry free...!
I self designed and built my 50' 23 ton Daedalus from an assortment of polyestyer and epoxy resins and launched her 35 years ago. She is USCG certified, sailed almost daily and will last indefinately into the future. One problem was the the top fiberglass over the saturated balsa insulation on the forward deck was replaced after 25 years. No big deal! Also, this big boat is run up on steep-to undeveloped beaches every day for the passengers to comfortably climb down to explore or swim. I sold her 10 years ago.
Capt.Fred Saas...see my album...
I understand bullet proof vests are made out of epoxies and so is the armament on Israeli tanks

[Tanielle]

I am building a Hoek Design Truly Classic 79ft to Lloyds. See tanielle.com.au

First decision was hull material and I favoured Corten having had a yacht with a Corten hull but mild steel frames. Lloyds refused Corten, Ibelieve due to brittleness in very low temperatures. So finally we went ahead with Duplex stainless steel (SAF 2205). Using a pulsed MIG welder we tested a 30mm x 6mm flat bar welded join, and it took 3 attempts with a 100t brake press to break the piece.

The stainless is painted inside and out with International 820 primer 4 coats and the 3 coats of Jotun glass flake.
Duplex is a mixture of high tensile steel and austentic stainless, if there is too much heat introduced the phase may change ie it reverts to mainly one or the other. We tested this using a ferrite scope to give the percentage of ferrite . Lloyds insisted on qualifying the welders and
XRaying the welded hull. The mill certificates with the plates showed an average yield strength of 780mpa. 316L is 290mpa.
A little known fact is that all hi-tensile steels suffer from hydrogen embrittlement. This occurs in warm waters ie above 26deg C and then the zinc anodes react with the duplex (at 750mv ) to create hydrogen which migrates into the steel.Of course this cannot happen if the paint barrier is sufficient to prevent the salt water acting as a conductor.
In the offshore oil industry with extensive use of duplex this is countered by connecting the anodes via a diode that limits the current to 700 mv .
We are doing the same, and in addition limiting stress areas to 350 mpa, using finite element analysis , as this also affects hydrogen migration. All underwater parts are duplex including prop shaft and custom folding prop and valves.
The stainless was indeed expensive at around 25% of complete build cost but she can hit a container a hull speed and only scratch the paint.

[GordMay]

Greetings and welcome aboard the CF, Tanielle.

[IslandHopper]

Very nice lines.....

https://tanielle.com.au/

[Psy at SEA]

Wow....beautiful

[Tanielle]

Thank you GordMay don`t know why I didn`t join earlier.
Island Hopper you`re very kind. The web is still a work in progress and if you click on the 3 bars on top right of the sea pic it will show you the build pics.
Psy at Sea thank you

[Psy at SEA]

OMG ...when will she go to the water?



Congratulations she is a masterpiece....well done.

[capn_billl]

I just looked at a boat that used a kevlar layer in the glass mat.

[delmarrey]

Tanielle,

Very nice! Wish I could be there for the build.

And Welcome to the forum.

[leftbrainstuff]

Stainless is definitely not the ideal material to build a yacht from. We probably also need to qualify what stainless? 300, 400, duplex, etc.

In terms of metals Titanium would be my preference for an 'ideal' metal for a boat.

But in reality I'll stick with composites...

[leftbrainstuff]

Originally Posted by s/v Beth

Getting into welding and machining has made me realize that there is a whole bunch of materials out there that may be great for construction but may cost a little more. I priced quarter inch steel, Aluminum and Stainless Steel plate- the costs were 150, 350 and 550 for a 4 by 4 plate. Higher but doable.
I went on to Yachtworld and saw- there are a few SS yachts out there. I would think this would be the ultimate material- if it has a high enough Chromium level it would be highly rust resistant, tough and and last forever with very little care. Anyone that has one care to comment?

Originally Posted by leftbrainstuff

Stainless is definitely not the ideal material to build a yacht from. We probably also need to qualify what stainless? 300, 400, duplex, etc.

In terms of metals Titanium would be my preference for an 'ideal' metal for a boat.

But in reality I'll stick with composites...

Is this ss boat actually being built?