In article , DSK
wrote:

Peter Wiley wrote:

High carbon steel has somewhat greater tensile strength, but so what.

IIRC the biggest difference is a straighter yield curve,
maybe slightly stronger too. If high carbon steel were
really stronger in tension, they'd make cable from it.

Bad argument. Yachties use s/steel cables and structurally they're
inferior to galv steel cables. Instrument packages often use synthetic
cable, in fact I'm looking at buying 4000m of 12.7 OD with fibre optic
cores for underwater video work.

Steel yacht hulls are massively overstrength anyway, the plate
thickness is set by the need for min thickness for corrosion allowance
over the life of the hull.


It's the best stuff if somebody is going to be shooting at
you,

Only with a peashooter. I can pop a 7x57 or 7.62 NATO round clean thru
1/4" 1020 carbon steel plate at 200m. Done it plenty of times.

or you plan to bounce over a lot of rocks. Other than
that, the only reason I can think of to build a boat of less
than 20 tons (or so) out of steel is because you are already
a skilled metal worker and have a lot of supplies, and
really really like the concept of a bulletproof boat
(although it should be recognized that fiberglass can also
be bulletproof).

I disagree but we've done this argument to death. My personal tradeoff
point is about the 8 tonne mark for a steel boat.

The other bit you missed is that steel lends itself well to 'one off'
builds pretty readily. Fibreglass, at current prices, is better for
mass production from moulds.

I wonder how well a boat would hold up if sprayed both sides
with that plastic pick-up truck bed liner material?

Wondered that myself for the bilge areas where it's hard to inspect and
hard to repaint.

High carbon steel does *not* slow rust appreciably. Some steel alloys
have greater corrosion resistance but this is due to the alloying
elements, not the carbon. In fact, very *low* carbon steel resists
corrosion better than high carbon steel.


IIRC most stainless steels are very very low carbon.

Stainless steels may be low carbon, but that's irrelevant. They're
alloy steels containing a heap of chrome & nickel.


OTOH there is a lot of truth in Joe's statements if you take
them to their logical conclusion and use the highest
carbon material... carbon fiber!

Yep. And the difference in tensile strength between yield point and
ultimate failure point is...... ? Personally I don't like the idea that
what I'm sailing on might crack in half like an eggshell.

PDW