wrote:

Skipper wrote:
There are differences in the Specific gravity of salt vs. freshwater,
and Atlantic vs.Pacific waters. Wondering how this effects boat speed.
Are boats faster in Pacific waters? Are boats faster in sal****er? Seems
to me a boat would ride higher in sal****er and thus be faster in an
equal sea state.

Boats do float at different heights in fresh vs. salt water.

Check the plimsoll lines on tankers and container ships, for instance.
They are calibrated for fresh and salt, and also for differences in
water temperature.

That said, one has to wonder whether the resistance of the denser
medium wouldn't just about cancel out the tendency to float the vessel
slightly higher. For most boats, the difference is probably measurable-
but so slight it would only be significant to the most extreme nit
pickers.

I've experienced a consistent 2 MPH delta with a planning hull at WOT
from fresh to salt. That translates into a 6% difference. Even though
that's been my observation, it just doesn't seem right. I'm also curious
about the East/West Coast speed delta. Suspect there is one. Bet there
is also a corresponding fuel penalty for displacement hulls due to this
effect. Perhaps one of the boating rags will publish some data on this
in the future. Would seem the mix of fresh and salt you have in your
area would have had someone looking into this...

--
Skipper

Skipper wrote:


I've experienced a consistent 2 MPH delta with a planning hull at WOT
from fresh to salt. That translates into a 6% difference. Even though
that's been my observation, it just doesn't seem right. I'm also curious
about the East/West Coast speed delta. Suspect there is one. Bet there
is also a corresponding fuel penalty for displacement hulls due to this
effect. Perhaps one of the boating rags will publish some data on this
in the future. Would seem the mix of fresh and salt you have in your
area would have had someone looking into this...

--
Skipper

The challenge with a real-life comparison is that it would never be
possible to change only the salinity and temperature of the water.
Differences in wind and current would dwarf any tiny difference between
fresh and salt buoyancy. There's no way to duplicate wind
and current, exactly, in any two locations even pretty nearby in Puget
Sound....and there will alway be more or less wind, and typically less
current, inside the locks in the fresh water. The best test for this
difference would probably be conducted in a test tank at one of the
boat factories, but I doubt they have any provision for filling their
tanks with sal****er.