Jessica B wrote:

At first someone claimed that the waterline difference would be tiny.
I found to be what seems a recent photo where that's not the case, and
now you're claiming it's a relic? I don't get that. Either it can be a
factor or it can't be.


If I may again...

Compare a Catalina 27 and My Catalina 26.

My waterline is 3 inches longer.

That's because the 27 has significant overhangs on both ends.
Overhangs are the part of the hull above the waterline forward or aft of the
waterline/hull point.
If there is a lot of hull forward of where the water meets the hull then you
have a long bow overhang. Same for the stern.

Heeled 30 degrees (quite a bit actually) the 27's waterline length just about
matches my 26's.

Any less heel and the 27 is shorter than the 26. Waterline length that is...

So, what does it mean as far as speed goes?

Three inches is 1/4 of a foot.
So..

1.33 * sqrt (.25) = ?
1.33 * .5 = .665 knots difference In theory, at least.

Which can be easily hidden by sail trim, rudder position, sea state, etc


Yes, I get that current is only a real help in a few instances. What
about the gulf stream example? I don't think that changes direction
does it?

Current is not tide.
Tides change direction. Currents usually do not.


--

Richard Lamb