On Mon, 21 Mar 2011 16:48:18 -0700, Jessica B
wrote:

On Thu, 17 Mar 2011 13:07:57 -0400, "Wilbur Hubbard"
wrote:

"Bruce in Bangkok" wrote in message
. ..
On Wed, 16 Mar 2011 16:02:48 -0700, Jessica B
wrote:
snip


Ok... so if you have boat that'll go 10 mph and the reverse tide is
pulling you at 5 mph vs. you have a boat that'll only go 5 mph....

You are still looking at speeds in excess of what the "normal"
cruising boat is capable of sustaining for any cruise.


No Jessica is NOT. For example, my fast, blue water yacht, "Cut the Mustard"
made a passage from Mobile Bay to Egmont Key (Tampa Bay). The time from sea
buoy to sea buoy was 36 hours. The distance was 300 miles.

300 divided by 36 = 8.3 mph average! The LWL of my fine yacht is 22 feet.
Theoretical hull speed is only about seven knots. But, as you can see, the
theory doesn't always describe fact. So, Jessica is not talking speeds in
excess of normal. If my small yacht can average 8.3mph then imagine the
speeds a fast sailing yacht with a LWL of forty feet could average.

Now, Bruce, if you had ever sailed a real fast cruising boat and not that
big fat rotten old tub you live at the dock in you might have gotten around
the world in half the time it took you just to get to Thailand.


Wilbur Hubbard


Hmmm... well, I looked up theoretical boat speed... 1.34 x the root of
LWL. But, I read that when the boat leans (heels) then the LWL would
get longer, so the theoretical speed would go up right? Also, what
about the water moving. If it's going in the same direction, then that
would decrease the time you spend traveling.

Goodness Jessie, but you seem to be learning about boats.

You are talking about boats designed with long overhangs, usually
relics of an old racing rule system that penalized unduly long
waterlines. Modern boats are designed with nearly vertical ends which
benefit very little from being heeled.

Another point is that boats sail fastest when vertical and heeling
results in a less efficient hull form which theoretically is slower so
speed under sail is very much a trade-off between caused by carrying a
lot of sails and the angle of heel that is decreasing the hulls
efficiency.
Cheers,

Bruce
(bruceinbangkokatgmaildotcom)