Welcome back Jax.

We are looking forward your enlightening explanation of how to calculate
hull power requirements.

Mark Browne

top posting corrected

"JAXAshby" wrote in message
...
try Dave Gerr, for power required. He makes some dumb comments regarding
theory
but his formulae are "close enough" to be more than useful for specific
power
needed for specific speeds for "displacement" type boats. Double check
with
your propeller vendor, and LISTEN to them, for they have some views that
don't
necessarily map one to one with DG's thoughts.

btw, Bob Perry publicalycalled me "an asshole" (his words, several times)
for
pointing out that a sine function does not EXPLODE at zero degrees (in
fact it
does nothing at all at zero degrees), which of course means that tens of
millions of people across the country are -- by Bob's definition --
"assholes"
for knowing from sine functions.


I did a little digging on the US navy training sites, as related to ship
design and propulsion.
I saw a fair amount on traverse wave systems, with analysis on wave-making
resistance as affected by beam to length ratio,
displacement, shape of hull, Froude number (ship length & speed), skin
resistance, laminar flow, and interaction between the drive system and the
hull. Most of it was fairly simple and easy to follow.

It would seem that the traverse wave system is the key to understanding
"hull speed".

The traverse waves travel at approximately the same speed as the ship
- At slow speeds, several crests exist along the ship length because the
wave lengths are smaller than the ship length
- As the ship increases speed, the length of the transverse wave increases
- As the wave length approaches the ship length, the wave making resistance
increases very rapidly
- When the transverse wave length equals the ship's length the vessel has
reached its HULL SPEED
It takes energy to produce waves, and as speed increases, the energy
required is a square function of velocity!
(Wave making resistance drastically increases above hull speed)


Here are my source links.
http://www.usna.edu/NAOE/courses/en2...efficients.ppt
http://www.usna.edu/NAOE/courses/en2...es/chap7_a.ppt
http://web.usna.navy.mil/~phmiller/en200/Chapter7.ppt
http://www.gidb.itu.edu.tr/staff/emi...cteristics.pdf
Some of these are long links - you may have to cut-n-paste to follow them.
The files are in PowerPoint or PDF format.
Most Military training material comes this way - sorry if you have trouble
reading it.
If you are on a Microsoft platform you can download free viewers (Search for
viewer) from Microsoft at:
http://office.microsoft.com/

Jax,
Help me out here; I seem to have missed the sine function thing.
Would you please elaborate?
Perhaps just a link to it and I will read up on it myself?

Mark Browne