Hull speed theory?
 

In article ,
Jacques Mertens wrote:
How about the Pierre Gutelle book?
I have it in french but it is available in english, Wooden Boat sells it.
I found all the math theory about wave resistance with formulas in the 2nd
chapter then, it is applied in chapter 5.
He also shows a good bibliography listing many papers and books about wave
resistance.
Gutelle may give you all the answers you are looking for.

Thanks, but I think anyone writing on boats is more interested in
applying the theory (of fluid dynamics) than explaining or, indeed,
deriving it.

I'm quite prepared to read a textbook on the subject. It's not
_quantum_ physics...


Sakari Aaltonen

Hull speed theory?
 

In article ,
Stephen Baker wrote:

"THe energy associated with the transverse wave system travels at the "group
velocity" of the waves, which equals one-half of the phase velocity in deep
water. The propulsion system of the ship must therefore put additional energy
into the wave syste, to replace that which "falls behind". A nominal
relationship between ship speed and the length of the corresponding transverse
wave may be found by equating the ship velocity with the _celerity_ (phase
velocity) of a small-amplitude gravity wave in deep water,

Vship = Cwave = sqrt( g.Lw/(2.pi)) = 2.26 sqrt(Lw)

Yes, this is the formula. But what I'm interested in is the theory
it's based on - the general theory of waves in fluids, of which
small-amplitude deep-water surface waves are one particular case.



Thank you,
Sakari Aaltonen

Hull speed theory?
 

Sakari says:

Yes, this is the formula. But what I'm interested in is the theory
it's based on - the general theory of waves in fluids, of which
small-amplitude deep-water surface waves are one particular case.


What you need is not a discussion on the hull-speed theory, but a degree in
fluid dynamics.

;-)

Seriously, however, this is what you need to read, although you may need more
background first.

http://www.amazon.com/exec/obidos/tg...=1058555603/sr
=1-6/ref=sr_1_6/002-5456679-7453635?v=glance&s=books

Steve "application not theory" Baker

Stephen C. Baker - Yacht Designer
http://members.aol.com/SailDesign/pr...cbweb/home.htm

Hull speed theory?
 

In article ,
Al wrote:
Amazing what the net holds, but... I'm not looking for formulas,
I'm looking for the theory behind them. One good book on fluid
dynamics should do it.

can I get back to you in a couple of years when I've done my engineering
degree?

Not on Usenet you can't. Too many Greek letters. Partial derivatives.
Nabla. Stuff.


Sakari Aaltonen

Hull speed theory?
 

In article ,
Stephen Baker wrote:

Seriously, however, this is what you need to read, although you may need more
background first.

http://www.amazon.com/exec/obidos/tg...=1058555603/sr
=1-6/ref=sr_1_6/002-5456679-7453635?v=glance&s=books

Lighthill, James: "Waves in fluids"? Yes, our library has several
copies. However, I happened to pick up "Mathematical theory of wave
motion" by G.R. Baldock and T. Bridgeman; it might be just enough.

But I'm leaving for a three-week sailing vacation on Sunday, and
shall, for some time, be concentrating on real waves instead of
theoretical ones.


Sakari Aaltonen

Hull speed theory?
 

Don't misjudge that book, you clearly have not seen it.
It shows around 50 pages of formulas and graphs just about your question and
Pierre Gutelle is not shy about using math. It is not a vulgarization book.
You need to be fluent in integral calculus to understand those chapters.

--
Jacques
http://www.bateau.com

"Sakari Aaltonen" wrote in message
...
In article ,
Jacques Mertens wrote:
How about the Pierre Gutelle book?
I have it in french but it is available in english, Wooden Boat sells it.
I found all the math theory about wave resistance with formulas in the
2nd
chapter then, it is applied in chapter 5.
He also shows a good bibliography listing many papers and books about
wave
resistance.
Gutelle may give you all the answers you are looking for.

Thanks, but I think anyone writing on boats is more interested in
applying the theory (of fluid dynamics) than explaining or, indeed,
deriving it.

I'm quite prepared to read a textbook on the subject. It's not
_quantum_ physics...


Sakari Aaltonen

Hull speed theory?
 

Hi

"Sakari Aaltonen" skrev i en meddelelse
...
In article ,
Al wrote:
Amazing what the net holds, but... I'm not looking for formulas,
I'm looking for the theory behind them. One good book on fluid
dynamics should do it.

can I get back to you in a couple of years when I've done my engineering
degree?

Not on Usenet you can't. Too many Greek letters. Partial derivatives.
Nabla. Stuff.


Sakari Aaltonen

It's beauty that make a boat fly fast ;))
But you must trust the vision of the designer , ----- boats is not just about
going fast or efficient, but being able to do so by generations´of craftmen and
designers. Colin Archer had the Wave-theorie , that was easily understood, but
this guy scrapped the Viking style hull details, lost the speed got safe
vessels, but a dead end road.
Just like doing a foam boat at the cost of a farm, not to develob new Digital
technology good for making space craft's , but fine to support an old much
bigger petrochemic industrie.
You want speed , ask new technology and hire a Designer, ------ or check the
web.
Look for positive side effects, like ease of building.
P.C.
http://www.designcommunity.com/scrapbook/2648.html

Hull speed theory?
 

Principles of Naval Architecture
www.sname.com

Volume 2

"Sakari Aaltonen" wrote in message
...
In article ,
Brent Benson wrote:

The derivation of the dispersion relationship for gravitational surface
waves on fluids is somewhat complex and not obvious. It is found in many
fairly advanced mechanics texts. You will need to go to a college or
university library to find it.

No problem - I work at a university. Can you name one book?


Thank you,
Sakari Aaltonen

Hull speed theory?
 

it ain't any theory whatsoever. It was merely a "scientific" explanation given
to 19th century British naval brass to "help" them understand why putting 2x
the power in a boat didn't make the boat go 2x the speed.

The "theory" sounded scientific and it had numbers in it and it was called a
theory so the brass accepted it.

most sailboats built in the last several decades will easily exceed
"theoretical" hull speed. in fact, a deep vee hullled Hobie cat (displacement
hull by any standard) at 18 feet will under many points of of sail easily pass
a 45 foot sailboat (also a displacement hull for most every 45 sailboat out
there).

but please use the term, for it lends credibility and pananche when talking to
young lovelies at the yacht club bar.

Hull speed theory?
 

and the sine of zero degrees is what?

(hint: zero, meaning zero needed addition power to "climb the bow wave" at hull
speed)

A "wave" traveling in water, air or even an electromagnetic wave traveling
in a vacuum, is limited by certain rules.

Don't forget, the "wave" may appear to move forward, but the water is only
moving up and down.

--
Dennis Gibbons
S/V Dark Lady
CN35-207
email: dennis dash gibbons at worldnet dot att dot net
"Sakari Aaltonen" wrote in message
...
I have seen lots and lots of references to the formula "X times
square root of waterline length" as defining hull speed with X
normally about 1.3 (speed in knots, length in Imperial feet.)
However, I have never seen an explanation of this.

Pictures of boats "trapped" between their bow and stern waves seem
to make sense. But they do not explain why a long wave would travel
faster than a short one.

Surely there is a book with the theory?


Thank you,
Sakari Aaltonen