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#11
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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 |
#12
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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 |
#13
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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 |
#14
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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 |
#15
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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 |
#16
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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 |
#17
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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 |
#18
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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 |
#19
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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. |
#20
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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 |
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