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Hull speed theory?
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 |
Hull speed theory?
It is not uncommon in nature for waves of different wavelength to have
different speeds. Light waves in transparent media have slightly different wavelength dependent speeds, which leads to dispersion into the spectrum by prisms. 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. The result: wave speed is 1.3 times sq rt of wavelength, where the 1.3 is a combination of the gravitational constant and water density. Brent www.bensonsails.com From: (Sakari Aaltonen) Organization: Helsinki University of Technology Newsgroups: rec.boats.building Date: 16 Jul 2003 05:54:55 GMT Subject: Hull speed theory? 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 |
Hull speed theory?
|
Hull speed theory?
Sakari, there is a Usenet group that discusses hydrodynamics but I can't
remember the exact name. The word "fluid" was part of it. -- Jacques http://www.bateau.com "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?
sci.engr.marine.hydrodynamics - but this is not very active.
However, you might find what you need by doing a Google search in the "Groups" section for "hull speed". There was a large tread about hull speed in rec.boats.builder a couple years back. You'll find more opinions than you ever wanted... Regards, Don Donald M. MacPherson VP Technical Director HydroComp, Inc. email: http://www.hydrocompinc.com tel (603)868-3344 fax (603)868-3366 "Jacques Mertens" wrote in message .. . Sakari, there is a Usenet group that discusses hydrodynamics but I can't remember the exact name. The word "fluid" was part of it. -- Jacques http://www.bateau.com |
Hull speed theory?
In article ,
D MacPherson wrote: sci.engr.marine.hydrodynamics - but this is not very active. However, you might find what you need by doing a Google search in the "Groups" section for "hull speed". There was a large tread about hull speed in rec.boats.builder a couple years back. You'll find more opinions than you ever wanted... Thanks, but I'm not looking for _opinions_, really. I went to the library today and found quite a number of books on fluid dynamics. Some had sections on surface waves; the mathematical derivation shows, indeed, that the propagation speed of such a wave is directly proportional to the square root of the wavelength. I'll need some time to work through that derivation...:-) Sakari Aaltonen |
Hull speed theory?
Sakari Aaltonen ) writes: Thanks, but I'm not looking for _opinions_, really. I went to the library today and found quite a number of books on fluid dynamics. Some had sections on surface waves; the mathematical derivation shows, indeed, that the propagation speed of such a wave is directly proportional to the square root of the wavelength. I'll need some time to work through that derivation...:-) well, you start with V = N x L where V = wave velocity, N = frequency of vibration, and L = length of wave. that dosn't give you the square root of wavelength, but something about the boat sitting down into the wave trough gives an equation with boat length (water line length) as a factor but darned if I remember how. I've seen it in one or two library books but never wrote it down. you'll have to post the derivation so its preserved in the newsgroup archives for all time. -- ------------------------------------------------------------------------------ William R Watt National Capital FreeNet Ottawa's free community network homepage: www.ncf.ca/~ag384/top.htm warning: non-freenet email must have "notspam" in subject or its returned |
Hull speed theory?
"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. What confuses me is the variability of the 1.3 value depending on the source. |
Hull speed theory?
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. You'll see why that hull speed formula is very crude. The French title is "Architecture du Voilier", volume 1 of 3. -- Jacques http://www.bateau.com "Sakari Aaltonen" wrote in message ... In article , D MacPherson wrote: sci.engr.marine.hydrodynamics - but this is not very active. However, you might find what you need by doing a Google search in the "Groups" section for "hull speed". There was a large tread about hull speed in rec.boats.builder a couple years back. You'll find more opinions than you ever wanted... Thanks, but I'm not looking for _opinions_, really. I went to the library today and found quite a number of books on fluid dynamics. Some had sections on surface waves; the mathematical derivation shows, indeed, that the propagation speed of such a wave is directly proportional to the square root of the wavelength. I'll need some time to work through that derivation...:-) Sakari Aaltonen |
Hull speed theory?
Here's a quote from a reputable source (which I won't name since they may not
like it) that explains it - sort of. "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) where Cwave = celerity or phase velocity of the wave in ft/sec and Lw = length of the transverse wave in feet. This can be converted into speeds in knots: Vs = 1.34.sqrt(Lw) (sorry, no workings shown - trust me) William Froude first pointed out the practical limiting speed for surface-displacement ships whe he observed that "the speed with which wave resistance is accumulating mosr rapidly, is the speed of an ocean wave the length of which, from crest to crest, is about that of the ship from end to end" (Froude 1955 p.280) This condition is found by substituting the length of the ship for the length of the wave, giving a relationship commonly referred to as the _hull speed_, or critical speed-length ratio: Vs/sqrt(Ls) = 1.34 end quote And there you have it. Steve |
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 |
Hull speed theory?
bye-bye.
this subject has been tossed around far too many times on the net and always always always always those who read it somewhere *insist* it is a Law of Physics. it ain't. |
Hull speed theory?
Now look what you have done. I told you so.
-- Glenn Ashmore I'm building a 45' cutter in strip/composite. Watch my progress (or lack there of) at: http://www.rutuonline.com Shameless Commercial Division: http://www.spade-anchor-us.com |
Hull speed theory?
Don't forget, the "wave" may appear to move forward, but the water is only
moving up and down. To be more accurate - it is going round and round. There is an up and down component, to be sure, but ....... Steve |
Hull speed theory?
Mathematical modelling, even with things as simple as earth surface gravity,
always involves a hypothesis regarding the physical principles involved. If the apparent results line up with the hypothesis, the "theory" could be said to be correct. In the case of Hobie Cat versus 45 footer, one only has to look at the theory in a different way, one that takes slenderness into account. Obviously, as a given hull becomes finer, less wavemaking potential exists, and load carrying ability of the hull diminishes. As the extreme of a knife edge in the water is approached, load carrying capability approaches zero, and friction with the water becomes the dominant drag force, making wave drag less relevant, as friction becomes greater and greate compared to wave drag. The opposite extreme is found in hovercraft, where there is little friction (in smooth water), and the body making the wave is broad, and wave making theory comes into play, with friction of minor concern. (High drag in rough water is a problem with hovercraft, which may be overcomeable, but not at all explored by the industry.) To analyse the wave making problem on my surface skimmers, I took a different approach from classical marine analysis, and got roughly the same results. I assumed the craft influences a semi-circle section of water under it and gives that body of water a downwards force, the vertical momentum of which is the dynamic lift on the hull, as lift from displacement diminishes as forward speed builds. Whadiya know, it works for broad barge-like hull bottoms with no friction. After all, the theory of earth surface gravity breaks down when you start to get away from the earth's surface, yet we use the theory in many engineering endeavors. (When you leave the planet, Neutonian physics "theory" breaks down.) Subject: Hull speed theory? From: (JAXAshby) Date: 7/20/03 5:52 AM Pacific Daylight Time Message-id: 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). Barry Palmer, for A HREF="http://members.aol.com/sevtec/sev/skmr.html"Sevtec/A |
Hull speed theory?
That subject line always has great success: close to 100 messages each time
and always the same guys splitting hairs. Now that it is running out of steam, what do you think is the best epoxy and should I use cheap plywood? -- Jacques http://www.bateau.com "Glenn Ashmore" wrote in message ... Now look what you have done. I told you so. -- Glenn Ashmore I'm building a 45' cutter in strip/composite. Watch my progress (or lack there of) at: http://www.rutuonline.com Shameless Commercial Division: http://www.spade-anchor-us.com |
Hull speed theory?
Jacques Mertens wrote: That subject line always has great success: close to 100 messages each time and always the same guys splitting hairs. Now that it is running out of steam, what do you think is the best epoxy and should I use cheap plywood? No, Antifreeze, wallpaper paste and curtain liner are all you need. :-) -- Glenn Ashmore I'm building a 45' cutter in strip/composite. Watch my progress (or lack there of) at: http://www.rutuonline.com Shameless Commercial Division: http://www.spade-anchor-us.com |
Hull speed theory?
Barry Palmer wrote: Mathematical modelling, even with things as simple as earth surface gravity, always involves a hypothesis regarding the physical principles involved. If the apparent results line up with the hypothesis, the "theory" could be said to be correct. In the case of Hobie Cat versus 45 footer, one only has to look at the theory in a different way, one that takes slenderness into account. Obviously, as a given hull becomes finer, less wavemaking potential exists, and load carrying ability of the hull diminishes. As the extreme of a knife edge in the water is approached, load carrying capability approaches zero, and friction with the water becomes the dominant drag force, making wave drag less relevant, as friction becomes greater and greate compared to wave drag. A hobie is a different study. The side of the hull may be considered as part of a system most easily understood as one hull lifts clear of the water, balanced somewhere between the sideways, upwards and downwards forces acting on the sail and the keel effect of the more deeply submerged lee hull. The balancing act works because it uses the keel area of the side of the hull as a planing surface. The lift from planing is not vertical, but presents a vertical component in a vector analysis of all the forces at work. If you have ever ridden one, you can see the flat water behind the lee hull. A hobie on one hull is not in pure displacement mode any more. The narrownwess of the hull means it does not make a large hole in the water, requiring energy to move a lot of water aside. A hobie does not climb over it's bow wave, it slices like an edge on a ski on ice. It works more like a skipping stone. I do not know why someone has not built a catamaran with flat bottom rails angled so as to enable a more stable balancing act, with perhaps 10 % of the weight still on the windward hull, supported by the flat portion on plane. There would still be a possibility that a lump in the water would launch the windward hull towards orbit. It would still require twice the level of concentration as driving a car on only two wheels. The opposite extreme is found in hovercraft, where there is little friction (in smooth water), and the body making the wave is broad, and wave making theory comes into play, with friction of minor concern. (High drag in rough water is a problem with hovercraft, which may be overcomeable, but not at all explored by the industry.) To analyse the wave making problem on my surface skimmers, I took a different approach from classical marine analysis, and got roughly the same results. I assumed the craft influences a semi-circle section of water under it and gives that body of water a downwards force, the vertical momentum of which is the dynamic lift on the hull, as lift from displacement diminishes as forward speed builds. Whadiya know, it works for broad barge-like hull bottoms with no friction. After all, the theory of earth surface gravity breaks down when you start to get away from the earth's surface, yet we use the theory in many engineering endeavors. (When you leave the planet, Neutonian physics "theory" breaks down.) Subject: Hull speed theory? From: (JAXAshby) Date: 7/20/03 5:52 AM Pacific Daylight Time Message-id: 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). Barry Palmer, for A HREF="http://members.aol.com/sevtec/sev/skmr.html"Sevtec/A -- Terry K - My email address is MY PROPERTY, and is protected by copyright legislation. Permission to reproduce it is specifically denied for mass mailing and unrequested solicitations. Reproduction or conveyance for any unauthorised purpose is THEFT and PLAGIARISM. Abuse is Invasion of privacy and harassment. Abusers will be prosecuted. -This notice footer released to public domain. Spamspoof salad by spamchock - SofDevCo |
Hull speed theory?
Barry Palmer wrote: The poster is adding another factor, side load, when the hull is forced by a sail but we are referring to hump generating capability, where it should be stated that rationality would assume side load were low or negligble unless otherwise stated. However, the aspect of the Hobie Cat "planing" on its outboard topsides (sounds weird, I know, to a monohull sailer) is another story. Isn't a Hobie faster in a broad reach, where side loads are small, than with one hull flying, where side loads are great, close to the wind? Not to forget, hobies have no centerboard and do not go to windward as well as boats that do, except during a few perilous seconds while control may be maintained. While one one hull, they slide sideways (upwards?) as well as foreward, and steering gets wonky too. I think it's a control problem and some one is gonna get it tuned just right one day. Perhaps a few square inches of skeg / keel / lifting foil in the right place would work out? At speed, a little surface area could do a lot. The world in't over, yet. Advances are still to be made. The 'bump in the water' idea doesn't go away, it just looks like a square or maybe triangular wave, instead of a sinusoidal dent. The harmonic content in the waves created contain energy left behind by the boat as it passes, as well as the tonic wave left behind a displacement or a planing hull. Planing lift is a result of the reaction to moving the water out of the way of the hull, which happens at a rate of accelleration determined by the speed of passage. The faster you plane, the less water need be moved, but the lift is proportional to the 4th power, I believe, of the speed, or the cube of the accelleration. Or was that the square of the accelleration of the water. Ahhh, all that math was so long ago, so unused since. Gotta go now, to deliver meals on wheels. G'day, eh? On a hobie at the tilt, the water is pushed only one way, partly sideways, partly downward, not out both sides and down without the 'recoil' energy which pushes a displacement hull foreward, but is left behind by a planing boat. Only the 'bottom' side of a hobie hull planing on one foot is wet, reducing friction synergistically to the energy system examined. Terry K Barry Palmer wrote: Mathematical modelling, even with things as simple as earth surface gravity, always involves a hypothesis regarding the physical principles involved. If the apparent results line up with the hypothesis, the "theory" could be said to be correct. In the case of Hobie Cat versus 45 footer, one only has to look at the theory in a different way, one that takes slenderness into account. Obviously, as a given hull becomes finer, less wavemaking potential exists, and load carrying ability of the hull diminishes. As the extreme of a knife edge in the water is approached, load carrying capability approaches zero, and friction with the water becomes the dominant drag force, making wave drag less relevant, as friction becomes greater and greate compared to wave drag. A hobie is a different study. The side of the hull may be considered as part of a system most easily understood as one hull lifts clear of the water, balanced somewhere between the sideways, upwards and downwards forces acting on the sail and the keel effect of the more deeply submerged lee hull. The balancing act works because it uses the keel area of the side of the hull as a planing surface. The lift from planing is not vertical, but presents a vertical component in a vector analysis of all the forces at work. If you have ever ridden one, you can see the flat water behind the lee hull. A hobie on one hull is not in pure displacement mode any more. The narrownwess of the hull means it does not make a large hole in the water, requiring energy to move a lot of water aside. A hobie does not climb over it's bow wave, it slices like an edge on a ski on ice. It works more like a skipping stone. I do not know why someone has not built a catamaran with flat bottom rails angled so as to enable a more stable balancing act, with perhaps 10 % of the weight still on the windward hull, supported by the flat portion on plane. There would still be a possibility that a lump in the water would launch the windward hull towards orbit. It would still require twice the level of concentration as driving a car on only two wheels. The opposite extreme is found in hovercraft, where there is little friction (in smooth water), and the body making the wave is broad, and wave making theory comes into play, with friction of minor concern. (High drag in rough water is a problem with hovercraft, which may be overcomeable, but not at all explored by the industry.) To analyse the wave making problem on my surface skimmers, I took a different approach from classical marine analysis, and got roughly the same results. I assumed the craft influences a semi-circle section of water under it and gives that body of water a downwards force, the vertical momentum of which is the dynamic lift on the hull, as lift from displacement diminishes as forward speed builds. Whadiya know, it works for broad barge-like hull bottoms with no friction. After all, the theory of earth surface gravity breaks down when you start to get away from the earth's surface, yet we use the theory in many engineering endeavors. (When you leave the planet, Neutonian physics "theory" breaks down.) Subject: Hull speed theory? From: (JAXAshby) Date: 7/20/03 5:52 AM Pacific Daylight Time Message-id: 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). Barry Palmer, for HREF="http://members.aol.com/sevtec/sev/skmr.html"Sevtec -- Terry K - My email address is MY PROPERTY, and is protected by copyright legislation. Permission to reproduce it is specifically denied for mass mailing and unrequested solicitations. Reproduction or conveyance for any unauthorised purpose is THEFT and PLAGIARISM. Abuse is Invasion of privacy and harassment. Abusers will be prosecuted. -This notice footer released to public domain. Spamspoof salad by spamchock - SofDevCo Barry Palmer, for A HREF="http://members.aol.com/sevtec/sev/skmr.html"Sevtec/A -- Terry K - My email address is MY PROPERTY, and is protected by copyright legislation. Permission to reproduce it is specifically denied for mass mailing and unrequested solicitations. Reproduction or conveyance for any unauthorised purpose is THEFT and PLAGIARISM. Abuse is Invasion of privacy and harassment. Abusers will be prosecuted. -This notice footer released to public domain. Spamspoof salad by spamchock - SofDevCo |
Hull speed theory?
Fred Williams says:
How 'bout swim fins and a snorkel mask? Cheap'r 'n' a real boat, but dang tough to heat.... And, of course, you have that really short waterline, so speed's a problem ;-P Steve. |
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