joe, what do you expect me to say? i have never encounterd a field of hunman endeavor where uninformed opinion is stated as loudly as fact as i have in sailing. the fact that someone had a boat going a certain velocity does not mean it was going that velocity through the water. if you can't get this concept, do not turn the page in the fluid dynamics book.
gps & depth sounder
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Morty,
I guess the point is getting the boat above the water. Less displacement, more sail area. After all, what is the explanation for 20' planing dinghies that go faster than our C-30? In PHRF, a Melges 20 or a Viper are rated way faster than ANY Catalina. It's just a fact. That is absolutely a variance to the theoretical hull length/speed limit. You have to admit there are more design issues and characteristics to consider than just length. You seem to be arguing that the earth IS flat and nothing could possibly change that "fact", when it's demonstrated all over the globe that some sailboats can go faster than "hull speed", even when cancelling out the effects of current and waves... (we agree not Catalina 30's, though)
Rob
I guess the point is getting the boat above the water. Less displacement, more sail area. After all, what is the explanation for 20' planing dinghies that go faster than our C-30? In PHRF, a Melges 20 or a Viper are rated way faster than ANY Catalina. It's just a fact. That is absolutely a variance to the theoretical hull length/speed limit. You have to admit there are more design issues and characteristics to consider than just length. You seem to be arguing that the earth IS flat and nothing could possibly change that "fact", when it's demonstrated all over the globe that some sailboats can go faster than "hull speed", even when cancelling out the effects of current and waves... (we agree not Catalina 30's, though)
Rob
Surfin'
Happens all the time.
My boat goes waaay above THS when we're coming in The Gate on big waves.
Not really unusual at all.
rob, when a hull planes, it's ON the water not IN the water. maybe you've seen a sailboat with a keel plane, but i have yet to. hull speed for a planing body is meaningless since the hull is not in the water. i spent time desinging and testing floats for airplanes and never heard the float bottom referred to as a hull.
Did you even bother to look at the links I provided? Do you think I don't understand what theoretical hull speed.... displacement speed... means? Morty.... there are many examples of displacement hulls going faster than the bow wave they create....... a kayak is one... please, read the articles..
Our discussion is not about the difference between speed through the water and speed over ground. It is about your reference to a displacement vessel not being able to exceed theoretical hull speed. You said no.... I said yes..
As a scientist or engineer, you should at least be curious.... but your argument is close minded, with no supporting evidence. I provided some content to support my position. You, however, have not provided anything other than mentioning a course you took in "fluid dynamics".... and the fact that you have a masters degree in aerodynamics.
Look Morty, you can get all indignant at my stupidity.... but that doesn't validate your point.... so lose the rhetoric and try to prove your point... or let it go....
The misconception is that people think the theoretical hull speed is some kind of magic, absolute speed limit.... which it is not.
Joe, right on. I think it would behoove "some people" to read up a tad on displacement, semi-displacement and planing hulls, too.
what in heavens name makes you think a kayak is a displacing hull? i'm done with this thread. is a seaplane float a hull because it dislaces water? i suggest you find out the difference between hysdrostatics and hydrodyamics before the next bite you can't swallow. but you are correct in assuming my five years of college and all the salary i was paid was for nothing. an opinion at the dock would have sufficed, and a catalina 30 dropped from a crane does go much faster than hull speed.
and i am not indignant about your stupidity. i am on this web site because of how much i still don't know and because i can help others with what i do know. if your literature says a displacing hull can exceed hull speed in still water, you are correct, i have no inerest in reading it. if this is in fact true it would not be buried in a web site. paper and ink reject nothing.
AND, fyi, conce a canoe reaches a particular speed it is in a very different hydrostatic environment from the lower speed, know as 'getting up on the step' unless the canoes where you are very heavy and/or have keels.
Morty..... please don't freak out.... I simply asked you to take a look at the links I provided and to open your manner of thought just slightly enough to see how the rest of the world explains the displacement phenomenon.
You seem to view theoretical hull speed as some kind of constant in the universe.... like the speed of light. I have suggested otherwise... providing examples that led me to this understanding.
And yes..... a kayak is a displacement hull... it doesn't plane... but it can routinely exceed hull speed. How do you explain that..... oh .... you don't have to... because I already provided you a link that explains it for you.
What is annoying is your insistance that I be the one who needs to do the research to prove YOUR point. What kind of scientific argument is that?
You make a statement and challenge ME to prove it... no, no, no my funkadelic brother..... that's not gonna work.
I see this happen way too often. The thread was why do a GPS differ from the water speed meter under the boat. It has veered into who is right. It doesn't look like anyone is going to change their mind here and is it that important who is right? My GPS tells me my speed over the ground and the Knot meter under the boat tells me how fast the water is going past my hull. The difference between the two tells me if I am going with a current or against one (usually the tide).
I think everyone was in agreement regarding the diff between stw and sog. The issue was another person's statement that a vessel's speed through water could NEVER exceed its theoretical hull speed.... and I disagreed.
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