Myth: Hull Speed

[barnakiel]

Originally Posted by s/v Jedi

Barnie: the maxi tri's that I see going fast only have their leeward ama in the water ;-) I'm not even sure because they are gone before I can get a good look... I have seen one doing 11 knots in not even 8 knots wind.

I would love one for a cruiser. Just to try out. This season our anchorage was nearly 50% cats, and a couple of tris too. So, at least on this side of the pond, cruisers seem to be looking more and more towards multis.

I have seen the Dragonfly and liked it. Many say 'too narrow', but I don't like the modern, super beamy interiors, so maybe a tri is something for (the future) me.

b.

[daddle]

Originally Posted by Tropic Cat

The graph does go vertical indeed.
The nice thing about CF is anyone can spout...Bull crap

Wow. Really?!? A graph is posted and you say it "vertical"? That graph is totally damning to the arguments presented by the armchair sailors here. It's anything but vertical at the hull speed of that boat. Indeed it shows tahr the power required for transitioning thru hull speed is a continuous function. Not some kind of dicontinuity or wall. It both proves my point and confirms reality. Thanks.

Sheesh!

[Randyonr3]

Originally Posted by Tropic Cat

The graph does go vertical indeed.

The nice thing about CF is anyone can spout anything they like. Readers believing it is something entirely different. If someone were to tell me they have the perfect 12 knot 30 foot monohull, I'll say that's nice and ignore any post they ever make.

Prove a 360 mile day and I'll believe you. Until then ...

Bull crap

No One said that they had done a 360 mile day.. so get over it.. all that was was posted was a question concerning a 360 day and if in the right conditions, could it be done...
The answer was Yes, I believe so.. Reason being that I myself have looged a 280 mile day and did it with ease with the wife and I sailing from San Francisco to Avalon Harbor.. Dirring this trip I often saw 14 and at times 16.. I have no doubt that with an experenced crew and in the right conditions, a 300 mile day is reality and a 360 mile day is possible..
And again, I used the right conditions..

[Randyonr3]

A "Bumble Bee" cannot fly, Thousands of hours have proven that it is impossible for a Bee to hover or fly......It just cannot be done..
Its all BS..........

[Ex-Calif]

Originally Posted by Randyonr3

A "Bumble Bee" cannot fly, Thousands of hours have proven that it is impossible for a Bee to hover or fly......It just cannot be done..
Its all BS..........

Or would that be, "Bee S*#T"?

[Bash]

Originally Posted by Randyonr3

A "Bumble Bee" cannot fly, Thousands of hours have proven that it is impossible for a Bee to hover or fly......It just cannot be done..
Its all BS..........

The difference between the bumble bee's flight seeming to defy the laws of aerodynamics and Randy being able to exceed hull speed lies in the fact that hull speed, from its inception, is a "rule of thumb" formula, not a physical law. Further, hull speed should not be seen as a constant such as the speeds of light or sound. It's just a rule of thumb, one which we've already been informed is considered irrelevant in modern marine architecture.

To insist that anyone who is exceeding theoretical hull speed is, de facto, planing, is to misunderstand the nature of hull speed as a rule of thumb formula.

Parenthetically, to insist that those participating in this discussion are "armchair sailors" is equally misguided.

[GordMay]

Originally Posted by Randyonr3

A "Bumble Bee" cannot fly, Thousands of hours have proven that it is impossible for a Bee to hover or fly......It just cannot be done..
Its all BS..........

Perhaps you'd be prepared to share the alleged proof that bumblebees can't fly.

It's a wonderful old piece of urban folklore (pure ********) that the flight of the bee is impossible by the laws of physics.

The "science has proved that bees can't fly" urban myth originated in a 1934 book by entomologist Antoine Magnan, who discussed a mathematical equation by Andre Sainte-Lague, an engineer. The equation proved that the maximum lift for an aircraft's wings could not be achieved at equivalent speeds of a bee. I.e., an aeroplane the size of a bee, moving as slowly as a bee, could not fly. Although this did not mean a bee can't fly (which after all does not have stationary wings like the posited teensy aircraft), nevertheless the idea that Magnan's book said bees oughtn't be able to fly began to spread.

It spread at first as a joke in European universities, at Sainte-Lague's & Magnan's expense. But later it became a "fact" among the gullible or the uneducated not smart enough to get the joke. Later still it became a "fun" experiment to develop complex mathematical theories both to explain how insects fly, or why they can't - scientific intellectual sophism.

[Randyonr3]

Originally Posted by GordMay

Perhaps you'd be prepared to share the alleged proof that bumblebees can't fly.

It's a wonderful old piece of urban folklore (pure ********) that the flight of the bee is impossible by the laws of physics.

The "science has proved that bees can't fly" urban myth originated in a 1934 book by entomologist Antoine Magnan, who discussed a mathematical equation by Andre Sainte-Lague, an engineer. The equation proved that the maximum lift for an aircraft's wings could not be achieved at equivalent speeds of a bee. I.e., an aeroplane the size of a bee, moving as slowly as a bee, could not fly. Although this did not mean a bee can't fly (which after all does not have stationary wings like the posited teensy aircraft), nevertheless the idea that Magnan's book said bees oughtn't be able to fly began to spread.

It spread at first as a joke in European universities, at Sainte-Lague's & Magnan's expense. But later it became a "fact" among the gullible or the uneducated not smart enough to get the joke. Later still it became a "fun" experiment to develop complex mathematical theories both to explain how insects fly, or why they can't - scientific intellectual sophism.

Gord,
you've been on the hard to long..... Maybe some white sandy beaches and a bottle of rum...

[s/v Jedi]

Or.... Bee - Wikipedia, the free encyclopedia for some more info ;-)

cheers,
Nick.

[GordMay]

Originally Posted by Randyonr3

Gord,
you've been on the hard to long..... Maybe some white sandy beaches and a bottle of rum...

You hit the 'post' button; I check the facts. Your facts, and the implication are wrong!
Ergo: I need a holiday.

If you believe what you said (in your last 2 posts), give yourself an IQ test; but be prepared for a failing grade.

[Stillraining]

Originally Posted by GordMay

But later it became a "fact" among the gullible or the uneducated not smart enough to get the joke. Later still it became a "fun" experiment to develop complex mathematical theories both to explain how insects fly, or why they can't - scientific intellectual sophism.

Sort of like Evolution..

[Randyonr3]

Originally Posted by GordMay

You hit the 'post' button; I check the facts. Your facts, and the implication are wrong!
Ergo: I need a holiday.

If you believe what you said (in your last 2 posts), give yourself an IQ test; but be prepared for a failing grade.

Ya Gord,
You need to freggin lighten up guy... It was all in Jokeing Gord... Sometimes I think you do more damage to this forum than you do good...and you are deffinatly wound to tight...

[Randyonr3]

Originally Posted by GordMay

You hit the 'post' button; I check the facts. Your facts, and the implication are wrong!
Ergo: I need a holiday.

If you believe what you said (in your last 2 posts), give yourself an IQ test; but be prepared for a failing grade.

and the facts are, i didnt hit the "Post" button, I hit the "Reply" button, so your facts are wrong!

[AK_sailor]

Originally Posted by Randyonr3

Ya Gord,
You need to freggin lighten up guy... It was all in Jokeing Gord... Sometimes I think you do more damage to this forum than you do good...and you are deffinatly wound to tight...

Personally, I really like Gord's comments. Sometimes these threads spin way out into the ozone, and it's nice when someone occaisionally calls "bullsh!t" on the "beesh*t". Maybe it's my inner scientist, but I tend to like facts and reallity.

Cleared a foot of snow off the boat last weekend. Time to start transitioning from white fluffy frozen water fun to wet water fun!

[nautical62]

Charles Kanter writes about hull speed and the basic formula quite a bit in his book: "Cruising in Catamarans" A point he makes is that the formula isn't really 1.34 times the square root of the waterline length, but rather a K value for that hull times the square root of the water line length. 1.34 is a commonly accepted K value for many cruising monohulls, but problems arise when people use 1.34 for hulls having very different K values including catamarans.

He for example suggests the following K values for some other boats (p74)

Alden 72: 3.9, giving a hull speed of 10.8
Bristol 60: 3.6 giving a hull speed of 9.07
Island Pack 32: 2.5 with a hull speed of 7.4

I believe the K value is largely a function of hull width to length, shape and displacement. Adding or subtracting weight will change the K value.

Obviously things like planning, surfing, and aid from current can cause SOG to exceed hull speed.