Rod, you are arguing with dougies and dougies don't care what you say. dougies
only cares what dougies says.
Rodney Myrvaagnes wrote:
Count me as lunatic fringe. I see planing boats every day.

Planing boats have the same limit, in other words as they go faster,
each incremental increase in speed takes an increasing increment in
power. Eventually the power/speed curve gets just as steep as
displacement hulls...


What you describe is not an asymptotic relation.

?

Looks like it to me. It's just much farther to the right on the graph

In neither case does it get vertical, as an asymptote would.

In the case of planing boats, the slope of the curve doesn't even
increase everywhere, buty goes over a hump at the onset of planing.

But ordinary medium-to-light-displacement sailboats zip right past
hull speed when the wind rises.


Rodney Myrvaagnes J36 Gjo/a


Let us restore integrity and honor to the White House

1- an asymptote doesn't have to be vertical (or horizontal) on the graph

huh?

You are using "asymptote" in a metaphoric, rather than mathematical
sense.

dougies doesn't know the difference. dougies sells concrete slabs to first
time single wide trailer buyers for a living. dougies thinks that makes him a
scientific genius.

Dan, don't confuse them with facts. they are their minds (such as their minds
are) made up.



I've really resisted jumping into this one, but....

I guess that if you consider VERY high speeds (approaching the speed of
light), it does go asymptotic. However, at anything significantly below
that, to suggest that there is some "brick wall" velocity that cannot be
surpassed no matter how much thrust is applied is just plain incorrect.

Now, the thrust required may not be achievable by any normal engineering
and forces on the hull may cause any it to disintegrate if built out of
any of the standard materials and methods. And even if you could build
it strong enough, stability and control problems will rear their ugly
heads when you start going fast enough. Afterall, if you could keep it
from pitch poling first, and pushed my Tayana fast enough, you'd get
seperation occuring with the water flow where my hull starts curving
back to the stern. Once the rudder is high and dry in this seperation
area, it'd be a might difficult to control.

So in the real world, I guess that there is a limit to how fast my
Tayana can go no matter how many JATO units you strap onto it. But it
is a pratical matter, not some theoretical "hull speed" value beyond
which the resistance somehow becomes infinite.

A quick thought experiment to show the point: Picture yourself speeding
along on glassy smooth water in a speed boat. You have a small model of
a displacement hull sailboat in your hand (only a few inches long).
Now, since the hull speed of this model is only a fraction of a knot, if
there were a hard and fast limit beyound which it is impossible to go,
then you could not reach over the side and drag this toy through the
water. It would wrench your arm off. If you had it somehow affixed to
the boat, it would stop the speed boat cold.

Can we find something else to agrue about now?



Rodney Myrvaagnes wrote:
You are using "asymptote" in a metaphoric, rather than mathematical
sense.



On Tue, 31 Aug 2004 13:31:46 -0400, DSK wrote:


Looks like it to me. It's just much farther to the right on the graph


Rodney Myrvaagnes wrote:

In neither case does it get vertical, as an asymptote would.

1- an asymptote doesn't have to be vertical (or horizontal) on the graph

2- if the power/speed curve does not go vertical (or approach it very
very very closely) then you're saying that the boat can reach infinite
speed. This is impossible, nyet?


In the case of planing boats, the slope of the curve doesn't even
increase everywhere, buty goes over a hump at the onset of planing.

Depends on the boat. Some don't have much of a hump at all.

"Hump" is kind of a misnomer IMHO... what happens is that the boat's
power/speed curve trends increasingly upward as marginal power increases
faster than speed, then flattens out again as it starts planing. It's
not a hump, more of a plateau or shelf.


But ordinary medium-to-light-displacement sailboats zip right past
hull speed when the wind rises.

Do they reach infinite speed?

You're right about fast boats zipping right past hull speed like it's
not there... that's why I always say that "hull speed" is not a hard
limit... also you have to consider the speed-length ratio (or Froude
number if you prefer) is not the same for all boats. Two different boats
(say, a J-35 and an Island Packet 35) should not really have the same
"hull speed" even if their LWL is exactly the same.

The power/speed curve of all boats... power, sail, diplacement, planing,
mulithull, whatever... trends toward vertical as the speed increases.
For some boats it's way to the right, at impressively high speeds. But
it's there!

Fresh Breezes- Doug King



Rodney Myrvaagnes NYC J36 Gjo/a

"Religious wisdom is to wisdom as military music is to music."

--
Dan Best - (707) 431-1662, Healdsburg, CA 95448
B-2/75 1977-1979
Tayana 37 #192, "Tricia Jean"
http://rangerbest.home.comcast.net/TriciaJean.JPG

If on further consideration, you might allow that there is SOME upper
power and speed for a given hull, then perhaps you might even describe
the relation as asymptotic?

sorry, brian, that is not what the word "asymptotic" means. And **certainly**
the "professor" (if he were not bogus) who used the word would indeed know what
it means.

brian, obviously it did not clarify yours.

that is what happens when one expects a 10 second sound bite from CNN and/or
Google to bring universal enlightenment.



You are using "asymptote" in a metaphoric, rather than mathematical
sense.

Hah, another bald statement of what's right and what's wrong:
let's go for some clarifications:

[lifted from a math site]

Definition of a horizontal asymptote: The line y = y0 is a "horizontal
asymptote" of f(x) if and only if f(x) approaches y0 as x approaches +
or - inf
Definition of a vertical asymptote: The line x = x0 is a "vertical
asymptote" of f(x) if and only if f(x) approaches + or - inf as x
approaches x0 from the left or from the right.

Definition of a slant asymptote: the line y = ax + b is a "slant
asymptote" of f(x) if and only if lim (x--+/-) f(x) = ax + b.
************************************************* ********************

Does this clarify your thoughts on what is and is not asymptotic?

:-)

Brian W

dougies, PLAINLY you don't have a clew what the word "asymptote" means.
PLAINLY.

Now, KINDLY knock it off.

You are using "asymptote" in a metaphoric, rather than mathematical
sense.

Not at all.

Some realistic numbers, for example:

Let's say 1 horsepower (applied) will drive a given boat 4 knots.
2 horsepower will drive it 5.5 knots
3 horsepower will drive it 6.7
4 horsepower will drive it 7.5
6 horsepower will drive it 8.1
8 horsepower will drive it 8.5
12 horsepower will drive it 8.7
20 horsepower will drive it 8.8
50 horsepower will drive it 8.85

Now, is this a boat capable of planing? If yes, then we'll see an
increase in the amount increased speed for the next increase in
horsepower... then the trend will reappear.

Next thing you know, each increased bit of speed, down to hundredths of
knot increments, require many hundreds of horsepower to attain. Is this
asymptotic enough for you?

No?

Okay, let's keep going... we have hypothetically infinite horsepower
If we were adding millions of horsepower for each hundredth of a knot
increase in speed, is *that* asymptotic enough for you?

No?

How far do we continue this trend? We're inventing new universes to
contain the number of added horsepower for each increased femto-knot.

For the last umptysquintillion trillion horsepower we've added, we have
not seen a 1/8 knot increase.... Let me guess, you don't consider that
asymptotic?

I would, and so would most mathematicians & most yacht designers. YMMV

Fresh Breezes- Doug King

On Tue, 31 Aug 2004 22:45:18 GMT, Brian Whatcott
wrote:

On Tue, 31 Aug 2004 00:22:00 -0400, Rodney Myrvaagnes
wrote:

I am puzzled. What quantity approaches an asymptote and against what
independent variable?


Rodney Myrvaagnes NYC


Comments from the lunatic fringe aside: if one plots power versus
water speed for any water borne hull there is an upper limit to speed
no matter HOW much power is applied to the hull.

(motive power is ultimately limited by flotation. Speed is ultimately
limited by propeller immersion or hull stability)

Count me as lunatic fringe. I see planing boats every day.
What you describe is not an asymptotic relation.

Rodney Myrvaagnes J36 Gjo/a

Hmmm...you feel that if a boat planes, then it has no upper speed
limit? 100 mph? 500 mph? 1000 mph?

And if you wish a planing hull to go faster, you merely fit a more
powerful engine: 100 HP? 1000 HP?? 10,000 HP??? 100,000 HP????


For any equilibrium speed, if you add thrust it will go faster, unless
it falls apart. I didn't say anything about how the thrust is applied.

If on further consideration, you might allow that there is SOME upper
power and speed for a given hull, then perhaps you might even describe
the relation as asymptotic?

No. Unless you can show an asymptotic function (mathematical) that
describes the situation.

I hold that the situation I describe, though fanciful, is aptly
called asymptotic. Telling me that my description is not asymptotic as
I describe it, is called an assertion "Ex Cathedra". How are your
ecclesiastical affiliations?

You may consider it an apt metaphor. I consider it a rather vague one.
In any case it is only a metaphor.


:-)

Brian Whatcott Altus OK



Rodney Myrvaagnes NYC J36 Gjo/a

"Religious wisdom is to wisdom as military music is to music."

On Tue, 31 Aug 2004 22:55:08 GMT, Brian Whatcott
wrote:

On Tue, 31 Aug 2004 17:01:57 -0400, Rodney Myrvaagnes
wrote:

You are using "asymptote" in a metaphoric, rather than mathematical
sense.

Hah, another bald statement of what's right and what's wrong:
let's go for some clarifications:

[lifted from a math site]

Definition of a horizontal asymptote: The line y = y0 is a "horizontal
asymptote" of f(x) if and only if f(x) approaches y0 as x approaches +
or - inf
Definition of a vertical asymptote: The line x = x0 is a "vertical
asymptote" of f(x) if and only if f(x) approaches + or - inf as x
approaches x0 from the left or from the right.

Definition of a slant asymptote: the line y = ax + b is a "slant
asymptote" of f(x) if and only if lim (x--+/-) f(x) = ax + b.
************************************************* ********************

Does this clarify your thoughts on what is and is not asymptotic?


No, because I already knew what it was.
:-)

Brian W


Rodney Myrvaagnes NYC J36 Gjo/a

"Religious wisdom is to wisdom as military music is to music."

"DSK" wrote in message
...
Rodney Myrvaagnes wrote:
You are using "asymptote" in a metaphoric, rather than mathematical
sense.

Not at all.

Some realistic numbers, for example:

Let's say 1 horsepower (applied) will drive a given boat 4 knots.
2 horsepower will drive it 5.5 knots
3 horsepower will drive it 6.7
4 horsepower will drive it 7.5
6 horsepower will drive it 8.1
8 horsepower will drive it 8.5
12 horsepower will drive it 8.7
20 horsepower will drive it 8.8
50 horsepower will drive it 8.85

Now, is this a boat capable of planing? If yes, then we'll see an
increase in the amount increased speed for the next increase in
horsepower... then the trend will reappear.

These figures are not realistic. Up to the point of the hull speed they
resemble reality, but as soon as the hull starts planing, more 'ordinary'
rules of resistance/drag apply and as far as I know the function becomes
more like a square root function, which is mathematically definately not an
asymptote.

Meindert