NORDHAVN Rewrites Physics Textbooks
 

UglyBetty wrote:

I hope for your sake you are trolling, joking or both.



I'm not. It's just the knowledge of basic physics in these groups
leaves a lot to be desired, and it *really* bugs me.

Andy

NORDHAVN Rewrites Physics Textbooks
 

On 14 Oct, 19:24, Andy Champ wrote:
UglyBetty wrote:

I hope for your sake you are trolling, joking or both.

I'm not. It's just the knowledge of basic physics in these groups
leaves a lot to be desired, and it *really* bugs me.

You can't find it that basic or you'd show the formula for energy
required to push a windmill against a certain windstrength, show the
formula for energy you can gather from a windmill in a certain
windstrengh and triumphantly substitute numbers to prove your case
beyond any argument.

If you or anyone else on UKRS found the maths "basic" this issue would
have been kicked into touch months ago.

NORDHAVN Rewrites Physics Textbooks
 

I trust you studied my numbers?

toad wrote:

How does the windmill know the wind is not true wind? It has no
concept of 'true' wind, it lives exclusively in apparent wind.

It doesn't know the difference.

Assume the windmill direct into wind concept works:

You can take your windmill cart, put it on another cart and tow it at
20kts. It sees 20kts and will move forwards along its cart. If you
stop the cart and blow 20kts at the windmill cart it will move
forwards at exactly the same speed.

Same speed *relative to the the surface it is on*.


In other words there is some spare energy left over to drive the cart
forwards after the energy required to hold the windmill in equilibrium
with the wind is expended. In my example above that spare energy is
used to drive the cart forwards but in your example of the windmill on
the foredeck that surplus energy can be used to save petrol.

Now we both accept that idea is laughable so you have to explain why
it's not laughable when the wind blowing is caused by nature.

...but most importantly, why oh why oh why doesn't someone just post
the mathmatical proof, the last time this came up I said I'd leave the
thread 'till proof turned up and none did. Odd that.


Lets take this step by step.

Do you accept that it is possible for the cart to move directly upwind?

Andy.

NORDHAVN Rewrites Physics Textbooks
 

On 14 Oct, 19:38, Andy Champ wrote:

Same speed *relative to the the surface it is on*.

Yes, so you accept it has spare energy left over after it has overcome
the drag of the windmill. So the windmill on the foredeck of our power
boat has enough energy to push against the wind pushing back on it. It
also has enough energy left over after this to move it forwards.

Which means you can gear that spare energy to the engine and save some
petrol.

Yet you and I both accept you can't do that.

So there's a paradox.

In other words there is some spare energy left over to drive the cart
forwards after the energy required to hold the windmill in equilibrium
with the wind is expended. In my example above that spare energy is
used to drive the cart forwards but in your example of the windmill on
the foredeck that surplus energy can be used to save petrol.

Now we both accept that idea is laughable so you have to explain why
it's not laughable when the wind blowing is caused by nature.

...but most importantly, why oh why oh why doesn't someone just post
the mathmatical proof, the last time this came up I said I'd leave the
thread 'till proof turned up and none did. Odd that.

Lets take this step by step.

Or to put it another way "Lets take this step by step so I can keep
talking rather than posting the maths that I claim is simple to prove
my case."

Do you accept that it is possible for the cart to move directly upwind?

It is essential that we assume that to be the case so you can explain
the paradox exposed by the windmill on powerboat example.

If in a headwind the windmill pushes back harder than it is pushed
then it must do that no matter how that headwind comes about. Which
leaves us with a power boat with a windmill on it's foredeck getting a
net gain in energy from wind that it is creating.

NORDHAVN Rewrites Physics Textbooks
 

On 14 Oct, 19:14, (Steve Firth) wrote:
toad wrote:
How does the windmill know the wind is not true wind? It has no
concept of 'true' wind, it lives exclusively in apparent wind.

Most amusing that you call me a troll for pointing out that this also
applies to motor sailers.

You claimed the apparent wind on boat motoring in a flat calm would
not be on the nose.

Like saying that if I sit on a motorway in a convertable the wind
blast will be coming from the left!

NORDHAVN Rewrites Physics Textbooks
 

toad wrote:
On 14 Oct, 16:52, Andy Champ wrote:
toad wrote:
Care to explain why a windmill which is capable of powering itself
forward against it's own drag can only do it with a true wind? How
does it know if the wind it is 'feeling' is true or not, it has no
concept of true wind which is merely the wind speed and direction at
an arbitary stationary point.

There will be a level of gearing low enough somewhere, so that the
boat can wind itself forward against the winch.
Even so, if the true wind is zero you get no excess of power whatever you do.

How does the windmill know the wind is not true wind? It has no
concept of 'true' wind, it lives exclusively in apparent wind.

Assume the windmill direct into wind concept works:

You can take your windmill cart, put it on another cart and tow it at
20kts. It sees 20kts and will move forwards along its cart. If you
stop the cart and blow 20kts at the windmill cart it will move
forwards at exactly the same speed.

In other words there is some spare energy left over to drive the cart
forwards after the energy required to hold the windmill in equilibrium
with the wind is expended. In my example above that spare energy is
used to drive the cart forwards but in your example of the windmill on
the foredeck that surplus energy can be used to save petrol.

Now we both accept that idea is laughable so you have to explain why
it's not laughable when the wind blowing is caused by nature.

...but most importantly, why oh why oh why doesn't someone just post
the mathmatical proof, the last time this came up I said I'd leave the
thread 'till proof turned up and none did. Odd that.

If the apparent wind, say, decreases *any* resistance by, say lifting
the boat a fraction, or changing the effective hull shape that is
hitting the water, then NORDHAVN's statement is technically correct.
There are other ways hull design can return energy to the sytem. Look at
hydrofoils.

NORDHAVN never claim that their design produces a net energy, just that
it returns some energy to the system, thus reducing the amount of energy
needed to propel the boat. This surely is physically possible. Many
designs, like hybrid cars, capture the energy of one engine for another
engine which then returns some of that energy. In the sailboat example,
this amount may be trivial, but their statement would still be
technically correct, if energy is returned.

Stephen

NORDHAVN Rewrites Physics Textbooks
 

"Ian" wrote in message
oups.com...
On 14 Oct, 15:28, (Steve Firth) wrote:

If one is motoring in a calm on a flat millpond then there is an
apparent wind equal to the speed of the boat from dead ahead. Hoist a
sail and you can make no use of that wind, agreed. However that only
applies if you maintain the same course. Now do what any sensible
bloke
would do and adjust your course to make use of the wind as well as
the
motor.

Umm. What happens to the apparent wind from dead ahead when you turn
and make "dead ahead" a different direction?

Ian


That's where unimaginative folks go astray. If there's no wind and the
only wind is the apparent wind, in this case a wind from straight ahead,
you can turn the boat through 360 degrees and the wind will continue to
be directly on the bow. In other words the apparent wind, when there is
no other wind, is the sole function the speed and direction of the boat.
It will always come from dead ahead provided the vessel is moving
forward.

Wilbur Hubbard

NORDHAVN Rewrites Physics Textbooks
 

"Stephen Trapani" wrote in message
...
If the apparent wind, say, decreases *any* resistance by, say lifting
the boat a fraction, or changing the effective hull shape that is
hitting the water, then NORDHAVN's statement is technically correct.

Poppycock! NORDHAVN's statement is fiction. Pure fiction! Had they said
light air instead of dead air they would have been correct on any point
of sail other than with the wind dead ahead but they didn't say that.
They said dead air which means NO WIND. No wind will always cause the
apparent wind to be from dead ahead when motoring ahead and this dead
ahead wind can't impart any forward force to the boat because it can
only shake the sails around and cause drag on the sails and rigging
which slows the boat.

There are other ways hull design can return energy to the sytem. Look
at hydrofoils.

Sorry but the the 56MS has no hydrofoils.

NORDHAVN never claim that their design produces a net energy, just
that it returns some energy to the system, thus reducing the amount of
energy needed to propel the boat. This surely is physically possible.

It is only physically possible if there's a wind and provided the wind
is not from dead ahead. It is physically impossible in "dead air" as
claimed by NORDHAVN.

Wilbur Hubbard

NORDHAVN Rewrites Physics Textbooks
 

"toad" wrote in message
s.com...
On 14 Oct, 15:16, (Steve Firth) wrote:

Nor in the case of the motorsailer will the apparent wind be from
dead
ahead.

Oh yes it will!


If only these ******s could learn to draw a simple vector diagram. They
would soon see there are no other vectors than one from the rear (motor
power) and one from the front (apparent wind drag). Duh!

The vector from the rear will be longer than the one from the front. But
the one from the front will effectively shorten the vector from the
rear. The result is a slower forward speed than if the boat was powering
forward in a vacuum where there would be no vector from the forward
(from the apparent wind, at least.)

Only when there is some wind other than apparent wind can you add any
sort of sideways vector to the diagram. The advert is WRONG! It
demonstrates a common ignorance that many sailor harbour.

Wilbur Hubbard

NORDHAVN Rewrites Physics Textbooks
 

"David&Joan" wrote in message
...
Wilbur:

Obviously from reading this thread it seems that there are enough
boaters who believe this BS. If you write ad copy and more than 50% of
the readers believe it, then it is good copy. However, that doesn't
make it right.

David


One would like to think more than 50% of sailors had a realistic mind
vision of apparent wind but you could very well be correct. From the
replies to the OP it seems there is, indeed, a large subset of clueless
sailors. Pie in the sky types! Confused minds that can't keep things
simple or straight.

Wilbur Hubbard