NORDHAVN Rewrites Physics Textbooks

Well-known and well-respected motorboat manufacturer, NORDHAVN has
produced a new addition to their lineup, a 56-foot motorsailer called
the 56MS. On page 109 of SAIL magazine, October 2007 issue they have a
full-page advertisement touting how great it is.

Among other things, they claim to be able to create something from
nothing. The advert states, "Even in dead air the apparent wind when
motorsailing generates lift and reduces the amount of engine power
needed to maintain the same speed the engine would produce on its own."
Huh? Tell me I ain't dreaming . . .

Now let me see if I got this straight. In dead air one assumes there is
no wind from any direction. Right? Therefore, any motion of the boat
produced by the motor in forward gear would result in an apparent wind
from dead ahead. Agreed? So, unless they've hired Old Thom Stewart, who
knows nothing about apparent wind, to write the ad script there's no way
they actually believe this nonsense that sails can be powered up by a
wind from directly ahead, is there? Seems to me the sails would just
luff and cause drag thus reducing the speed through the water produced
by the motor.

But, I guess when you're selling motorsailers you can count upon your
customers being quite stupid so perhaps some will fall for this ruse.

Wilbur Hubbard

Wilbur Hubbard wrote:

Among other things, they claim to be able to create something from
nothing. The advert states, "Even in dead air the apparent wind when
motorsailing generates lift and reduces the amount of engine power
needed to maintain the same speed the engine would produce on its own."
Huh? Tell me I ain't dreaming . . .

You're not dreaming, they're right and you don't understand physics.

Is there any more help that you need?

"Steve Firth" wrote in message
.. .
Wilbur Hubbard wrote:

Among other things, they claim to be able to create something from
nothing. The advert states, "Even in dead air the apparent wind when
motorsailing generates lift and reduces the amount of engine power
needed to maintain the same speed the engine would produce on its
own."
Huh? Tell me I ain't dreaming . . .

You're not dreaming, they're right and you don't understand physics.

Is there any more help that you need?

I had the utmost confidence that the post would usher forth the Looney
bin, perpetual motion crowd! Welcome, to you, sir. It's good to see a
Brit is the first to insert his foot into his mouth.

Wilbur Hubbard

Wilbur Hubbard wrote:

"Steve Firth" wrote in message
.. .
Wilbur Hubbard wrote:

Among other things, they claim to be able to create something from
nothing. The advert states, "Even in dead air the apparent wind when
motorsailing generates lift and reduces the amount of engine power
needed to maintain the same speed the engine would produce on its
own."
Huh? Tell me I ain't dreaming . . .

You're not dreaming, they're right and you don't understand physics.

Is there any more help that you need?

I had the utmost confidence that the post would usher forth the Looney
bin, perpetual motion crowd! Welcome, to you, sir. It's good to see a
Brit is the first to insert his foot into his mouth.

Well, perhaps the idea is that when sailing into a "dead" wind, the
sails be set horizontally, so that the lift generated by them is in
the direction which is traditionally associated with "lift", i.e. "up".
Like hydrofoils, these aerofoils would cause the hull to ride a fraction
of an inch higher in the water, reducing water resistance.

Alternatively, the idea might be to back the sails, which would generate
a sideways force on the boat, so that it actually travels with some
leeway. If the leeway angle is big enough, and the drag from all this
doesn't slow down the forwards speed much, the effective speed will be
enhanced by the Pythagoras effect. The helm must be instructed to steer
a few degrees off the intended destination, to compensate for this
beneficial leeway.

Wilbur Hubbard wrote:

It's good to see a
Brit is the first to insert his foot into his mouth.

Ah no, that would have been you, as usual, Craptain. I bet you think
that ice yachts can't reach 146mph either.

Steve Firth wrote:
Wilbur Hubbard wrote:

It's good to see a
Brit is the first to insert his foot into his mouth.

Ah no, that would have been you, as usual, Craptain. I bet you think
that ice yachts can't reach 146mph either.

Wilbur seems to have it right this time. Either the article is
misquoted, very badly written, or just plain wrong.

An apparent wind from dead ahead can add nothing but a force directly
astern.

The case where a true wind from ahead can be used to drive a windmill
that can drive a propeller to propel the vessel is different; but this
requires a true wind.

BTW ice yachts cannot make 146mph *directly* upwind.

Andy

On 14 Oct, 14:17, Andy Champ wrote:

An apparent wind from dead ahead can add nothing but a force directly
astern.

The case where a true wind from ahead can be used to drive a windmill
that can drive a propeller to propel the vessel is different; but this
requires a true wind.

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.

As far as the windmill is concerned it has a 20kt headwind and
(alledgedly) it can take that energy, use some of it to hold itself
stationary against the wind and _still_ have surplus energy to drive
forwards. If it can do that you could gear it to the engine of the
20kt powerboat and save petrol equivalent to the surplus power that is
left over once you subtract the energy required to overcome the
windmill's own drag from the total energy harnessed by the windmill.

"Andy Champ" wrote in message
news:j-idnSDiMoeUio_anZ2dnUVZ8q-
An apparent wind from dead ahead can add nothing but a force directly
astern.

The case where a true wind from ahead can be used to drive a windmill that
can drive a propeller to propel the vessel is different

I have such a vessel you can buy, she's called "Bhaskara's Wheel".

Andy Champ wrote:

BTW ice yachts cannot make 146mph *directly* upwind.

I didn't say they could, in fact close hauled at those speeds they are
usually sailing close to downwind, an apparent wind close to directly
ahead.

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

On Sun, 14 Oct 2007 14:17:54 +0100, Andy Champ
wrote:

Steve Firth wrote:
Wilbur Hubbard wrote:

It's good to see a
Brit is the first to insert his foot into his mouth.

Ah no, that would have been you, as usual, Craptain. I bet you think
that ice yachts can't reach 146mph either.

Wilbur seems to have it right this time. Either the article is
misquoted, very badly written, or just plain wrong.

An apparent wind from dead ahead can add nothing but a force directly
astern.

The case where a true wind from ahead can be used to drive a windmill
that can drive a propeller to propel the vessel is different; but this
requires a true wind.

BTW ice yachts cannot make 146mph *directly* upwind.

Andy

This is got to be one of the stupidest threads I have ever read.
Anyone who has ever been in a boat motoring directly into the wind
knows that the sail produces no forward force. I can only assume that
the individuals who argue otherwise have never been a boat under those
conditions.

In this one (and perhaps only) instance I must admit that I agree with
Willie.

BTW ice boats (yachts?) don't do 146 MPH directly down wind either.




Bruce in Bangkok
(brucepaigeATgmailDOTcom)