A question sometimes asked is that if you have a large fan at the
stern on a
sailboat blowing forward into the sails would that propel the boat
forward? The usual answer given is no because the fan blowing air
forward would produce momentum propelling the boat backwards. This
would swamp the effect of an effective wind acting on the sails.
But suppose instead you had the fan in front blowing rearward into the
sails?
In this case the momentum would propel the boat forward. Furthermore by
using the method of tacking into the wind, the wind blowing into the
sails could produce a force with a forward component as well. Then the
acceleration forward should be higher than that produced by the
momentum flow of the fan alone. The speed could also be higher than the
speed of the air created by the fan since tacking into the wind can
give you a higher speed than the wind speed.
Would this work?


Bob

Yes, you won't even need the sail!
http://www.answers.com/topic/air-boat-jpg
Scout

wrote in message
oups.com...
A question sometimes asked is that if you have a large fan at the
stern on a
sailboat blowing forward into the sails would that propel the boat
forward? The usual answer given is no because the fan blowing air
forward would produce momentum propelling the boat backwards. This
would swamp the effect of an effective wind acting on the sails.
But suppose instead you had the fan in front blowing rearward into the
sails?
In this case the momentum would propel the boat forward. Furthermore by
using the method of tacking into the wind, the wind blowing into the
sails could produce a force with a forward component as well. Then the
acceleration forward should be higher than that produced by the
momentum flow of the fan alone. The speed could also be higher than the
speed of the air created by the fan since tacking into the wind can
give you a higher speed than the wind speed.
Would this work?


Bob

wrote in message
oups.com..
..
A question sometimes asked is that if you have a large fan
at the
stern on a
sailboat blowing forward into the sails would that propel
the boat
forward? The usual answer given is no because the fan
blowing air
forward would produce momentum propelling the boat
backwards. This
would swamp the effect of an effective wind acting on the
sails.
But suppose instead you had the fan in front blowing
rearward into the
sails?
In this case the momentum would propel the boat forward.
Furthermore by
using the method of tacking into the wind, the wind
blowing into the
sails could produce a force with a forward component as
well. Then the
acceleration forward should be higher than that produced
by the
momentum flow of the fan alone. The speed could also be
higher than the
speed of the air created by the fan since tacking into the
wind can
give you a higher speed than the wind speed.
Would this work?


Of course it will. Haven't you ever watched a Popeye
cartoon?

SV

Would this work?



No, and we promptly removed our GE fan from the swim platform at the
start of the season. The fan cost more than Scotty's boat.


RB
35s5
NY

Wind blowing on bare poles will make the boat go.

The apparent wind created by a boat drifting withe the current (in still air
relative to the ground) will make it go faster than the current.

Yes, the fan blown into the sail at the correct locations will increase boat
speed. Blowing it from the rear and using ballistic theory will not yield
the true answer. Blowing the fan over the sails and correctly applying
Bernoulli's Laws shows the sailboat will indeed move forward. Under the
right conditions the sailboat will move faster than the windspeed of the
fan.

I am an intellectual (Mensa member in good standing), look great in Speedos
and wonder if LP is available. Kates keeps on standing me up - without
Viagra!

Jax

Jax wrote:
snip
I am an intellectual (Mensa member in good standing), look great in Speedos
snip..

Jax



Sez who? We've been subjected to the pictures unfortunately.

wrote:
A question sometimes asked is that if you have a large fan at the
stern on a
sailboat blowing forward into the sails would that propel the boat
forward? The usual answer given is no because the fan blowing air
forward would produce momentum propelling the boat backwards. This
would swamp the effect of an effective wind acting on the sails.
But suppose instead you had the fan in front blowing rearward into the
sails?
In this case the momentum would propel the boat forward. Furthermore by
using the method of tacking into the wind, the wind blowing into the
sails could produce a force with a forward component as well. Then the
acceleration forward should be higher than that produced by the
momentum flow of the fan alone. The speed could also be higher than the
speed of the air created by the fan since tacking into the wind can
give you a higher speed than the wind speed.
Would this work?



Yes it works!
I'm in the process of mounting this fan on my bow pulpit.
Making the swivel braket is the hardest part, air flow entry angle is
important.
I hope to gain 13kts:
http://www.superiorairparts.com/Wall...er1024x768.jpg

Joe



Bob

wrote in news:1153667730.918826.254080
@p79g2000cwp.googlegroups.com:

Would this work?


No.

Airboats with just the fan go 70 mph, even over wet grass. I haven't seen
any sails on any of them to increase speed.

Let's think....If we put an airboat engine/fan on the bow blowing through
all that wind resistance of rigging and sails and tackle and measure the
speed.....then, clean the deck of all sailing paraphenalia and let the
airboat fan power the boat with no sailing equipment, its drag, its weight,
its moment pulling the boat over...

Which do YOU think would be faster?

I'm picking Door Number Two!

Somebody said that you died of aids...



Jax typed:
Wind blowing on bare poles will make the boat go.

The apparent wind created by a boat drifting withe the current (in
still air
relative to the ground) will make it go faster than the current.

Yes, the fan blown into the sail at the correct locations will
increase boat
speed. Blowing it from the rear and using ballistic theory will not
yield
the true answer. Blowing the fan over the sails and correctly
applying
Bernoulli's Laws shows the sailboat will indeed move forward. Under
the
right conditions the sailboat will move faster than the windspeed of
the
fan.

I am an intellectual (Mensa member in good standing), look great in
Speedos
and wonder if LP is available. Kates keeps on standing me up -
without
Viagra!

Jax

Jax (which I doubt)

Jax doesn't subscribe to Bernoulli's Theory but believes in Newton's
Law. (For each and every force there is a egual AND opposite force
created) I have to admit my own acceptance (Maybe) to this theory.

The question does a lot to bisporove Bernoulli and adds to Newton.

With Newton's law the force created (and this is my own observation,
right or wrong I don't know) is the force deflecting the with the
leading edge of the sail away from the curved side of the sail. The
reaction of the air, not the deflected air but the normal atmospheric
air to rush in and equalize the reduced air on the curved side, which is
moving and slides off the trailing (Leech) edge. This courses the
tell-tales to stream, sometimes even hooking to the windward side.

This is my reasoning and why I don't think the fan theory would make the
boat move faster. It would be a a disruption to the Action/Reaction of
the Sail surface by introducing a independent air supply.

For any of the racing sailors that have ever stopped a windward boat
from the leeward side by getting close enough to put the exhaust air
from your sails to the curved side of their sail will know what I'm
talking about.




http://community.webtv.net/tassail/ThomPage