Joe wrote:
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



Have you performed any tests that lead you to believe the speed can be
greater than by putting the fan at the stern?
That is, will the fan in the front blowing over the sails increase
speed more than when it is at the rear and not blowing over the sails?


Bob Clark

This brings back memories of long and
heated discussions about whether a
windmill on a boat could propel the boat
directly into the wind.

Assume either electric power generated
by the windmill or direct mechanical
connection to the prop.

Have at it!

Chuck


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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


Okay, here's what you do:

Install a high-efficiency air compressor belowdecks. Connect this to a
modified luff foil into which precisely sized holes have been drilled at an
angle which allows for maximum efficiency of turbulated airflow across both
the back and front of the sail, with the speed at the back being greater
than that at the front (precise differential you will have to calculate
yourself for your specific sail). Do this for all sails. Report back. :-)

Karin Conover-Lewis
Rawson 30 ketch "Escapade"
Marinette WI

chuck wrote in news:1153691380_100797
@sp6iad.superfeed.net:

This brings back memories of long and
heated discussions about whether a
windmill on a boat could propel the boat
directly into the wind.

Assume either electric power generated
by the windmill or direct mechanical
connection to the prop.

Have at it!



Jacques Cousteau did it. The windmill was vertical so it ran the
propulsion with apparent wind from any direction. There were 4 of them as
I remember on a good-sized ship.

http://openweb.tvnews.vanderbilt.edu...21-CBS-19.html

IT worked but had mechanical problems.

Actually, someone from Australia did just that. Well engineered, and
successful. Would go about the same speed in all directions.
I wish I could remember where I read about it but it must have been 20 years
ago.

"chuck" wrote in message
...
This brings back memories of long and heated discussions about whether a
windmill on a boat could propel the boat directly into the wind.

Assume either electric power generated by the windmill or direct
mechanical connection to the prop.

Have at it!

Chuck


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News==----
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Newsgroups
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Questions like this remind me of the old Popeye cartoons, where Popeye
thows an old bathtub into the sea, and then, whith a shower head on the
end of a pipe, crams it into the drain. viola! Instant water jet! town
pressure on tub forces water through shower head, and instant
propulsion.

Another Idea that looks good on paper.......



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?


Bob

like the cartoon axiom which states, "cartoon characters may be unaffected
by gravity and may be supported by thin air, but only so long as they are
unaware of their current, unsupported status."
Scout

wrote in message
ups.com...

Questions like this remind me of the old Popeye cartoons, where Popeye
thows an old bathtub into the sea, and then, whith a shower head on the
end of a pipe, crams it into the drain. viola! Instant water jet! town
pressure on tub forces water through shower head, and instant
propulsion.

Another Idea that looks good on paper.......



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?


Bob

That reminds me of: If from the top of your mast you drop a hand tool when
your boat is sailing a 5 - 6 knots where will it land? The answer is right
on you boat. I wonder why? Could the same phenomena applies to a fan
attached on a boat blowing on its sail to provide propulsion?

"Scout" wrote in message
...
like the cartoon axiom which states, "cartoon characters may be unaffected
by gravity and may be supported by thin air, but only so long as they are
unaware of their current, unsupported status."
Scout

wrote in message
ups.com...

Questions like this remind me of the old Popeye cartoons, where Popeye
thows an old bathtub into the sea, and then, whith a shower head on the
end of a pipe, crams it into the drain. viola! Instant water jet! town
pressure on tub forces water through shower head, and instant
propulsion.

Another Idea that looks good on paper.......



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?


Bob

wrote:
That reminds me of: If from the top of your mast you drop a hand tool when
your boat is sailing a 5 - 6 knots where will it land? The answer is right
on you boat. I wonder why? Could the same phenomena applies to a fan
attached on a boat blowing on its sail to provide propulsion?


Sorry to break this to you, but any hand
tool dropped while on a boat will
immediately and directly land in the
water, regardless of from where it is
dropped.

Chuck

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wrote:
Joe wrote:
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



Have you performed any tests that lead you to believe the speed can be
greater than by putting the fan at the stern?
That is, will the fan in the front blowing over the sails increase
speed more than when it is at the rear and not blowing over the sails?


Bob Clark

Here's another way to look at the scenario. Suppose you had your giant
fan on a raft with no sail or keel. This raft is connected to the
sailboat by a rope. Suppose this rope initially is slack. You turn on
the fan directed towards the sailboat. The wind produced by the fan
allows the sailboat to move forwards by tacking into the wind. The raft
and fan also move forwards separately due to the momentum thrust of the
fan. The instant the rope is about to become taut you turn off the fan.
When the rope tightens, the sailboat will get a higher speed because of
the forward momentum of the raft. The raft will also be pulled backward
but it won't affect the forward speed of the boat as long as it does
not contact the boat. You make the rope long enough so this doesn't
happen. Once the rope is slack again. You turn on the fan again. The
process repeats.
You see the result will be that the sailboat will wind up having a
speed due to *both* the wind produced by the fan acting on the sails
and from the momentum thrust produced by the fan.


Bob Clark