On Sun, 14 Oct 2007 23:31:30 -0700, Ian
wrote:

What force do you think does work against gravity to allow aeroplanes
to ascend?

Thrust from the engine, of course.

Casady

On 15 Oct, 14:19, (Richard Casady) wrote:
On Sun, 14 Oct 2007 23:31:30 -0700, Ian
wrote:

What force do you think does work against gravity to allow aeroplanes
to ascend?

Thrust from the engine, of course.

Nope. How many aircraft do you think are capable of vertical takeoff?

A Boeing 747-400 has a take off weight of 875,000 lbf and a total
thrust of 4 x 63,300 = 253,200 lbf.

My own aircraft has a take off mass of 370kg and no thrust whatsoever,
and yet I can get it to go up.

Ian

"Ian" wrote in message
ups.com...
On 15 Oct, 14:19, (Richard Casady) wrote:
On Sun, 14 Oct 2007 23:31:30 -0700, Ian
wrote:

What force do you think does work against gravity to allow aeroplanes
to ascend?

Thrust from the engine, of course.

Nope. How many aircraft do you think are capable of vertical takeoff?

A Boeing 747-400 has a take off weight of 875,000 lbf and a total
thrust of 4 x 63,300 = 253,200 lbf.

My own aircraft has a take off mass of 370kg and no thrust whatsoever,
and yet I can get it to go up.

Ian

But in your example, gravity is still causing you to descend through the
air. Unless converting excess speed to height, you only climb because the
air in which you are flying is rising faster than your sink rate.

Presumably, if a boat's motion is generating apparent wind from dead ahead
and a fully battened sail (I say fully battened because it's a better
aerofoil shape) could be set far enough out to achieve sufficient angle of
attack to produce some lift, then a keel boat "may" go a little quicker.
Would the lift produced be greater than the drag though?

Graham.

On 15 Oct, 20:11, "Graham Frankland"
wrote:
"Ian" wrote in message

ups.com...

On 15 Oct, 14:19, (Richard Casady) wrote:

Thrust from the engine, of course.

My own aircraft has a take off mass of 370kg and no thrust whatsoever,
and yet I can get it to go up.

But in your example, gravity is still causing you to descend through the
air. Unless converting excess speed to height, you only climb because the
air in which you are flying is rising faster than your sink rate.

Whether in a zoom or a thermal, I can get my glider to rise without
smuch as a millinewon of thrust...

Presumably, if a boat's motion is generating apparent wind from dead ahead
and a fully battened sail (I say fully battened because it's a better
aerofoil shape) could be set far enough out to achieve sufficient angle of
attack to produce some lift, then a keel boat "may" go a little quicker.

Nope. Lift is - by definition - always at right angles to the free
stream air velocity. You might get the boat to go sideways a bit, but
the assoiated drag will always slow you down as you do.

Ian

On Mon, 15 Oct 2007 08:01:24 -0700, Ian
wrote:

On 15 Oct, 14:19, (Richard Casady) wrote:
On Sun, 14 Oct 2007 23:31:30 -0700, Ian
wrote:

What force do you think does work against gravity to allow aeroplanes
to ascend?

Thrust from the engine, of course.

Nope. How many aircraft do you think are capable of vertical takeoff?

Handwaving. The only possible source for the increase in the
gravitational potential energy is the engines. Wings impart no energy
that is not their function. There is drag that goes with lift, and
engines have to impart energy to overcome it. I have had a commercial
pilots license for more than forty years, if you want more handwaving.

A Boeing 747-400 has a take off weight of 875,000 lbf and a total
thrust of 4 x 63,300 = 253,200 lbf.

My own aircraft has a take off mass of 370kg and no thrust whatsoever,
and yet I can get it to go up.

Not in still air. You can get it to sink into a mass of rising air.
Or do you have a balloon. Those burners suck fuel like an engine, the
chief concern is having a source of energy same as with an engine.

Casady

On 16 Oct, 00:11, (Richard Casady) wrote:
On Mon, 15 Oct 2007 08:01:24 -0700, Ian
wrote:

On 15 Oct, 14:19, (Richard Casady) wrote:
On Sun, 14 Oct 2007 23:31:30 -0700, Ian
wrote:

What force do you think does work against gravity to allow aeroplanes
to ascend?

Thrust from the engine, of course.

Nope. How many aircraft do you think are capable of vertical takeoff?

Handwaving. The only possible source for the increase in the
gravitational potential energy is the engines. Wings impart no energy
that is not their function. There is drag that goes with lift, and
engines have to impart energy to overcome it. I have had a commercial
pilots license for more than forty years, if you want more handwaving.

The question was not "where does the energy come from?". The question
was "what force ... does work against gravity ...?" and (save for a
trivially small downwards component) that ain't thrust.

My own aircraft has a take off mass of 370kg and no thrust whatsoever,
and yet I can get it to go up.

Not in still air.

A glider can climb in still air. Not for very long, normally, but it
can certainly climb. No thrust.

Or do you have a balloon. Those burners suck fuel like an engine, the
chief concern is having a source of energy same as with an engine.

How do you think helium balloons work?

Ian

On Tue, 16 Oct 2007 01:13:56 -0700, Ian
wrote:

How do you think helium balloons work?

You have me there. However, how many do you think are in use? I would
guess somewhere between zero and none. For all practical purposes they
don't exist.

Myself, I like to fly small hydrogen balloons. Dry cleaner bags. You
dissolve aluminum chips in lye to get the hydrogen.

Casady

Richard Casady wrote:

On Tue, 16 Oct 2007 01:13:56 -0700, Ian
wrote:

How do you think helium balloons work?

Same as a boat, displacement.


You have me there. However, how many do you think are in use? I would
guess somewhere between zero and none. For all practical purposes they
don't exist.

What about the Goodyear fleet?


Myself, I like to fly small hydrogen balloons. Dry cleaner bags. You
dissolve aluminum chips in lye to get the hydrogen.

Really fun if you can get them to ignite at altitude.

Cheers
Marty

On 16 Oct, 14:32, (Richard Casady) wrote:
On Tue, 16 Oct 2007 01:13:56 -0700, Ian
wrote:

How do you think helium balloons work?

You have me there. However, how many do you think are in use? I would
guess somewhere between zero and none. For all practical purposes they
don't exist.

Doesn't mean they don't work.

Ian

In article . com,
says...
On 15 Oct, 14:19, (Richard Casady) wrote:
On Sun, 14 Oct 2007 23:31:30 -0700, Ian
wrote:

What force do you think does work against gravity to allow aeroplanes
to ascend?

Thrust from the engine, of course.

Nope. How many aircraft do you think are capable of vertical takeoff?

A Boeing 747-400 has a take off weight of 875,000 lbf and a total
thrust of 4 x 63,300 = 253,200 lbf.

My own aircraft has a take off mass of 370kg and no thrust whatsoever,
and yet I can get it to go up.

Jeez you must be strong!

--
Duncan