P-63 (?) Airacobra/Kingcobra power question

A question for the physics-minded among us, or for anyone who just has
the answer.

I have heard the Airacobra was underpowered and that got me to
thinking;
Does having an engine at the middle of the fuselage (in any plane for
that matter, like the XP-58) and connected by a long shaft contribute
to a loss of power delivered to the propeller? In other words; would
there be more power delivered the closer the engine is to the prop?
Does the shaft "eat up" power in any way? I am a mechanic and pilot
and fairly knowlegable about a/c physics & aerodynamics but this has
me stumped.

Thanks in advance for your ponderings and/or solution!

Ricky

"Ricky" wrote in message
...
Does having an engine at the middle of the fuselage (in any plane for
that matter, like the XP-58) and connected by a long shaft contribute
to a loss of power delivered to the propeller? In other words; would
there be more power delivered the closer the engine is to the prop?

As its name "rec.aviation.piloting" implies, this group is more for airplane
drivers than for aircraft designers or aviation historians. You will get better
answers at rec.aviation.military, and perhaps some very interesting answers at
rec.aviation.homebuilt.

Regards
Vaughn

On Nov 3, 9:09*am, "vaughn"
wrote:

As its name "rec.aviation.piloting" implies, this group is more for airplane
drivers than for aircraft designers or aviation historians...(rest snipped) *

Regards
Vaughn

Hey, thanks for your suggestion. I've been in Usenet since the early
90s and am very careful (generally) about on-topic discussion. This is
totally on topic and useful, interesting & beneficial to this
particular community. I am an "airplane driver," and, I'm sure you
know or will learn, drivers run the gamut of interest in airplanes in
every aspect.
I submit this topic with absolutely NO reservation that this is
violating the traditions of an "airplane driver's" group.

Thanks anyway,

Ricky

On Tue, 3 Nov 2009 08:10:54 -0800 (PST), Ricky wrote:

On Nov 3, 9:09*am, "vaughn"
wrote:

As its name "rec.aviation.piloting" implies, this group is more for airplane
drivers than for aircraft designers or aviation historians...(rest snipped) *

Regards
Vaughn

Hey, thanks for your suggestion. I've been in Usenet since the early
90s and am very careful (generally) about on-topic discussion. This is
totally on topic and useful, interesting & beneficial to this
particular community. I am an "airplane driver," and, I'm sure you
know or will learn, drivers run the gamut of interest in airplanes in
every aspect.
I submit this topic with absolutely NO reservation that this is
violating the traditions of an "airplane driver's" group.

Thanks anyway,

Ricky

This article should answer that for you. Good Luck!

http://tinyurl.com/5gt7

On Nov 3, 9:13*am, Ricky wrote:
A question for the physics-minded among us, or for anyone who just has
the answer.

I have heard the Airacobra was underpowered and that got me to
thinking;
Does having an engine at the middle of the fuselage (in any plane for
that matter, like the XP-58) and connected by a long shaft contribute
to a loss of power delivered to the propeller? In other words; would
there be more power delivered the closer the engine is to the prop?
Does the shaft "eat up" power in any way? I am a mechanic and pilot
and fairly knowlegable about a/c physics & aerodynamics but this has
me stumped.

Thanks in advance for your ponderings and/or solution!

Ricky

Ricky, the question you'd have to ask is, if the energy is put into
the shaft at the engine end, where could it go? One answer is heat,
the the other sound energy, but really most of it is delivered to the
prop. Long shafts do cause vibration problems, but those can be
overcome.

As it happens, there are other reasons for putting engines close to
the front of a single engine airplane. The middle is a good place to
park passengers, you avoid the weight/space issues with the shaft.

My aerodynamic question had always been why there are fewer pusher
props. In a puller some of the wind energy is used up against the
airplane. In fact one of the things that made the Mooney 201 better
than the Executive is the windscreen and cowling were redesigned to
more effectively deflect the wind. In the case of the Mooney, the wind
against the airplane is airspeed plus that contributed by the prop,
and losses go up like something of the square of wind velocity.

This could be a long thread, and some posters may actually contribute
to the discussion.

a wrote:

My aerodynamic question had always been why there are fewer pusher
props. In a puller some of the wind energy is used up against the
airplane.

In a pusher, the prop has to operate in turbulent air stirred up by the
structure in front. Depending on the design of the airplane, the prop
also has to be stronger (e.g., heavier) to withstand the cycling loads
if there's a wing or something blocking part of the prop disk from the
slipstream (think Long-EZ).


Ron Wanttaja

On Nov 3, 10:55*am, Ron Wanttaja wrote:
a wrote:
My aerodynamic question had always been why there are fewer pusher
props. In a puller some of the wind energy is used up against the
airplane.

In a pusher, the prop has to operate in turbulent air stirred up by the
structure in front. *Depending on the design of the airplane, the prop
also has to be stronger (e.g., heavier) to withstand the cycling loads
if there's a wing or something blocking part of the prop disk from the
slipstream (think Long-EZ).

Ron Wanttaja

Thanks! I seem to remember the pusher in the C310 was less effective
too.

In article
,
a wrote:

On Nov 3, 10:55*am, Ron Wanttaja wrote:
a wrote:
My aerodynamic question had always been why there are fewer pusher
props. In a puller some of the wind energy is used up against the
airplane.

In a pusher, the prop has to operate in turbulent air stirred up by the
structure in front. *Depending on the design of the airplane, the prop
also has to be stronger (e.g., heavier) to withstand the cycling loads
if there's a wing or something blocking part of the prop disk from the
slipstream (think Long-EZ).

Ron Wanttaja

Thanks! I seem to remember the pusher in the C310 was less effective
too.

Cessna?

The C-336/337 turns out to perform slightly better in single-engine
flight on the rear engine than the front.

a wrote:
On Nov 3, 10:55 am, Ron Wanttaja wrote:
a wrote:
My aerodynamic question had always been why there are fewer pusher
props. In a puller some of the wind energy is used up against the
airplane.
In a pusher, the prop has to operate in turbulent air stirred up by the
structure in front. Depending on the design of the airplane, the prop
also has to be stronger (e.g., heavier) to withstand the cycling loads
if there's a wing or something blocking part of the prop disk from the
slipstream (think Long-EZ).

Ron Wanttaja

Thanks! I seem to remember the pusher in the C310 was less effective
too.

As Steve pointed out, you were thinking of the C336/337 Skymaster. It
*did* have a better rate of climb on the rear engine. One theory I read
was that it was due to the aerodynamics of the rather blunt back end
being better when there was an engine to help suck the air past....

There's no real pat answer; you can find efficient pusher aircraft, just
like you can find efficient tractor planes.

For an example, see:

http://www.ar-5.com/

Years ago, when there was a controversy as to whether paddles or
propellers were most efficient for ships, the British came up with a
simple test: They built two identical ships, with identical engines,
one with paddles and one with a prop. They tied a rope between the
sterns, and had the captains go to full power to see which had more thrust.

Pity you can't do this with a couple of airplanes....

Ron Wanttaja

Ron Wanttaja wrote:
Years ago, when there was a controversy as to whether paddles or
propellers were most efficient for ships, the British came up with a
simple test: They built two identical ships, with identical engines,
one with paddles and one with a prop. They tied a rope between the
sterns, and had the captains go to full power to see which had more
thrust.

Wikipedia says that "In 1848 the British Admiralty held a tug of war
contest between a propeller driven ship, Rattler, and a paddle wheel ship,
Alecto. Rattler won, towing Alecto astern at 2.5 knots (4.6 km/h)...."

http://en.wikipedia.org/wiki/Propeller

However, it is probable that the paddle wheel ship simply didn't have the
right size paddles. Paddle wheels should be capable of efficiencies similar
to propellers - but it takes very large wheels.