Could soundbarrier be broken with a prop plane ?

[First time Juke]

Re: Could soundbarrier be broken with a prop plane ?

The prop in a pusher actually addes lateral stability. Case in point: Northrop YB-49. Flew fine with props, re-engined with jets and they had to add vertical surface area. Even though the prop is creating thrust, there is still all the disk area behind the CG which helps.

If you ever get to see a BD-5 in person, you'll get why the fuse is shaped the way it is, and aero s not the reason. There is no room in fuse for any other shape!

We'll probably never see it advance far enough to make it feasable for the simple reason is jets do it so much better. An unducted fan is probably the best route.

YB-49 case may be so but XB-42 did suffer yaw problems; http://en.wikipedia.org/wiki/XB-42_Mixmaster

One thing that bugs me is the long distance from the prop to the aerodynamical center in rod connected fan pushers. The gyro forces really do exist and lot more effective area thus needed in elevator rudder section.

What about situation where engine siezes..and stop propelling the thing ? again the ailerons have to compensate and are far from tha cause of the twist...this was a big problem in P-51D ( increase of power at low speeds caused bank to the left ).

I have to start believing you Red in this Bede-5b size matter...it has a lot of radiator and use of the tricycle retractable landing gear also takes room.

Why I think pushers will inevitably win is the less gas burning layout travelling at reasonably fast speed...evident also in XB-42. Jetmaster XB-43 with same frame wasn't much faster: http://en.wikipedia.org/wiki/XB-43_Jetmaster

[First time Juke]

Re: Could soundbarrier be broken with a prop plane ?

Scott Pullman !


Here is another one for them ( out from my blog ) !

Thanks for rising the spirits here.



Keep posting and welcome to the forum !

[Leo]

Re: Could soundbarrier be broken with a prop plane ?

The YB-49 and Mixmaster are apples and oranges. The XB-35 flight descriptions mention nothing about lateral instability, maybe because it did not fly much, whereas one of the reasons for the YB-49's "failure" was it's instability and tendancy to wander which made it a weak bombing platorm. The P-51 had weakened lateral stability when the razorback was removed, never adequately solved until the taller tail of the H (The dorsal on the D helped).
I have no idea what the result of all those blades spinning far back of the wing on a mixmaster would do to it's handling. Wasn't the RB-51 a little weak laterally also, resulting in the large tail and at some times in it's career a dorsal?
I would agree with Red on the BD designs tho, everything he did was a little boxy, I feel due to a combination of needed room and simplicity of design and construction.

[Leo]

Re: Could soundbarrier be broken with a prop plane ?

Spullsit, I did something similiar by taking a bunch of my pics and using the coloring book setting to change them. Aircraft, cars, landscapes. Her pre-school class loved them!

[Red]

Re: Could soundbarrier be broken with a prop plane ?

You got it right Leo. The propellor is a destabilizing force (it has disk area among other things) ahead of the CG. When you change that (ie add blades) there has to be something to counter that force, which is why you see more tail on the modded planes like the Bear, Furious, RB, CM, PM etc..

[First time Juke]

Re: Could soundbarrier be broken with a prop plane ?

How does bringing the wing and tailmounted prop on the same axis affect in stability ?

I see Mixmaster had it..but LF 2100 had them pretty far apart..could this be the cause of the loud bangs in the structure Mr. Penney informed in the LF 2100 thread when flying it...that caused the people at LF 2100 to make a new wing again etc.?

Hey and thanks all the comments Red, Scott, Leo and all ! My pusher needed them...

[First time Juke]

Re: Could soundbarrier be broken with a prop plane ?

Ever seen what a raindrop actually does when it falls? The tail is actually from surface tension as it separates. It does some things you wouldn't expect. Pretty enlightening!

I'm sure there is a youtube vid somewhere.

Here is a story about raindrops...not very aerodynamical.

http://ams.allenpress.com/archive/1520-0469/11/6/pdf/i1520-0469-11-6-478.pdf

I recall this myth about raindrops being somewhat ideal aerodynamical form has been broken long ago. Strange it still lives on strong.

I remember it was repeated over and over again when Pik-20 the sailplane was being marketed.


Stop this vid at 1 sec to see a drop before impact.

http://www.youtube.com/watch?v=CJ-AX1G0SmY&feature=channel

[Peashooter]

Re: Could soundbarrier be broken with a prop plane ?

BTW, Col. Joe Kittinger went supersonic with no airplane at all!

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

[SpinB]

Re: Could soundbarrier be broken with a prop plane ?

BTW, Col. Joe Kittinger went supersonic with no airplane at all!

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

Yeah, those shockwaves set-up a coanda effect at his feet and untied his bootlaces! Thus, destabilizing at around 97,000 feet...ya know, flailing boot-laces and all*......


Did that french guy ever succeed in getting his 'supersonic' jump effort of the ground?


* jus' kiddin-round

[First time Juke]

Re: Could soundbarrier be broken with a prop plane ?

Yeah, those shockwaves set-up a coanda effect at his feet and untied his bootlaces! Thus, destabilizing at around 97,000 feet...ya know, flailing boot-laces and all*......


Did that french guy ever succeed in getting his 'supersonic' jump effort of the ground?


* jus' kiddin-round

Yeah me too...

If he has plane propeller headgear ( seen ofter in sports events )

...would he then be first propeller plane to reach MACH 1.0 ?

[RB77fan]

Re: Could soundbarrier be broken with a prop plane ?

"Chris is right..there is lotsa stress on the blades. Since the tips of the blades are what counts...why does both LF 2100 and MB I have so thin end section in the fuse ?"...what about the blades on that biplane that look like stretched dimonds

[First time Juke]

Re: Could soundbarrier be broken with a prop plane ?

Chris,

That prop thing is very crucial as you have rightfully pointed out.

I was just figuring out that my MAX III ( in my blog ) would need only 35% power for take off if I could use the right pitch and create optimal thrust..but since the prop has to be optimised ( fixed as it is ) for higher cruise speed ( some 165 mph ) I need over 90% power for take off. That kinda fixed prop windmilling in emergency causes lotsa twist that has to be compensated by some x-tra speed to get some aileron forces into play and preventing anything nasty from happening.

Prop itself is interesting..as are the wings.

Juke

[TOR_DP]

Re: Could soundbarrier be broken with a prop plane ?

I'd say the Merlin to too wimpy.

The Griffon will give 3-4000 ponies at a slight weight penalty.

The salami slicer prop wouldn't be my choice... I'd try a swept blade composite with 5-7 blades.

[Skyracer]

Re: Could soundbarrier be broken with a prop plane ?

There is a very interesting article in the current "EAA Experimenter" about prop efficiencies (dispells a whole lotta prop myths).

[First time Juke]

Re: Could soundbarrier be broken with a prop plane ?

AASI's JetCruzer 500 ( 350 + mph 6 seater ) has 5 blades and looks pretty cool.

http://www.pilotfriend.com/acft_manu/images/jetcruzer500.gif