Could soundbarrier be broken with a prop plane ?

[First time Juke]

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 ?

That type will be hard to cope with the vibrations that occur in the prop...I say the end of the plane has to be rock solid. No wonder Burt stated doing Vari-Ez etc after BD-5 project.

Look at the Shinden pusher...ok it was not very succesful but it flew and had lotsa wheels too ...5 altogether.

http://www.youtube.com/watch?v=KL0GFQL1BFo

BTW: Anyone know the Sierra Sue top speed ?

[racingjoe27]

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 ?

That type will be hard to cope with the vibrations that occur in the prop...I say the end of the plane has to be rock solid. No wonder Burt stated doing Vari-Ez etc after BD-5 project.

Look at the Shinden pusher...ok it was not very succesful but it flew and had lotsa wheels too ...5 altogether.

http://www.youtube.com/watch?v=KL0GFQL1BFo

BTW: Anyone know the Sierra Sue top speed ?

Lars Giertz explained the reason for having a thin fuse. He said that it is to minimize the disrupted airflow into the prop thereby maximizing the efficiency of the blades.

With material technology nowadays, you could build a small yet robust product that would still help in weight savings (not that weight is an immense issue anymore with the 4500lb rule).

[First time Juke]

Re: Could soundbarrier be broken with a prop plane ?

Lars Giertz explained the reason for having a thin fuse. He said that it is to minimize the disrupted airflow into the prop thereby maximizing the efficiency of the blades.

With material technology nowadays, you could build a small yet robust product that would still help in weight savings (not that weight is an immense issue anymore with the 4500lb rule).

That does not make much sense. You have to disrupt the airflow anyhow by the cockpit bulge and the wings and tailfeathers and engine exhausts.

I think this is the reason why BD-5B fuse was so square to spread the air flow more even thus causing less disruption.

I think Giertz cause was more simple...less induced drag like in gliders..unfortunately less drag in fuse means also need for bigger stabilizers...they were minimalistic in VmaxProbe...prop almost looks bigger than the horizontal stab. IMHO

[Red]

Re: Could soundbarrier be broken with a prop plane ?

That does not make much sense. You have to disrupt the airflow anyhow by the cockpit bulge and the wings and tailfeathers and engine exhausts.

I think this is the reason why BD-5B fuse was so square to spread the air flow more even thus causing less disruption.

Actually quite the opposite is true. Having the fuse neck down after the cockpit bulge helps reattach the disturbed aiflow. It is called a pressure recovery area. You can see the same pricipal in the NACA laminar section on any P-51 wing. this delays flow separation, thus reducing drag.

The BD-5 was square and boxy for two reasons. One, it was made of metal and needed the box to be strong. Two it needed the area for the Hirth/Subaru/Honda engines it used. There is no transonic aero in that design at all.

You would be surprised to find out how things change aerodynamically when near the speed of sound. Just because it looks slick and fast doesn't make it so.

I suggest a little light (or heavy if you prefer) reading to get a better idea of what you are trying to guess at.

[King]

Re: Could soundbarrier be broken with a prop plane ?

Actually quite the opposite is true. Having the fuse neck down after the cockpit bulge helps reattach the disturbed aiflow. It is called a pressure recovery area. You can see the same pricipal in the NACA laminar section on any P-51 wing. this delays flow separation, thus reducing drag.

The BD-5 was square and boxy for two reasons. One, it was made of metal and needed the box to be strong. Two it needed the area for the Hirth/Subaru/Honda engines it used. There is no transonic aero in that design at all.

You would be surprised to find out how things change aerodynamically when near the speed of sound. Just because it looks slick and fast doesn't make it so.

I suggest a little light (or heavy if you prefer) reading to get a better idea of what you are trying to guess at.

And almost all of Jim Bede's designs were boxy because they were easier to build.............except for the BD-10.............very sexy looking but under analyzed with a very tragic outcome. Even the re-analysis of the tail section was done wrong with tragic results.

[thunderstangfan]

Re: Could soundbarrier be broken with a prop plane ?

how about this for a little light reading

http://history.nasa.gov/SP-4219/Chapter3.html

[Red]

Re: Could soundbarrier be broken with a prop plane ?

Exactly my point. Airplane design isn't about drawing pretty shapes.

[racingjoe27]

Re: Could soundbarrier be broken with a prop plane ?

We have all been told that the most aerodynamic design is a teardrop. The point of the tear drop is the pressure relief. It may or may not look good but it sure ie effective.

But in an application with this speed as the goal, the tail feathers could experience area ruling. Just one more thing to think about when you have very limited space and require lots of power.

[Red]

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.

[King]

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.

Whats a raindrop?

heard about those when I was a kid, but we never see those around here.

Thank gosh for youtube.

[First time Juke]

Re: Could soundbarrier be broken with a prop plane ?

Actually quite the opposite is true. Having the fuse neck down after the cockpit bulge helps reattach the disturbed aiflow. It is called a pressure recovery area. You can see the same pricipal in the NACA laminar section on any P-51 wing. this delays flow separation, thus reducing drag.

The BD-5 was square and boxy for two reasons. One, it was made of metal and needed the box to be strong. Two it needed the area for the Hirth/Subaru/Honda engines it used. There is no transonic aero in that design at all.

You would be surprised to find out how things change aerodynamically when near the speed of sound. Just because it looks slick and fast doesn't make it so.

I suggest a little light (or heavy if you prefer) reading to get a better idea of what you are trying to guess at.

Ok Red,

I have to explain a bit more ( and don't start patronizing me again ).

I said he wanted to cut down the drag like in gliders..I know that theory and reattachment of the flow...but I specifically said he needed more tailfeather...BECAUSE..thet airflow will not reattach in abnormal flightsituations...it attach only in windtunnel conditions or in level flight.

I agree that BD-5B was not transonic design, but dare to argue about reason why the fuse was square ...it was to get maximum directional stability for small plane like BEDE-5 is. It added drag, but gave more control..I could be wrong about spreading the air flow.

cheers !

Juke



PS: I am taking back 10 aviation books back to library today ( some of them concern aerodynamics and designing an aeroplane ). Thanks for the link.

[First time Juke]

Re: Could soundbarrier be broken with a prop plane ?

Exactly my point. Airplane design isn't about drawing pretty shapes.

Thanks for the compliments Red ( do you mean the Max III gear arragement in my blog ? ).

I think we discussed the problem of going into transsonic region with BLUE FOAM ( Eric Alstrom ) about a decade ago here. The foil issue has been pretty good in memory ever sice.

Those who have joined discussion later this appears perhaps very new.

The wing foil of the transsonic region indeed looks very different from of those that were designed before the discovery of compressibility.

What in fact was also ever since those discoveries taken for granted is how the lift in wing is produced....before everyone said it is Bernoulli and now all agree it is Newton teories that rule.

I have underlined Newton theory ever since I read about it first time..it is also the one I understand.

Alstroms DART and supercritical wingfoil can be found in the web. I think the main problem is windtunnel time....there are few windtunnels capable to reach even transsonic speeds and they are all taken . I say this that Eric doesn't have to repeat it.

Will prop plane go supersonic remains to be seen. I suggest we remain in the topic and discuss the matter at hand. In other words....could it be done ?


--------------------

I go OT immediately:


Here is BTW the VmaxProbe 3-views:

http://www.webcamsue.nl/pagedrw1.gif

The tailfeathers are in good proportion to the wing ( 24 sq ft exposed ).

I just wonder if the pusher actually needs more tailfeathers ( than a tractor lay out ) due to the gyroscopic forces ?

Sierra-Sue and LF 2100 seem to have a lot of tailarea.

Reason why I went OT is that only way to go super sonic with a prop plane is a pusher..and these are the few examples we have.

[Red]

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!

What is clear is that yes, a propeller aircraft could be designed to break the sound barrier. The vehicle math is well understood, the shortcoming is in prop design. 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.

[Red]

Re: Could soundbarrier be broken with a prop plane ?

Ok Red,

I have to explain a bit more ( and don't start patronizing me again ).

I'm guessing English is not your native tongue? Easy there tiger.

[First time Juke]

Re: Could soundbarrier be broken with a prop plane ?

I'm guessing English is not your native tongue? Easy there tiger.

No Red..my native tonques are finnish and swedish.

I hasn't stop trying to speak english before.

But I do misspel length as lenght every now and then.


Here is a Tiger for ya ( finnish rock band from early eighties )!

http://www.youtube.com/watch?v=LOwObMbuKg0

I added a pic with Vmax probe and BD-5 profiles in same scale at my site.