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-   -   Why still no dive acceleration difference? (http://forum.fulqrumpublishing.com/showthread.php?t=31464)

Crumpp 05-23-2012 09:21 PM

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Hardly, the electrical priming on the Fw could deal with synchronised fire rather easily. Much better than other systems.
Yes it could compared to a mechanical sychronization but the electrical priming cannot change the limitations of the weapon itself.

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As for what you said about 4 blades propeller and cowling/wingroot weapons firing through the prop disc, although very rare, there were some aircraft with this configuration:
Interesting and rare....

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I was very surprised to see a German aircraft with a 4 blades propeller
If the performance differences had been noteworthy, I think the Germans would have used a 4 bladed design. As it was, they had good propeller designs and increased chord width which accomplishes the exact same goal of being able to load more power onto the disc.

The Germans also used wood in many of their later designs as it is a much better material for power loading than metal.

BlackBerry 05-24-2012 05:30 AM

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If the performance differences had been noteworthy, I think the Germans would have used a 4 bladed design. As it was, they had good propeller designs and increased chord width which accomplishes the exact same goal of being able to load more power onto the disc.
I don't believe that. Broad chord 3-blade prop lost 8% efficiency when a/c speed is around 0.55 Mach, although this design outperforms old design a lot when speed is low.

German had no naca16 airfoil, what they used in WWII is just WWI standard-gottingen airfoils and the modified broad chord version.

For all of WWI airfoils(RAF6,ClarkY,Gottingen), 4-blade design is useless, but for the newly developed NACA16, story is different.

Crumpp 05-25-2012 03:24 AM

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I don't believe that.
So?

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For all of WWI airfoils(RAF6,ClarkY,Gottingen), 4-blade design is useless, but for the newly developed NACA16, story is different.
Did you read the NACA's own findings on the Clark Y and NACA 16 series?

The 16 series has poor lift production and its only real application was in propellers. It was generally considered to be worse than the Clark Y even in that application. The NACA 16 series was supposed be low drag at high speed and designed for the very high transonic realm. It was a real disappointment to the NACA.

Go back a few pages and re-read it. It will confirm there was no difference at speed and the Clark Y was actually better overall.

BlackBerry 05-25-2012 06:27 AM

1 Attachment(s)
Quote:

Originally Posted by Crumpp (Post 429038)
So?



Did you read the NACA's own findings on the Clark Y and NACA 16 series?

The 16 series has poor lift production and its only real application was in propellers. It was generally considered to be worse than the Clark Y even in that application. The NACA 16 series was supposed be low drag at high speed and designed for the very high transonic realm. It was a real disappointment to the NACA.

Go back a few pages and re-read it. It will confirm there was no difference at speed and the Clark Y was actually better overall.

This is my comprehension. Criticism welcome.

Attachment 9791

Crumpp 05-25-2012 01:08 PM

That is a nice chart, Blackberry. Couple of things to keep in mind.

NACA 16 is a whole series of airfoils each with their own characteristics. You can make some very general statements about them but for the most part, the only characteristic that really sets them apart is the method they were derived. A method with extremely mixed results and sometimes not so very good agreement between calculator and the wind.

Gottingen is also a series of airfoils each with its own characteristics. These were derived from practical work in the wind tunnel.

http://www.aerospaceweb.org/question...ls/q0197.shtml

Once more, just as the NACA was aware and used Gottingen airfoils, so did the German designers use NACA airfoils. The Focke Wulf FW-190A uses the NACA 23015.3 at the root and NACA 23009 at the tip.

K_Freddie 05-26-2012 08:42 PM

Ah!.. the numbers ;)

BlackBerry 05-27-2012 01:18 AM

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Originally Posted by Crumpp (Post 429140)
That is a nice chart, Blackberry. Couple of things to keep in mind.

NACA 16 is a whole series of airfoils each with their own characteristics. You can make some very general statements about them but for the most part, the only characteristic that really sets them apart is the method they were derived. A method with extremely mixed results and sometimes not so very good agreement between calculator and the wind.

Gottingen is also a series of airfoils each with its own characteristics. These were derived from practical work in the wind tunnel.

http://www.aerospaceweb.org/question...ls/q0197.shtml

Once more, just as the NACA was aware and used Gottingen airfoils, so did the German designers use NACA airfoils. The Focke Wulf FW-190A uses the NACA 23015.3 at the root and NACA 23009 at the tip.


So I suggest Daidalos Team make detailed prop efficiency model.

Crumpp 05-28-2012 07:27 PM

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So I suggest Daidalos Team make detailed prop efficiency model.
On what data???

There is a good reason why n = .85 in a CSP is a valid assumption in subsonic aerodynamics.

BlackBerry 05-29-2012 03:50 PM

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Originally Posted by Crumpp (Post 429844)
On what data???

There is a good reason why n = .85 in a CSP is a valid assumption in subsonic aerodynamics.

P47's 3-blade prop drops to 63% efficiency when diving to 0.7 Mach which is subsonic. When you have 20% efficiency advantage over your opponent, you have 400 extra Horse Power, that's a Huge difference.

To model detailed prop efficiency by softwares such as xfoil, ansys,etc.

AndyJWest 05-29-2012 04:36 PM

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Originally Posted by BlackBerry (Post 430034)
P47's 3-blade prop drops to 63% efficiency when diving to 0.7 Mach which is subsonic. When you have 20% efficiency advantage over your opponent, you have 400 extra Horse Power, that's a Huge difference.

To model detailed prop efficiency by softwares such as xfoil, ansys,etc.

You are asking TD to rewrite the entire flight physics modelling based on a single number? Yeah, that's going to happen...


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