Why still no dive acceleration difference?

[BlackBerry]

Originally Posted by Crumpp

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.

screen.jpg

[Crumpp]

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]

Ah!.. the numbers

[BlackBerry]

Originally Posted by Crumpp

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]

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]

Originally Posted by Crumpp

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]

Originally Posted by BlackBerry

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...

[Crumpp]

P47's 3-blade prop drops to 63% efficiency when diving to 0.7 Mach which is subsonic.

How do you figure?

[BlackBerry]

Originally Posted by AndyJWest

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

I don't know whether detailed propeller efficiency is calculated in il2 FM. Someone told me it's only a simple value. It's ridiculous that a propeller a/c simulation game dosn't provide accurate efficiency curve. Simply setting 85% for all of CSP ? No, that's totally unacceptable.

People will spend quite a lot time to collect different propeller data such as prop diameter, reduction ratio, airfoil section shape, angle, etc. Next step is to use Xfoil/Ansys(software) to calculate complete efficiency curve for every propeller. It's worthy because <<cliff of Dover>> could also benefit from this work. Don't forget 10% efficiency difference will cause 100-200 HP error.

like this:
a.JPG

BTW, efficiency drops as altitude increases. If a CSP get 85% at sea level, there is only 85%*80%=68% at 6000m altitude(800KM/H TAS).
b.JPG