Comparison Albatros D-II vs Albatros D-III

[Dan_San_Abbott]

Pips:
While the Albatros airfoils were not the thick Gottingen airfoils used on the Fokker DR.I, D.VII and the E.V, they were medium thick and also had a high drag factor. I have alway wondered what these machine could have done with propellers designed for speed. The German fighters kind of maxed out between 180 and 200 km/hr, the Junkers D.I was the exception, at 240 km/hr @ sea level. It was good thing for the Allies, that Prof. Junkers was a tinkerer, otherwise the Allies would of had a real problem with the Ju.D.I. Another thought, The Pfalz. D.IIIa with a high speed airfoil, like the Pfalz D.XII
with a propeller designed for speed???
Blue skies,
Dan-San

[Pips]

Thanks for clearing that up Dan.

[Kacey]

Originally Posted by Dan_San_Abbott

Pips:
While the Albatros airfoils were not the thick Gottingen airfoils used on the Fokker DR.I, D.VII and the E.V, they were medium thick and also had a high drag factor. I have alway wondered what these machine could have done with propellers designed for speed. The German fighters kind of maxed out between 180 and 200 km/hr, the Junkers D.I was the exception, at 240 km/hr @ sea level. It was good thing for the Allies, that Prof. Junkers was a tinkerer, otherwise the Allies would of had a real problem with the Ju.D.I. Another thought, The Pfalz. D.IIIa with a high speed airfoil, like the Pfalz D.XII
with a propeller designed for speed???
Blue skies,
Dan-San

DSA,

Mostly, agree great info. The Albatros aerofoils were (I believe German Sections #168-#176). These had thickness/chord ratio's of around 0.07-0.10, with an ordinate point around 0.30 (from leading edge).

This would be in comparison to a Halberstadt or Hannover with a thickness ratio of 0.050 and an ordinate point of 0.33.

And, in comparison to RAF #14 with a thickness ratio of 0.050 and a ordinate point of (oh let's say) 0.30-0.50 (it's hard to say on those puppies).

And, in comparison to (of course) Fokker D.VII with a thickness ratio of 0.14 and an ordinate point of 0.26-0.30.

So, you are quite right a medium thickness aerofoil.

However, it wasn't necessarily a high drag aerofoil. The German Cw's (drag coeffients) on it were between 3.3 and 3.8, with L/D's of 9.7-14.7@0 deg. (this I would call average speed)

This would be in comparison to a Halberstadt or Hannover with a Cw around 3.9-4.0 and L/D's of 9.0-9.5@0 deg. (this is a slow aerofoil)

And, in comparison to (of course) Fokker D.VII with Cw around 3.9 and L/D of 13.4@0 deg.(this I would call average speed)

Now, compared to RAF#14 with a Cw around 2.5 and a L/D of 14.0, they ALL had a SPEED handicap. (this is a fast WWI aerofoil!)

Yes, the Pfalz D.XII was very close to the RAF#14 above.

I think I'll attempt to estimate that Pfalz D.IIIa with the D.XII aerofoil and a normal speed providing propeller! The improvement won't be as much as one might expect from the aerofoil change. Since the wings are only providing around 30% of the total parasite drag. The prop change will add much more.
So we will see how it comes out.

Oh, by the way, thanks so much for the reasonable looking Junker D.I speed data. (all the other sources have it way LOW). However, your figures with the BMW IIIa(185ps) with Benzol added petrol @msl has it dropping in right where I was predicting (149mph/240kph@msl)!!!!

Another, anomally erased from my DB.

Repectfully Submitted,

KC

[Dan_San_Abbott]

Kacey:
I shall look forward to what you come up with on he Pfalz D.XII with RAF 14 airfoil. I had always thought the Pfalz D.VIII/D.XII airfoils were copies of the SPAD VII/XIII airfoils.
The Last Parachute I designed had an L/D of 5.12:1 glide ratio with an all up weight of 360 lbs. The ground speed in full flight was 59mph and could modulated to zero with brakes. It was called the "Mach III Alpha". In military jargon, it was a High glide, Tactical Insertion Parachute System". My competitor tried to improve the airfoil, which I considered a gross waste of time for a fabric wing. I went after drag reduction and flutter/noise abatement. Their designs achieved L/D of 1.99:1 When I retired, I gave my engineerig people a task to raise the deployment altitude to 35-40k and increasing the L/D to 10?? That will take some doing, has not been accomplished as far as I know. The German were looking 50 mile stand-off in deploying their insertion teams.
Blue skies,
Dan-San