Why still no dive acceleration difference?

[Crumpp]

However, why allied engineers accepted the weight(drag) increased by the 4th blade, and why german engineers denied?

You do know a Clark Y is not a laminar flow airfoil?

You use a propeller analysis for a Clark Y and then start talking about the benefits of laminar flow.

I am also not sure what I supposed to remember with compressibility effects. Transonic drag rise is included in the statements I made. It is one of the components of drag our thrust must overcome.

I am confused as to what you want to say now.

You are right in that the dive limits of WWII aircraft leave very little to chose. They all hit the wall about the same point. The diagram you form the 1940's enthusiast magazined has no scaling information at all.

I will attempt to answer your question as to why the Germans chose three blades and the allies four blades.

The Germans increased the chord to raise the coefficient of power. The Allies added a blade to increase the coefficient of power.

The Germans were resource and production limited so not having to produce another blade is attractive. Saving weight in any airplane is attractive. The German fighters had sychronized weapons firing through the propeller disc. Less blades means more bullets on any given target.

The Allies and especially the United States had much higher production capacity and nearly unlimited resources. Making more blades and the resources to make them was not an issue. The USAF main fighters used wing mounted weapons that did not fire through the propeller disc.