Propeller Cox .020 opinion / experience?

Back in the 1970's, I flew Top Flite all balsa 27" R/C Schoolboy and 20" Roaring 20. Then in early 1980's, 20" Ace R/C Littlest Stick, all with .020 Pee Wee's. I found that flying then with the white nylon Top Flite 5.25x3 prop gave the same airspeed as the Cox competition grey 4.5x2 prop, but added about another minutes worth of flight with the 5.25x3 prop. Slight lower rpm with greater prop area gave better economy. This was all on single channel Ace R/C pulse proportional equipment on rudder only. I used various fuels from 15% to 30% nitro. The Pee Wee is a torquey little bugger. Not sure today what modern prop would be a close equivalent to the Top Flite white nylon.

A drawback to the grey competition prop, it was easy to break and more expensive. The Top Flite nylon was nearly indestructible. Flying rudder only, I had no elevator to flair the aircraft. It landed like a chuck glider. Although I flew over grass, I broke a few competition props.

In the 1980's, had a House of Balsa Nomad glider with Tee Dee .020, but I covered it all in Monokote making it too heavy for successful flight. Tee Dee with 4.5x2 competition prop just didn't have enough thrust with the extra weight. If I had tissue or silk covered the wing and clear doped the fuselage and empenage, it would have probably flown. Would like to say more about the Tee Dee, but that was the extent of my experience. Reading Sceptre Flight Aeromodeller July 1962 Tee Dee .020 Test, would benefit with the Cox 4.5x2 competition prop over larger ones. H.R. Warring liked the Cox 3.125x2.5 3-bladed prop. It likes to scream.

Thanks for the info!,    
From what I can understand is;

Bipolar propeller 4.5 x 2 Gray (Cox):
Less RPM
Less deformation.
Less fuel consumption
More traction - Speed
More possibilities to break
More expensive ($)

Bipolar propeller 4.5 x 2 Black (Cox):
More RPM
More profile deformation
More Fuel Consumption
Lower traction speed
Less chance of breakage
Less expensive ($)

Black Tripala Propeller (Cox):
Better adjustment in carburation.

White Propeller 5.25 x3 Top Flite:
The same speed as the cox gray propeller.
Additional minutes of time spent.
Less RPM
More economy in fuel consumption.
Greater durability against friction and shock.

Here I did some tests with the engine:

Propeller gray:


Propeller black:


I have to try in flight then and see the results!

1/2A Nut wrote:The black will flex add a bit of pitch over time and always unload
better (less weight for one) and always perform better. The Grey is
for a solid pitch constant's for those contestants in competition flying.

I have used electric motors with the black ones if over powered  
the high torque /rpm  motor will permanently increase pitch in just one flight.

Grey props can be modified and they sand very smooth / buffed to a shine.
The black plastic ones are much harder to re-shape for swept tips and sand.

Higher rpm will always increase fuel consumption it's the price for performance.

Hi 1 / 2A nut, thank you very much for all your explanation that siemrpe is welcomed and appreciated.
regards!!