Aeroplayin
70cc twin V2
Pitch speed is the velocity the plane would travel in a solid medium, like a screw through wood per each revolution, taking into consideration the pitch angle and RPMs.
MPH = (((Pitch in Inches / 12 inches) x RPMs) x 60 seconds) / 5280 ft
Also, power in torque is the factor that typically defines forces of rotational velocity. So going to a calculation for torque, which is simply a relationship between HP and RPMs, make sense when comparing props of different lengths and loads. I don’t have all the weights of these props, but taking a guess at them:
20x8 Mejzlik at 8210 RPMs produces 2.4 lb-ft of torque
21x8 Mejzlik at 7530 RPMs produces 2.4 lb-ft of torque
20x8 Xoar Beechwood at 7500 RPMs produces 2.2 lb-ft of torque
A 20x10 Xoar Beech at 6950 produces 2.4 lb-ft of torque
A 20x9 CF Falcon at 7680 produces 2.3 lb-ft of torque
A 20x7 CF Falcon at 8860 produces 2.4 lb-ft of torque
My guess is that the 20x8 Xoar can be spun up a little higher, and it may just be an engine tuning issue, or my weight estimate is off and the load constant I'm using is wrong. Going to 7720 RPMs would bring it in line with 2.4 lb-ft.
Either way, we need to know which are with a pipe and which are without because from what I think is being reported, it looks like the DA35 may be putting out as much torque without a pipe than the DLE35 is producing with one. Something to consider carefully, and just my assumption from the measured values being reported. But if anyone is really impressed with the DLE35 numbers with the 20x7 Falcon, there's no evidence yet that this is something wonderful. In fact, perhaps more disappointing.
For many of us here in Florida, we use/used synthetics, lik Royal Purple, to get about another 150-180 RPMs while dropping the temps a bit too. This is very important when it’s hot and the air density is low. We could fatten it up a bit to fly safer in 3D without losing a step.
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