I've been working with Craig Catto to find a prop design that is fine tuned for the O-375 from Aero Sport Power. We did some pull tests with the airplane attached to a dynamometer yesterday with three different props. The tests were all done at Flytek's shop on Lake Hood with Shawn Lidey. The dyno is the line pull type, with units in lbs, originally designed for applying proper tension to electrical lines, but is used in many applications. It has a scale of 0-1200lbs.
The engine is Bart's O-375, 9.6:1 pistons, port/polished, exhaust from Custom Aircraft Parts.
The airplane is a Steve Bryant Producer, it has straight skis on right now, so the tests were performed with dollies under the skis. As equipped, it has an empty weight around 1180ish lbs. (Mods have been happening and I don't have the exact weight tracking right now...)
Here are the test results, each prop was tested three times, for each test I'll give the data in this order...prop:test #:max static rpm:manifold pressure:OAT:Lbs Pull
Catto 84/43: 1: 2440: 27.9: 34: 730
Catto 84/43: 2: 2440: 27.9: 33: 750
Catto 84/43: 3: 2440: 27.9: 33: 745
Catto 84/44: 1: 2320: 28.0: 34: 770
Catto 84/44: 2: 2320: 28.0: 33: 800
Catto 84/44: 3: 2320: 28.1: 34: 775
McCauley: 90/37: 1: 2270: 28.0: 34: 820
McCauley: 90/37: 2: 2270: 28.0: 34: 820
McCauley: 90/37: 3: 2270: 28.0: 34: 820
(thx to Dave Calkins for the 90" prop)
It should be noted the mid-span blade area is quite different between the two Catto props, the 84/44 has larger blade area and longer chord at the mid-span as compared to the 84/43.
In discussions with Craig Catto yesterday, the next prop will likely be something in the range of an 84/42, but with the larger mid span chord similar to the current prop I have that is an 84/44.
Nitrous was tested with the 84/44 prop, when boosted, the #'s were as follows...84/44: 1: 2500: 30.0: 34: 895
That is it for now, curious to here the chatter...some things I wonder about is whether or not max pull at static rpm is indicative on a given set of props of which prop will perform the best from a short take-off point? Craig Catto is going to work up some thrust curves based on this data that should help illustrate this and look at the curve relating to the increase of thrust for each prop as rpm increases in t.o. roll...
Obviously, proof is in the pudding, and we didn't have time to test all the props and fly each of them...that will be for next time...