Yesterday I tested a new prop on my Hatz. The test is inconclusive, with some oddities (more on that later). The test was a series of climbs with first the old, and then the new prop. The flights were recorded with an old Garmin 60CSx which has a pressure sensor, so it's a lot more accurate than GPS altitude. That data was analyzed with "Trackreader", a windows program I wrote myself: At the same time, a GoPro was looking at the instrument panel to record time, speed, altitude, rpm (note the tach display on the phone on the right): Finally, I put the climb date into a spreadsheet. It was a bumpy day, so I really don't trust the numbers: This is the weird part. Climb vs. airspeed should be a smooth curve with a single high point. The dip at 65 knots shouldn't be there, the strange part is that it's there in both tests. The data at 55kts is suspect, too. If I delete the 55 and 65 knot values, I get curves that, although probably not correct (Vy shold be closer to 55kts), look like what you would expect: Clearly I need to do more testing under better conditions, though I probably won't put the original prop back on. Once I believe I have accurate data I expect to send the prop back for rework to have some pitch taken out (I was looking for more climb, hopefully without too much loss of top speed).