Originally Posted by wjcalhoun

Teckbot - a couple of things:

1. The details are important when reporting speed. Are you talking straight and level, maintained speed, or max speed coming out of a dive? Is that a radar gun, or an on-board pitot tube, or an on board gps, or a phone app (doppler). If you are using ground-based technology (radar, doppler), then you have to run exactly upwind and exactly downwind runs, both straight and level, and average the two. Best to do several replicates. The same idea is true with on-board gps, which references to ground (obviously). The only real airspeed device is an on-board pitot tube, and that has to be calibrated.

With a 6-pitch prop (assuming 10,000 rpm), your theoretical speed is just under 60 mph, so unless you were in a dive, or moving downwind in a stiff breeze, it is hard to see how you got her to 100 mph relative to ground, or airspeed.

I have set my R70 up for speed. For my bird, best prop is an APC 14x12, and can turn about 9800 rpm in the air (measured by Eagle Tree on board instruments). My top airspeed is 118 mph, averaging true upwind and downwind runs, straight and level. With that setup, my theoretical prop speed is 111mph, so it is in the same ballpark.

For me, the performance of the R70 is best with a quicker (9 or 10 pitch) prop. YMMV.

2. A 16x6 xoar is a great prop, but may not be quite enough load for the DLE20. Jody Haack (used to be at valley view) ran and posted rpm / thrust numbers with the DLE20 on a number of props, and thought that the loading of the xoar 17x6 was about ideal. From there, adjust diameter and pitch to get the speed you want.

A fast R70 is a fun flying airframe. Roll rate 600-700 */sec on low rates!

Bill