I’m starting on a build project for an electric self-launch system for paraglider soaring. The goal of the project is to have a motor system that can be used with my existing wing and can get me from a flat, open field up into the lift band of a soarable ridge. With that in mind, these are my design goals for the project:
2000’ total altitude gain
Minimal impact on the handling of the paraglider with the power off
I’m basing it on the Nimbus project that has been flown successfully by a couple of people. I think there is someone else here on the forum who is working on one as well. It’ll be a single motor, direct drive setup, probably using 18s lipo for power.
Right now I’m playing with some power system calculations in eCalc. Since my target parameter is really altitude gain, I’m thinking that I should be optimizing the system for specific thrust (grams of thust per watt)? Climbing slowly isn’t an issue as long as I have the power to climb to 2000’, and if I can make the whole system lighter as a result that will be helpful. Based on eCalc, it looks like the best way to increase specific thrust is to keep RPM down by increasing prop pitch and/or adding blades. A single 30x20 prop looks like a good configuration according to eCalc but I’m skeptical of eCalc’s aircraft performance calculations. It is showing a 390 FPM climb rate, but my beer math says that much thrust (26 kg at 22 mph) should barely produce a climb at all. Do any of you have any experience with eCalc vs real world values on an ePPG system?