In a previous email, you described how to electrify a 2m Chrysalis and gave me the down & right thrust angles recommended.

Now that I'm about to mount an Astro 020 with planetary gears, I realize that I have no idea what the reference line is for thrust angle measurements. If the thrust angle is relative to the chord line of the center of the wing, how do I transfer that reference to the fuselage on the Chrysalis?

From : Don Stackhouse

The fuselage datum on the Chrysalis is the fuselage bottom. The wing is a little more than +1 degrees from that, the tail is at 0 degrees and the thrust line should be at -5 degrees, with 2 degrees right thrust. The exact numbers aren't super-critical, the airplane can still be flown successfully even with the thrust line at 0-0 (in fact that's the setting we used for the first flights). If the thrust line is off a bit, it just means that the model may tend to turn a bit or nose up or nose down a little when you change power settings. Even with the 5 & 2 settings you are likely to see a minor change with the direct-drive Speed 600 we originally designed for, and probably a little more than that with the more powerful 020 and its bigger prop. We decided that a little pitch change is a good thing, just to give the pilot some visual indication that the model actually felt a throttle change.

There's also the question of whether the model should stay at the same angle of attack (which would therefor result in a nose-up into a climb but at the same airspeed when you increase throttle), or should it hold the same flight path but increase airspeed? It's largely a matter of personal preference and what makes sense for that particular airplane's primary mission. For a racer you'd want it to stay level and go faster, but for a powered sailplane you'd want it to climb while keeping constant airspeed. There's nothing magical about the 5 & 2 setting, it's just a starting point. You should adjust it after flight testing until the model flies the way you want it to.

Don Stackhouse
DJ Aerotech