Wright Stuff C

[CrayolaCrayon]

You guys crushed your last basketball game! It says 133 to 0!

[lechassin]

Ha, yeah, IDK what was going on. It was just the two of us in the gym but the scoreboard was active and would even throw a really loud buzzer at us randomly. The first few times it was very jolting and we were glad not to be tweaking the plane.

So, is anyone else flying yet? We would really appreciate hearing about any experiences you are willing to share (in the context of competition, of course).

[coachchuckaahs]

We are flying, but so far only F1D. Gotta get through the team trials and then we can do WS.

Coach Chuck

[lechassin]

Your high school students also compete in F1D or is it just you? I also wonder, if the WS kids are great but the rest of the kids/events are so-so, how do you get past regionals?

[coachchuckaahs]

I am an outdoor R/C [pylon racer. I had never done indoor. I know what I know now from coaching these kids, starting in 2016 with WS. I coach mid and high school teams flying events, because I was the only Dad that knew anything about flying! The kids then wanted to try AMA competition (mainly because I had 6 kids wanting to fly and only 2 per team could compete), so we built LPP's last Spring and competed in Eager AZ. I built one, but was so busy cutting rubber and advising the kids, I got 4 flights in 3 long days.

Due to our strong victory in WS this year, we were encouraged to try out for US Junior Team. Again. not knowing anything, I relied heavily on advice from people like Mike Kirda, Dave Lindley, Brett Sanborn, and Kang Lee to buy stuff, arrange builds, and learn how to fly. The kids started F1D builds in mid August, and just completed. I would love to build one myself, but there was no time. It took about 50 hours per plane, and each kid built 2 planes.

These kids are SOLD OUT to flying. I have explained to them they MUST do well in all other events so we can make it to Nationals. So they put in the effort, just so they can get to Nationals and fly. Because of the F1D commitment, I have 4 returning HS kids, as I did not want to take on new kids with a short WS schedule this year. Three of these kids are doing F1D, and all four do LPP. Being from NM, getting past State is not as great a challenge as, say, Michigan, but it is also not a given. The AMA competition gives a fallback if we do not make Nationals.

It is a VERY different competition. There is not the 8-minute clock, you can focus all day (or multiple days) one one class of competition, and put in 6 or more official flights (depending on the contest).

The Junior team trials are Oct. 12-14 at Lakehurst Hanger 1 (Think Hindenburg). This has been a MAJOR time and funds commitment. We have logged the building noted above, plus building spare parts, plus over 25 hours in the gym, mostly at 6:30am, testing and learning. I am SO PROUD of these young adults, as they have accomplished everything they set out to do, in a ridiculously short time.

Maybe once we get through this year I can take up Indoor as a hobby!

Coach Chuck

[bjt4888]

Eric,

Flight videos look pretty good. Early flight character indicates a little tail heavy. Seems crazy to have the CG need to be so far forward, I know. We had some of this extreme nose up attitude until we moved the CG a little (maybe another 1/8” forward). Small stab makes the pitch trim very sensitive. We tried to fix this a little by building very light in the tail, which allows a little longer tail moment arm. Not sure this is the best solution, but this is our initial design. When playing with CG, It’s very helpful to have calculated the Neutral Point.

Probably you already know this, but a good way to control roll (or bank) is with washin on the inboard wing(s). As little as 1-2 mm can make a difference. The trick to this though is that opposite washin is needed for each turn direction.

We have only two flying sessions so far but I need to keep the students flight data private, sorry. We’re in a very competitive State for Aero Events (Michigan).

Brian T

[lechassin]

The Wiki page for Longitudinal Static Stability looks like math garbledeegook to me beyond the concept of moment arms.

The good news I have a good intuitive sense of all this from RC aerobatic experience, plus we inadvertantly discovered the neutral point for our design (33%) by producing a perfectly vertical nose dive after a hit, lol.

At 20% the design recovers nicely but the resulting decalage is too draggy. The small stabilizer mandated is why I originally proposed that a Tandem wing is in fact a Biplane without a stabilizer, which we decided would violate the definition of "Biplane"

Therefore our only option seems to be too lengthen the tail moment beyond 4x wing chord, ergo a very long motor stick the center of which is forward of the CG. This violates one of our design premises. It will allow an even longer tail moment, but the plane will need to be re-balanced for any given motor (right now we can change motors without affecting the CG).

[bjt4888]

Eric,

Yes, we are rebalancing with changes in motor weight. A little bothersome, but, once we have selected the competition motor, we’ll hopefully be done with this step.

I agree, the pitch trim that eliminates the initial power stall doesn’t look quite as good later in the flight. We’re still considering moving the CG back about 1/8” and maybe dealing with the power stall using down thrust or a controlled (hopefully) amount of roll. I believe that the F1D fliers use down thrust to control power stall when launching at high torque for very high ceilings (I believe they also use slightly loose top truss wire to allow a controlled amount of stick bowing). Chuck would know more about this as his team is flying F1D. I have observed and studied F1D, but haven’t built and flown yet.

Keep up the good work.

Brian T

[coachchuckaahs]

Brian:

Yes, both those techniques are utilized. F1D high power launches are a balancing act, with controlled MS flex, down thrust, MS twist (torsion), and static left wing wash-in.

I am hoping we do not need the full gamut of adjustments on WS planes. MS twist is likely to be a minor impact, as the wing chord is small.

Coach Chuck

[lechassin]

Letting go of the Sacred Cow in which the CG is kept at the center of the motor stick helped a lot. The tail moment is now about 5x wing chord (37 cm from the wing TE to the stab LE). CG is at 17mm from the LE with 1mm wing incidence (basically some down thrust, but our prop hub is solidly mounted) and some "up" trim as needed.

In trials in the house, pitch angle is appropriate at launch torque 50% higher than what we had in the two recent videos, and the plane glides flat when the motor runs out of knots. In yesterday's videos we had about 3600 knots and maximum torque was limited by the erratic climb that resulted. Today's launch torque should put us over 4000 knots with a full motor at 90%.

The wing and tail assembly come off easily as full units, so the modification didn't take long. Total length is now >2.5x span and it looks very odd. 18" MS with 32" 2.9g motor.