Flight B/C

[bjt4888]

Hey gz839918,
I have already responded to epicSus's post. I think that got buried, too...

Hey coachchuckaahs,
Ohh, I see. I think the FF kit has some down and left thrust already built in. Incidence is currently at ~5mm for the wing, and 0mm for the stabilizer(although I might have glued the tailboom at an angle. I looked carefully and used a ruler, and there's a slight gap, but I'm not sure if it's my imagination or not...).
There is some left skew. I originally thought left skew turned the plane left... It's very slight, and I might be seeing it wrong(1-2mm?) but I'll attach pictures when I get the chance to. I'll mess around and see if I can get it to warp, with no skew...
I'll add negative incidence to the stabilizer and go from there, thanks! CG is definitely off by quite a bit, and I'll take you and Coach Brian's advice and move CG back. Although I'm still pretty worried about the end of the flight(The stalling is back) I'll just fly and see how it goes.

Cat,

Sorry to be not responding the last few days. Been really busy as I had 9 teams (5 varsity and 4 JV) at Regionals on Saturday and have been helping four of them get ready for States next month.

I've noted that you are getting very good feedback from Coach Chuck, of course.

Brian T

[pumptato-cat]

Hey gz839918,
I have already responded to epicSus's post. I think that got buried, too...

Hey coachchuckaahs,
Ohh, I see. I think the FF kit has some down and left thrust already built in. Incidence is currently at ~5mm for the wing, and 0mm for the stabilizer(although I might have glued the tailboom at an angle. I looked carefully and used a ruler, and there's a slight gap, but I'm not sure if it's my imagination or not...).
There is some left skew. I originally thought left skew turned the plane left... It's very slight, and I might be seeing it wrong(1-2mm?) but I'll attach pictures when I get the chance to. I'll mess around and see if I can get it to warp, with no skew...
I'll add negative incidence to the stabilizer and go from there, thanks! CG is definitely off by quite a bit, and I'll take you and Coach Brian's advice and move CG back. Although I'm still pretty worried about the end of the flight(The stalling is back) I'll just fly and see how it goes.

Cat,

Sorry to be not responding the last few days. Been really busy as I had 9 teams (5 varsity and 4 JV) at Regionals on Saturday and have been helping four of them get ready for States next month.

I've noted that you are getting very good feedback from Coach Chuck, of course.

Brian T

It's fine--Good luck to your teams at States! I get that coaching 9 teams and additional people online is hard, don't worry about it. Thank you so much
States venue information has been released! We're getting 60x90ft and 26' high ceilings. AC may or may not be on...
I'm very excited(although, not about the possibility of having to bring a table)! Hopefully things go better than they did at Regionals. It's time to grind--peak SciOly season!

[pumptato-cat]

Went flying again today...
It still glides right. I know now where the left skew comes from--I decided to build in 1/2" wing warp(Wow such a smart idea right) because my old plane flew well with that setting. My reasoning was that I could simply use shims to reduce that wing warp, but that has the effect of making the back post tilt to the right, causing the entire center rib and wing to skew left. I'll be regluing that to no wash-in, or very little--although I'm not sure if this is the problem with the right turn. I tried switching wings from my old plane(no built-in warp), and it still glides right although skew is gone...

The odd thing is that it flies tight left circles now. I reglued the tailboom to add negative stab incidence, and I think I may have overdone the stab angle(pictures, videos, and measurements coming later if that helps). While doing glide tests, the plane will float slowly to the right(looks a lot better than previous glide tests, travels further too I think!). It seems stable enough, but in flight, it's pretty bad... around halfway through cruise, the plane will wobble and dive(hitting boxes or walls, or the floor). I thought this was due to CG being too far back, which would make sense as the circle size is small, too. But after moving CG forward, it flies flat again and still dives. The plane has barely made it through one proper flight as it keeps crashing...

Another odd thing I noticed was the curious tendency to climb VERY steeply at the beginning of the glide, and then flatten out. The plane would be almost at a 45 degree angle(This is from eyeballing, but it's significant) and climb for 2 seconds, and then slowly climb to a cruise--this was on low torque, too. On 0.24oz torque, the plane flew to almost 26 feet, which was pretty strange(although I did increase incidence...).

Why would the plane turn tight left circles, but glide right? I'm pretty confused... The glide is not slightly to the right, either--it's a 90 degree turn.
Time to check glue joints again... I must've messed up the tailboom joint badly.

[bjt4888]

Went flying again today...
It still glides right. I know now where the left skew comes from--I decided to build in 1/2" wing warp(Wow such a smart idea right) because my old plane flew well with that setting. My reasoning was that I could simply use shims to reduce that wing warp, but that has the effect of making the back post tilt to the right, causing the entire center rib and wing to skew left. I'll be regluing that to no wash-in, or very little--although I'm not sure if this is the problem with the right turn. I tried switching wings from my old plane(no built-in warp), and it still glides right although skew is gone... I suspected this, but didn’t mention. The only way to get left skew was to be mounting shim at the bottom edge of the wing saddle. Clever to build in the washin, but unplanned for consequence.

The odd thing is that it flies tight left circles now. I reglued the tailboom to add negative stab incidence, and I think I may have overdone the stab angle(pictures, videos, and measurements coming later if that helps). While doing glide tests, the plane will float slowly to the right(looks a lot better than previous glide tests, travels further too I think!). It seems stable enough, but in flight, it's pretty bad... around halfway through cruise, the plane will wobble and dive(hitting boxes or walls, or the floor). I thought this was due to CG being too far back, which would make sense as the circle size is small, too. But after moving CG forward, it flies flat again and still dives. The plane has barely made it through one proper flight as it keeps crashing...

Another odd thing I noticed was the curious tendency to climb VERY steeply at the beginning of the glide, and then flatten out. The plane would be almost at a 45 degree angle(This is from eyeballing, but it's significant) and climb for 2 seconds, and then slowly climb to a cruise--this was on low torque, too. On 0.24oz torque, the plane flew to almost 26 feet, which was pretty strange(although I did increase incidence...).

Why would the plane turn tight left circles, but glide right? I'm pretty confused... The glide is not slightly to the right, either--it's a 90 degree turn.
Time to check glue joints again... I must've messed up the tailboom joint badly.

See note in bold above.

[bjt4888]

Went flying again today...
It still glides right. I know now where the left skew comes from--I decided to build in 1/2" wing warp(Wow such a smart idea right) because my old plane flew well with that setting. My reasoning was that I could simply use shims to reduce that wing warp, but that has the effect of making the back post tilt to the right, causing the entire center rib and wing to skew left. I'll be regluing that to no wash-in, or very little--although I'm not sure if this is the problem with the right turn. I tried switching wings from my old plane(no built-in warp), and it still glides right although skew is gone... I suspected this, but didn’t mention. The only way to get left skew was to be mounting shim at the bottom edge of the wing saddle. And, yes, this is where your right turn is coming from. Wing skew is a powerful setting. Especially on the wide wing, short tail moment airplane this year. Clever to build in the washin, but unplannedfor consequence.

The odd thing is that it flies tight left circles now. I reglued the tailboom to add negative stab incidence, and I think I may have overdone the stab angle(pictures, videos, and measurements coming later if that helps). While doing glide tests, the plane will float slowly to the right(looks a lot better than previous glide tests, travels further too I think!). It seems stable enough, but in flight, it's pretty bad... around halfway through cruise, the plane will wobble and dive(hitting boxes or walls, or the floor). I thought this was due to CG being too far back, which would make sense as the circle size is small, too. But after moving CG forward, it flies flat again and still dives. The plane has barely made it through one proper flight as it keeps crashing... now that the skew is fixed, all the other left turn settings are too much. Our FF kit flies with very tiny stabilizer tilt (about one degree and equally small rudder offset (same as kit recommendations; pictured and described in the instructions) and it circles pretty small with relatively aft CG. Wobbling is nose light or excess decalage angle. The tailboom negative incidence should be only 1.5 mm or 1/16” over a 4” tailboom. We set this angle with a jig. Since you have new negative inc in the tailboom, you will have to decrease the wing incidence. And with CG moved back (do this 50 mg of ballast at a time) you will need less wing incidence. For example, if wing incidence was 5 mm, with 50 mg ballast moved nose to old CG and 1 degree of negative tailboom, you might need only 3 mm of wing incidence. As you have seen in previous trimming, the airplane is super sensitive to CG and incidence, so make changes in very tiny increments (tiny=1 mm in incidence and 50 mg ballast nose to old CG move).

Another odd thing I noticed was the curious tendency to climb VERY steeply at the beginning of the glide, and then flatten out. The plane would be almost at a 45 degree angle(This is from eyeballing, but it's significant) and climb for 2 seconds, and then slowly climb to a cruise--this was on low torque, too. On 0.24oz torque, the plane flew to almost 26 feet, which was pretty strange(although I did increase incidence...).This is what the climb looks like on our airplanes too. But this strange climb profile gives very good duration. This profile tells you that you are flying right on the verge of a stall (unless you are already stalling; then fix with tiny move of CG or incidence). When we shifted our CG back slightly (from “flat” but good looking flights) and fine tuned incidence, we got another 15 seconds.

Why would the plane turn tight left circles, but glide right? I'm pretty confused... The glide is not slightly to the right, either--it's a 90 degree turn. Much of the turn to the left is due to torque roll on this year’s tricky to trim airplanes. So you can glide basically straight with no power and then circle left under power.
Time to check glue joints again... I must've messed up the tailboom joint badly.

See note in bold above.

More in bold above.

[Astronomyguy]

Regionals are tomorrow for me and I just want to check in with you guys one more time before I'm ready to go. My plane is flying well and we're hoping to crack 2 minutes at regionals, maybe 2:20 if we're good. The blowers will might be on, though if they follow the same schedule as the blowers in my high school (same school system), they could be off.

I've been able to test with the blowers off and our plane performs well. We haven't really had a perfect flight without the blowers, but the highest we've gotten was 2:30 with the blowers on. I feel that the ceiling is a limiting factor - I've had one run where I upped the torque a bit too much and it could've easily pushed 3 minutes had the ceiling been higher. However, I think there could still be some reasonable trim optimizations that could be done to at least near 3 minutes tomorrow.

Lately (the last two sessions), I've been launching the plane from a different area in the gym so that the circle it makes only covers half of the gym (to avoid the divider that hands a couple feet below the girders), which would increase the max height by a couple feet. This works great when the blowers are off, but when they are on, the plane seems unable to climb past a certain height, no matter the torque and adjustment on them. I've captured videos of this and they are shared with the coaches. Today, I had time to test 3 flights, each with more torque than the last. All three were unable to punch past the barrier and reached similar heights. However, I feel that this could be advantageous in that you can wind to maximum without worrying about the height of the plane. As the torque got greater, the time the plane spent at the "soft ceiling" increased, and the times increased as well. Let me know if you have any thoughts on this. It's unlikely to happen in tournament, but it's an interesting strategy nonetheless.

As for the flight in general, I think that the plane could benefit from slightly more instability. The climb is gradual and is unlike the steep climb into a slower climb mentioned by Cat in her recent post. However, slight changes in CG result in slight stalls in the descent that lose time. Any solutions, or is my CG already optimized?

Also, I've removed the little bit of clay I've had on my plane. It was massing at 8.20 grams and by removing the clay it went down to 8.06. I assume this is worth it but let me know if I should keep it for whatever reason.

[bjt4888]

Regionals are tomorrow for me and I just want to check in with you guys one more time before I'm ready to go. My plane is flying well and we're hoping to crack 2 minutes at regionals, maybe 2:20 if we're good. The blowers will might be on, though if they follow the same schedule as the blowers in my high school (same school system), they could be off.

I've been able to test with the blowers off and our plane performs well. We haven't really had a perfect flight without the blowers, but the highest we've gotten was 2:30 with the blowers on. I feel that the ceiling is a limiting factor - I've had one run where I upped the torque a bit too much and it could've easily pushed 3 minutes had the ceiling been higher. However, I think there could still be some reasonable trim optimizations that could be done to at least near 3 minutes tomorrow.

Lately (the last two sessions), I've been launching the plane from a different area in the gym so that the circle it makes only covers half of the gym (to avoid the divider that hands a couple feet below the girders), which would increase the max height by a couple feet. This works great when the blowers are off, but when they are on, the plane seems unable to climb past a certain height, no matter the torque and adjustment on them. I've captured videos of this and they are shared with the coaches. Today, I had time to test 3 flights, each with more torque than the last. All three were unable to punch past the barrier and reached similar heights. However, I feel that this could be advantageous in that you can wind to maximum without worrying about the height of the plane. As the torque got greater, the time the plane spent at the "soft ceiling" increased, and the times increased as well. Let me know if you have any thoughts on this. It's unlikely to happen in tournament, but it's an interesting strategy nonetheless.

As for the flight in general, I think that the plane could benefit from slightly more instability. The climb is gradual and is unlike the steep climb into a slower climb mentioned by Cat in her recent post. However, slight changes in CG result in slight stalls in the descent that lose time. Any solutions, or is my CG already optimized?

Also, I've removed the little bit of clay I've had on my plane. It was massing at 8.20 grams and by removing the clay it went down to 8.06. I assume this is worth it but let me know if I should keep it for whatever reason.

Astro,

We have seen this exact same flight character when the blowers are on. The airplane won’t punch through the rough air and climbs about 50%-60% of normal for a particular launch torque, etc. And, yes, more launch torque and winds does give a little longer flight time at the lower “blowers on” height. Trim for blowers on would typically be with CG slightly further forward (very slightly; as in an almost unmeasurable amount more forward from ideal) and slightly more decalage angle (like 1 mm more). We definitely get longer flight times by experimenting with very slight rear movement in CG, but with blowers on, this trim doesn’t penetrate the rough air very well. 2:30 in rough air at 60% normal height is pretty good in our experience.

Brian T

[coachchuckaahs]

Astro

You indicate moving cg back results in staking. You need to redo your incidence whenever you move cg. So moving cg back, reduce incidence until stall is just barely removed

Coach Chuck

[Astronomyguy]

Thanks for the responses Coach Brian and Coach Chuck! I’ll update on my performance later today.

[Astronomyguy]

Update on Regionals Results:

Short story: I got tiered.

Long story: Because of the way the event was scheduled (Flight was only available in the first 4 blocks probably due to limited participation), I had to fly in block 2 due to conflicts with my partner. I wanted to test the plane during impound, but they wouldn't let me because "too many things were in the way", even though it was far more crowded during the actual blocks. Unfortunately, we were unable to test at all, which would have been fine anyways because my plane could fly well enough on a random flight to win the tournament. However, testing would have alerted me to a critical mistake which I'll mention later.

Their check in was incredibly poor and probably broke many rules. My box was not measured because it was "clearly under the limit", even though it was only 1 cm under in each dimension at most. They had nothing to hold the plane when weighing it on the scale (which only weighed to the nearest gram, mind you) so the wing was resting on the table as they took the measurement. It was then when I realized that I only had one rubber band remaining. I should have pulled out of check-in to make more rubber, but I continued.

I went conservative with winding (85), but it broke when I put it on the torque meter. I had a quick glance at the break, and it looked like the cyanoacrylate I used to strengthen the knot made the rubber band brittle, which nearly snapped the rubber and allowed the o ring to slip off. I quickly made another rubber band and had it done with 2 minutes left. I made it longer than normal (not by too much) to ensure that it was not underweight. I figured that they wouldn't check my rubber after the flight, because judging from the check-in the ES had no idea what they were doing. I had a flight of 1:47 in a gym similar to the one I test in, with the blowers off and a slightly lower ceiling, without any prior testing and winding on a new rubber band. This would have won the tournament by 20 seconds.

As I finished my flight, everyone was impressed, but a new ES (turns out the previous one was an assistant or something) came in late with new scales (the proper milligram ones this time) and requested to re-weigh my plane, because my flight had superseded all the previous flights by at least 90 seconds and they wanted to make sure that "no one would ask any questions". My rubber weighed at 2.7 grams and it was illegal, so I got tiered.

There was an unfortunate series of events on both my part and the tournament that led to this:
1. Me forgetting to make new rubber the night before
2. The tournament not allowing me to test my plane during impound, which would have allowed me to find my mistake (rulebook says that testing is at discretion of the TO, so that's fine but inconvenient).
3. Me not pulling out of check-in when I should have.
4. The tournament not having proper instruments, which created the need to re-impound my flight after it was over (not sure if this is even allowed but it's probably at the discretion of the tournament)
5. The actual equipment being brought by an ES who knew what he was doing, which happened during my 10 minute window.
6. Me not bothering to make a legal rubber band in the rush, even though I had a scale with me.
7. The decision to reimpound my plane but not anyone else's, because the people before me had already left and the people after me had proper scales. My initial impound had everything legal, and anyone besides me could have pulled this off without getting caught. I highly doubt that the ES were attentive enough to realize that we were making a new rubber band and not repairing an old one, except maybe the guy who re-checked me.

I decided not to appeal because this was on me as much as it was on the tournament. Lesson? Always have enough rubber. I try to have 4 going at the same time, and I'll make more if there's less than 3. 6 would be the ideal number though, since it's the maximum number you're allowed to check in.

Our team still placed second to our A team, which was the goal. My season is over unless I'm allowed to participate in the Aerial Scramble trial event at regionals, if there is one. I'll look forward to that.

Biggest lesson for next year? Start early. I had the kit for a while but didn't bother with it until December, missing out on months of testing. Teams who are already on the ground running by the time invitational season rolls around in January and February will see the most success.

I'll still be active here, mostly invested in Division B since I'm helping the local middle school team with their flight.