Flight B/C

[jander14indoor]

For those of you that have been to tournaments: I have two planes, an impound box, and a toolbox to carry by myself after impound. Since the 10-minute flight period starts as soon as the ES finishes measuring the motors, would you guys recommend disassembling the plane and carrying it? I'm worried about losing time, because I'll likely need the full 10-minute period. I'm also probably going to have to take two trips from the impound table to carry everything so I'm pretty anxious. For those also flying solo, any ideas? Is it just: pile stuff in your arms and hope that nothing falls?

A lot of it depends on how the ES manages things.
For one thing, not sure where "impound" is coming from. Not in the rules.
Also not in the rules is any requirement that the ES immediately return your motors after weighing them and starting the 10 minute clock. At a big tournament, they often can't because the timers may still be busy with the previous team.
Yes your 10 minutes starts when the ES (or their timers) hand you the rubber. But a good ES should allow you to set up your equipment and only hand you motors when you are ready.
- If that is the case, just move your equipment to where you intend to wind from and get it all ready to go. Don't dawdle, but don't rush either. Once you are ready, let the timers know, if they are free, you should get motors immediately. If not, you may have to wait a short time.
- If you have an ES that acts as you describe.
-- Consider having a teammate just for transport, even if they just stand around for the actual flying .
-- Get to the competition area early. Scope out where you will wind (short distance from check in) and make a plan to move their quickly and set up after the ES hands you motors.
-- When you go for check-in (not impound), or perhaps even before, ask if the ES can hold your motors while you move your equipment to where you plan to wind. If they say yes, you are back to the previous plan.
-- Alternatively. Ask them if you can set up your equipment BEFORE checking in. Then you only need to transport your planes and rubber to check in and back to where you've set up to fly.
-- If not, plan to leave the box somewhere near checkin. Tool box too if large, have a smaller box with minimum equipment. Maybe instead of a box of minimum flying equipment, get a shoulder bag or back pack to carry that stuff in. Leave your hands free to safely carry your planes.
-- Transport the minimum equipment to wind and your planes. Under no circumstances do you HURRY. Broken planes likely can't be fixed, or if fixed won't fly as well.
-- Get one good, safe flight in. Focus on that. Then go for the ceiling banger for a second official if you have time.

Oh, and I would NOT disassemble your plane. Just adds opportunities for mistakes in the pressure of competition. Have it set up and ready to go (mostly at least) before you even check in.
Another "Oh", if you have two planes, I think you need two inspection boxes. Just checked the FAQs and the rules, yes, rule 2.a requires each plane in its own box.

Jeff Anderson
Livonia, MI

[Astronomyguy]

For those also flying solo, any ideas?

Cat,

How do you wind your rubber band when flying solo? I avoid solo flight sessions because I can't stretch my rubber band far enough to get a good number of winds on it. I've seen some people at tournaments with torque meters that you hold down with your feet while standing up, but my rubber bands are ~15 inches unstretched, so they would have to be stretched 7.5 feet to meet it. Holding the winder high above your head could work for me but it's dependent on a person's height. What method do you use to wind the rubber bands solo?

[danxmemes]

Does your plane have a long motor stick? If so, it's bending under the high torque you're winding to(0.5oz, right? that's pretty high. I wind to ~0.25oz to get to 23ft). If you look at this year's Div C FF plane, you'll see a kevlar truss with a balsa support on the plane. That is to help with the long motor stick's flexing and prevent the stabilizer's angle from changing, like BrianZ said above.

I have a standard stinger motorstick, and I don't think that it is flexing. I think that more of the issue might be because the speed and the climb rate? I' going to check if its flexing though

[coachchuckaahs]

For those of you that have been to tournaments: I have two planes, an impound box, and a toolbox to carry by myself after impound. Since the 10-minute flight period starts as soon as the ES finishes measuring the motors, would you guys recommend disassembling the plane and carrying it? I'm worried about losing time, because I'll likely need the full 10-minute period. I'm also probably going to have to take two trips from the impound table to carry everything so I'm pretty anxious. For those also flying solo, any ideas? Is it just: pile stuff in your arms and hope that nothing falls?

Cat:

I agree with everything Jeff said.

We have never been to an event where the kids were put into a rush, even Nationals. But, it is your responsibility to not hinder process, to be prepared.

My team will enter the contest area with their equipment, pick a location to safely wind and limit the walking distance to a launch point. They will COMPELTELY set up PRIOR to approaching the check-in table. This minimizes the opportunities for officials to get impatient. Our setup includes a table with velcro attachment of our torque meter, a shoe for our winder, set to the proper distance for our motor stick. Also set up is our glue tote, our tool suitcase, some scotch tape, stands for the planes, and our recovery pole.

When they approach the check-in, they ONLY bring the items required for check-in. This includes the plane(s), the box(es) (require this year), the logs, and the rubber. This year we transfer the planes from the transport box to the check-in box before approaching the check in, as the rules indicate that you need to present the plane in the box. The plane is fully assembled, as required in the rules. In fact, we have a large enough transport box that we never disassemble the plane for transport, especially this year with the very sensitive adjustments of decalage and CG.

While the rules spell out what may be brought in (very broad, any "tools" needed. We include "table" as a "tool"), they do not require such items to be brought to check-in.

As an ES, and also watching other ES's at events, my team does not return the rubber motors to the students until they are at their winging location and ready to start. We do not need to cause a rush at the check-in station, where forcing the student to move on the clock could be hazardous to their plane as well as other schools' planes. Talk to the ES or timing team and let them know your intent. If they want to give you the rubber motors at the check in table, calmly explain the hazards to your entry as well as that of others.

Move carefully, but do so with purpose so that officials have no reason to push.

Coach Chuck

[coachchuckaahs]

I have another question, about rubber this time.

1) how do I adjust my propeller/rubber setup so that I am able to land with the least number of winds possible?

2) What is the process of adjusting to thinner rubber with the same propeller? I know that some teams are using less than 3/32, but with the standard propeller. Is it something to do with the overall wings and design?

3) is flared props better? I have tried them but I end up landing with a bunch of rubber left, and less time left, but I would like to figure out how to get flared props to work

4) not as much to do about rubber, but I notice my plane vibrates during flight, especially so during takeoff and high torques, what causes this and how can I fix it?

5) Lastly, what are everyone else getting on their 3/32 rubber winds? I get around 1650 maximum at .5 inch ounces torque. I have to wind to 1800 and wind down for the torque. Otherwise (even in high ceilings) my plane's stab starts curving and the entire plane crashes to the ground. Should I be able to get more winds if I stretch longer and stay out longer? and how can I not make the tail bend like that and have the plane dive?

Thanks in advance!

1) "Least number of winds possible" is not the correct criterion. "Longest duration" is what you want, even if it leaves winds. Generally, if the ceiling is low enough that you must unwind some, then the winds remaining are similar to the winds removed before flight. This is only a guideline, the stopwatch will tell. This year's plane requires some horsepower to stay aloft, so we are seeing some evidence of more winds remaining for optimal flight. The adjustments: Thicker rubber will leave fewer winds at the end (more power in letdown), but will take fewer winds. A decrease of prop pitch will leave fewer winds, but will also provide more climb, and will spin faster, using winds faster. So it is a two-variable optimization. At a given pitch, you will find an optimal rubber width, but then you need to change pitch and re-optimize to find the overall optimum. Note also that decalage and CG will determine how "flat" the plane flies. A flatter flight may use winds faster, but a nose-up flight may have more drag and need more power. Changing decalage/CG may change your optimal rubber for a given pitch. Now you have 4 variables to co-optimize!

2) See answer #1. I mentioned 4 parameters that optimize together. Other trim factors (wash-in, rudder offset (circle size), and others will affect the drag and overall trim, and higher drag will optimize at a thicker rubber motor.. There is no such thing as a "standard" propeller. While there are two Ikara style props (symmetric and flaring), there is little consistency in pitch. You NEED to measure, record, adn adjust your pitch. If you adjust too many times, be sure to have spare props because the plastic spar will fatigue and fail. Some have seen a higher horsepower (lower pitch than traditional) do well this year, you can go too far. See #1 above, work on the global optimization

3) Flared propellers offer the advantage of absorbing higher launch torque (higher pitch at launch), so you do not have to unwind as much, potentially leaving more "fuel in the tank". If done right, they then flex to a lower pitch later in the flight, potentially using more of the remaining winds and therefore emptying the tank more in flight. The stock "flaring prop" is far too stiff and thus does not add much flaring. Some have sanded the blades carefully to get flex in the blades. Others replace the spar with something more flexible (sanded basswood, or multiple 0.020 carbon rods). IF done right, you are adding SEVERAL new variables: Flare softness, flare percentage (how much of the prop is ahead of the spar), and initial (static) pitch (actually static pitch was a variable already with the symmetric prop). If done right, the flaring prop can be a significant benefit. But, until you are at or over 3 minutes, you probably have other areas (trim, prop/rubber matching) that are lower hanging fruit.

4) One commenter noted your prop could be out of balance. Fix this as needed. However, it is more likely that you have not checked the pitch of your prop. Small differences a degree or two) in the pitch between the two sides will cause high-torque wobble. The "stock" props may vary tip to tip over 5 degrees.

5) I do not have numbers in front of me, run Coach Brian's turns calculator to see if you are in the right range on winds. A torque of 0.5 is probably a good max launch torque until you have exhausted other areas of flight optimization. In standard gyms we are using 0.4 to 0.5 torque, adjusted to ceiling height. And that is with a flaring prop, so with symmetric you may be less. But you are having issues beyond just too much climb. It sounds like your stab is on the weak side. The aero forces are resulting in a twist of the stab (leading edge and trailing edge tilting differently. For very high launch torques you may need something stiffer for your stab spars (we use the 1mm tall carbon). However, we fly LPP planes with 0.020 carbon stab spars, and launch as high as 1.2 torque in a very high facility (96 feet). Check your stab spars. Are they exactly parallel to each other? Are they STRONGLY fastened to your MS/Tailboom? Is the tailboom portion between the stab spars stiff enough in torsion to keep the spars parallel? If your plane has tip plates on the stab, are they straight and parallel?

Coach Chuck

[Vive]

Unexpectedly (the scheduled ES didn't show), I got to run the University of Michigan Invitational, Flight B this weekend. Results:
Top Team 3:20ish
Second just short of 3 minutes
Two teams at 2:30 or so
Four teams around 2 minutes
This is out of 27 teams total.

I didn't get the div C times.

Tiering for oversize boxes. I used a very precisely built gage that I'll use at regionals, Mi State and Nationals. I only tiered 5 teams for oversize boxes, and talked to many teams who had cut down boxes from failing at previous invitationals. The best times were not in boxes that pushed the limits, they were pretty clearly OK in the gage, except one. Seems teams are getting the idea.

Jeff Anderson
Livonia, MI

What was the ceiling height?

[bjt4888]

Vive,

The ceiling was tall, but as there were tricky air currents, it was only safe to fly 25 - 27 ft. Any higher and there was a very good chance of hitting girders. The two best flights in B were were at about 23- 25 ft climb height.

The gym ceiling was “peaked” and had a center height to the girders of 40.8 ft. The FAI ceiling height (height to fit a 15 meter diameter column) was 29.5 ft. But any team above 25 ft. Had a high likelihood of drifting into the side girders or the walls.

Brian T

[jander14indoor]

Vive, what Brian T said! He was there with his team.

Jeff Anderson
Livonia, MI

[pumptato-cat]

For those also flying solo, any ideas?

Cat,

How do you wind your rubber band when flying solo? I avoid solo flight sessions because I can't stretch my rubber band far enough to get a good number of winds on it.

I clamp my torque meter to a table. It's quite a hassle to find a table so sometimes I'll clamp it to gym railings, chairs, or anything I can find. Works for me! (I think clamping to the tool-box works fine, too) Definitely possible to fly solo--I've never done it any other way and you just get used to it after a while.

jander14indoor,
THANK YOU!!! That cleared up so many questions I had. How do you not disassemble the plane? I don't have a big enough box to transport assembled planes. Do you mean to transport them unassembled and then assemble them before impounding with the ES?
I'd use my partner, but the last time she touched my planes, she broke the stabilizer off.. That was four months ago.

coachchuckaahs,
Thank you so much! I will talk to the ES. That's very helpful--I'm glad I won't have to rush and run around with my plane...
I have more questions but my computer is currently at a whopping 5% battery! I'll probably be back in a couple of hours :| Thanks everyone!!!

[pumptato-cat]

Okay I'm back--12% now without charge?? I think my computer's secretly laughing at me...
Anyways here are my questions!
1) Are you allowed to set tables up on the sidelines? I'm worried this might interfere with others' official competition flights. (50'x100' gym width and length)
2) Are you allowed to impound/"check in" in multiple trips? So for example, "check in" one plane, go back to the table I bring to the competition, and then repeat the process with the next plane?
3) For any recent competitions you guys have attended, are trim flights normally allowed? The rules state that they may occur "At the Event Supervisor's discretion". Not sure if that that they're not allowed if the ES says they aren't.
4) Has anyone noticed significant variance between launch torque, different flying sites, and different climb height? I've noticed slight variances but I'm not sure if that is due to rubber or different air.