Wright Stuff C

[coachchuckaahs]

In addition to the rubber, if you have a plane with balsa spars, look for new warps that could cause new trim even with same wing post settings.

While rubber does degrade from use, usually not this much. We wind hard, and get 5 to 8 flights out of rubber before failure, which means breakage. We use new rubber at events, with break in, and find the data very repeatable. We have accurate measurement of rubber linear density.

You did not mention flight character. Was climb altitude on each lap the same as testing? We estimate altitude every lap, which can give clues as to what has changed.

If no trim changes, it is possible something is damaged or changed on your prop, especially if a flaring prop.

The science does work. We have about 20 columns of data, and by nationals probably 400 flights. We can easily see how different flight characteristics are impacted by settings or issues.

Look the plane over carefully. Let us know more about what changed behind just time. Try a new prop.

Coach Chuck

[Airco2020]

Thanks Coach Chuck. You've confirmed one thing, something changed, I just don't know what yet!

I haven't taken it out of the box since the competition Sat. I'm hoping to get some time later this week to work on it and test again.

Thanks for all the advice on the forum! Our school doesn't have much of a tradition in this, or the other build events, so it's great to come here!

[coachchuckaahs]

Glad I can help. Keep us informed as you look for changes.

I try to give back. Three years ago I was asked to help, and knew nothing. Our team was afraid of builds because you never know what will fail. I am an engineer, and brought a different view. If you test enough and perfect your build, you KNOW what it will do, and what the limits are, and the competition becomes a given. Unlike the test events where you have no idea what the es might put on the test.

We have done well by relying on the data and the science, and learned a bunch on this and other forums. So it is a pleasure to pass on what I have learned!

Coach Chuck

[Rossyspsce]

Anyone know how to wind using torque burners?

[CookiePie1]

Anyone know how to wind using torque burners?

This might be a stupid question, but what is a torque burner?

[bjt4888]

For torque burner discussion, see replies 95 through 99 here:

http://www.hippocketaeronautics.com/hpa ... c=17412.75

This strategy requires a lot of gym time to perfect. As in A LOT. Your time would be better served by improving propellers and propeller and rubber matching and getting lots of turns into the motor.

Brian T

[calgoddard]

Brian has given excellent advice, as usual. I would like to expand on this topic so that you understand that employing a torque burner is only something to try after you are already consistently flying over 3 minutes in a typical-size high school gym with an airplane that meets the specifications of the 2019 WS rules.

After you read the earlier posts on HPA explaining how to construct and use a torque burner, be sure you read my Reply #99. I explain how difficult it is to properly use a torque burner to achieve an advantage over a flier with a well-trimmed and properly wound model that does not have a torque burner.

I saw a team use the torque burner technique at the 2015 SoCal State finals in WS. That team's plane initially climbed to about half the height of the gym, and then descended to about 3 - 4 feet from the floor. I then heard a pop or zing noise and all of a sudden the airplane started climbing again, but once again it only climbed to about half the height of the gym. I immediately concluded that this team had used a torque burner. The unusual flight pattern was not the inadvertent result of a knot in the rubber motor momentarily hanging up. Afterwards I complemented this team on its semi-successful use of a torque burner. They were apparently reluctant to confirm its use because they did not want to give away their "secret." This team only divided the rubber motor in half, i.e. they had the fully wound rubber motor surround a single pin inserted into the motor stick that was positioned halfway between the prop hook and the rear hook. This team did not win the WS competition at the SoCal State finals that year. I think they finished in the top five. The WS event at the SoCal State finals is brutally competitive.

Torrey Pines High School (TPHS) won the WS event at the SoCal State finals that year with a time of 3 minutes and 45 seconds. The competition took place in a typical-size high school gym with a flyable height of about 24 feet. TPHS did not employ a torque burner. I believe that the team that used a torque burner would have needed to divide the rubber motor into thirds, and then perfectly execute the technique to have a chance of beating TPHS. By perfectly executing the technique, I mean that the airplane would have needed to fly at least 3/4 of the distance between the floor and the ceiling on each of the three legs of the flight. Here is a link to a video of TPHS's winning flight:

https://www.youtube.com/watch?v=lmW6yvFQOIE

The rubber motor size of the TPHS plane was perfectly matched to the prop. The rubber motor was perfectly wound to achieve a long slow climb, a long cruise just below the beams, and a long descent. Brett Sanborn, who perfected the torque burner, is probably the only person who could have flown longer than 3 minutes and 45 seconds in a similar size gym with a 2015 WS airplane when he was a high school student. Brett Sanborn won the world F1D championship in 2018. That is the single most difficult indoor flying championship to win.

Brian is correct. Follow his advice. I wish everyone who is still going to compete in the 2019 WS event the best of luck.

[newflight]

'The rubber motor was perfectly wound to achieve a long slow climb, a long cruise just below the beams, and a long descent. '

How to perfectly wind the motor? I read past threads and got some general ideas on how to wind the motor, however, how do I know it is perfect or not?

[bjt4888]

Newflight,

By perfectly wound, I believe what is meant is both perfectly selected by extensive testing of various rubber densities and lengths matched perfectly to propeller pitch, flaring softness and other propeller specs and this perfectly selected motor length and density wound repeatedly in many test iterations to discover exactly the greatest number of maximum turns and the maximum torque and the number of backoff turns and launch torque that will cause the airplane to rise to the particular ceiling height and cruise there for a good duration; maximum duration tells the tale.

So, lots of testing and a logical progression of rubber and prop variations along with good winding technique.

Brian T

[coachchuckaahs]

Brian said it! Data, Data, and more Data! You cannot have too many log entries. What is "perfectly wound" for my team will not be for your team. Depends on plane, trim, prop, etc.

Look through prior posts for keys to tuning prop to rubber, or vice versa. Change one variable at a time. Take data.

Coach Chuck