Re: LittleSquare finally earns its wings!

From: Fred Tellier <fred-tellier_at_cogeco.ca>
Date: Tue, 5 Dec 2006 12:22:49 -0500

Gary

I speak of these things as a somewhat successful indoor modeller ( check USIC and World champs results ), I hold records for events in low and high ceilings and have learned the hard way what works. Theories and formulas are fun to play and I enjoy the brain challenges of flight, but experience is what is the most valuable. I also use the smallest cross section and weight motors I can get away with in all model classes but I will tell you that going to a larger cross section motor and more back off in low ceilings results in maximum times and contest wins. The stop watch never lies to us though we don't always think it runs fast enough on our flights and much to fast on our competitors. My goal is always to spend as much time getting to the ceiling as I can, 10 to 12 minutes with a F1D in cat 1 sites and at least 1 to 1.5 minutes with a Wright stuff type of plane this will shorten the time at the top and reduce the chance of bouncing into the walls after a ceiling hit or worse, a hang up.

In events with maximum rubber weight allowed ( Wright stuff, F1D and F1M for example ) we are going to carry all the rubber allowed. This is why Bill had 2 grams of rubber and not a lower amount.

I bet Bill didn't think his post on the new SO plane would generate this much activity on the list which has been very quiet lately.

Fred Tellier
  ----- Original Message -----
  From: dgbj_at_aol.com
  To: Indoor_Construction_at_yahoogroups.com
  Sent: Tuesday, December 05, 2006 1:29 AM
  Subject: Re: [Indoor_Construction] LittleSquare finally earns its wings!



  In a message dated 12/4/2006 9:55:40 A.M. Pacific Standard Time,
  fred-tellier_at_cogeco.ca writes:

  Low ceiling flying with duration models is all about cruise time and using
  the turns efficiently. The longer one can spend climbing to the ceiling the
  less time spent bouncing around the ceiling and the longer the flight. Even
  with VP props on F1D I use a larger motor cross section in low ceilings than
  high. The goal is to use up the turns in the cruise and the larger motor give a
  little more rpm in the later part of the flight which should and will
  increase the time.

  Fred,

  The thinner motor will spend more time climbing to the ceiling than the
  thicker motor. It has a "flatter" distribution of torque around the cruise point
  for a longer cruise without hitting the ceiling. It permits you to use more
  of the torque curve without exceeding the models ability to control torque
  roll or hitting the ceiling. This model clearly will fly better with a
  thinner motor. It is using a 60 foot ceiling motor in a 30 foot room. It would
  fly better with a better prop, too, but contest rules restrict it to
  inefficient props. For the given prop type, the best prop is the one that flies level
  with the least torque, an easy task.

  We are speaking here in generalities. Thin and thick are relative terms.
  Thinner isn't always better. There is an optimum size. My criteria help find
  that size. The optimum motor is the one that takes off from floor level,
  climbs to and levels off just below the ceiling and lands with few or no turns
  left on the motor. For such to happen, the cruise torque will be somewhere
  in the middle of the torque curve, the exact location depending on the
  distribution of propeller efficiency during the flight.

  In short, my rules for selecting motor size and prop pitch:

  Prop is selected for minimum torque to fly level.
  Motor cross section is selected to produce that level flight torque at about
  mid turns.
  (Motor is wound as close to 100% as you dare)
  Motor weight and length are selected for ceiling height.
  (This can be estimated (1.) from energy required to reach ceiling divided by
  average prop efficiency in climb, (2.) extrapolation from trial flight, in
  which the effect of the prop is implicit in the data or (3.) trials with
  progressively shorter motors. If the motor weight becomes significantly different
  from torque test motor, calculate or re fly level flight torque and
  recalculate cross section.)
  It is an iterative process. Starting with a close guess makes for a short
  iteration.

  Gary

  Note: I wrote this last night and was interrupted, just found it in my
  saved file.

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Received on Tue Dec 05 2006 - 10:26:30 CET