National Free Flight Society

SEN 3149

  1. Kinetic Energy and Shifts
  2. Stretching or Shrinking
  3. New model blog

Kinetic Energy and Shifts

From: Tapio Linkosalo
Two comments on messages in SEN 3148.

One, about reducing model performance. Many authors have suggested adding weight, but I have my doubts on this. First, there is a nice simulation paper in Free Flight Quarterly, where Sergio Montes studied the impact of glider weight onto performance. Taking into account that you can pack more kinetic energy to a heavier model, the outcome was that for gliders, the impact of adding weight to overall flight times was slight. For power models, pulling a heavier model up with the same energy budget probably would have more impact.

Another aspect is safety. Consider F1C, that has higher wing loading than any other FF class. Those models tend to be hazardous if things go wrong, even after a motor cuts. I have seen several spectacular crashes during my decades of Free Flight. Now consider F1C would be of same size but only 400 grams of weight? The model would slow down much faster after motor cut, as the kinetic energy would be much less, and drag still the same. Therefore I would not try to decrease performance by adding weight, but would rather see the weight of F1C models cut down considerably.

Two, Aram suggested a fly-off flown is shifts. This actually proposed and even applied as “group fly-offs”, the rules of which can be found in the 2016 edition of CIAM FF rules ( ). The next year, the group fly-off was removed from the rules. As a matter of fact, it happens on a regular basis, that in Nordic World Cups, where there are much more F1A fliers that power (or F1B) fliers, and weather condition tend to be easy for glider fliers, there may be so many F1A pilots reaching the fly-off, that all the other people on the field are not numerous enough to get even one timekeeper for the F1A pilots. In these conditions we are forced to fly the fly-off in groups, and those occasions show that the group fly-off method, as written down in CIAM rules (of 2016), is a sound and fair method of running the fly-off. So maybe the easiest solution to the problem that Aram pointed out (of extensive flyoff size) is to re-implement the tried and tested group fly-off again?


Editor’s Observation
Maybe Tapio’s posting is a version of the famous ominous prediction, the “writing on the wall”  Daniel 5 :25-29 Weighed, weighed, numbered and divided…

Stretching or Shrinking
From: gliderbohm
Roger, didn’t you mean to say that LH might work in a bit LESS of a stretch (of the flight line).

Stan, you are correct and LH  could take at least 50 poles before a little line shrinking or field stretching was needed.

New model blog

From: Nenad Batocanin

Hello Roger!
We have launched a blog dedicated to Free Flight modeling:

If you have an idea or something interesting to say for other FF modelers, I invite you to write a text about it and send it to my email 🙂
I would like to ask you to post this on the SEN list.
Regards, Nenad Batocanin