National Free Flight Society

SEN 2190

Table of Contents – SEN 2190

  1. F1A Riddle
  2. Award to Ken and Chuck
  4. More plus more on progress – Re: SEN 2189
  5. Altimeter timing – Canadian twist on a Bulgarian style flyoff.

F1A Riddle
From: Ken Bauer

The dynamics of a towline glider at high speed with high line tension seem
to be somewhat different than normal free flying models. Here’s a question
I’ve been thinking a lot about recently so I’ll post it here for technical

My father taught me that the rudder on a free flight model works as follows
considering a right turn. Right rudder causes a right yaw and because of
dihedral in the wings a right yaw means that the left wing has a greater
angle of attack than the right wing causing a roll to the right, and the
lift on the wings during the right roll is the primary force causing a
right turn.

Now consider a F1A glider with high line tension. It is well known that
wash-in on the right wing or a greater angle of attack will make the model
turn right, not left, so the increased drag of the right wing is
dominating. So if this is true how does right rudder under these same
conditions make the model turn right, or is rudder even effective in this
case? Right rudder will cause a right yaw which should increase the angle
of attack on the LEFT wing or act like wash-in on the LEFT wing, but if
drag dominates as just stated then the model should turn left, not right.
Could the side-slipping effect of the right yaw be dominating in this case
allowing the model to turn right on the towline?


Award to Ken and Chuck
While there is no doubt that Free Flight face many difficult issues these days to keep it alive.

There are many difficult issues and we have seen discussed. It is very important to discuss the issues so we can some to the right answers rather than have one spring upon us.

But we must not forget we like flying this stuff because it is a technical sport/hobby. So a couple recent pieces by Ken Bauer with a comment from Chuck Markos serve to remind of the things we like doing with the dsign and operational problems we need to solve.

From: Stuart Darmon

Hi Roger,
in with the gum shield, here we go again…I don’t think there is an answer in the altimeter timing debate, because like all our other disagreements involving technology & performance, both sides are equally right. Time and again we skirt around the real issue, which is a paradox at the heart ofFAI flying. It used to be simple; pursuit of excellence, period. You built the best model you could and flew it to the best of your ability. Performance through technology was placed on a pedestal, because it spoke for the skill and ingenuity of the guy who flew it. Then we decided that you don’t need to build your own model. There were many sound reasons for this, there’s no going back, and I’m not trying to re-open old wounds. However, we can’t just pretendvnothing else changed. Only the flying of the model is now judged- who made it is irrelevant, yet the model and the technology it contains have never played so great a part in determining who wins. This is the paradox.

In the years since that decision, two divergent views of the sport have emerged, even if those who hold them don’t always consciously realise it. One side cannot understand why technology remains a sacred cow as before, even though for most flyers it now only indicates the size of his cheque book rather than his skill or ingenuity. Surely, they say, the expense and complexity of the models deters people? And isn’t allowing performance to endlessly escalate while flying sites shrink and vanish like fiddling while Rome burns?

The other opinion is that FAI flying provides access to the best technology for all, and that curbing it goes against the very spirit of FAI, and would be a triumph for mediocrity over excellence. “Sorry if you have no where to fly, but that doesn’t
give you the right to drag us down with you.”Let’s be honest, some even like the fact that the models are expensive as it bestows certain prestige, like membership of an exclusive club.These differences are fundamental and colour our outlook in every debate. As external pressures mount the debates will only intensify. Surely we could give some real thought to developing a parallel set of rules to satisfy both factions?

Taking Martin Dilly’s specifications for example (nobody wants wooden airframes and straight-tow gliders), all that
would be needed is a separate classification in each contest for such models,
which because they also conform to the existing sporting code would not require
a different event of their own. I know there have been various piecemeal attempts to try this –I ran one myself this year-
but without the gravitas of FAI status it isn’t a fair trial (although we actually had a good contest), so somebody needs to
bite the bullet and propose it as a rule.

Yes, it might wither on the vine like F1P, but that wouldn’t affect the championship classes,so no harm done, and at least the technophiles get to say “told you so”.

Regards, Stuart

Editors’s comment – Stuart’s text had a number of words run together and dis jointed paragraphing. It is SEN’s policy not fix these things. In this case we did fix some but if in doing so we make Stuart’s piece harder to read we apologise in advance

More plus more on progress – Re: SEN 2189
From: John Carter

More plus more on progress .
Hi just to keep the record straight as Bernard Guest does not know me please be assured antsy technology i am not indeed not only do I fly the current carbon skinned models but back in the 80s I did quite a bit of work myself building what was then Kevlar and Glass skinned wings over blue foam . now that’s settled I am concerned not for me I would just simply install the approved altimeter and bobs your uncle up to speed . The issue is we are in danger of adding technology just because it’s possible .

Address performance issues and reduce flight times and no need to add this timing technology . Any way with out telemetry and ad happen at Equinox cup some models got stuck up trees so how do you get the flight score ?
It’s probably that in the UK we fly open events with no max in the fly offs that we are more used than most in timing large flights .

Some more thoughts to help contain performance .

Ban thermal detection equipment thermistors wind meters long streamers etc.
Reduce fly off periods to first fly off 5min working time ok to set up fuel up and wind prior slot
Second and subsequent fly offs 2minute working time .
We still have a chance to ban flappers in A,B and Q ,some about but as yet not highly used .
f1a reduce line to 40 metres

Also reduce number models to 2 not 4 .This means you need to think more what conditions will be !

Remove the 20 second attempt rule,left over from ROG days .
No doubt the forgoing will temp some interesting replies, we need the debate .

John Carter UK

Altimeter timing – Canadian twist on Bulgarian flyoff
From: Craig Limber

Although I don’t fly in contests I’ve been fascinated by the discussion
regarding tackling timing challenges using altimeters.

I wonder if it might be worth considering using the height attained
at certain periods of the flight to determine the score. For example,
the height at the four minute mark would count. To do well still
requires all of the expertise to attain a good launch, pick good
air and have an excellent glide while simultaneously limiting the
flight duration.


Editors ( and software developers) comment – One of the issues, Craig is that all altimeters do not measure altitude with equal accuracy. Having worked on altimeter software and used a number of the different product that are available there are a number of relatively complex calculations that need to be done in the software to get a very accurate reading. If you intend to use the measured altitude in any way then the devices would need to be certified. Allard’s proposal just relies on the altimeter just showing that the airplane is still flying this avoiding this issue.

Roger Morrell