National Free Flight Society

SEN 2021

Table of Contents – SEN 2021

  1. Kommunication is King on C RDT
  2. Remote Dethernalization of F1C Models – Kaynes
  3. Further RDT Clarification – Etherington
  4. Allards F1C reply
  5. Dino on SEN 2020
  6. Should we really be talking about RECO – Schlosberg
  7. Marty Thompson
  8. F1C Aussie style

Kommunication is King on C RDT

In this issue we have 3 important posting on the RDT for F1C

Firstly a message from Ian Kaynes that explains the cuurent rule and the new rule.

As Ian notes there was quite a lot of confusion around this. Clearly many people thought the rule was ‘worse’ than it is.

Secondly Chuck Etherington, the USA person on the FFTSC goes into some detail on how and when RDT might be used. Chuck shows that in spite of what some people thought the FFTSC is aware of many of the issues surrounding RDT and F1C.

Thirdly the posting from Aram defines a new term RECO – remote engine cut of and shows how it different from RDT. Ian and Chuck’s posting also make this distinction but the do not call it out as clearly as Aram does.

Remote dethermalisation of F1C models

From: Ian Kaynes
To: ‘Walter Ghio’

[Explanation – Walt Ghio requested Ian Kaynes to share details of the outcome of the CIAM meeting about RDT. Ian had previously answered some of these questions in a private email to Henning . Note that the official minutes have not come out yet. So here is Ian’s explanation with time lines. This clarifies a number of points]


Yes, of course. It is probably worth adding a bit of explanation to help
stop the usual misunderstandings, making a possible insertion:

The proposal from Austria modified just the single sentence taken out of the
F1C characteristics paragraph on RDT. The remaining words about RDT stay the

The current rule reads:

F1C models may use radio control only for irreversible actions to control
dethermalisation of the model. This may include stopping the motor if it is still running. Any
malfunction or unintended operation of these functions is entirely at the risk of the competitor.

And from January 2016 it will be

F1C models must be fitted with functional radio control only for
irreversible actions to control dethermalisation of the model. This may
include stopping the motor if it is still running. Any malfunction or
unintended operation of these functions is entirely at the risk of the

And this means that the REQUIREMENT is to have radio DT. It remains an
OPTION to have it stop the motor. There is no requirement on when it is or
is not used, specifically no requirement to use the DT at any time when the
model is flying faster than glide speed.



Further F1C RDT Clarification

From: Chuck Etherington


You are correct. In the technical meeting the Austrian proposal was changed to read: “F1C models must be fitted with functional radio control only for irreversible actions to control dethermalisation of the model.” Motor shutoff is not mandatory and actually using the RDT is also not mandatory. The thinking was that if it’s available on F1C models, the flyer can use it at his discretion. The problem is that his opportunity to use RDT safely is extremely limited prior to the glide phase.

With non-folding F1Cs, there is a critical velocity below which RDT will provide more safety for those on the ground, and above which RDT will provide less safety. The defining speed is that which causes the wings to come off turning the model into a more dangerous ballistic spear. Below are a couple of different scenarios:

1. Models fitted with mechanical timers (no motor shutoff):
A) DTing mechanical models before reaching the glide phase is difficult (because no single line can be released to allow DT). By the time a model is gliding, the safety issue has passed. Although useful for the remainder of the flight, it will not enhance safety.
B) Even if there was a way to DT it prior to glide, the model would be in climb or transition mode and be above the critical speed. At no time prior to going to the glide phase would the model be going slow enough to DT safely. DTing it would fold the wings and turn the model into a corkscrewing ballistic spear.

2. Models fitted with electronic timers:
A) The engines can be shut off ahead of the activation of RDT but it is only useful if the model is still pointing up. If the model has gone off pattern there is little opportunity for the model to slow below the critical speed, and the flyer has to decide whether to fold the wings and turn it into a ballistic spear or let it crash with the wings on.

My feeling is that the rule will mandate that flyers have the ability to separate the wings from their model during the climb and transition phase which, rather than increasing safety, will actually decrease it.

Allards F1c reply

From: John Cuthbert

Allard appears to miss my point entirely. His original opening statement said Quote “Flappers and folders have less drag than conventional ships” Somewhat obvious. He then follows this by saying Quote ” The acceleration and speed in the first 2 seconds is almost identical” No it is not. Simple physics: less drag -higher acceleration and speed. More drag- just the opposite. So performance in first 2 seconds is significantly different.
My reason for introducing comparisons between geared and non geared engines was to highlight the difference between how the two engines deliver their power and hence perform. It is still clearly possible to win with a geared, conventional fixed wing model. Reference Peter Watson’s World Champs win in 2011 against the original and most winning folder i.e. Leonid Fuzeev’s. What I do believe is that a straight drive, fixed wing model on 4 secs. has no chance now because of the reasons I highlighted in my first response. This is why this rule is so damaging. It does not equal things up, it drives them further apart resulting in lost participation I’m afraid. Which we CANNOT, CANNOT afford.

Regards, John Cuthbert.

Dino on SEN 2020

From: michael achterberg

It is what it is.
We are throwing geared into the argument. Eugene produced the flappers. They are all geared. The folders are produced by Artum and they are all direct drive. Fixed wing are a combo of both.
We are comparing what the F1c community flies.. Geared fixed wings get higher, but glide worst. By the time they reach ground its pretty much a push.
But in either case the time it takes for them to reach terminal velocity verses the other two options they are affected more by 4 sec than the other two options.
Not that they were really viable options to win anymore anyway. But as a stepping stone to get people involved in the event they had value. With 4 sec the value is greatly reduced. Why even try and invest with zero chance of being competitive?
This is a multi faceted issue. Does the CIAM want to eliminate this lower cost, basically entry level option from new flyers and old flyers from the event?
That is why I was proposing a .5 sec more engine run for fixed wing direct drive models verses flappers, which are all geared and folders which are almost all direct drive.
I have both, and like the idea of balancing the field so to speak. But there has been little discussion on this idea, so I will bow out and let the flying community decide what they prefer. But in my opinion a flat 4 sec will kill the event and only real option is the folder.
Michael Achterberg

Should we really be talking about RECO?

From: Aram Schlosberg

Literally, RDT (remote/radio dethermalization) means that an irreversible change in a
model (popping up the stab) triggered by a radio signal. It causes the model to switch
from a gliding/climbing mode to a dethermilizing mode. RDT is optional. In practice,
models are RDTed to prevent models getting off the field, hitting hazards or to save
them in bad launches.

F1C can be prone to dangerous climb patterns, and if the model crashes under power it
can cause serious collateral damage. Cutting off the engine as soon as the model
seriously veers off course is the critical step in reducing such hazards. To be effective,
the cutoff should be done before the model is diving under full power. So we are really
talking about a Remote Engine Cut Off, or RECO.

For C models, RECO and RDT are different functions. If a RECO is performed on a C
model and it lands under 20 seconds, with or without a RDT (meaning popping up the
stab), the flier is granted an attempt. I’m surmising that CIAM intended to mandate
RECO for C models, not RDT (stab popping).

In fact, calling the new C mandate RDT is confusing. The two functions are distinct.
RECO should only require that the engine be cutoff by a radio signal. To encourage its
usage I think a Mulligan (a 30 seconds attempt) and operation by a safety officer would
be nice features. The issue of how to DT the model, particularly in the case folders is
really outside the scope of a RECO mandate. ///

[note Aram’s posting came in before the clarification from Ian so there is no requirement for RECO as Aram calls it]

Marty Thompson

From: Shailor, William

I am shocked by the news of Marty’s passing. The Free Flight community has lost a really great guy. I saw Marty fly at the NATS in the 70’s but didn’t get to meet him until the Taft Finals in 1980. A true gentleman and superb builder. He will be missed.
Bill Shailor

F1C Aussie style


Regarding F1C rule changes.
I have enjoyed seeing my fellow fliers excel in thier choice of F1C category, and have been inspired by there achievements. Particularly Roy Sommersby current F1C World Champion. Now to read so many negative comments regarding rule changes to this category saddens me. I take on board every perspective of readers comments, But I wont be adding F1C to my wish list during this time.

Matthew Hannaford.

I love the smell of silicon lube in the morning.

Roger Morrell