SEN 2220a - 21 Nov 2016

Table of Contents - SEN 2220a


  1. F1P design problem
  2. German F1C Proposal
  3. Reply to Ross altimeters and all that !
  4. Altimeters.
  5. J again
  6. F1j then F1p.
  7. Looking for a J
  8. Reminder


Some users reported not getting all of SEN 2220 so we stopped it and changed something and sent it again. Apologies to those whose SEN was messed up and those who got two!


F1P design problem


From: gil morris
Hi Roger. I think the major problem with F1P lies with the broad wing so dicted by the rules. The wing has a light wing loading and glides slowly (low RN) with center of lift forward because of air separation over aft part of wing. However,if the model gets into an awkward position, as it might at end of power run and hammerhead stalls and dives and picks up speed (high RN), then center of lift moves rearward causing further diving tendency and model dives into the ground or long swooping dive and loss of altitude. The broad wing has considerably more shift of center of lift than narrower wing exasperating trim problems. Solution: Use thinner wing section to minimize lift shift. Admittedly this introduces less  wing rigidity but that's a different problem. And so it goes.  Gil

German F1C Proposals



From: Ed Carroll
Roger,  Please post on SEN.  I would hope a vote is taken of all active USA F1C flyers regarding support of the German F1C proposals as binding advice to our CIAM representative.   Is that still Chuck?  Thermals, Ed Carroll

Summary of Changes 

Change 1 - affects motor run

Distinguished are:
a)         Models with variable geometry (changes of camber, incidence or area) grade A with Maximum duration of motor run 4 seconds from release of model.
b)         Models with fixed geometry (fixed camber and fixed area) grade B with Maximum duration of motor        run 5 seconds from release of model.
Type the reasons in the space below:
The season 2016 shows clearly that there is a big difference in using a Folder or Flapper with 4 seconds motor run time in comparison to a normal straight model. In more of 90% of fly offs models with variable geometry are wining competitions. Test shows that after climb there is a difference from about 30 m in high and in glide there is a difference from round about 60 to 90 sec or more in dead air.
To compensate the performance difference between categories A and B there should be a difference in model specification and a difference in motor run time. In this way new developments are not blocked, investments keep valued.
The competitor can make his own choice, to take a grade A or grade B model, depending on circumstances. Most important is to avoid that many members of the F1C community will leave the sport; because they feel it is no fun anymore because they have to buy and use a model that is not easy to handle. For a beginner it is easier to start with a model grade B, because handling is easy and low tech only. And he will have fun in competition because he is able to have success with simple models. Later he can change to grade A if he wants. So everybody can make a free choice and have a fair competition on the level he wants.

Change 2 - affects Radio D/T

Effective 1.1.2020
Type the text changes in the space below (show deletions as strike-through and additions as bold underlined):
F1C models must be fitted with functional radio control only for irreversible actions to control dethermalisation of the model. This may  must 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.
Type the reasons in the space below:
The requirement to have a radio control for dethermalisation was introduced as a safety measure. But with a running engine the actuation of the dethermalisation may destroy the model there will be not increase of the safety. Thus it is necessary, that the radio control includes the possibility to stop the motor. As this might have some impact to the timer (likely an electronic timer to be used), this change should become effective 1.1.2020, only.


Reply to Ross altimeters and all that !


From: John Carter

I think that Ross is missing the point Youth indeed is interested and turned on by technology just not toy aeroplanes so adding technology will not lure youth to playing with model aircraft . A bigger profile more marketing and sponsorship plus places to fly near urban areas   are what is needed to attract youth and more . We are a secret sport .
On the performance front Ross again assumes we only go down wind a few hundred metres well again experience tells me it's easy to see a F1A at 600 to 800 m downwind
Even with my old eyes 60 plus years . It's the fact that in a wind of say 8mph approx 3and bit m/sec the model is the best part of a mile down wind at 8 minutes.
Yes unlike in the U.S. we actually fly models in a breeze plus when it's windy.I think the other problem is the American scene assumes all flights land near by as we are lead to believe the U.S. never  as windy days (not true)
Now I have alienated my American friends please realise generally the world is windy and many contests terminate with fly offs in breezy conditions so the models go farther than they can be seen .
The time was when FAI class contests were won on five and six minute flights generally this is not a problem .
The issue now is all A ,B and C models get to high on launch,end of power run.
Reduce  height generally reduce overhaul performance .
Why not try in fly offs . Fly off 1 five minute working time any additional fly offs reduce working time to two minutes . This will reduce the number of large scores
John c UK




From: Michael Achterberg

They would enhance free flight, not be a deterrent.. Kids love high tech. Not ignore it.
It's a techy world we live in. Like it or not.
When I was a junior we flew on a field 1/2 mile sq. We chased on foot,climbed over fences, went into corn fields to retrieve models.. This is the case for many smaller fields now, here and in Europe. So please explain how altimeters for timing as a backup to a timer hurts free flight???
One competitor gets higher than another and in the wind goes further down wind. Chances are higher he goes out of site first. Doesn't mean he stays up longer necessarily, but doesn't it seem fair to actually know who won? Altimeters will actually help. High tech makes free flight better in this case..
Altimeters makes the results at small fields with trees and hills more useable and fair to all competitors. It's that simple.. Yes, the chases are harder at small fields, but that has always been the case. But as freeflighters, we are all use to that. Altimeters make small fields a plus not a minus as some have written. I don't get it... Hell, they can save free flight.
Semi high tech dinosaur.


J Again


From: Mike Roberts

For me, F1 J is just plain fun, no matter how I do.  I don’t disagree with Dan Berry’s comments although I think anytime we add more classes of models it dilutes the available flyers that will participate in the events. I was drawn to flying the FAI classes because I so enjoy schlepping my F1 C model box and support equipment through airports and because their will be more competing flyers than the local AMA contests where it seems most everyone has settled on a few classes where they have become most proficient, but not a big group in any one class.

I have just finished my second of two new F1 J models with RDT so I know with a little searching, the parts can be found to build them.  The little suckers are a serious “hoot” to fly….just say’in.



F1j then F1p.


From: Michael Achterberg
The reason F1j fell out was because of F1p. The dads wanted to teach their kids to fly. The dads didn't want to fly F1p. The juniors didn't like them. The whole movement to F1p killed interest for juniors. They loved flying F1j. Easy to fly. Fun event! F1p is hard to fly.. You put a Cyclone on F1p it still goes fast but have to have rolling climb for transition and is hard to achieve consistent flight pattern without bunt.  It's that simple. F1j easy to fly. Straight up and bunt..
All the powers to be decided too much performance so event no good.. Yes way too much performance. I agree. But the fix was simple. Change to 5 sec. motor run and put 3 minute max.. Oh yes change fuel to standard FAI fuel... Easy! Great event, great class and lots of fun to fly.
But instead we have F1p.... Harder to fly, ugly dimensions, and no interest.. Great Fix!!!!


Looking for a J


From: Allegedly from Jim via Michael Achterberg -
Looking for an F1j model for sale. Want to get back into Freeflight. Would like a 6 panel Achterberg model with Cyclone. Heard thru grapevine that Bob Gutai or Austin Gunder models might be available. Don't have their contact numbers..
Thank you.
Jim Luekin

Reminder :Fab Feb online entry form is available at:
It lets you sign up for all the FAI events at the Kiwi Cup, Ike Winter Classic, North American Cup, California Cup and The MaxMen International.  Held at Lost Hills from 11 to 20 February 2017.
The Ike Winter Classic also has a lot of other AMA Free Flight events but advance sign up is not needed for those.  The online advance sign up will speed things up for everyone, particularly International visitors who need to do extra paperwork.
Roger Morrell