Author Topic: Snap Roll  (Read 10465 times)

Offline Nigel Armstrong

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Re: Snap Roll
« Reply #30 on: 20, January 2014, 11:06:33 PM »
Just picked up the latest copy of RCM&E. In it is an article on snap rolls. Would anybody like to clarify if this is a work of fact or fiction. Just so I also have some idea of what the current format of snaps is.

Offline Keith Jackson

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Re: Snap Roll
« Reply #31 on: 21, January 2014, 10:10:22 AM »
Quote
Hi Sam I am on the edge of my seat, can't wait to see your interpretation of a snap.
Adrian
  :)

Offline Keith Jackson

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Re: Snap Roll
« Reply #32 on: 21, January 2014, 11:25:20 AM »
For what its worth I'd love someone to video my snap rolls with sufficient resolution for me to tell if thy're real or otherwise. The standard videos you come across on the internet place the model far away and without any background reference such as a sky line. Without this how can anyone be sure if the flightline is broken during the snap?
 
My control input for snap rolls always start with an elevator up / down motion, which enables a rate change at about 90% of stick movement. This just allows me to avoid taking my hands off the sticks to actuate a rate change using a switch. So whether I've really broken the line or otherwise I'm not sure but I sure am trying. In addition the snap rolls I do don't appear to me to look anything like a fast axial roll and are clearly faster than an axial roll flown with the same aileron deflection. As others have said in this thread if you try to emulate what full size aircraft do when they snap, your model will run out of inertia and you will lose the line you are trying to draw for that particular manoeuvre. So compromise is necessary to achive an acceptable snap and maintain your line. Obtaining this balance is key to scoring points.
 
Some of the very axial snap rolls I have witnessed over the years may not not have given me any sense of "that was a great snap" but they maintained the lines. I guess one hopes the marks awarded address both the quality of the snap and and the line before and after. I believe Bob Skinners advice that "if its not a barrel roll or an axial roll then it must be a snap", may have been used to avoid the issue of whether the snap looks good or otherwise, leading to the disbelief over points awarded when pilots fly overtly axial snaps.
 
Best wishes
 
Keith
 
 

Shahid

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Re: Snap Roll
« Reply #33 on: 21, January 2014, 07:49:47 PM »
Alan! Good to see ya  8)

As per my last RCM&E article (excuse the diagram error, I assure you it was not me), IMAC roolz actually specify a change in line in order to stamp a snap as valid. In other words if you were doing an upline snap, post snap you'd expect the model to be vertical still, but offset to the left/right (depending on what way ya snapppepeppepepepepped)



The break rule in the latest (albiet old) sporting code is cool.


Anyway I'll disappear back into the shadows now

Offline Sam Wragg

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Re: Snap Roll
« Reply #34 on: 21, January 2014, 08:46:48 PM »
So then; Once again I'm correct  8)

Offline Keith Jackson

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Re: Snap Roll
« Reply #35 on: 22, January 2014, 07:51:57 AM »
Quote
In other words if you were doing an upline snap, post snap you'd expect the model to be vertical still, but offset to the left/right (depending on what way ya snapppepeppepepepepped)

Hi Shahid,
I'm not clear why you would expect the model to start on one line and then jump to another? Surely if the snap was a rotation about the C of G then why would this lead to a jump to the left or right?
 
Keith

Offline Ashley Hoyland

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Re: Snap Roll
« Reply #36 on: 22, January 2014, 08:46:56 AM »
Hi Sam
 
I have filled a lengthy reply to the snap roll debate, whowever I am not sure if you can decide whether you are correct or not until you have flown in a few competitions and I hope you have some new plans after reading your post on another board.
 
Come on Sam only 10 weeks now to our first competition of 2014.
 
Best wishes
 
Ashley
 
 

Offline Adrian Mansell

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Re: Snap Roll
« Reply #37 on: 22, January 2014, 11:17:50 AM »
Hi Sam,


I haven't followed the whole of this thread, but...


You may want to look at this thread : http://www.gbrcaa.org/smf/index.php?topic=2010.msg10949#msg10949, as much of the commentary still applies.


From my judge's perspective:
: No visible line break - downgrade (except in K.E. snaps where I wouldn't expect to be able to see the line break)
: Loss of line - downgrade
: Under/over rotation - downgrade
: barrel flight path rather than nose and tail describing antiphase circles - severe downgrade or zero
: "shallow" snap or glorified roll which otherwise meets the above - I chose to address this by deducting - or not adding - style or grace marks.


Get familiar with your model and understand how different styles of snap can be flown with it.  It is then little stress to modify your style as the season goes on to maximise the marks.
A

Offline Alan Wild

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Re: Snap Roll
« Reply #38 on: 22, January 2014, 12:02:02 PM »
I was hoping this chestnut had finally been burnt to ashes, but:
"No visible line break - downgrade (except in K.E. snaps where I wouldn't expect to be able to see the line break)"
Can't you break the line with the rudder? Likewise with end manouevre snaps on vertical up/down lines with the canopy/belly facing the centre?
(And I struggle to believe that most "snaps" with an F3A model ever have a stalled element in them--with their loading, the angles of attack needed to stall are just too big, surely?)
(just asking--I'd still be inclined to follow whatever was fashion on the day----after all, the whole thing is arbitrary shapes in the sky)

Offline Sam Wragg

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Re: Snap Roll
« Reply #39 on: 22, January 2014, 02:32:16 PM »
I will continue to Snap the way I have always done this manoeuvre as I used to score 6,7 & 8s  when I last competed. At the end of the day I believe its all down to perceptions and?......... consistency in judging.
 
Its was also nice to read how Keith approaches this manoeuvre which I believe is similar to how I do it.
 
 

Offline Adrian Mansell

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Re: Snap Roll
« Reply #40 on: 22, January 2014, 02:39:10 PM »
Hi Alan,


You can break the line with the rudder if you want, but I'm looking for a line break in pitch in order, supposedly, to precipitate some element of stalling. I can't downgrade for not seeing that if the model is in an attitude such that I couldn't really see it even if it was there.  Just my opinion.


For me, the sporting code, is reasonably clear in its description of a snap roll.  The criteria I describe are my solution to meeting the objective requirements of the sporting code in a way that is roughly aligned with what appears internationally accepted as a snap roll in F3A competition.


Overall though, I couldn't agree more; I have flown genuine stalled snaps with an F3A model and they are very different from what is flown in competition, which are just nice looking arbitrary shapes in the sky fitting an interpretation of a description :-)


A

Offline Kevin Caton

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Re: Snap Roll
« Reply #41 on: 22, January 2014, 06:56:58 PM »
As the F-17 has a barrel roll in it (yes really...) I am looking forward to the debate on how that should be flown!


The P-17 and F-17 are in the 2014 Sporting Code that can be downloaded from the FAI web site. Health warning - there are a couple of errors in the manoeuvre descriptions but these will be put right later in the year.

Offline Stuart Mellor

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Re: Snap Roll
« Reply #42 on: 24, January 2014, 04:31:57 PM »

 with effect I have to cheat to gain extra points.
 
Sam -1 last thing from me: You cannot cheat as a competitor in F-3A. You have 8 minutes to do your thing & the judges decide your score.  At the centralised events all models are weighed,scrutinised and noise tested. At domestics, a model simply has to be under 7kgs.
 
Cheating by a competitor is impossible - you interprete the manoeuvres as you see fit. Thus, when flying a schedule, you can never be accused of cheating, abuse of or not flying to the rules. Basicly, you can do anything you like during that time (apart from unsafe flying).
 
BUT - Clever competitors will find out what the judges are looking for & fly accordingly to get more points. This happens all the time at International comps & to some extent over here. So, in the end, the choice of how you want to fly the manoeuvres is yours. But don't be surprised or disappointed if a majority of others and the judges interpret the rules a litte differently.
Stuart
 
ps - looking forward to seeing you back - with the same batteries?!!!

Offline Bill Michie

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Re: Snap Roll
« Reply #43 on: 24, January 2014, 04:42:40 PM »
Can we move on now..................... ;)

Bill

Offline Alan Wild

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Re: Snap Roll
« Reply #44 on: 24, January 2014, 06:12:42 PM »
Can we move on now..................... ;)

Bill

Not quite!
As a relative youngster(no comments please), I've never flown a barrel roll (at least not deliberately).
I appreciate the shape in pitch (I think),but: should the nose deviate laterally as well?e.g say you're rolling right from upright,should the nose yaw right in the first half, then left in the second half, to return to straight on at the finish of the roll?