[NSRCA-discussion] Snaps

[Ron Van Putte]

On Jul 8, 2006, at 11:12 PM, Ed Alt wrote:

> To Doug's point re. the long tail moments & added stability of  
> Pattern designs, this can be overcome pretty well with enough  
> control throw.  Granted, it's not going to be just like a Scale  
> Aerobatic design, but real snaps can be done and barrel rolls can  
> be avoided.  I remember the angst that was generated by the reverse  
> avalance in Masters in '05.  Fears of bent wing tubes, busted wings  
> etc.  Locally at least, there were several examples where very good  
> pilots had to re-do their setups to get enough throw to make this  
> maneuver happen properly and not bend their airplanes.  Well, not a  
> single airplane in the district was damaged that I know about, but  
> I do remember having discussions about upping the elevator and also  
> rudder throws to get the autorotation to happen properly. Hey, I  
> admit to having only a short 2.25 year Pattern flying history, but  
> as far as I can tell, it doesn't seem to be part of the Pattern  
> "DNA" to set airplanes up with enough throw in alot of cases.   
> Having the deal with a schedule including the loaded snap in the  
> reverse avalanche has advanced the knowledge because guys had to  
> figure it out.

Here's a good example of what Ed's talking about relative to using  
enough control throw to get a good snap: I have a Focus I (very long  
tail moment) and use 6 degrees of elevator throw for normal flying,  
but it requires 20 degrees of elevator throw to get a good snap.  It  
sounds excessive, but, if I use less elevator, I have to cut way down  
on aileron throw to be able to stop it before it over rolls the snap  
and the snap doesn't look "right".

Ron Van Putte
> ----- Original Message -----
> From: Doug Cronkhite
> To: 'NSRCA Mailing List'
> Sent: Saturday, July 08, 2006 8:54 PM
> Subject: Re: [NSRCA-discussion] Snaps
>
> The INBOARD wing dumps lift as a result of the increases angle of  
> attack AND the rapid reduction of airspeed (by a sharp yaw moment –  
> rudder input). The outboard wing’s lift and drag increase rapidly.  
> If the outboard wing dumped lift you’d get no rotation at all or  
> very little. Some airplanes actually snap much better with no  
> aileron usage as the changes in angle of attack on the inboard wing  
> causes it to keep flying and not dump the lift from the yaw input.
>
>
>
> I think the biggest problem pattern aircraft have with performing  
> proper snaps is the long long tail moments keep things so stable  
> that it’s very hard to generate the critical angle of attack  
> required to get the stall to happen. So you see barrel rolls with  
> VERY high G-loads on the aircraft.
>
>
>
> In full scale aerobatics, there is nearly no G-loading once the  
> stall occurs, except for the rotational forces of the autorotation  
> of the aircraft. There is some G leading up to the break, but once  
> that happens, it’s all kind of non-stressful.
>
>
>
> -Doug
>
>
>
>
>
> From: nsrca-discussion-bounces at lists.nsrca.org [mailto:nsrca- 
> discussion-bounces at lists.nsrca.org] On Behalf Of Rcmaster199 at aol.com
> Sent: Saturday, July 08, 2006 12:45 PM
> To: nsrca-discussion at lists.nsrca.org
> Subject: Re: [NSRCA-discussion] Snaps
>
>
>
> In a message dated 7/8/2006 2:09:25 PM Eastern Standard Time,  
> natpenton at centurytel.net writes:
>
> Matt
>
> Regards. Two comments.
>
> Snap characteristics are independent of scale. The only thing that  
> changes is the clock ( due to changes in moments of inertia ).
>
> When the rudder is applied it is the outboard wing that exceeds the  
> stall AOA and dumps. Actually it is not much of a lift dump but a  
> huge jump in drag.
>
> Nat true. Moments of inertia are design parameters. So are several  
> other key parameters that may make or break a model's ability to  
> perform snaps. That was my point.
>
>
>
> I agree in terms of AOA (outboard aileron low) and drag increase  
> but I am not as sure regards to lift. I know what you are saying  
> though.
>
>
>
> One question: how does the outboard panel lift over the top if its  
> lift has been dumped?
>
>
>
>
>
>
>
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