Snap rolls (long)

[Ron Lockhart]

I'm in agreement with Earl's discussion of snaps.
Ron Lockhart

----- Original Message -----
From: EHaury at aol.com
Date: Monday, June 23, 2003 11:03 am
Subject: Snap rolls (long)

> With the Nats fast approaching I thought it might be useful to 
> review / 
> discuss the snap roll and its proper judging. My observation is 
> that there is a 
> lack of quality demonstrated by many snaps. There seems to be some 
> tendency for 
> folks that fly the maneuver poorly to judge it leniently, or worse 
> yet, judge 
> well executed snaps harshly because they look unfamiliar. No other 
> maneuver is 
> executed so quickly, making it even more demanding to judge.
> 
> Please refer to page 78 of the rulebook under "Snaps." Consider 
> Item 1 
> carefully. 
> "the nose should show a definite break" and "while the track 
> closely 
> maintains the flight path" are key criteria for judging the 
> entrance to the snap. A 
> rapid pitch attitude change, simultaneously or closely followed by 
> a yaw 
> attitude change will create a stalled wing in the direction of the 
> snap and rapid 
> autorotation rotation generated by the opposite wing. The track 
> will "closely" 
> follow that established before the snap.
> 
> I ask that you consider the often seen snap entrance. The aircraft 
> pitches, 
> yaws, and rolls quite a bit off track before the stall occurs. The 
> aircraft 
> then stalls and maintains that track, finishing with considerable 
> offset from the 
> initial track. In my opinion, the rules require the change in 
> track during 
> the snap iniation to be downgraded. Typically the changes are 15 
> to 30 degrees 
> in the vertical and horizontal plane, so 1 or 2 points for each 
> plane. At the 
> same time, due to concurrent application of aileron, some 15 to 30 
> degrees of 
> roll occurs before the stall. Another point or 2 off for lack of 
> proper snap 
> rotational angle at the entrance. At the same time, please realize 
> that there 
> will be some small change of track as enough attitude change 
> occurs to initiate 
> stall. This is recognized in the rules i.e. "track closely 
> follows." Certainly 
> this is another one of the approximation words that shouldn't be 
> in rules. I 
> believe, however, that "closely" better defines 5 degrees or so of 
> track 
> change and certainly does not allow 15 to 30.
> 
> Observe also that some pilots will change the track horizontally 
> (yaw) 
> opposite the snap to accommodate the poor entry and facilitate 
> exit on the desired 
> track. This change of entry track should also be downgraded at 1 
> point / 15 
> degrees.
> 
> Item 2 describes a barrel roll (zero). If the events described in 
> the 
> discussion of Item 1 occur without an eventual stall, the maneuver 
> is a barrel roll. 
> It may be fairly tight and still be a barrel. This is tough to 
> call, I've 
> video taped a number of snaps that appeared fine but were clearly 
> barrels when 
> viewed in slo-mo. The trick in judging this is to look for the CG 
> to stay on the 
> original track, as stated in the rules. In my opinion, so many 
> snaps are 
> barrels that this look may be becoming the standard, with true 
> snaps on track are 
> being judged as axial rolls.
> 
> Item 3 deals with wing position at start and stop and seems well 
> understood.
> Item 4 mentions that snaps may be either positive or negative. 
> Look for the 
> proper horizontal break direction.
> 
> Item 5 "If model returns to an unstalled condition" "such that 
> autorotation 
> is not visible" "model rolls to complete" indicates that rolling 
> to finish a 
> snap must be severely downgraded. I suggest that 1 point / 15 
> degrees is 
> appropriate, as most of these rolled finishes will be 45 to 90 
> degrees which results 
> in a 3 to 6 point downgrade. As per Item 1 there should also be a 
> severe 
> downgrade for unstalling early. 
> 
> Item 6 discusses airspeed as not being a criteria.
> 
> OK, recognize that there is a lot going on in a snap in very short 
> period of 
> time. Look for all the elements to be there, clean break, with the 
> nose and 
> tail autorotating in an attitude different from the track, and a 
> unstalling and 
> rotation stop at the proper point. Please be aware that there are 
> many details 
> to be considered beyond "it is or isn't" and "the wings finish in 
> proper 
> plane." Also recognize that well performed clean snaps may look a 
> bit different 
> depending on technique and aircraft. 
> 
> These interpretations are my own and outside of any official 
> capacity. I 
> welcome discussion, addition, and disagreement.
> 
> Good flying
> 
> Earl
> 

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