Snap rolls (long)

[Mike Mueller]

 Snap rolls that guys are doing today are making it hard to even know whats
right anymore. You get so used to looking at lousy ones that you think a
good one is bad. This is even a worse problem when the people judging them
fly in a lower class and they get used to looking at bad snaps because of
lack of experience. I'm of the opinion that a proper snap has to roll,
pitch, and yaw and leaves the original path if done properly. You shouldn't
be able to score a 10 on the manuever because it's not possible. But hey
that's just my opinion and untill someone shows me a better way I'll
continue my lousy snaps. Mike

-----Original Message-----
From: EHaury at aol.com [mailto:EHaury at aol.com]
Sent: Monday, June 23, 2003 9:04 AM
To: discussion at nsrca.org
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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