Displacement during snap rolls (was Why is it so quiet?)

[Doug Cronkhite]

No track downgrade Dean. Since a snap roll is a yaw induced maneuver (or
should be at least) it's nigh-impossible to actually snap the airplane and
not displace the line a little. Especially when you consider the low weight
and inertia of our airplanes as compared to full scale.
 
-Doug
 
 


  _____  

From: discussion-request at nsrca.org [mailto:discussion-request at nsrca.org] On
Behalf Of Dean Pappas
Sent: Wednesday, December 29, 2004 1:10 PM
To: discussion at nsrca.org
Subject: RE: Displacement during snap rolls (was Why is it so quiet?)


After re-reading the post, it occurred to me I should clarify:
I was writing about what I thought a good standard might be.
For right now, the book is it, and as Bob pointed out, there is no specific
track downgrade.
Anyone have an IAC judges' guide handy? I'm curious.
By the way, the full scale guys do horrible things to snaps, including
completely unstalling the plane (particularly during consecutive snaps).
That don't make it right!
Archie has a good point, not only does the standard need to be better nailed
down, but some people may never be trained to "see fast". 
Add in some "tired from 4 hours in the chair" and you have mush.
 
This is a good discussion!
 
 
Dean Pappas 
Sr. Design Engineer 
Kodeos Communications 
111 Corporate Blvd. 
South Plainfield, N.J. 07080 
(908) 222-7817 phone 
(908) 222-2392 fax 
d.pappas at kodeos.com 

-----Original Message-----
From: discussion-request at nsrca.org [mailto:discussion-request at nsrca.org]On
Behalf Of Dean Pappas
Sent: Wednesday, December 29, 2004 1:15 PM
To: discussion at nsrca.org
Subject: RE: Displacement during snap rolls (was Why is it so quiet?)


Hi All,
before I crawl back to the lab ... and see what's on the slab ...
 
While I agree that some displacement is inevitable, I wouldn't want to see a
rule that says that if you don't see any, then it's not a snap.
The very best high energy snaps will displace so little that it will be
really hard to say that it's there.
 
1) My guess would be that most really good snaps probably displace about 1/2
wingspan, both up and to the side.
Gravity will possibly kill any evidence of the UP part. Try doing an inside
snap from inverted, or try a snap from knife edge. You'll see the UP
displacement! 
2) As the elevator throw is reduced, from that needed to do a good snap, the
airplane displaces worse and worse, as it takes longer for the plane to
stall deeply enough, to make little enough lift to continue changing the
airplane's course appreciably.
3) If the elevator throw is further reduced, the displacement goes away!
Hmm.
4) Leading the elevator reduces the necessary amount of throw, for a good
snap. 
 
Here's the aesthetic question behind the argument:
Do we all agree that when you see a snap with an "in your face" break that
it really is a thing of beauty?
Or do some of us think it's untidy, and not"on a line"? I had a judge ask me
(back in '91) "What's with the twitch before the snap?"
 
I'm as confused as anybody. I guess that's as good a way to start the new
year as any.
 

Dean Pappas 
Sr. Design Engineer 
Kodeos Communications 
111 Corporate Blvd. 
South Plainfield, N.J. 07080 
(908) 222-7817 phone 
(908) 222-2392 fax 
d.pappas at kodeos.com 

 

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