I have been doing snaps with full up ele full left rudd and full left arl or vis virsa. But then someone told me to do it with only elevator and rudder??? Wich way is right.

RCFLYER:

Its just like sex, do it anyway you want as long as it feels and looks good. A good snap roll is quick and ends in a orientation that is intended. A neet looking snap is streight and level entry, snap-back to streight and level. I need everything moving correctly to do this. ENJOY

Check out this article. Best write-up on snaps that I have ever read.

http://www.modelairplanenews.com/ME2...C5440640A0D018


Hope that huge link works. It is Model Airplane News, March 06, by Mike McConville.

Mike

Depending on the type of aircraft ailerons may or may not be required to perform a snap roll, but elevator and rudder are the primary controls for this maneuver. Think of a snap roll as a spin occuring along the flight path of the aircraft. Because pattern and F3A aerobatic models tend to have long tail moment arms they are not very good at performing snap rolls compared to short coupled aircraft such as CAPs, Sukhois and Extras. In order to get pattern and F3A aircraft aircraft to perform snap rolls it was found that the use of ailerons was beneficial.

In the official IAC and IMAC judging guide one can read the following:

"In full-scale and IMAC aerobatics the judge must see two things to determine that a snap roll has occurred. The nose must depart the flight path in the correct directions and autorotation must be initiated. If the judge does not observe both events, the figure must be given a zero (0)..."

"For a positive snap roll, the nose must move away from the wheels. This puts the aircraft’s wings near the critical angle-of-attack. Either very shortly after the nose moves, or simultaneously with the nose movement, the aircraft must be seen to yaw around its vertical axis, thus initiating a stall of one wing and subsequent autorotation. If any movement about the longitudinal (roll) axis is observed before the nose departs the line of flight, the figure is downgraded..."

"Snap rolls must be observed very carefully to ensure that the competitor is not “aileroning” the aircraft around its longitudinal axis. Aerobatic aircraft with very high rates of roll can occasionally fool a judge in the execution of snap rolls. The movement of the aircraft’s nose departing the flight path prior to autorotation is a good clue to the proper execution of snap rolls."

Red B.,

That is very informative and interesting. I will try it next time I fly to see if I am doing it right.

Barry

The Hangar 9 FS One sim also has a series of lessons on snap rolls. Similar to the MAN article (Thank you for the kind comments) but in more detail and it focuses on snaps in various orientations; up line, down line, horiz, etc.

That's a good article Mike. I can't wait to get the the field and try it. After watching Mike McMurtry fly I have been doing most of my snaps from knife edge. Maybe this will keep me from pitching the nose so much.

David

I've tried snaps with my Harrier 90, and with the ailerons it would snap nicely. I tried snaps w/o ailerons, and the plane would snap but would eventually bleed off energy and start a flatspin. I'm not sure if what I'm doing matches the IMAC judging guide, but it looks like a snap. That's good enough for me!

Thats what the rulebook says allright, but go to an IMAC contest and waitch the unlimited flyers that are really good and score well on snaps. Its predominantly aileron with the least hint of rudder that you can get away with and make it "look" something like a snap with just the least amount of coning you can get. Its the slickest thing you have ever seen.


Thats not to say that its not the way to make them "look" like the rulebook intenteds them to look, but then if you actually execute the snap with the control inputs as indicated in the rulebook (a real snap) your snap ends up displaced with the nose pitched this way or that and the airplane loses a ton of forward momentum. There is a contradiction in presentation vs. proper execution of a REAL snap as far as I am concerned. Its almost impossible to keep a real snap on track and keep your forward speed fairly constant, especially if you use the rudder and elevator w/ minimal ailerons like you are "supposed to. . I dont have a problem with the way snaps look in pattern and IMAC, it looks nice, but I dont like that they tell you that you should execute in a way that its impossible to give the presentation that they are asking for. To get the scores you have to exit on track and wings level on all axis, to do that you HAVE to cheat more with the ailerons and stay off the rudder and elevator as much as possible.
Now that I have learned to make my snaps look like the big boys snaps, this means more to me than ever.

I digress.


As far as how I personally like to do snaps.

IF you want a deep snap that is a REAL snap then lead with the elevator and then a lot of rudder (maybe 40-45 degrees) with just a little aileron. But hang on to your hat, its going to autorotate with a WHOOSH and it may be hard to stop.. It will also slow the plane to nearly a stop and fall off or continue to roll. Real snaps can really bring meaning to the term autorotation.

If you want a pretty, basic competition snap that looks nice then to start try about 20-25 degrees rudder (maybe less), 15-20 degrees of elevator and 30 degrees of ailerons, that should make it look nice and crisp. Just lead with the elevator by a fraction of a second and then be ready to get out of the rudder/elevator as soon as it starts to cone and then finish with the ailerons.