Hi Guys
Not sure if this should be in this forum or the pattern?
Anyway, I fly a not so aerobatic plane that I want to get to snap roll.
I want to use the Tx mix to do it, could someone give me a good starting point on the % throws.
Also do I just flick the Tx switch or hold the switch till the plane has completed the roll?

Thanks
Don

you can use a TX to do it?

Dang, I just whamn the sticks over to the left or right , without changing throttle, and snap she goes. Well that is what i think in my head, my fingers on the other hand ALWAYS close the throttle, stupid fingers DOH!

Falcon...100% is a good place to start, but it's a waste of time, just bang the sticks and release when you are at the desired position i.e. 1/2 snap, full snap...1 1/4 snap...etc..

Remember that some planes just dont want to snap, specially the ones with constant chord (broad wingtips), because in a snap only one wing stalls and that planes does not lik stalling wingtips

Posittive snap: add up elevator, ailerons and rudder to the same side
Negative snap: Down elevator, ailerons and rudder to the opposite side

Often you will want to do neg snap from flying inverted and possitive if you are upright

Extra throw and high airspeed helps planes that do not snap roll willingly

Move your CG back some and follow the suggestions above.

Don't use the snaproll button - it is a crutch and won't teach you a proper snap.
The basic snap is to just slam the right stick into one of the lower corners and feeding rudder in the same direction, but it is still not the correct way to snap. A correct snap is a very difficult thing to master, but since you are talking about doing it wit a "not so aerobatic plane", here are a couple things I found that I need to do to get snaps to look right on an Ultrastick, which is what I consider a not-so-aerobatic plane. I have to have servo-binding full throws in the rudder and elevator. I cannot be at the noseheavy end of the CG, and I have to dump the elevator, then dump rudder as I am releasing most of the elevator and dump the aileron just slightly after the rudder (so close it is practically at the same time). By the time the plane get's 1/4 of the way around, the elevator is neutralized and I am just holding the rudder and elevator. when it comes time to stop, I neutralize the aileron and bump a touch of opposite rudder and then neutralize the rudder. This is the only way that particular plane will start to gyrate immediately. If I just slam the sticks into the corners, it does 2/3 of what looks like a barrel roll and then finally starts to gyrate - doesn't look as good.

As mentioned above, 100% is a good place to start. If you just flick the Tx switch, you will get part of a snap roll. I put this mix in for my foamy just cause I didn't need the switch to start the timer. I found that with the mix I could do a four point snap roll by pulsing the switch.( I thought it was funny.) So to answer your question, you would have to hold the switch for as long as you wanted to continue to snap. You might have to let off the switch a little early to stop the snap level.
If you're !QUOT!not so aerobatic plane!QUOT! still doesn't snap very well or fast. You might look into aileron differential. There is a good article on it in this months AMA magazine.

Later,
Dave

Well there's quite a mix of different answers here but not the one I was looking for!
What I need to know is something like this:-
Useing the snap roll button on the TX, Mix 60% aileron - 50% elevator - and 15% rudder.
So what I need is someone to suggest better percentages.

Thanks

Don

best suggestion is simply not to use the snaproll button on the transmitter and fly the snap with your thumbs! Besides, it's only good for one type of snap and in one direction, like positive snap to the left. So what if you want to do a negative snap to the right? See, you're gonna have to start using your thumbs at some point - might as well be right from the start.

Hi Bodyworks
Thanks for your input here.
I take your point about flying it manually but I'm guessing you use mixes from time to time even if it's only a bit of rudder input for knife edge or something right!
I'm not looking for the plane to fly itself without any input from my thumbs, I'm just experimenting with what I consider to be a cool facility on my transmitter.

Mixes can be used to make the plane fly perfect, but I don´t think they are usefull to do maneuvers... think this way: do it takes the same amount of inputs to do a snap flying at low speed that high speed? what if (as many 3d setups) I have an enourmus amount of rudder? (it will look like a barrel more than a snap) a % of what do I use.. high rates or low rates? how many degrees are high rate?
So, what I´m trying to say is; there are other variables that a mix can´t manage better than your thumbs

Ever accidentally flipped a switch on your transmitter? I've accidentally hit rate switches, timer switches and even a choke switch that caused a dead stick. If any of those switches had been a snap roll switch, I'd have crashed because it is something you need to be prepared for. Accidentally hitting a snap roll switch at a slow speed will most likely put the plane in an awkward position and while your brain is trying to figure out what just happened "First thought is radio hit" your plane could be plummeting to the ground.

Learn to snap with your own input, don't leave it up to chance.

I have thought of accidentaly hitting the switch and what the result would be, thankfully so did Futaba, thats why you can mix it to the gear switch as a safety, and I don't think I'm going to hit two switches at the same time by mistake.
OK so now I have to move two switches to get it to snap!! Oh well might as well learn how to do it properly

That's pretty much what everybody is trying to tell you. Every plane and every flier is different. So get up high enough to recover and start experimenting. It won't take that long to figure what works best for your airframe and your fingers. Aerobatics, and flying in general, is something you really can't learn by the numbers.

As far as what mixes, the only thing I do is, after setting up proper CG, thrust, aileron differential, lateral balance and such, I roll to knife edge at half throttle or so and input only enough rudder to maintain altitude and watch what happens. I then mix the appropriate amount of (typically opposite) aileron so that I can fly horizon to horizon with virtually no aileron input. I also mix the appropriate direction and amount of elevator to do the same. After I get it pretty close, I attempt a flat turn with the same amount of rudder and make sure the plane doesn't want to climb, drop or roll. Beyond that, the only other mixes I use are throttle/elevator mix for straighter downlines. When it comes to the snap, I don't know of anyone that has special programmable mixes they use specifically for snaps. However, I do have a specific flight mode that I use for snaps, that limits the throws to an amount that I had to experiment with. With a typical aerobatic plane, a proper snap only requires a low rate rudder and elevator, and a medium-to-low rate on the ailerons. I am not sure this helps you but it is the only mixes I ever set up on my plane, and I think it's the same for most people.

OK, what airplane ARE you flying? "Not so aerobatic" does not help. Is it a glider, Warbird, trainer, quickie 500, extra, cub.... what is it?

Snap Roll by AMA aerobatics code is "a simultaneous, rapid autorotation in the pitch, yaw and roll axes in a stalled wing attitude."

Now, to do a snap roll there are some things the plane must do.
1. You need to increase the angle of attack to put the plane into a position where it will stall. This is done with a quick pulse of up elevator to "break" the nose and put the wing in a position to stall.
2. Within a split second of that pulse of elevator input you push the rudder full over (to start learning to snap) and at the same time input full aileron deflection in the same direction as the rudder.
**What you should see then is called "rapid autorotation". When you input the rudder you get "YAW" which means one wing speeds up, and the other slow rapidly and stalls. This initiates a sharp roll in the direction of the rudder input becuase one wing stops flying. Technically you should not "Need" to use ailerons, but with RC models the ailerons help to get the process started. You should not be depending on the ailerons for the rotation, if you are its not snapping they are just there to clean it up a little.
3. To keep the plane on heading as stated about you neutralize the elevator 1st and then the ailerons and rudder. All of this happens in less than 1 second.

Again,
Initiate stall in the wing by sharply pitching.
Stall the wing by inputting the rudder
Ailerons to clean up the rotation.
Neutralize at just the right moment to stop roll.

It is sortof a J pattern laid on its side.

Here is a video of what a snap really looks like. I captured in at normal speed and then slow motion so you can see the timing of the inputs. I used high rates so its pretty easy to see whats happening in slo mo.

Pay close attention to the CG, nose and the tail in the slow motion. You can see the CG stay on a pretty straight track and the nose and tail cone tightly around the CG.

I am sure someone is going to criticize. If you can backup your crituque with helpful information, help yourself. [8D]

I dont really like the way youtube reproduces these videos. It plays a lot better if you save it to your harddrive.

[link=http://dodvideos.com/snaprolls.wmv]Snap Roll Video[/link]

Hi Guys
Now there's some really usefull information comeing out here.
Bodywerks Your input is most welcome.
The plane is a Seagull 40 low wing trainer, constant chord , so it's very stable ,but it does roll quite well considering.
I have'nt been solo that long so I'm at that stage where I'm beggining to experiment and I just thought it would be cool to be able to snap just by the flick of a switch [8D]
Mike Your description and video is exellent , I can see just what is going on with the different inputs!!
BTW what sim are you useing?
Looking forward to Sunday when I can try to put some of this to practice.

Thanks again
Don

That is aeroflypro deluxe. You can get it at www.aeroflypro.com . Its a really great sim program.

1 thing I wanted to mention is that I did those snaps on 3D rates with HUGE throws for demonstrative purposes, that is so you could clearly see what the surfaces are doing in the video. In reality you should not use near that much elevator and aileron throw. The rudder you might use a pretty good bit to really get the plane to snap. The rudder and elevator are really the key, too much and you get too deep and the snap is hard to control, too little and the plane does not stall enough to autorotate.

That being said, on that plane, since the surfaces are so small you are going to need all of the elevator and rudder throw you can get out of it to get it to snap. The more tailheavy it is the easier it will snap, but the worse it will fly.

Got plenty of rudder but elevator going to need some work to get more throw!

Thanks
Don

Hi Falcon32

IMHO if you are to achieve proper snaps with a Seagull 40 you will have to move the CG back to the point where the model is hard to fly.

It is designed NOT TO SNAP which requires wing stalling to occur.

Play around with increased elevator/aileron/rudder movementd and move the cg back in stages but I think it is the wrong aircraft to work on snaps.

Hi j.dunker
Your probably right it's a constant chord wing for stability in training but I'm going to give it a go

I fly the crap out of a mini Ultrastick, which has a constant chord wing. It is not tailheavy at all and does negative snaps with ease, and will do a positive snap quite well, too, but just takes the proper inputs at the right time - the most important being to very quickly dump the elevator then unload it at the same time that I input rudder and elevator. If you were to draw a line with the right-hand stick movement, it would look like a checkmark. You will probably have to do something similar with the Seagull plane.