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Learning snaps

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  • Learning snaps

    Business is shut down for the virus, my engine is at DA for service so I can’t practice, and this forum is quiet. So it’s time for thinking and a question.

    I’m moving up from Basic to Sportsman this year. One difference is Sportsman introduces snaps. Just one in the Known and I suspect no more than that the Unknown. They're limited to positive, exactly one full rotation, and on horizontal lines. So they’re simple and few.

    Snaps of course need different control deflections than normal precision flight. For learning snaps at this level, do people find it best to start programming snap conditions right from the start, or have a single condition for precision+snaps and hold off on the programming til later?

    For upper categories with more/difficult/varied snaps, conditions based on stick positions are a godsend. For just starting to learn snaps, I'd be concerned that when a snap doesn’t go well, it could be difficult to know whether it's caused by poor technique (most likely!) or a programming/deflection problem (almost as likely!). That would seem to make isolating the right fix more difficult.

    The other option would be to use a single condition for everything, with deflections needed for snaps, then dial them way back with expo to smooth the response for precision. The problem there is you’re limiting the stick travel you can use for precision flight. That seems like a bad idea for a few reasons.

    Here’s what I’m thinking to start. Set up snap rates on a physical switch so I always know exactly what's active. Turn it on to practice snaps. Flip it back to precision condition to practice everything that isn’t a snap. Once my snaps are consistent, move the snap rates to a logical condition. Then if my snaps suddenly become more of a freak show than they already are, it’s probably the programming.

    Any advice or thoughts?

  • #2
    I'm sure someone with more experience than me will chime in, but I made it through Sportsman and Intermediate with a single snap condition programmed in my radio and no switches. If you use absolute values for the stick position, the same condition will work for positive and negative snaps. I don't have the radio with me, so I can't give you the values I used, but once the stick reaches a certain position (I used > 80% of stick travel for elevator AND rudder AND aileron - all three to satisfy condition) then the radio announces "Snap Roll" and elevator and rudder are reduced and aileron throw is increased. You have to release the sticks to exit the snap roll, and after much practice you will get the timing down to exit wings level, or somewhere close. LOL Eventually you will want separate conditions for snaps on an up line vs. down line vs. horizontal.


    • #3
      I use a logical switch that activates when I bury my sticks. I leave my elevator and ailerons at the same rate, but I adjust my rudder based on the how the plane flies.
      Newsletter Editor
      @RC Aerobatics Podcast


      • #4
        I flew Sportsman last year. What I did was worked on my snap rate with a switch. Once I got close to the rates I felt worked I created a logical switch for snap conditions. But there wasn't any easy way for me. It still took me some time of fine tuning as well as training to get it where I was able to be somewhat consistent.


        • #5
          My favorite way to think about snaps came from an article by Mike McConville. For us mode 2 pilots, the right stick follows a check mark. Pull down, then get to full aileron and rudder at the same time as all elevator is released. You could try and setup some logical switches on your radio to make it easier, but I never was able to get it the way I wanted it for all possible scenarios (wind, etc.). Also, you generally need far less elevator and rudder than you think. Too much of either, and the snap gets too deep and hard to control.

          Here's the article from Mike:

          My recommendation is to learn how to "fly" a snap and then use your radio's programming features to help make them more consistent and repeatable. Here is a good article by Mike McConville from a few years ago:

          Snap Rolls

          Mike McConville explained how to perform a "proper" snap roll in the March 2006 issue of Model Airplane News, page 126. In the article, he describes how the common pilot snap rolls by inputting full stick deflections, and how this makes the snap too "deep", causing the model to lose too much energy. He then goes on to describe an "unloaded" snap, that is still a full snap that is legal in competition and retains much of the plane's energy.

          Here is part of the article, where he explains the procedure:

          "The snap is initiated with elevator only. For a positive snap, first pull hard up elevator. For a negative snap, push hard down. As soon as there a visible pitch up of the nose, move the aileron and rudder simultaneously to full deflection. The same applies to a negative snap, except there will be a visible pitch down of the nose before moving the ailerons and rudder to full deflection.

          At the same instant as you start to move the ailerons and rudder, also start removing the elevator. The object is for the elevator to return to the neutral position at the same moment as the aileron and rudder reach full deflection. A very easy way to look at this is for the right stick (mode 2 pilots) to draw an imaginary checkmark (he then refers to a figure). When done correctly, you will see a fast pitch in the direction of the snap, meaning up for positive and down for negative. Immediately, the model will begin to autorotate around the roll, yaw, and pitch axes. Because the elevator is unloaded, however, the model wont go as deep into the snap and it will stop faster, lose less energy, and remain on the original heading it was on before the snap. .....

          The ailerons control the snaps speed. As you do a snap with this technique, if the speed of the snap is too slow, increase the amount of aileron travel. If its too fast, reduce the aileron travel. Rudder input controls how deep the model stays through the snap. If the snap is too axial (that is, if it looks like a fast roll and the nose doesn't move far -if at all- off the model's line of direction as it snaps), increase the rudder input. If, however, the snap still looks too deep, there is probably too much rudder throw even though you are unloading the elevator correctly. Using a computer radio makes these adjustments very easy.

          Do everything as described above, and you will be 95% there. But there's one last thing: when you exit the snap, release rudder and aileron when the model is where you want it to be. With the unloading technique, the model wont really over-rotate much. At time, though, the model will wiggle a little as it stops rotating.

          Here is one last tip and you will know just as much about snaps as I do: When the model is a 1/4 turn from where the snap is supposed to stop, release the rudder. When it gets to where you want it to stop, release the aileron. This will get rid of the wiggle, and it will look great."


          • #6
            Hi all

            We are going to talk about these issues on our upcoming online judging school.
            Snaps, Spins and rotational element.
            We are going to use a flight simulator and videos to show what is the proper way to fly and to judge them.

            Adi Kochav is inviting you to a scheduled Zoom meeting.

            Topic: IMAC Online Judging School #4
            Time: Apr 24, 2020 09:00 PM Rome

            Join Zoom Meeting

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            Password: 1717
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            • #7
              Thanks for the replies, guys. I haven’t done enough snaps yet to know exactly what works best for my particular airplane. The McConville “checkmark” sounds right (and who am I to argue with him?) so it seems the ideal would be to create a logical condition that gives the best snap rates with that stick movement. I haven’t yet figured out a way to program that, that doesn’t have drawbacks. Maybe it’ll come to me in a dream 🤔but more likely to be a lot of experimentation to see what works best for my airplane and for me.


              • #8
                What I do is set the ailerons to approx 24 degrees up and down and then fly a lot of expo, somewhere in the neighborhood of 75 to 80 percent. It gives a nice feel for precision flight and enough deflection for a nice snap at the end of the stick travel. Other throws are 10 to 12 up and down on elevator, and 15 to 20 each way on rudder. Then I do a logical switch that decreases rudder and elevator throw for upline snaps that is activated with full throttle and full aileron. It helps to keep from getting too deep in the snap on the upline.


                • #9
                  Question for the Unlimited Pilots: DO you fly your precision mode with full aileron travel?
                  Ie: with the transmitter programmed at 100% rate

                  Also, question for pilots, what length servo arm on the elevators and what is your transmitter rate in % for that?


                  • #10
                    Kevin, you answered my 1st question! thanks


                    • #11
                      Hi Cam

                      My level flight is set as a "snap condition" so basically I fly like that every time my throttle stick is in the middle.
                      I do not use "conditions" at all I just fly the plane with ailerons set to snaps.

                      What I did was making a mix that the throttle is my "switch". Ail to Ail mix.
                      When throttle goes to 100% then the mix ADD 10% Ail (the logic is because now the plane is on an up line and i will need more throw)
                      When throttle goes 0% then the mix will REDUCE -10% Ail (the logic is because now the plane is on a down line and i will need less throw)

                      I never exceed the expo above the throw so if my Ail are 70% the Expo wont be above 40%
                      Ele the same, the ele is 35% expo will be 30%.

                      lesson I've learned about all the conditions is that you need to set the plane for the unknown flights, and not for the knowns, that's why The only switch I flip is the rudder for more throw on stall turns.
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