All flying horizontal stab movement.
05-02-2012, 07:33 AM
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All flying horizontal stab movement.
Hi
Anybody got a good rule of thumb for how much up and down control movement is optimum for an all flying horizontal stabiliser on a high performance sailplane similar to the Bubble dancer?
Tony
Anybody got a good rule of thumb for how much up and down control movement is optimum for an all flying horizontal stabiliser on a high performance sailplane similar to the Bubble dancer?
Tony
05-03-2012, 12:47 PM
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RE: All flying horizontal stab movement.
The travel at the trailing edge of an all flying tail should mimic what you'd expect from the travel at the trailing edge of a regular elevator attached to a regular fixed stabilizer. That'll get you into the ballpark and provide a flyable option which won't be either too responsive or feel "dead". Once you fly the model a couple of times at that setting you can adjust for a little more or less throw to suit your own desire for response.
So on something the size of a Bubble Dancer I'd expect to start my first flight with something like 5/16 to 3/8 inch of travel either side of neutral.
The bigger issue if finding a good initial neutral point for an all flying stabilator. I like to hold the model up over my shoulder pinched lightly between two fingers at the balance point. I then jog or run into the wind while allowing the model to "fly" in my light grip. If the stabilator angle is close the model will get light in my hand but not want to either nose up and lift away strongly or pitch nose down and stay heavy. You're looking for a light but stable bouyancy for the amount of air speed over the wing and without any sort of strong pitching moment to either bury the nose or pitch up and try to "kite" away. It sounds a bit airy fairy but it's surprising how easy it is to do and feel with a decent degree of accuracy. Even if you can't run fast enough to actually get it over the stall speed just the lighter feel with a stable non pitching attitude is idicative that you're close enough for the first test flight to go ahead without any strong surprises.
So on something the size of a Bubble Dancer I'd expect to start my first flight with something like 5/16 to 3/8 inch of travel either side of neutral.
The bigger issue if finding a good initial neutral point for an all flying stabilator. I like to hold the model up over my shoulder pinched lightly between two fingers at the balance point. I then jog or run into the wind while allowing the model to "fly" in my light grip. If the stabilator angle is close the model will get light in my hand but not want to either nose up and lift away strongly or pitch nose down and stay heavy. You're looking for a light but stable bouyancy for the amount of air speed over the wing and without any sort of strong pitching moment to either bury the nose or pitch up and try to "kite" away. It sounds a bit airy fairy but it's surprising how easy it is to do and feel with a decent degree of accuracy. Even if you can't run fast enough to actually get it over the stall speed just the lighter feel with a stable non pitching attitude is idicative that you're close enough for the first test flight to go ahead without any strong surprises.
