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Stabilizer Design Discussion.

Discussion in 'Aerodynamics' started by Snoopy1, Dec 31, 2015.

   
  1. Snoopy1

    Snoopy1 640cc Uber Pimp

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    Sorry if I am a little long winded but would like to explain why this interested me. Been in the hobby for well over 30 years. Built a fully moving stabilizer about 20 years ago. It works but not well. Moved the pivot point of rotation back and forth and eventually came up with a location that worked. But the servos that we had at the time were at most 125 oz-inch and were not digital, the centring was not strong. Just getting interested in 3D and have 2 plans so far. looking at the stabilizer on the 2 planes more than 60% is elevator. My question is would the elevator not be more effective if the whole stabilizer would rotate. (Like on some jet planes). With the power and centering of today's servo would it not be a better design.
     
  2. dhal22

    dhal22 GSN Sponsor Tier 1

    Can you imagine a 45 degree full horizontal stab deflection?
     
  3. Flyingjon

    Flyingjon 70cc twin V2

    ...
     
  4. Terryscustom

    Terryscustom 640cc Uber Pimp

    Flutter would be the main issue with a full actuating stab. It would require two servos in a push-pull configuration and a VERY strong structure and linkage system not to induce catastrophic flutter.
     
    thurmma likes this.
  5. Snoopy1

    Snoopy1 640cc Uber Pimp

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    Flutter was one of the main problems when trying to this. By moving the pivot point ahead it stopped that problem but then the servo was not strong enough to get a decent amount of deflection. With the servos of today this should not be a problem. I agree with you Terry the drive system is not easy but doable. But the design thought is about 3D where every thing low and slow where I believe that this design could have some merit.
     

  6. Jetpainter

    Jetpainter 640cc Uber Pimp

    Keeping it light to avoid it being tail heavy could be an issue as well.
     
  7. @Terryscustom is right. The configuration would be to much. The best thing for a really powerful stab would be to just make the stab itself barely big enough to hold the servo and 90% of the stab would be the elevator. But not sure its needed. All of my plane already have a huge elevator that does plenty for me.
     
    Snoopy1 likes this.
  8. okay so this is a blast from the past... look up the leo loudenslager shark... it was a full scale airplane that would have changed modern aerobatics if he hadn't been killed on a motorcycle.. it has a cruciform tail and once the elevator and rudder hit 45 degrees of travel the entire surface would move to 60 degrees... on that other terrible site someone actually built a 40% version with the moving surfaces. pretty neat and it worked...
     
    WMcNabb and Snoopy1 like this.
  9. this is the full scale.. could you just imagine???
     

    Attached Files:

    WMcNabb likes this.
  10. ghoffman

    ghoffman 70cc twin V2

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    On full scale planes (like F-16) the center of pressure is slightly aft of the pivot on the stabilator. This is something that you have to trade off. The closer they are to equal, the less force it takes to move it, but the more likely it is to flutter.
     
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