Control System Question (Banshee)

[Motorman]

Actually trying to get the geometry right on this one. Drew it all out on paper and made my own bolt on control horns. I got the bellcrank centered with the lead outs same length and the flaps at neutral. I even made one of those flap horns that tilt forward to get 90 degrees on the pushrod. my problem is with the elevator. The pushrod that came in the kit was a bit too long so I had to move the horn aft to get neutral. Now I get more travel up than down. If I make a shorter push rod and move the horn forward as designed will that fix the problem?

Thanks,
MM

[Howard Rush]

Yes. 

If you really want your controls symmetrical, I can send you a spreadsheet.

[john e. holliday]

I'm gong to be nasty and ask why you didn't make adjustable links on the push rod?

[Mike Griffin]

Doc, you ole rebel rouser you.

[Tim Wescott]

I'm gong to be nasty and ask why you didn't make adjustable links on the push rod?

I'm going to be all nice and recommend that you make at least one adjustable link on the push rod.  And make the push rod out of carbon fiber, to boot, and lose the pushrod guide on the fuselage.

[Dan McEntee]

  The usual method for using pushrods of fixed length, is to install the bell crank before gluing the horizontal stab in place. Then you install the control horn on the elevator with the holes for the pushrod centered on the hinge line. You attach the pushrod at both ends, and slide the stab back and forth until the levator is level, then mark the position, and then glue the stab in place. I think thi is spelled out in the Banshee instruction sheet.  If there is a minor deflection after glueing, and it's in the correct direction, you can tweak the pushrod by bending it a bit to shorten it. Another old school method if using music wire push rods is to make it in two pieces with about an inch and a half over lap. Wrap the over lap tightly with thin un-varnished copper wire until it is sort of stiff and will hold a position. If the stab is glued on already, shorten or lengthen the push rod as necessary at the over lapped section and test the controls. When all is well and good, just solder the joint securely. And with any method, don't forget to install a fair lead to limit flex in the push rod. About half the airplanes hanging in my garage have push rods made in one of these methods with no problems.
   Type at you later,
    Dan Mcentee

[Motorman]

I can make the push rod adjustable by cutting it and soldering on a roll pin. I just threw it on there to see the flippers go up and down.

Thanks Howard, I see the problem. The push rod goes up to the elevator which makes it worse. I need a horn that goes forward of the hinge line.

Can anybody give me flap and elevator angles for a Banshee?

Thanks,
MM

[Howard Rush]

And with any method, don't forget to install a fair lead to limit flex in the push rod.

You can get away without this if the pushrod is stiff and straight.  If the pushrod has a dogleg in it or even if it has an L bend at the end, it will tend to bend and need support.

[Dan McEntee]

I can make the push rod adjustable by cutting it and soldering on a roll pin. I just threw it on there to see the flippers go up and down.

Thanks Howard, I see the problem. The push rod goes up to the elevator which makes it worse. I need a horn that goes forward of the hinge line.

Can anybody give me flap and elevator angles for a Banshee?

Thanks,
MM

    All control horns should have the push rod holes on the hinge line, both flap and elevator. Forward or aft of the hinge line will give you the differentiation, or more one way than the other. Elevator and flap difflection should be good at 35 degrees or so for a properly balanced model, and be more than enough. Check the plans and the instructions closely.
    Type at you later,
      Dan McEntee

[wwwarbird]

The pushrod that came in the kit was a bit too long so I had to move the horn aft to get neutral. Now I get more travel up than down. If I make a shorter push rod and move the horn forward as designed will that fix the problem?

Thanks,
MM

 Um, let me think about this.

[Motorman]

Got it fixed. Seems so simple now. The line between hinge pivot and horn pivot had to be 90 degrees to the pushrod to get equal travel in both directions. At the angle the pushrod approached the tail, the horn pivot had to be 1/8 ahead of the elevator hinge to achieve the 90.  I've got 22 degrees on all flippers up and down. Seems like allot of flap, maybe I'll make the elevator horn shorter as I sometimes need to do emergency pull outs. I was going for 1:1 but plans show 1/16th shorter.

MM

[Tim Wescott]

If I remember correctly you're a beginner or intermediate pilot.  If that's the case, then leaving it alone will probably give you a plane that flies better than you do.

Of course, if you currently have to burrow up through the snow to see if it's light outside, there's no reason not to spend time fussing with your plane.

[Motorman]

Just did a weight and balance on the Banshee. The battery box in the wing was a fail.  Looks like my dream of having a full length nose is over. Balance point was 1-1/4 ahead of the plans. I have to move the motor back 3" to get anywhere close. Could add 50g to the tail but I'm already at 44oz. with batt. Where do you balance your Banshee?

MM

[Don Coe]

I've got an electric Banshee and had to cut 2 1/2" off the nose to get an "in range" balance point.  Mounted the battery box above wing for final balance point.  Plane flys terrible.  Think I have to remount engine.  Thinking it may be thrust line???  Please post as this project continues.

[Douglas Ames]

If I remember correctly you're a beginner or intermediate pilot.  If that's the case, then leaving it alone will probably give you a plane that flies better than you do.

Of course, if you currently have to burrow up through the snow to see if it's light outside, there's no reason not to spend time fussing with your plane.

Can't the guy make an attempt at furthering his knowledge? Isn't that what this forum's about...

[Motorman]

It's a problem with certain size planes. I made an E Flight Streak with the battery completely below the wing and it flew like a duck with a broken wing. That's why I made a box in the wing to get it on center and far enough back. The system is big enough for a 650 sq in plane and I'm sure that's part of the balance problem. I'd like to move the battery back but I'd have to cut the spar in half. The answer is build bigger planes lol.

MM