chashint

If the max deflection of the ailerons on the lower wing is mechanically limited is it OK to make the ailerons on the top wing deflect more by having the connecting rod be in the outer hole on the bottom wing connector and the inner hole on the top wing connector ?
To improve the roll rate would be the reason to do this.
If it is not OK to do this please give a little theory about why.
Thanks in advance.

MajorTomski

Only possible drawback is that you'd be driving the upper aileron too far and just making a drag plate out of it. Play around with the linkage and see what gives the best results

Great outside the box thinking!

Rodney

On some of my bipes, I have found that differential pays off well. Makeing the "up" travel more than the "down" travel will often help the roll rate.

broke_n_bummin

The roll rate also depends on the airfoil of the wings. If you have a straight wing on bottom and dihedral wing on top, you can fly and land alot slower, but the roll rate woun't be that great. If you have a straight wing on bottom and a swept wing on top, a little bit of aileron will go a long way. You can try the connecting rod theory, but remember, you only have 1 servo, and it has to move both ailerons. I would try the inner or second hole on bottom and outermost on top. Just be carefull not to strip out the servo.

da Rock

It's worth testing. So try it and see.

But as for there being any discussion of the idea showing up in aeronautical literature, I doubt you'll find anything applicable.

BTW, if you don't have the connecting rod connection in the same relationship to the hinge lines top to bottom, you're already getting differential motion.

There are a couple of ARFs that provide hardware to connect the ailerons that actually cause the slave ailerons to deflect differently than the driver ailerons. AND the difference in throw differs from the amount difference with up deflection compared to the amount difference from down deflection.

chashint

Thanks for the quick replies. I appreciate it very much.

da Rock

Here is a test setup I made that simulated exactly the setup on a Chinese manufactured ARF biplane. The lower ailerons were the driven ailerons. The measurements of the hardware provided and the design of the connection between the upper and lower ailerons is duplicated.

With that airplane, when the lower ailerons were moved, there was a general cockup. The lower aileron that went up the commanded 20degrees pushed it's paired upper aileron 23degrees up. And the lower aileron on the other side went 20degrees down but pulled it's paired upper aileron down 26degrees.

So when you expected to get 20degrees out of all four ailerons you got 20degrees out of two, 23degrees out of the third, and 26degrees out of the fourth.

chashint

Hi da Rock,
The pic you posted in your last post is very close to the connectors I have.
Only difference is I have both of the control horns mounted on the bottom of the ailerons.
Since it appears that unequal deflection is not abnormal at all I will proceed and see how it goes.
All I need now is a few days without rain so we can get down to the business of flying.
So far this summer has been rained out.
Thanks for the info, it is much appreciated.

da Rock

Yup, it works good enough for lots of flyers.

But take a look at the way I did the SkyBolt in the picture above. Notice that all I had to do was cut a slot in the top aileron to have both connectors arranged identically. I used the supplied hardware, but simply cut out what pieces I wanted to use and glued them in. No extra cost. And with the equal movements, IF that airplane ever snaps out of anything it shouldn't, it'll be a big surprise. I've done the same on an ARF Ultimate that has the reputation of snapping out of maneuvers and being touchy to land. Mine flies with none of that mess. So keep it in mind for your next one. And if your present one shows some nasty, think about how little work it'd be to simply retrofit the upper aileron rigging. And then you can come back and give us a rundown on your experiences with the airplane.

What makes the whole subject so frustrating, is that the ARF mfgs could so easily provide lots better design and hardware for some of these biplanes. They're just throwing rudder hardware into the box for the ailerons and shipping it out.

da Rock

Bumped to bring it into a recent discussion of this topic.