I am trying to work out some details on my bird ahead of actually building some details. I am trying to compute the hinge moments for the control surfaces and then design the aileron hinge positions to give good harmony between elevator, ailerons, and rudder.
My first problem is that I am trying to apply the formulae I have found in "Theory of Wing Sections". h=q*Ch*cf^2. Hmmm. Shouldn't I have to multiply by the span yet? Some other method? Please help.
After that, ToWS has (for plain flaps) a way to compute both the Clf and the Ch. How far off is this for the bottom pivoted frise aileron (like Orion favors) and for the off-wing pivot for the slotted flaps? If I can estimate these, I can take Ch/Clf to get the approximate effective radius for where the airload applies, and by stuff they taught us in statics, be able to compute moments for any other pivot location. Can I indeed do this and get a reasonable idea of the moments? Since the ailerons are slotted, and ToWS warns that the hinge moment calcs are not very accurate, should I pony up the c-note to get Hoerner's "Fluid Dynamic Lift"? Will the knowledge conveyed by Hoerner do a better job?
Anyway, the plan is to do this for the rudder, elevators, and ailerons, then estimate what the control harmony would look like. On first blush, it would seem to me that I could work out the hinge moments (knowing that the ailerons are linked), work back to the control forces with reasonable travels, and see how they compare. Except that our legs are way stronger than our arms, and we can push/pull more easily on the stick than we can apply lateral forces. To make it feel harmonious, wouldn't we want some ratio between the three? I figure that there has got to be some empirically derived ratios out there someplace. Anybody have any help for me on this? Buying books is OK if it will help...
One thing that I have done to make balancing the controls easier is the elevator trim tab is rigged so that I can run the tab from being strongly anti-servo to being strongly servo in its operation, and I can settle in upon a setting that works well for me. For rudders, well, there are always centering springs to stiffen things up. Yeah, I fly a Cherokee. But for the ailerons, I am a little afraid that changing the pivot location to tune them will be an exercise in making new hinge mounts and ailerons for each try, so I want to get it closer than that if I can.
So, who has any advice on this?
Billski
My first problem is that I am trying to apply the formulae I have found in "Theory of Wing Sections". h=q*Ch*cf^2. Hmmm. Shouldn't I have to multiply by the span yet? Some other method? Please help.
After that, ToWS has (for plain flaps) a way to compute both the Clf and the Ch. How far off is this for the bottom pivoted frise aileron (like Orion favors) and for the off-wing pivot for the slotted flaps? If I can estimate these, I can take Ch/Clf to get the approximate effective radius for where the airload applies, and by stuff they taught us in statics, be able to compute moments for any other pivot location. Can I indeed do this and get a reasonable idea of the moments? Since the ailerons are slotted, and ToWS warns that the hinge moment calcs are not very accurate, should I pony up the c-note to get Hoerner's "Fluid Dynamic Lift"? Will the knowledge conveyed by Hoerner do a better job?
Anyway, the plan is to do this for the rudder, elevators, and ailerons, then estimate what the control harmony would look like. On first blush, it would seem to me that I could work out the hinge moments (knowing that the ailerons are linked), work back to the control forces with reasonable travels, and see how they compare. Except that our legs are way stronger than our arms, and we can push/pull more easily on the stick than we can apply lateral forces. To make it feel harmonious, wouldn't we want some ratio between the three? I figure that there has got to be some empirically derived ratios out there someplace. Anybody have any help for me on this? Buying books is OK if it will help...
One thing that I have done to make balancing the controls easier is the elevator trim tab is rigged so that I can run the tab from being strongly anti-servo to being strongly servo in its operation, and I can settle in upon a setting that works well for me. For rudders, well, there are always centering springs to stiffen things up. Yeah, I fly a Cherokee. But for the ailerons, I am a little afraid that changing the pivot location to tune them will be an exercise in making new hinge mounts and ailerons for each try, so I want to get it closer than that if I can.
So, who has any advice on this?
Billski
