I just reread the flight gear references on torque. Excellent articles and written so it is easy to understand what is happening. In looking at your picture, I realized when in high alpha we only have one rudder doing all the work. The inboard deflected rudder is doing the thrust vectoring. The contribution of the outboard deflected rudder is minimal. I have always been surprised about how much rudder input I use in high alpha. Now it makes sense, I only have "one" rudder in high alpha to generate yaw.
For a design solution to improve right turns the answer is increase the surface area of the rudder and to increase the prop wash to the outboard deflected rudder.
On my next build, I would increase the rudder surface area. With the extended leading edge as we have now, it would be easy to add height and width. Going back to the stock leading edge, there is less room to increase the surface area. Definitely would need to glass the vertical stabilizer where it gets narrow. Here is what I was thinking doing on my next build:
Why not extend the rudders the length of the vertical stabilizer? I tried this on an earlier build but it made the plane very unstable in knife edge which is a flight characteristic I have been chasing. Leaving the top part of the vertical stabilizer adds lift and stability in knife edge.
Increasing exposure of the outboard deflected rudder in high alpha is more difficult. The v4 vertical stabilizers and tail plate are a half inch wider than the v3. In comparing the two planes, I don't think there is much difference in prop wash to the rudders. The ultimate solution would be a counter rotating dual engine setup. The torque issue would be negated and there would be equal prop wash to the inboard and outboard deflected rudders. This would be a great winter project.
In the meantime, just like NASCAR, turn left!
Stephan
Hi Stephan -
ReplyDeleteI agree, I was very happy to find that article, it makes sense of a lot of things that are going on in high alpha with our park jets, always rewarding when you can read the theory and realize you have been seeing those phenomena at the field... :)
As I mentioned in my last post, I think that is exactly what I am going to do, is to extend the rudder all the way up to the top, similar to the FRC Su35 MK2 rudders, they are very effective and by tilting the rudder trailing edge and vertical stab back by just 3 degrees, it will put the leading edge of the vertical stab back closer to stock and hopefully allow even more airflow to get back to that outside rudder when attempting right turns in high alpha. At least that is my theory for now, only building and assessing will tell the truth... :) I will start that as my next project hopefully this week, my next Su35 MK2 will be put on hold until I try this new Mig out, can never have too many Migs in my "hangar".
The dual motor, counter rotating setup would definitely be an interesting project for the winter among a few others I have planned. I'm headed to the field this morning to do some grass cutting and a bit of flying, so I'll further assess the rudders of my FRC Su35 MK2 and my Mig29 V4M3e3.
Cheers,
Scott