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New log flap drive crank idea
Mark wood:
I've been working on a bunch of elements for new airplane design. It's been a slow process. As a total geek, I tend to deep dive in to elements. In my endeavors for the design I look at as many adaptations as possible. One of the observations I have is that stunt models seem to use much more flap deflection than is necessary and / or desirable. I performed multi configuration airfoil analysis and have begun some flight test videos with a tufted SV-11 wing which I'll post some results here. One of my 4/4 efforts is posted elsewhere on here. All of these tests and analysis support the premise. Igor Burger has developed his Logarithmic flap drive which is a proven step in this arena. From my analyses and testing, I think that even the 27 degrees of this flap system is a bit much and better performance can be had by a further reduction.
How to test this premise? Make a configurable flap drive. Have CAD. Have 3D printer. It can be done. I've spent a bunch of time working on this model, maybe a bit more than I should but it is addictive. I've also made several iterations along the way. The primary difference between what I have and Igor's is that I have turned the drive crank around and turned the flap horn into a "flap drive horn" which is connected independently to the flaps. With four turnbuckle connecting rods between the bellcrank the flaps independently and the elevator the entire system can be tweaked at one location accessed by a single hatch.
Mark wood:
I have found a collision with the pushrod to elevator linkage and need to make a revision. Again I posted something a little early in the development stage. It's not a huge problem as I can move my intended connection over and get clearance
Oh well. At least I learned about making control joints in solid modeling.
Dennis Toth:
Mark,
What is the advantage to using this system over conventional flap drive? What problem are you having or did you have/notice with conventional hookups that you are working to overcome?
Best, DennisT
Tim Wescott:
--- Quote from: Dennis Toth on November 09, 2021, 12:40:56 PM ---Mark,
What is the advantage to using this system over conventional flap drive? What problem are you having or did you have/notice with conventional hookups that you are working to overcome?
Best, DennisT
--- End quote ---
Mark isn't pioneering the idea of a logarathmic drive -- he's building on the works of others. Logarithmic flap drives have been in planes that have won the World's, so at worst they don't hurt.
The idea is that for straights and round maneuvers, you want a fairly high flap-elevator ratio. At some point, the flap deflection just isn't help any more, so when the deflection is high you want to add a smaller increment of flap for each increment of elevator. Basically, in the corners you want more turn, in the flats and rounds you want more lift.
The logarithmic flap drive provides this.
Dennis Toth:
Not to criticize development work just want to understand what it is trying to advance. So does this system reduces the amount of flap input to elevator as you apply more control? Or is it adding more flap as the amount of control is increased? And we can't do this with different mechanical ratio variations why? Does this allow a more rearward CG for tighter corners? What is it doing that is different from the basic Nobler flap/elevator setup? How much better is it?
Best, DennisT
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