You're All Trash*, Part 234,567,988 - DarkAero

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BJC

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It seems this is a passion rather than profit endeavor.
The principals are young, and told me that it is a full time effort, that none had another job. Their original schedule had them flying early this year. They are young, energetic, enthusiastic, but naïve and way overly optimistic, in schedule, aircraft weight and performance, and market potential.

I do wish them well. It is good to have young people devote their professional lives to GA.


BJC
 

davidb

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Anyone care to offer thoughts on the split rudder? Sounds like I’d have to retrain my feet lest I’d be inadvertently getting speed brake affect.
 

BBerson

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I don't think the small split rudder I saw at Osh will have much drag effect, in the mixed flow behind the airplane. Also might be hard to get a stiff and light part, by splitting the skins it then has almost no torsion stiffness of a normal rudder.
 

BoKu

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Showing my ignorance, does sandwich refer to a core in layup and no ribs or?
It refers to the use of foam core sandwich construction that gives the wing skin enough panel stiffness so it doesn't require a cellular internal structure with six or eight different shear webs. Fabricating and installing those shear webs takes a lot of time and effort, and bonding them to the last skin during closure adds a lot of extra mass in the form of squeeze out. I can understand that such a structure might look attractive when viewed in the SolidWorks palantir, but I think that most of the potential advantages cancel out in the real world.
 

delta

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Anyone care to offer thoughts on the split rudder? Sounds like I’d have to retrain my feet lest I’d be inadvertently getting speed brake affect.
That feature "on demand" might be nice in place of a spin chute.
 

wsimpso1

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That feature "on demand" might be nice in place of a spin chute.
Yes, a split rudder will work as a dive brake reducing speed build-up and to facilitate descent at modest speeds.

I will need a lot of validation modeling testing to think that it could help with spin recovery:

If full rudder will not effect a spin recovery, how is deflecting one rudder face fully in the anti-spin direction and the other rudder face fully in the pro-spin direction going to be an improvement?

Spin recovery chutes pull the tail aft along the line of travel while bringing speed down and holding it there. I have a very difficult time believing that we could achieve anything approaching that result with rudders opened.

Looking at spin recovery videos, spin recovery parachutes tend to have a diameter somewhat larger than the span of the horizontal tail. That makes its area an order of magnitude larger than the area of the rudder.

Billski
 
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davidb

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I’m having trouble envisioning the split rudder “speed brake” actuation. If I heard correctly, pushing both rudder pedals simultaneously achieves the both left and right displacement. I guess that works but it seems like it would be awkward if you wanted speed brake and rudder at the same time.
 

Rik-

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Yes, a split runner will work as a dive brake reducing speed build-up and to facilitate descent at modest speeds.
Will it? I mean force is equal to a mass and there's little area to have any affect especially on this design. It would need to go full 90 degrees of movement to start to show an effect due to the tiny size of it.

They are not shy about where their ideas (or lack of ingenuity) come from. They are merely looking at Rutans rudders on the LongEz and copying those. Will a LongEz slow down rapidly with full deflection or? I know that a lot of builders have increased the size of their rudders as they were originally felt to be ineffective on Rutans designs.

If Rutan's work then these should in theory too
 

BJC

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Will it? I mean force is equal to a mass and there's little area to have any affect especially on this design. It would need to go full 90 degrees of movement to start to show an effect due to the tiny size of it.

They are not shy about where their ideas (or lack of ingenuity) come from. They are merely looking at Rutans rudders on the LongEz and copying those. Will a LongEz slow down rapidly with full deflection or? I know that a lot of builders have increased the size of their rudders as they were originally felt to be ineffective on Rutans designs.

If Rutan's work then these should in theory too
Rutan designs use a belly flap for a speed brake.


BJC
 

wsimpso1

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Will it? I mean force is equal to a mass and there's little area to have any affect especially on this design. It would need to go full 90 degrees of movement to start to show an effect due to the tiny size of it.
Force is not equal to mass, but force is equal to mass times acceleration - what are you getting at there?

Split rudder dive brakes were used on the Space Shuttles. There are two split dive brakes at the base of the horizontal tails on the F-16. The Fokker 100 airliner has a clamshell brake on the very aft end of the fuselage. There are others. None that I have looked over appeared to go 90 degrees, and the story out there is they all do work.

Will a LongEz slow down rapidly with full deflection or? I know that a lot of builders have increased the size of their rudders as they were originally felt to be ineffective on Rutans designs.

If Rutan's work then these should in theory too
I am told that you can stand on both rudder pedals and watch a modest sink rate develop in Long EZ and derivatives. Remember also that the rudders are on wing extensions, so they will influence flow over the wings as well as over the vertical tail, resulting in more effect than if they were on an independent vertical tail.

Long-EZ rudder effectiveness compared to what? I do know that you have enough rudder to deflect one and have the airplane skid/roll into big bank angles.

Billski
 

ScaleBirdsPaul

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The A-10 uses split ailerons as brakes as well. Just eyeballing it, I would venture a guess that’s it’s performance is roughly equivalent to two split flaps. I don’t think it’s going to turn the airplane into a Stuka, but it will give you the ability to quickly dump drag during a go around simultaneously with adding power without significant pitching moment or lift changes.
 

ScaleBirdsPaul

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The A-10 uses split ailerons as brakes as well. Just eyeballing it, I would venture a guess that’s it’s performance is roughly equivalent to two split flaps. I don’t think it’s going to turn the airplane into a Stuka, but it will give you the ability to quickly dump drag during a go around simultaneously with adding power without significant pitching moment or lift changes.
As I hit enter I realized a slip would accomplish the same thing, but this is probably more comfortable than being cross controlled.
 

12notes

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The assumption being made is that it's possible to push both pedals and have both rudders deploy, but they may have the pedals designed to prevent this. Symmetrical deployment, if needed, may be on a separate control.
 
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