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Old Dec 29, 2012, 04:07 PM
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Originally Posted by bigjohn View Post
I think you know less about aerodynamics than you think you do.
A Computational Fluid Dynamics study early in the FA-18E/F development program indicated the possibility of a Mk 84 series bomb yawing (nose outboard) upon release from an inboard wing station such that its fin would impact a targeting pod mounted on the inlet. The FA-18E/F program was extremely risk averse, and a hasty decision was made to cant the pylons outward to "unwind the spring" to reduce the probability of such an impact. It turns out that the stores configuration this "solution" was intended to address is hardly ever flown (Super Hornets are frequently flown operationally with the inboard pylons removed). The result of this design decision is significant reduction in top speed when carrying stores, and a significant increase to the fatigue life impact of catapult shots and arrested landings. I've flown the Super Hornet with empty bomb racks on the canted pylons and watched the max Mach number go from about 0.93 to about 0.98 after selecting full afterburner (increasing total thrust from about 25,000 lbs to about 40,000 lbs). I've flown the same profile with empty pylons and accelerated above Mach 1.25. I've spent many hours while commanding an FA-18E squadron deliberating over how best to configure Super Hornets to preserve operational flexibility while minimizing damage to the wing spars from cats and traps. All just to mitigate the effects of an ill-conceived design decision.

I believe I am qualified to offer the canted pylons on the FA-18E/F as an example of "reducing the performance of an airplane, for no particular gain".

Perhaps you know less of my grasp of aerodynamics than you think you do... NOTAC.
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Old Dec 29, 2012, 08:42 PM
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messerschmitt me p-1111

Hey Paul haven't seen you around. Keven, I'm still at it with airfoil calculations.

So I have a few questions about flying wings control surfaces.
Right now the control surfaces are inboard and outboard elevons and rudder. So would the inboard elevon serve better as any other type of flight control? Plane has not flown and elevons rates are -40%, roll 70% and pitch 100%
Airfoil is a MH-60 with 78" W/S. AUW 14lbs

So Paul I am looking for a helmet cam. Have any suggestions? I have a camera that is the size of a Bic cigarette lighter, but do not have a clue how to aim it.
Thanks
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Old Dec 29, 2012, 09:05 PM
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United States, TX, Fort Worth
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Quote:
Originally Posted by ShoeDLG View Post
I tried to find some pictures that highlighted the canted pylons on the Super Hornet, which fall squarely in the category of a "creative way to reduce the performance of an airplane, for no particular gain." They may have been canted for a reason, but not for particular gain.
For every gain, there is a tradeoff. I think avoiding ordinance striking an airframe is a gain, even if performance is impacted. Like you said, they are rarely operated with the inboard racks installed, in any case.

With loads like that, even when they are not canted, performance is significantly impacted. What would the top speed be with empty racks mounted straight?

Every aircraft is a huge group of compromises flying in close formation. This is just one more.

Comparing the canted inboard store stations on a Super Bug to that silly pitch control on that one-off flying wing seems an odd way of trying to make some point, though.

It is a rare aircraft that does not have a wart or two in evidence, either visible or hidden away.
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Old Dec 29, 2012, 10:44 PM
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Nederland, GE
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actually i do have a airplane i make now and then, which has pitch stability by drag above the CG, hovever it flies at 1:1 glide ratio at best lol.
it is a rectangular piece of sturdy paper but not really card, 10 by 6 cm, folded as follows:
1 time folded in half along the length, then one half folded open again till it stands at a right angle on the "wing".
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Old Dec 29, 2012, 11:43 PM
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Palmdale, CA
Joined Oct 2000
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Quote:
Originally Posted by p901P901 View Post
Hey Paul haven't seen you around. Keven, I'm still at it with airfoil calculations.

So I have a few questions about flying wings control surfaces.
Right now the control surfaces are inboard and outboard elevons and rudder. So would the inboard elevon serve better as any other type of flight control? Plane has not flown and elevons rates are -40%, roll 70% and pitch 100%
Airfoil is a MH-60 with 78" W/S. AUW 14lbs

So Paul I am looking for a helmet cam. Have any suggestions? I have a camera that is the size of a Bic cigarette lighter, but do not have a clue how to aim it.
Thanks
.
The B-35 and B-49 had flaps for the inboard surfaces. I see no need for those on a model. The outboards should be more than adequate for control anyway.
The MD-80 cameras I have come with a couple of clip-on mounts. Adding the camera and mount to a hat brim would be easy. Hat cameras need some method of assuring they're aimed where you're looking.
The 808 Keyfob style makes a better hat-brim camera.
http://www.angelfire.com/indie/aerostuff/HatCamera.htm
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Old Dec 29, 2012, 11:56 PM
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Keven:
Is this the one? http://www.google.com/patents?id=FYK...page&q&f=false
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Old Dec 29, 2012, 11:58 PM
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Thanks Paul
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Old Dec 30, 2012, 01:20 AM
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ShoeDLG's Avatar
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Quote:
Originally Posted by Thomas B View Post
Comparing the canted inboard store stations on a Super Bug to that silly pitch control on that one-off flying wing seems an odd way of trying to make some point, though.
Was just trying to suggest that unique and demonstrably poor design "solutions" aren't confined to black and white newsreel footage, or one-off designs.
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Old Dec 30, 2012, 11:17 AM
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Originally Posted by p901P901 View Post
.
That's an interesting patent. A method to solve a solved problem... by making the system more complex.
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Old Dec 30, 2012, 01:34 PM
An itch?. Scratch build.
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South Wales U.K.
Joined Mar 2003
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All it needed was for those drag plates to flap and,........

the precurser to single channel 'galloping ghost'

Boy, that brings back memories of the 50's and my first RC.

Found this on Youtube for those that don't know about three functions from one single channel -

Mighty Midget Galloping Ghost ( Simpl Simul - Pulse Proportional) demo rig (4 min 19 sec)
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Old Dec 30, 2012, 02:33 PM
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Drag rudders..... one servo for each side of the wing.
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Old Dec 30, 2012, 02:34 PM
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Quote:
Originally Posted by eflightray View Post
All it needed was for those drag plates to flap and,........

the precurser to single channel 'galloping ghost'

Boy, that brings back memories of the 50's and my first RC.

Found this on Youtube for those that don't know about three functions from one single channel -

http://www.youtube.com/watch?v=IBxXsRwRn1M
.
Spent many hours with Galloping Ghost. Betcha can't find a Mighty Midget motor today!
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Old Dec 30, 2012, 04:37 PM
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Fa-50

The Boeing FA-50 is one of my future fantasy builds. Since it does not have a vertical stabilizers it needs drag rudders. Still trying to figure out placements of the rudders. Wings are small so it looks like it needs to be combined with the other surfaces.
I am thinking of using a Guardian Inertial Stabilizer for this project or a alpha-beta sensor for yaw feedback.
Built a glider model with a vertical tail but glide path was about ten feet. So I need to power this thing to see how it flies.
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Old Dec 30, 2012, 05:55 PM
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The biggest problem with that FA50 design is not the absence of vertical surfaces per se, but the fact that there's more vertical area in front of the CG than behind it. It won't just be non-controllable, but actually greatly unstable in yaw. that can be compensated electronically, but you will need to read the actual yaw, you can't just use a gyro.
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Old Dec 30, 2012, 07:04 PM
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I thought the Guardian has accelerometers as well as gyros. I do not know the sensitivity of the accelerometers but they should detect slideslip. Drift would be a problem with this. So coupled in with a beta fin should fix this. I can only imagine near stall speeds (high Alph) how much drag rudder deflection that would be needed to keep the yaw stable.
This is all speculation because I have not calculated the dynamics of such a system. I do have a 24" W/S full body test bead that will fly with a vertical.
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