F3B & F3F rules on airfiol shape shifting! Sceptics welcome! - Page 2 - RC Groups
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Dec 08, 2010, 08:16 PM
Registered User
yyz's Avatar
Originally Posted by RetoF3X
Of course you want to keep the elevator servo (s) in the nose. There are kinematics with one or two bellcranks using one or two servos.

I made two sketches. The first one should be obvious, you use either two servos or if you use one, you adjust the leverage between bellcranks and servoarm.

The second one would work with only one bellcrank, which is offset to the rotation point of the tailplane. Owing to the offset, the elevator surface will be cambered when the incidence angle is changed.

I would need to write a little Mathematica file to optimize the geometry, but it would be doable.

My mistake. I thought you were trying to articulate the elevators and all-flying stab separately, like the eta, where the all-flying stab is used for trimming in cruise and the elevators are used in more immediate maneuvers (zoom, speed turns, etc).

You'd get kick ass elevator response using your technique

Seems like elastic skins, eliminating the control surface hinge lines altogether, might be an interesting thing to try. I fluttered a Ceres to death this year so, "Not it!".
Last edited by yyz; Dec 08, 2010 at 08:27 PM.
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Dec 09, 2010, 08:13 AM
What's wrong with heavy?
dephela's Avatar
In 1996 Ron Vann had a nice, simple way of cambering with two hinge points on the wing.
A single servo had pushrods attached at two different holes in the output arm. The inner rod went to the control horn on the forward "flap" and the outer one went to the rearmost "flap".
Dec 09, 2010, 08:45 AM
F3B and F3K
RetoF3X's Avatar
Hi Dennis

Yes, this was also the way how the Logo team did it on their Shark wing. But if you go to three or more hingepoints, it will get messy with conventional linkages.

Again, maybe RDS with a multiple bent rod might work.

Airfoil would also need to be designed for multi-hingelines. I guess the maximum thickness would need to be more forward (like Selig 7003) to allow deeper flap chords.

@Mike: Yes that all-moving tailplane with camber change is meant for optimizing turns, not stationary flight.

Dec 09, 2010, 09:13 AM
Registered User
Avaldes's Avatar
Yep, been thought of. When I was working on my PhD that was the exact subject of my thesis...shape adaptable wings. There was funding from the gov't and everything. I wish I could have finished my paper. I had some pretty innovative designs that involved some VERY unique control mechanisms.

Needless to say, if you want to tackle ALL of the design constraints, it is a VERY challenging task. NASA has an F-18 with a more flexible skin where they use actuators to deflect the LE and TE...No hinge lines. It is great but it takes a tremendous amount of energy to move those surfaces.
Dec 09, 2010, 11:42 AM
Daryl Perkins's Avatar
@Reto - Leeading edge droop - Only 10 servos in that wing. That was a neat experiment - and I think showed some merit. Only problem was I made the control surfaces too large and negated most of the benefit. I also didn't use a section designed for it, but a model that I had molds for. All the servos and linkages were molded into the wing during manufacture. It was a PITA!!! I used a live skin hinge on the upper surface and had to cut a slot on the lower surface and fill with a wiper. Obvious concern was drag... it didn't seem to have any noticeable effect on speed. The model launched slightly better, but turned much harder than its stock cousin. I blew a joiner box on one launch, costing me a tip, and just didn't have the energy to rebuild the thing. Did I mention it was a PITA???

Originally Posted by dephela
In 1996 Ron Vann had a nice, simple way of cambering with two hinge points on the wing.
A single servo had pushrods attached at two different holes in the output arm. The inner rod went to the control horn on the forward "flap" and the outer one went to the rearmost "flap".
Yeah - that was mine too. Ron saw mine, liked it, and built his own. It was a double hinged trailing edge. You could easily drive the TE from the one servo. The inner TE was driven from a low hole on the servo arm and the aft TE was driven by linkage through an outer hole. Ball clevises were used to separate the linkages. It looked really neat - but didn't provide much benefit. Again - maybe if a section was designed to use it, it may make a difference. That model flew really well, but I don't think had any significant aero advantages...

Mar 21, 2011, 06:20 AM
The wheels touch down FIRST??
BJ64's Avatar
Originally Posted by Phil Davy
...Dan Gurney, the only Man to ever design build and race a F1 car to victory in history...

There was this guy called 'Jack Brabham', who not only designed, competed in, and won F1 races, but also won the F1 World Championship in 1966 in one of his own cars.

The only one - ever - to have ever won the F1 World Championship in a car bearing his own name..

Mar 21, 2011, 06:35 AM
The wheels touch down FIRST??
BJ64's Avatar
..but.. I digress...

Back on topic - I've often thought of some sort of *description removed - patent check pending*

Last edited by BJ64; Mar 21, 2011 at 07:16 AM. Reason: checking for patent on the idea...

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