- Wed Feb 28, 2018 5:19 pm
#402459
Postings on other topics indicates that many, but not all, pilots would appreciate either reduced lateral bar forces or faster response times or both.
If I'm not mistaken the first Roll Augmentation device was the tall keel pocket. This was invented by whom I don't know at a time when designers were first reducing sail billow in an effort to improve performance of flex wing gliders. If you know who did it first please let us know.
When more augmentation was needed the cross-bar was disconnected from the keel so that the two components were free to move relative to each other. I recall that this was first referred to as a "floating cross-bar", but later on someone pointed out that it was the keel that was "floating". I suppose that one term or the other will get the point across, so call it what you will.
Both of these developments were low-tech, lightweight, and inexpensive to incorporate into a glider's construction, and they worked.
I personally have no need for my glider to be eligible for Class 1 competition, which stipulates that roll control must result from weight-shift alone.
For some time now I've wondered how an augmentation device that converts lateral bar forces directly into warping of the sail or wing twisting might look like.
So I've opened this new topic in the hope that a good discussion of the subject will take place.
Although my primary interest is in developing a whole new glider, a means of improving roll on our current designs is a more practical thing to pursue.
Hopefully we can come up with a system that, like the aforementioned ones, would be simple, lightweight, inexpensive and most importantly reliable.
The goal, in my opinion, is a glider that doesn't require what we now call a Variable Geometry system. Ideally a VG would only be used to modify a gliders flight profile to allow a steeper angle of descent for approach to landing, although it could also be used for other reasons, such as adding or reducing stuff like camber and reflex and what have you. But I resent having to decide whether I get a flat glide or being able to maneuver. I want both at the same!
An idea that I've thought about but haven't tried is a keel built so that parts of it could rotate, causing the trailing edge or the leading edges or both to be displaced one side up and the other down.
In describing this to friends the subject of adverse yaw comes up, and while it is a matter of concern I believe it can be accommodated as it is now, by having the just right amount of anhedral. However, it has been demonstrated that a vertical fin can be used with only minimal added weight and expense. My Sensor has one that takes probably only a minute to rig and weighs a few ounces, and some gliders have them for towing operations.
Making a vertical fin that also can be used as an active rudder shouldn't require a lot of engineering. But using it as a control may be problematic as the glider would need dihedral to convert the skid induced by a rudder into a rolling moment.
But a rudder might be used as a "servo tab" like thing to help with the pilot's workload, by using the force it generates to move something else, such as rotating a keel. Something to think about...
It's been a long time since the floating keel/X-bar and the VG were originated. It just doesn't seem to me to be a difficult task to create something that would make high performance flex wings more entertaining to play with. But flight testing can be hazardous to one's health, and I suspect that that is one good reason why we don't see developments being tried.
For testing purposes it might be a good idea to build a horizontal tail surface or canard to at least help a pilot feel confident with trying out a new device. Making it so that the new device can be disabled until a safe place to try it is reached would also be a good thing.
There's a "law of unintended consequences". It's not at all difficult to fail to see where one action could affect another, so it behooves one to approach any glider modification with caution. Bill Murray suggested "Baby Steps", and it's a good suggestion. Or was that Richard Dreyfus?
If I'm not mistaken the first Roll Augmentation device was the tall keel pocket. This was invented by whom I don't know at a time when designers were first reducing sail billow in an effort to improve performance of flex wing gliders. If you know who did it first please let us know.
When more augmentation was needed the cross-bar was disconnected from the keel so that the two components were free to move relative to each other. I recall that this was first referred to as a "floating cross-bar", but later on someone pointed out that it was the keel that was "floating". I suppose that one term or the other will get the point across, so call it what you will.
Both of these developments were low-tech, lightweight, and inexpensive to incorporate into a glider's construction, and they worked.
I personally have no need for my glider to be eligible for Class 1 competition, which stipulates that roll control must result from weight-shift alone.
For some time now I've wondered how an augmentation device that converts lateral bar forces directly into warping of the sail or wing twisting might look like.
So I've opened this new topic in the hope that a good discussion of the subject will take place.
Although my primary interest is in developing a whole new glider, a means of improving roll on our current designs is a more practical thing to pursue.
Hopefully we can come up with a system that, like the aforementioned ones, would be simple, lightweight, inexpensive and most importantly reliable.
The goal, in my opinion, is a glider that doesn't require what we now call a Variable Geometry system. Ideally a VG would only be used to modify a gliders flight profile to allow a steeper angle of descent for approach to landing, although it could also be used for other reasons, such as adding or reducing stuff like camber and reflex and what have you. But I resent having to decide whether I get a flat glide or being able to maneuver. I want both at the same!
An idea that I've thought about but haven't tried is a keel built so that parts of it could rotate, causing the trailing edge or the leading edges or both to be displaced one side up and the other down.
In describing this to friends the subject of adverse yaw comes up, and while it is a matter of concern I believe it can be accommodated as it is now, by having the just right amount of anhedral. However, it has been demonstrated that a vertical fin can be used with only minimal added weight and expense. My Sensor has one that takes probably only a minute to rig and weighs a few ounces, and some gliders have them for towing operations.
Making a vertical fin that also can be used as an active rudder shouldn't require a lot of engineering. But using it as a control may be problematic as the glider would need dihedral to convert the skid induced by a rudder into a rolling moment.
But a rudder might be used as a "servo tab" like thing to help with the pilot's workload, by using the force it generates to move something else, such as rotating a keel. Something to think about...
It's been a long time since the floating keel/X-bar and the VG were originated. It just doesn't seem to me to be a difficult task to create something that would make high performance flex wings more entertaining to play with. But flight testing can be hazardous to one's health, and I suspect that that is one good reason why we don't see developments being tried.
For testing purposes it might be a good idea to build a horizontal tail surface or canard to at least help a pilot feel confident with trying out a new device. Making it so that the new device can be disabled until a safe place to try it is reached would also be a good thing.
There's a "law of unintended consequences". It's not at all difficult to fail to see where one action could affect another, so it behooves one to approach any glider modification with caution. Bill Murray suggested "Baby Steps", and it's a good suggestion. Or was that Richard Dreyfus?