[Bob Kuczewski]

Sure is a lot of stuff to eliminate a motor and propeller from the glider.

Actually, the idea only eliminates the propeller because it still needs some kind of motor to operate the winch (or winches).

Having said that, I think the idea is very very clever, and I think it could be made workable. I would envision the two gliders starting out facing each other and pulling each other into the air. Then they both execute a mild right bank to begin corkscrewing upward (but the lockout issue would have to be addressed!!!). Then as their winch (or winches) bring them closer, they disengage the winching and expand the radius of their circle which pulls out the line. Once the radius of the circle has grown, they can begin winching toward each other again to climb. They just repeat that process corkscrewing themselves into the air.

There are numerous dangers here. For example, being in any bank while on tow invites a lockout situation. This would have to be addressed and eliminated for this to work. That's why I would recommend computer modelling to start along with building remote control models. This method requires a lot of thought and study before being put into practice!!!

[Frank Colver]

A big difficulty with this is that the two gliders need to be fairly closely matched in L/D and wing loading. Otherwise one will hardly climb at all while the other one zooms up as if it was a typical ground based towing situation.

I'll take the propeller and not need to depend on what the other person does. But then I've always been an independent sort. See yeah

FC

[JoeF]

All this great discussion will surely form soil for exploring versions of the general concept. Thanks, All.
RS notes how the door is open for future stepping!

It is not just the absence of propeller. RS noted the efficiency of direct winching for the kiting lift pathing. Bill noted the generally horizontal tether being shared by two hang gliders; similar line sharing goes for three or more wings in either the spoked or the perimeter-lined modes. Then then is the all-aerial line aspect. Notice how stunt kiting handles lock-out issues; full spirals even become part of the deal. Good sensor communications may so well coordinate the wing-local challenges between two (or more) wings that AoA and rolls may be smoothly coordinated to give net useful tension for both wings. Surely Bob's underlining modelling wins over losing any limb or life.

Notice how already there is a primitive occurring: Frank Colver on Sunday last had a great flight at Dockweiler; it gave him and us wide smiles. Not then noticed was that in that flight was a hang glider coupled to a hang glider via a short long line; no propeller. One of the hang gliders was called Frank Colver; the other hang glider in the gliding kite system was a WW Alpha 210. In this particular instance there was equilibrium of forces and the two-hang-glider system glided through the air windward; there was not a winch at the Alpha 210 nor at the Colver wing body. But, in all, that great flight may be a seed for longer lines and emplacement of powered winches. Good flight, Frank. See the flight of a hang glider coupled to a hang glider: https://vimeo.com/166914129

[KaiMartin]

A big difficulty with this is that the two gliders need to be fairly closely matched in L/D and wing loading. Otherwise one will hardly climb at all while the other one zooms up as if it was a typical ground based towing situation.

I don't think, differences in lift to drag are an issue.

Imagine a symmetric situation except for glider A has double L/D than glider B. Sure enough glider A initially climbs with double the rate of glider B. Pilot A reacts by pulling the bar. This will accelerate glider A and simultaneously reduces its climb rate. The tether restricts the the distance between the gliders. Circle size for glider A increases. The circle for glider A will be significantly larger than the circle of glider B. Glider A flies faster than glider B. But climb rates match.

This is similar to aero tow. With aero tow the glider pilot is expected to adjust his height with the speed bar. Pulling in lowers the glider relative to the ultralight.

---<)kaimartin(>---

[KaiMartin]

With four thousand and ninety one flights, the majority being tow flights, I see the biggest hurdle to spiral towing a weight shift hang glider as being a lock-out.

I agree, lock-out is a major concern for any tethered scenario.
Like I mentioned before, the concept of lock-out is unknown to sailplane pilots. This probably because their control on roll and yaw always exceeds the tendency to deviate from tow direction.

---<)kaimartin8>---

[Bill Cummings]

With four thousand and ninety one flights, the majority being tow flights, I see the biggest hurdle to spiral towing a weight shift hang glider as being a lock-out.

I agree, lock-out is a major concern for any tethered scenario.
Like I mentioned before, the concept of lock-out is unknown to sailplane pilots. This probably because their control on roll and yaw always exceeds the tendency to deviate from tow direction.

---<)kaimartin8>---

A while back on Youtube I watched as a big three axis control remote lifted a hang glider and pilot off the runway. Like the space shuttle on the back of a 747. At altitude the two crafts would uncouple and the ground controlled remote would be guided in for a landing on the runway. The HG pilot would try to find a thermal to go XC.

With the winches in each of the two, three axis controlled prop-less remote drones the two piggy backing HG's may be able to venture deeper into the jaws of the lock-out without falling prey to a lock-out. This may get the spiral tow to work.
Maybe sail planes (Kai Martin's idea stolen here) could have easier success in this R&D phase.

This is just brainstorming in the hopes someone will come up with a workable idea since this is a true Rube Goldberg nightmare.

[Bob Kuczewski]

A while back on Youtube I watched as a big three axis control remote lifted a hang glider and pilot off the runway.

Using a remote controlled tug is a really nice idea for a number of reasons. The HG pilot could be in control (or at least have an over-ride capability). You don't have to worry about conflicts of interest (or conflicts of survival) with the tug pilot. After release, the drone could be handed back off to a ground operator to bring it in for the next tow.

[Bill Cummings]

A while back on Youtube I watched as a big three axis control remote lifted a hang glider and pilot off the runway.

Using a remote controlled tug is a really nice idea for a number of reasons. The HG pilot could be in control (or at least have an over-ride capability). You don't have to worry about conflicts of interest (or conflicts of survival) with the tug pilot. After release, the drone could be handed back off to a ground operator to bring it in for the next tow.

Bob radio's: "Bill, my remote batteries just died, down here, and I know you're busy up there, working that thermal, --but -- could you fire up your remote again and I'll talk you in to land the drone?"

[JoeF]

Studying all the considerate posts ...
===========================================
Just came across an image where bending knees (winching) would alter loadings of the two canopies:
(copyrighted photo): https://xa.yimg.com/kq/groups/13890449/hr/1862328585/name/IMG-20160503-WA010.jpg

[JoeF]

Some lessons from Skyhook probably will feed this topic.
Notice the winching in of the person (could be a hang glider )
http://www.damninteresting.com/the-skyhook/