Part 103 Glider Tug designs

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b7gwap

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Which 103 design are you flying/considering modifying? What about vortex generators to lower the stall speed? Is there any wiggle room on cleaning up control surface gaps?
 

pictsidhe

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My own design. Not really planning to modify it, you just had me wondering how to modify an UL. Slots would likely be a bigger help on other ULs.
 

pictsidhe

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How about an unmanned tug?

[video=youtube;At3xcj-pTjg]https://www.youtube.com/watch?v=At3xcj-pTjg[/video]
That had occured to me. Take an ultralight, swap the pilot for drone control. Result: lower stall speed, faster climb, regulatory hassle.
 
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b7gwap

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Interesting idea. Are you thinking autopilot or remote pilot on ground?
 

pictsidhe

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I'm not doing either. Apart from the regulatory issues, it seems the easiest way to adapt an existing design: kick 200lb of excess weight out. You could program it to fly a fixed course. HG pilot has a remote to alter speed or tension.

I'm not sure what hoops the FAA would want someone to jump through. Maybe only giant drone ones, or maybe paperwork that would drown you.
 

b7gwap

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Part 107 has a pretty long list of exceptions for which one can attain special permission. I’m sure if your petition was well thought out and focused on safety of the flying public (ie away from airports or civilization) you could do this. The control receiver, power source, control servos, and FPV gear I’m not sure I would trust to RC grade components though.

I wonder if one could adapt a large, overpowered and lightly loaded RC model to be a part 103 tug? Something like this:
https://www.horizonhobby.com/33-pawnee-80cc-arf-han5190
 

pictsidhe

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Pawnee iniatially seems like a good idea, but a glider is going to suck around 20hp, it has Maybe 1/2 that.
Maybe we should start with the engine(s) and build a tug around it. Pusher shrouded prop could be worthwhile, but a pain to design and build.

A minimal tug might only need a 277. Or twin RC engines.
 

Aesquire

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Climb comes from excess power. You NEED excess power.

Just enough won't clear the trees. You want reasonable time to get to altitude. 2-3000 feet depending on terrain and local meteorology. The big flight parks in Florida and the now gone local park on flat terrain could make people happy with 1000 ft agl. Local cloud base is almost never over 5000, and you have a shot at catching a thermal at a grand. If your launch is in a valley with 2500 foot ridges on either side, you have to get up out of the valley. ( not every time, but often enough )

A Quicksilver with a HKS-700 or other 50+ pony engine is better than a 40+ engine, all else being equal.

Minimum is a fail in this context. Static thrust up to 35 mph is the dominant need. Ducted fans would do well in this application.
 

pictsidhe

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The glider manual I linked to suggested maximum pull of around 200lb. At 30mph, that's around 20hp worth of thrust. Add on whatever the tug needs to climb. A light engine with wings shouldn't need too much. For an ultralight conversion, add another 20up to whatever it needs for your specified climb rate.
 

Aesquire

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So..... 20 for me, 20 for you, & 20 for climb? That's actually about right since the base Bailey-Moyes Dragonfly uses a Rotax 582.
Or 50% excess power. Good call. HKS-700?
 

b7gwap

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I think the airplane out there with the biggest gap between max empty weight and as built weight might be the Sandlin Bloop. As designed with a 25hp paramotor engine it tops the scales at 210 lbs. that vittorazi moster 185 weighs 35-40 lbs per manufacturer website, not sure about weight of the 1.3m prop. If you subtract that weight, you have 175 lbs sans engine, leaving 79 lbs of power plant to play with. With, say, a Hirth F23 hanging out getting back, you should be able to tug up some 103 gliders up I would think. Thoughts?
 

b7gwap

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Does anyone know anything about the motor setup in this famous video from 2:34 to the end? I can’t find out much about it other than it appears to have been a Swedish builder. It almost looks like an adapted 2-stroke chainsaw engine, and the pod looks like unpainted fiberglass. Not particularly elegant but it appears to have done the job as a sustainer motor.

https://m.youtube.com/watch?v=86rOfjhsIIM
 

b7gwap

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Would the 2-axis control system inhibit the Bloop’s ability to tow a glider?
 

Aesquire

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Nope. Ptugs are two axis and work fine. Trikes are two axis. So are most hang gliders.

There's resistance to yaw on the tow plane in any glider tow operation. Unless you're trying to tow in a box canyon just as wide as the tow plane's unladen diameter of turn..... there's no problem.
 

b7gwap

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I think the Bloop uses rudder and would not yaw to rudder control if it were limited by a tow line. The trikes use weight shift to induce bank and don't care about yaw.
That is a good point I hadn’t considered. Sandlin’s other designs have full 3-axis controls, I’m sure that ailerons could be added for a weight penalty. You’d want to analyze the rear tube spar to make sure it could handle the aero loads.
 

Aesquire

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The Pterodactyl Ptug uses tip drag rudders. Turn radius goes up, but it's not a serious problem. OTOH the tip rudders are pretty powerful. You may need to enlarge the rudder on a Bloop. No reason not to add ailerons, and as noted in the Ultralight Wing thread, good reason to in some cases.

The Bailey-Moyes Dragonfly tug has cartoonishly large control surfaces. ( really looks like a parody of a plane :) ) The drag of a glider on tow does make for sweeping turns, but you don't make sharp turns with a glider on tow in any case, lest you get the glider too far out of position and lock it out.

https://www.youtube.com/watch?v=BdcmzViq6gA

https://www.youtube.com/watch?v=Nh1Py8gqVUI

12 knot headwind.

https://www.youtube.com/watch?v=FR4UiQ_ZtVc
 
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