# Paraglider self-launching system

I suspect we think completely differently. I take real values for thrust, climp rate, etc. confirmed by hundreds of flights. I do not know where you got your calculations to the climp rates? there is no software in my opinion that can calculate that someone would have to do something like that to program. But apart from very few, there are no people in the world who would have integrated the telemetry data into a software?

many times I have talked to people who said they could build a software on the office calculator that can calculate an eppg incl. wing. Nobody can build such a software without key figures and basis values as a basis. so yes people ask me if people want a sink / glide polarity of a paraglider if I make it available to them with my logged data.

In the case of airplane wings, of course, you can calculate and make simultion calculations since the values have come to a database for many years and the values have been evaluated. For many decades, the large corporate gliders have accurately measured in flight. this is still done with new developments as it was before. only the effort is less because many meters are easier and in the file format already processed.

So with 46kg of thrust at 35 kph, 105kg total weight, and 7:1 lift to drag ratio, what do you think the climb rate will be?

I still need to know is the thrust with 46 kg as worth of a motor on a test bench? or is the thrust of a test stand where a dummi simulates the pilot and frame and cage? it is about if it is with dummi and frame / cage is the output value is real. and always by about 15% less than the value without losses through pilot and frame, cage. I will give you a example: wing 24 m2 projected area or size “M” low EN-B classe. Temperature 20 degrees Celsius. Height 500 meters msl starting point. Moisture average. wind max. 10 kph. 1.3 to 1.4 m / sec. constant climp rate. it now depends on whether the 35 kph for the propeller are positive or negative for pitchspeed on. then possibly also 1.5 or 1.2 m / sec. possible. I measure the pitchspeed always in a fixed distance of 3 meters and in 1/3 of the diameter of the prop. if then at the stand about 52-57 km / h at full throttle, it is very good.

I made my first tangible progress on the project today (besides staring at eCalc and spreadsheets for hours). I got an appropriate conduit bender and experimented with making the 53- and 73-degree bends that I need for my frame. After the first attempt, I was able to make consistent bends to +/- 1 degree of my target, and the tubing is coming out pretty nice. Maybe not as nice as using a real tube bender with the appropriate dies, but it is not kinking and is only slightly flattened, probably about the same amount as with a tube bender on a stand.

the short-term load if not too much torque is required is approximately:
15 kw / 10-20 seconds
10 kw / 30 -60 seconds
6 kw / with very good additional cooling continuous operation
4 kw in the normal design without additional cooling.
as soon as the load is above average the propeller has too much pitch it can be that you have to accept about 30% less continuous power.

as a simple explanation: at 15kw, the engine generates a heat of around 1.5 kilowatts! That’s more than 10 strong soldering iron. this heat must be removed. due to the design and few poles that is not constructively possible.

at zb. 42 or 48 pole motors allow continuous power of about 2 - 3 kilowatts per 1 kg motor weight. because the diameter is larger and therefore the radiating surface of the copper turns is larger. also the amount of air due to the centrifugal effect. the peak power for start or short full throttle passages is about 4 kw per kilogram.

Progress update: I bent up the frame arms at work. Because the bends run in two directions I had to get up on a big table to do the second one. It turns out that if you bend a 10’ long section of tube 70 degrees it becomes very awkward to work with! The tubing connectors I ordered to connect the frame parts didn’t fit; the OD of the tubing was bigger than I expected. Luckily at 29.6mm the 30mm ID connectors from Kipp should fit great. I put in an order for those yesterday. I also ordered the batteries (6x HRB 6S 10,000mah)

Based on @bratwurst’s comment about motor heat I decided to downsize the prop to a 34x22 for the first round of testing. The predicted climb rate is ~374 fpm now, but the motor heat with “good” cooling in eCalc is down around 80C. I’m hoping the cooling is better than good, and I can move up to a 36x24 prop for a bit more efficiency. I have a RFQ in to Neumotor for the motor, controller, and prop adapter, so once that gets ordered I’ll have all all the expensive stuff on the way! I’m committed now!

More progress: https://photos.app.goo.gl/g9G3tet6bdKGueVe8

I de-soldered the potentiometer from a servo tester and added a jumper wire so that a hall-effect thumb throttle from an electric bike/scooter can control it. It’s running ok on a single lipo cell, but that is outside the voltage range for both the servo tester and the hall effect chip. I had a little 3A BEC, but when I got it all wired up the BEC is bad and it’s not regulating voltage, so I’m waiting on a new BEC to finish up the wiring. I also need to remove the little pushbutton switch that changes modes on the servo tester. I do NOT want that thing getting bumped into ‘cycle’ mode when the motor is armed!

My plan is to power the BEC off the balance plug for the first battery in series on the right arm, and to mount the BEC and servo tester in a small project box with a power switch to the BEC so I can disable the throttle control when I am not using it. The thumb throttle will go on a scrap of bike handlebar with a bike grip below it, and a strap on the outside to secure it to my hand. I realize it’s not an ideal throttle setup, but I’ve seen others using something similar and it should be a workable solution to start with.

More progress: I taped the frame together and attached it to my harness to hang in a simulator to check the fit and clearance. I taped some weights on the front to get it to balance out. It looks like my bends worked out just right, as it looks very close to what I drew up in CAD. I think I can shorten the rear up a couple of inches, which should let me bring the batteries an inch or two closer to center as well.

The frame is attached to the carabiners using two 22" slings that I sewed up from 16mm tubular webbing. They are prussiked around the frame arms, and the tails are clipped into the carabiners.

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That looks awesome! Are you planning on ground launching that or mountain launch? How will you control thrust angle on the ground?

The plan is to ground launch, since I want to use it to climb up into the lift band and then shut it off. It balances very well. I did some tests going from standing with the whole rig hanging off my shoulder straps, to lifting myself off the ground with the hoist, and then getting in the pod. It is not pitching more than 10 degrees, and with the prop spinning and providing some gyroscopic stabilization that should get a lot better.

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please consider the extreme twist danger with lateral front stall and one-sided stall. you can sit up straight and bring your legs to the center as you learn in safety training. but the drive mass will maintain a moment that favors the twist. only meant well.

It’s a very good point. I’m going to do all the initial test flying with an upright seat harness to decomplicate things and reduce the chance of a riser twist. I don’t plan on flying this in really rowdy thermal conditions; it’s more for late afternoon ridge soaring and glass-off (restitution, I think they call it in Europe), and with a B wing.

Project update: I got my 90 degree couplings from Kipp. They are just slightly too big, but I’m able to shim the tubes with a couple of layers of 3.5 mil aluminum tape so everything is secure. All the couplings and tubes are going to get drilled and through-bolted as a backup, but I want the clamp joint nice and tight so there isn’t any free play. I cut the side arms down to size, and that leaves 3" of clearance between the back of my fairing and the motor support. I can probably trim a little more off, but since the consequences of having too much clearance are minimal and having too little are disastrous, I’m leaving it long for now. I stll need to trim the motor support down so it is flush with the couplings.

I’m starting to experiment with mounting all the small parts.I got two of the same switches used on the openPPG, one for each arm, so the whole system can be shut off with the batteries still connected. The switch for the left arm (pictured) just barely fits inside the project box it is mounted to. I did it that way so I can protect the studs on the switch from the metal frame. The switch on the right arm will be inside a slightly bigger project box, that will also contain the BEC and servo controller for the throttle system, as well as @GliderPilot’s pre-charge system. That side will have an additional switch to cut power to the BEC, so I can arm/disarm the throttle control.

I’ve ordered virtually everything that I need to complete the project, at a total cost of \$2650. My motor, controller, batteries, and wiring should be here by the weekend so I can start getting things wired up. It looks like the last piece of the puzzle to arrive will be the prop; that should be another six weeks as it’s being custom milled by JC super props, and shipped to the US with a larger shipment going to Aircraft International.

This beast showed up today. It looks huge in the picture, but it is surprisingly small considering it’s rated for 22kW continuous. Same with the motor controller. I’m a little skeptical that those things are going to get me in the air, but even running them at half their rated performance should give me enough power. I guess I’ll find out when I get it all built and running!

Thanks! I read that when I was researching the motor. I doubt he was getting a lot of cooling air through the stator with the motor mounted transverse on an aluminum plate. I’m hoping I can do better with an in-line mount with holes to let airflow into the stator, and possibly some ducting to channel free airflow from the side of the harness into the stator vents.

At any rate, I’m planning to gradually ramp up the power and then the run times in ground testing so I can catch an overheating problem before something gets damaged. It also sounds like I need to research some kind of temp monitoring system that I can use in flight to keep tabs on the motor and controller while I’m in the air.

Quick update: I’m still just working on electrical odds and ends for the control system. I’m using some small project boxes to house the battery cut-off switches (one per battery bank, since they run in parallel).

The larger one also houses @GliderPilot’s precharge (anti-spark) circuit, and the throttle circuitry. The SAFE/ARM switch will cut power to the 5VDC power supply for the servo controller in the SAFE position, so if any part of the throttle system goes haywire (or just when I’m getting the thing strapped on, or for any other reason) I can totally disable the throttle while still having the motor controller powered up. I have a little more connecting/soldering/mounting to do before I can finish the big box up, but I’m waiting on some four-conductor wiring so I can send the throttle signal back to the ESC in the back and bring 7.4VDC power up from the right side battery bank to power the 5VDC power supply.

My battery packs showed up yesterday from HRB, and they look to be in good shape minus some slight creasing on one of the packs. All the cells in all six packs were 3.82 +/-.02VDC. What is unfortunate is that despite the listing on aliexpress specifying that the pack had 8AWG wiring, they came with 10AWG. Not really a show stopper, but I’m waiting to hear back from HRB on what they will do about it. They did wire up the packs with AS150 connectors with my specified polarity, which was nice. The packs are set up so that I can plug the positive plug from one pack into the negative plug on the next one, so I can get all three packs in series on each battery bank.

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I finished up the hand throttle, control circuit, and enclosure. The thumb throttle setup isn’t ergonomically perfect, but it’s good enough to get me in the air. The servo is just there for testing. Not pictured is the adjustable, releasable strap that runs around the outside of the throttle grip.

More update: just plugging along on small stuff. I went back and forth about how I wanted to build the motor and motor controller mount, stressing out about cooling air, ect. In the end I decided to just throw something together using 3/4" ply, just so I can get components mounted to the frame and start the wiring process.

I started playing with the cage design as well. I’m using 8mm carbon tube for the hoop, and 8mm fiberglass tube for the spokes, with some T connectors from the kite world to join them together. I expected to use the fiberglass for the hoop and carbon for the spokes because I thought the fiberglass would be more flexible, but it was the other way around. The spokes will attach to the hexagonal motor mount.

I cut out the battery mounts from the same 3/4 ply as the motor mount. It seems like 50% of this project is: drill holes in something, then drive to the hardware store to find screws that will fit.