Non overlapped 26" props would be more efficient than 19% overlapped 28" props If you are using a motor with the same efficiency and the same type of props.
I have been contemplating for a while how I could modify any paramotor currently on the market to accept non-overlapped 26" props. So far the only possibility I have come up with is to use a flat top paramotor with modified side cage pieces. Even the “off brand” skytap angel has specific changes such that this would not work with this. Excuse the sloppy hand sketch I did.
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It would still be about 10% less efficient than a comparable electric unit with a 135cm prop, but it would eliminate torque and gyroscopic effect, add resundancy, and the props would cost far less than a single 135cm prop. I have also come up with a method of quickly folding in the motors such that when unfolded, the thrust and torque from the motors would hold it out, and when folded it would be just as compact or more compact than a regular flat top. The flight time still wouldn’t be bad at around 50 minutes with a 4 kwh battery. The disadvantage would be that you would loose 5-10 minutes of flight time compared with a single prop unit, and there are more components that can fail.
If anyone can come up with another unit in production that could easily be modified, that would be great.
Finally flew with both packs of four mounted. Conditions were perfect. Steady breeze from the right direction for my field - South. Did a forward inflation but could have reversed. Amp draw was 265 or so. I get only 240 - 250 with one pack of four.
After flying for 10-12 minutes (longest flight with 4 bonkas is 14 minutes) it seemed like I could fly all evening. It was only 20 minutes but felt like more. Climbed up to a safe height and just cruised around for 10 minutes or so before heading back in. Definitely felt the extra weight on landing!
Nice! I really like your set-up with the four over four. Maybe one day I’ll reconfigure the top of my unit, with the four below that would be twelve, getting close to an hour…
And that would be almost 30kg (over 60lbs) of batteries. Check the load capacity of your main gear! Even if the knees were up to it I’d not want to risk a misstep with that much weight.
I’ve refined the setup pretty well.
One issue is due to the slight tilt back of the back plate both sets want to fall outward from the top. This is perfect for the top set because you strap in the top and the mounting rack is held inward. For the bottom set you’re strapping in the bottom where it wants to fall inward so it can still fall away at the mounting rack. One suggestion was a pair of safety pins on the mounting tubes. This would work well and be quick and easy however if a pin shakes loose it’ll be in the prop. I went with a couple of rubber “O rings” that fit tight over the tubes. The other solution is just to not fly bottom set only. The top set mounts over the bottom set and holds it in at the mounts.
I’ve gone to a single buckle nylon strap in a loop around each pair of motor arm mounts (upper and lower). I did have a buckle tied close to each mount with velcro loops and a strap between the buckles. This leaves two loops of velcro and two buckles that are all catastrophic fail points, for each battery set. With a single loop of strapping and one buckle there’s only the one point of failure on each set.
Because of the nature of the X4 flying with eight means a lot of wires and plugs. You have to keep the wire clear of the props and be absolutely sure you never plug in anything incorrectly. You’d basically be shorting a battery or two!
A tip for everyone who wants to fly with large batteries:
learn to flare your wing.
Just do 5-10 minutes of weightless squats every 2-3 days. like in training for skiing. that’s enough. (if you are not an athlete)
warms up the muscles at the start. to do this, it is sufficient to simply do the starting run 4-5 times without a motor. just simulate. it is also good to prepare yourself mentally and raise your arms evenly.
You can also jump rope for 2-3 minutes without a rope.
to 1. There are many video for example. from the pylon community who show how to properly flare a wing. I say that it is also possible to land a 20 m2 wing with a total weight of 140 kg without any problems in zero wind because I have often done this myself. with electric flying you usually fly very large wings so it is very, very easy.
you just don’t have to slow down to land, as you often see in videos. you can learn how to flare with few batteries and improve step by step.
it’s a matter of the mind and timing. In any case, it is less dangerous than steadfast charging. Why? simply because you are already touching the ground or being very close before you reduce your speed.
. Perhaps falling over and over is less bad than … landing hard and having to run. the injuries happen exactly when you touch down hard.
You can also learn a lot about flare by watching tandem pilots. here it is a duty to land gently and safely.
I have an older Advance Epsilon wing that I sized for paragliding with the motor. I have room for more weight. 81 pounds is a lot of weight, but not more than a ICE with a 5 gallons of fuel. But yeah, it would be hard on the legs if you miss stepped with that.
Thanks for the advice Thomas, much appreciated. Will have to get back to the exercises again.
I love paragliding first, but living on the flats of Ontario, Canada does not really allow for many foot launch opportunities. There was a lot of winching involved but the local club has been going through turmoil for the last decade or so, making use of the equipment “unreliable”. That is why I have the X4. Four batteries works for launching and a small amount of puttering, but the batteries do get warmer than I would like. Six is great for short flights to thermal etc. but it would be nice to have some extra capacity on the calm evening to just putter, especially on days with low thermal activity (the other 9 months of the year ).
For sure! My first landing with all 8 I flared a tad early and hit a bit - stiffly. Flew second time last evening with all 8 and when I landed there was almost no wind on the field. It was noticeably faster, I slid one foot on the wet grass, but gentle.
Even if the knees were up to it I’d not want to risk a misstep with that much weight.
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