FeiJi's blog View Details
Posted by FeiJi | Apr 28, 2021 @ 09:07 PM | 5,381 Views
Flying my new scratch-built wing. Flew just under 14 minutes on 800mah lipo.

Swallow EPP flatplate with modified KFm wing compared with scratchbuilt laminated EPP foam wing
  • 800 mah battery for both
  • 9 minute flight compared to 14 minutes
  • 230 grams AUW compared to 340 grams
  • faster landing speed compared to slower landing speed
  • needs more throttle compared to much much less throttle required
  • less aerobatic compared to highly aerobatic
  • cannot fly slow compared to slow and faster flying speeds
A laminated airfoil just totally wins out over a flatplate wing.

Scratch built EPP 800mm foam wing flight (1 min 59 sec)

Posted by FeiJi | Apr 21, 2021 @ 09:17 PM | 9,592 Views
Laminated my BoneYard VI 800mm EPP foam wing with lightest laminate (.05 mm) which perhaps is a little too light in that it wrinkles more easily when ironing on but wow, this wing is strong - can't bend it. The laminate cannot be pulled off the foam.
Weighs 150 grams total with the laminate weighing 50 grams. Didn't have to reinforce the elevons with spars as the laminate makes them very rigid.
Taped elevons to body with ugly yellow packing tape.

My iron got a little too hot so melted foam a bit in spots. Out of practice.

2204 motor. 15amp ESC. 9 gram servos. 800mah lipo. 340 grams AUW.
Servo wires run inside wing. May put other wires internally too.

An airfoil is so much better than a flatplate. My Swallow flatflat 800mm wing flies about 9 minutes on an 800mah lipo, while this wing flies 14 minutes on the same battery. The Swallow needs almost full throttle while this wing floats around on 1/3 rd throttle. The Swallow (with my KFm modification, has to land faster but this wing will float down to a nice slow flop landing. Swallow weighs about 250 grams while this wing weighs 340. Swallow cannot handle much wind but this wing, well I haven't flown it in any wing so don't know for sure but it probably handles it much better.

Scratchbuilt EPP Wing Maiden Flight (4 min 42 sec)

Posted by FeiJi | Apr 17, 2021 @ 09:35 PM | 6,009 Views
Building a wing that I haven't made in 6 years. 10mm EPP, 800mm width.
Found out that by wiping EPP with alcohol makes packing tape stick better. Had to tape top and bottom
halves of wings together long enough to hotglue the leading edge.
LE and TE look fairly seamless except for a few spots that I will glue together.

Next step is laminate entire wing to make it crashproof. Waiting on .05 mm laminate film as I want it as light as possible.
Will use 2206 motor and 7 or 8 inch prop. Should be a fairly light wing.
Posted by FeiJi | Apr 01, 2021 @ 12:53 AM | 9,658 Views
I put a KFM2 step on half of each wing of my Swallow EPP wing. It now flies faster and smoother. Amazing difference. Getting 9 minute flights on 3s 800mah lipo.
Also cut a bowtie around the prop and it reduced the whine by a lot.

1/2 KFm2 Swallow EPP Wing (5 min 16 sec)

Posted by FeiJi | Mar 29, 2021 @ 08:38 PM | 8,749 Views
I use an old cell phone to film my flights by attaching it to my baseball hat. The camera in the phone is really good and better than most action cams. But, it loses focus of the plane a lot. So I found this free software that allows you to set the focus to infinity so the plane is always in focus. And its free.
It is Cinema FV-5 Lite found here: https://apkpure.com/cinema-fv-5-lite...id.cinema.lite or on Google Play.
The funny thing about it is the Lite (Free) version has pretty good reviews but the paid for version has lots of complaints.

Anyway, it fixed my camera issues and I don't have to buy a Gopro or knockoff.
Posted by FeiJi | Mar 18, 2021 @ 09:33 PM | 17,214 Views
Finally got my WFLY WFT07 transmitter working with FMS flight simulator on my Windows 10 laptop. This technique will work with any RC transmitter.

1. First download and install FMS flight simulator from here: https://modelsimulator.com/

2. Then download and install SmartPropoPlus software which allows connection of RC transmitter to sound port on pc or laptop: https://smartpropoplus.software.info...d/#downloading

3. Connect your TX training port with training cable and 1/8 inch cable to headphone/microphone jack on pc.

4. Open SmartPropoPlus and set up your TX parameters.

5. Open FMS, select Controls/Analogue Controls/Joystick Interface and calibrate sticks.
(If you get an exception error the first time opening FMS then you must go here and run a few bat files to set up the port numbers on your PC: https://www.rcgroups.com/forums/showthread.php?t=374732 )

After doing the above then your TX works with FMS. You will always have to open SmartPropoPlus first and then FMS each time you use the software as the SPP feeds the joystick positions through a Vjoy interface to FMS.

All software is free and it takes a little while to set it all up but at least you don't have to buy any joysticks and you can use your own TX. So was worth it for me anyway. I did this years ago but had to go through the process again recently as I need FMS to learn how to fly inverted.)
Posted by FeiJi | Mar 15, 2021 @ 09:09 AM | 13,104 Views
I bought a kit here in the country of origin for about $12.00, cheaper than if I had bought the foam and spars and other stuff. The instructions were in Chinese but not hard to figure out and watched some videos on it. Filled battery void with foam as I had first just taped in the battery and it would break out on every landing.
First flight with 1806/2250kv motor, 4.5 prop and 800mah 3S lipo wasn't great though my cg was too far back. Just not enough torque. Battery too heavy.
AUW is about 198 grams.
So changed the prop to 5 inch and now it flies, even in a mild wind . Does nice rolls going downwind but just barely bucks the wind going up wind.

Will try a calm day and see how this configuration works but really plan to use a 2206/1500kv with bigger prop so that it doesn't scream so much.

Overall, nice enjoyable little wing that I don't have to worry about crushing the fuselage.

Swallow EPP Wing First Flights (7 min 14 sec)

Posted by FeiJi | Mar 05, 2021 @ 02:53 AM | 8,816 Views
My lastest two scratchbuilts aren't doing so hot so went back to an old faithful wing that always flies though it has it's peculiarities.
I installed a couple of new elevon horns to equalize the throws, and replaced folding prop with regular prop. Flies quite nicely except for rolls which are slow and ugly due to the long elevons flexing at the ends. Will try to stiffen them up with some laminate and see if that helps.

Bought a useless not GOPRO camera but did find an old cell phone that fits on my baseball cap mount and isn't too heavy and it takes great videos. Happy about that.

Will fly this one around a bit, try to get my scratchbuilt plank working and order a cheap 12 dollar EPP wing kit that I can fly closer to home in a small space. Cheaper to buy this kit than ordering the foam and parts to build my own.
Lighting EPP Plank Wing (3 min 50 sec)

Posted by FeiJi | Feb 26, 2021 @ 08:08 AM | 13,044 Views
This is the third plank I have ever made. Just completed, ready to fly, someday.
EPP (5mm). 2212/1400kv motor with 8 inch prop. 20amp ESC. 800mah lipo.
Control arms are bamboo spits and wire, hotglued with heat shrink wire wrap tubes.

Has single 1cm tube spar across wing and a sort of airfoil though I squished the back part of the wing flat when laminating it.

The fuselage is held onto the wing spar with a single zip tie and a few spots of hotglue. Hopefully it will break apart from the wing
in a serious crash. The wing is pretty well indestructable, being completely laminated. Very stiff and bouncy.
Should have used some ribs or lengths of foam to keep airfoil. So really is a modified airfoil with a flatplate section.
If it flies I may open up the ends and shove some foam spars in there to separate to upper and lower wing foils to get a little more
of a real airfoil. Will be interesting.

Heavy, 15.5 oz with 350sq/in wing area. Heavy because of 50grams of laminating film and 60 gram motor. WCL around 4.1 though so should be relatively floaty but with enough weight to tackle some wind.
Should be plenty of power as this motor generates 700+ grams of torque with 8x4 prop. Needed the heavier motor to balance CG. Could use 2206 motor but would have to extend fuselage or use heavier battery. I don't like counterweights.
28 in by 12.5. CG around 2in back from leading edge.
Tiny fins but I fly wings finless alot anyway.

I wanted to make a wing with as much area as possible but that can fit in a bag I have that I can carry easily on my ebike.
So it came out rectangular. I like the way planks fly too.
Posted by FeiJi | Jan 25, 2021 @ 10:45 PM | 13,053 Views
Sorry, KFm2 as it only has a single step on top.
Bought a few sheets of 8mm EPP foam and built a SuperFly clone (only about 2/3s sheet) based on 24 inch one here: https://www.rcgroups.com/forums/show...light=superfli Go there for dimensions - very nicely laid out.

Ready to maiden, maybe this afternoon. Built one of these years ago and really loved its controllability and fun factor. Also, I have less space to fly in here in my newer location so needed a baseball field size flyer. 230 grams AUW and using a tiny 1806/2400kv motor that I salvaged from a totally useless 800mm wing I finally decided to quite playing with. 800mah 3S lipo. Bamboo spit and a couple of CF spars. Also made control rods out of paper clips and bamboo spits because that's all I had around. Fins are super small but I often fly my wings without any fins at all so used to a little waggle. Cut prop slot too big but oh well, its a throwaway plane. Couple hours work. Maybe laminate it later.

Update Jan 29: would not fly, too tail heavy and too flexible in rear and elevons. So, laminated it front and back and elevons. Now really too tail heavy and took it out on windy day and nothing but crashes. So, moved motor forward and took it out again and it flew but mostly harrier so only would fly when at altitude and got some speed up. Motor spins fast with small prop and no torque so need speed. So, now am waiting on some long control rods and will move servos as far forward as possible and that should solve the...Continue Reading
Posted by FeiJi | Jan 21, 2021 @ 06:50 AM | 14,324 Views
Got my self balancing two inline wheeler working well and even balancing on a high wire. Don't think that has been done since 1907.

Can A Self Balancing Vehicle Drive on a High Wire? (6 min 30 sec)

Posted by FeiJi | Jan 21, 2021 @ 03:00 AM | 14,550 Views
Using 8mm EPP to make a fuselage with a fishing pole rod that will stay in the airframe for structural stiffness.
Posted by FeiJi | Jan 14, 2021 @ 02:01 AM | 14,519 Views
Using 8mm EPP foam, fishing pole sections and hotglue to make a fuselage. No templates, just eyeballing it. Wonder what it will be?
Posted by FeiJi | Aug 20, 2020 @ 11:55 PM | 13,173 Views
Latest incarnation of my self balancing two wheeler with horizontal axis rotor that allows right and left turns. Now need more powerful gimbal rotor to control sharp and fast turns. Have tried several motor drivers and settled on VNH5019 12amp controller. Now need more powerful motor than the 385 I am using. Tried a 550 motor and it works but jerks too much due to cogging. A coreless motor would be ideal but expensive and hard to find.

I wired the RC receiver to the Arduino Uno to control the drive wheel and steering and it works great.

Self Balancing Gyroscope Two Wheeler (Part 10) Right And Left Turns (6 min 37 sec)

Posted by FeiJi | Apr 06, 2020 @ 09:27 PM | 16,935 Views
Here is a free pdf ebook on how to make a self balancing vehicle. Contains details on my models, problems, resolutions, suggestions, etc.


What I have discovered with my current vehicle model:

1. Vehicle makes right turns very sharply without falling over (gyroscope rotor is spinning to the left at about 10000 rpm) but falls on sharp turns to the left. It also falls making backward right-hand turns but not backward left turns.
2. Programming requires taking into account the natural precession of the rotor and corrections must take into account which of four sectors the rotor axis is in. This is forced precession as you cannot just place the gyroscope rotor at the balance point - that will not work. It is like you have to coax the rotor into a balanced position.
3. Corrections to the gyroscope gimbal must be programmatically made in short (approximately 50 millisecond) spurts with a slight delay following to allow the gyroscope to naturally precess to a balanced point.
4. Balancing requires a gyroscope rotor of mass/total vehicle weight of anywhere from 15 to 20%. Some seem to have been successful at 8% but I think that must be because it is a full-sized vehicle and probably more efficient than at the model level. Not sure.

How can we make sharp left turns (gyro spinning to the left) without falling over and only using a single gyroscope (two gyroscopes solves this problem but has other issues). One possible solution that I have yet to try is to put the gyroscope on a 2nd gimbal and turn it when the vehicle turns (like the Gyro-X car).

Update Aug 21: I have since mounted the rotor on a horizontal axis and this allows right and left turns - just not fast ones, yet. Working now on a stronger gimbal motor to allow faster, tighter turns.
Posted by FeiJi | Feb 16, 2020 @ 07:23 PM | 13,639 Views
I have my gyroscopic two-wheeler vehicle mobile now. It turns left and right though I have not tested sharp turns yet. Need to change the steering linkage a bit and test that out. Usually, gyroscopic two-wheeled vehicles with a single gyroscope will turn well in only one direction and typically fall over in the other direction. I use RC electrics to drive the front wheel and the steering servo. A 550 12volt 18000rpm (no load) motor drives the 360gram gyroscope rotor. Using three 3S 800mah lipos for power, one for the Arduino Uno, one for the gyroscope rotor motor, and one for the RC electrics. Using an LM327 voltage regulator.
Self Balancing Gyroscope Two Wheeler (Part 3) (2 min 30 sec)

Posted by FeiJi | Feb 08, 2020 @ 03:03 AM | 15,894 Views
Here is something a little different: an inline two-wheeler that is balanced with a mechanical gyroscope. I have been building these for several years and finally got one working that uses a servo motor to control the gyro gimbal that keeps the model balanced. I used some of the ideas from Mori, Hiroshi who builds gyroscopic monorail trains and here is his excellent booklet that explains the theories of how they work: https://thebbb.net/free/theories-and...-monorails.pdf

Eventually, my two-wheeler will be RC controlled, except for the gyroscope which is controlled by Arduino Uno.

Self Balancing Gyroscope Inline Two Wheeler With Active Gimbal Control (14 min 57 sec)

Posted by FeiJi | Jan 31, 2020 @ 09:55 PM | 14,732 Views
Nice article showing that sharp leading edge on small models can improve flight performance in windy situations.

Go here: https://newatlas.com/drones/bird-inspired-drone-wing/
Posted by FeiJi | Jan 19, 2020 @ 10:07 PM | 21,369 Views
Yesterday my wife and I visited the Flying Tigers Museum in downtown Kunming. I didn't really know anything about them until we moved here and now I want to document any artifacts, memorials, and cemeteries that are left here....Continue Reading
Posted by FeiJi | Oct 16, 2019 @ 01:33 AM | 14,049 Views
Cut up a perfect new Lighting EPP wing kit into 3 pieces for portability and to carry on my ebike. Was an experiment that worked out pretty well. Kit cost me about $20 so no loss if I failed. The wings are now very stiff, the new wing is lighter than my old one which I had embedded LEDs. I hold the wings together with a couple zip ties. Takes about 5 minutes to assemble it at the field.
All up weight with 64gram 800mah lipo is about 330grams. That includes metal spinner on folding props and a bigger 15amp ESC. The old wing really flaps its wings on a windy day but this wing is very rigid. CG is at 10cm from leading edge. I don't know how anyone can fly with it at the recommended 50mm. Perhaps it is 3D at that point and I can't fly 3D. It is powerful enough with a 3S lipo to move out pretty quick. I fly around at about 40% throttle.

My maiden went ok but on the third flight the battery dropped out the bottom and I flew it down to a landing without any harm. Looked pretty funny flying with the battery hanging below by the wires. Guess that is the inevitable hazard with the battery hatch being on the bottom of the fuselage.
The video is kind of long and drawn out and out of frame sometimes. Maiden plus one flight is at the end. My wife kindly videoed but in portrait mode. I was training her to video my flights but she has already lost interest so will have to self video in future flights.

Very happy with how this wing turned out. I fly at a large university football field and it is perfect for that size field.

Backpackable Lighting EPP Wing (13 min 42 sec)