Here is another clip in my series on “Visualizing The KF-Vortex”.
Mounting a servo in the step area of the KF-Airfoil has been a very popular position for mounting servos. In this clip I demonstrate that mounting a servo here will disrupt the span-wise / sideways airflow possible in a KF-Airfoil-Vortex.
Michael_V commented to my previous post about “Visualizing The KF Vortex” and these comments were the perfect segue for me to expound on some of my theories.
Originally Posted by Michael V
Interesting. Love the crude wind tunnel.
Thanks, I am calling it a “Wind-Sluice” after water sluices that go to / from water wheel mills.
Originally Posted by Michael V
Since the vortex seems to travel towards the tip of the wing in a straight configuration, I wonder if the inner KF sweep is enough to reverse it completely, or if there is a neutral point along the wing where the flow reverses. That latter case could provide for some interesting tuning of wing characteristics and behavior. Reversing it completely might be a problem for the tip vortices as it may increase their size significantly, and that would be very detrimental to drag.
I already thought of this, and I see two best answers:
1A – A “Swept-Back” wing with KF-Step that always sweeps OUT and back like a flying wing or delta popular for slope soaring, without motor / propeller / prop-wash to mess with the directional flow of the vortex.
1B – Add motor / prop / prop-wash to the above flying-wing or delta but also add fences to isolate the prop-wash from the KF-Vortices.
2 – A “Forward-Swept” wing with KF-Step of course, that always sweeps IN, even if it is only 5...Continue Reading
A while back I had an idea, a real lightbulb moment, regarding the KF-Airfoil, and finally I have a way to communicate it visually.
I had been interested in the KF-Airfoil for a while and when I came across the “Voyager” by Viking60 http://www.rcgroups.com/forums/showp...&postcount=237
with its inward tapering KF-Step, it hit me that the faster propwash would not only pull the vortex inwards towards the wing root but also increase the speed / RPM of the vortex and increase the vacuum of the vortex. This is for a KF-Step that is at an angle to the primary airflow. I envisioned it as a rope-shaped vortex that curled under and at an angle. Here are a few still-photos of what I envisioned and a brief video that successfully shows airflow going at an angle instead of simply downwind. It looks convincing at 20 degrees, later I might go back and see how good it looks at 5, 10, 15 degrees.
This evening our local rc club was having its monthly meeting at the flying field so I went early to try to sell-off some of my larger / heavier / older batteries for ParkFlyers. Success, I made $40, ChaChing$
6 each 2,200mAh 3S 20C Turnigy LiPo Packs
2 each 1,800mAh 3S 20C Turnigy LiPo Packs
4 each 1,000mAh 3S 20C Turnigy LiPo Packs
And I donated to the club,
2 each 1,450mAh 3s(11.1v) 1c Transmitter Packs, and the transmitters they went with,
2 each FS_CT6B FlySky Transmitters, 6Ch radios that needs a PC to change settings
I will be flying planes under the 250 gram threshold. I already have electronics for four airplanes and a big bundle of blue Fan Fold Foam. My target size will be 40 inch wing-span (~1 meter) probably a little smaller
With my 250 gram threshold in mind I kept all of my,
800mAh 2s 20c LiPo Packs, and
500mAh 3s 20c LiPo Packs.
HobbyKing advertised this motor with some specifications that make it a very good match for models just under 250 grams flying weight. Somehow I managed to buy four of them before I got around to bench-testing or flying any of them. Today I got a-round-to-it and bench-tested the motor, and got about half the thrust that I was expecting.
I tested using the recommended propeller (APC-SF-8x3.8) and a two cell battery (2s800mAh20c) and a twelve Amp ESC. On my test-bench at full throttle the system maxed out at only 35 Watts and only 175 grams of thrust.
Checking for limitations and doing some math did not reveal any wattage limitations in the devices.
Motor 7.4Vx6A = 44.4W, capable of 44 watts steady state
Battery 7.4Vx0.8AHx20c =118.4W, capable of 118 watts available Now,
ESC 7.4Vx12A = 88.8W, capable of 88 watts steady state
Bummer I was expecting 44watts and 300 grams of thrust.
Further testing with a variety of 6, 7, and 8 inch props, gave a pretty consistent 5-to-5.5 grams of thrust per watt.
Since 175 grams of thrust was not what I wanted for a model just under 250 grams, I decided to swap-out the two cell battery (2s800mAh20c) and swap-in a three cell battery (3s500mAh20). Full throttle promptly exceeded 50Watts, so I continued my study while manually limiting...Continue Reading
I really wanted a table-top belt sander for my upstairs rc-airplane shop, but never got around to spending the money to buy one. Since I already had a hand-held-portable belt sander, I decided to build a base to hold the sander in a fixed position and also provide a work platform for the piece to be sanded. I used three layers of 1/2-inch particle board (MDF), the top two were cut in the outline of the sander, while the bottom layer held up the main body of the sander but had a cut-out for the motor air intake. Glued it together with gorilla-glue and clamped it overnight last night, and this evening after work I ran it through the table-saw to trim the sides. Used the sander in portable mode to finesse the edges and clean it up.
I like it, version-1 turned out a lot better than I thought it would.
My upstairs rc-airplane shop now includes:
-paint bucket vacuum usually attached to the band-saw.
I can do almost all of my building in my upstairs playroom
Thanks for reading
BTW not only is my portable sander on sale at Harbor Freight but so is the tabletop version that I wanted. This is still cheaper and good enough to meet my needs for a long while.
After carefully considering my options, I decided to stay under the 250 gram threshold for registration, for at least the next year or two.
Therefore I decided to get rid of the stuff in my fleet that was only use-able on planes heavier than 250 grams and having missed out on the opportunity to sell at a club swap meet, I took my stuff down to the rc airfield this afternoon and tried to sell it. Success! Somebody actually paid me a little money for my collection of stuff.
The stuff included:
2 HP SuperFly fuselages, modified, EasyStar derivative,
1 HK Bixler fuselage, modified, EasyStar derivative,
6 Wing sets joined together,
11 Motors, brushless, various sizes for ParkFliers,
2 HP Radios, 2.4GHz, Transmitter + Receivers sets
Come to think of it, this collection of stuff was not RTF or ARF but just KIT stuff for builders , I was lucky to get any money out of it at all.
The plane is dead, long live the next plane!
Based on a 16gram version of the Blue-Wonder brush-less motor, I will be flying planes under the 250 gram threshold. I already have electronics for four airplanes and a big bundle of blue Fan Fold Foam. My target size will be 40 inch wing-span (~1 meter).
Over in the “Model Aircraft & Drone Advocacy” forum, MeHere posted a news article and question.
Do you think Drones should be able to fly over people?
I responded in part:
Yes - If the aircraft has a usable Glide-Slope, so that it can avoid crashing into pedestrians on the sidewalk or cars on the freeway. Presuming that said drone would be flying at least 200 feet Above Ground Level*, even a bad glide slope of 2:1 would yield a 400 foot radius for avoiding people on the ground. *(Amazon proposed a 200 - 400 ft AGL band for commercial drones).
I also mentioned that Manhattan would remain off limits for lack of safe places to ditch a gliding drone.
My bungee-cord-catapult works much better now, stronger throws and more consistent. Thanks to replacing the skinny-cloth-covered-bungee-cord with fatter-yellow-latex-surgical-tubing. Also replaced the fixed eyelet (pulley) with a real pulley complete with enclosed ball bearing. Now I have a launch system that can give my models/experiments a worthwhile throw.
Well I got a chance to try out my catapult and it was totally wimpy I think there is too much friction in the “pully” system where the bungee cords' cloth covering goes around stationary eye-hooks. At the field I could not get it tightened-up enough to get a decent launch. After all that work building that catapult, I ended up hand launching after-all. So much for calibrated consistency.
The test glider, my JD-12, is a delta front with a squared off back, using a KF-step of 3/4 inch, swept back 30° bilaterally, 30 inches wide, 20 inches nose to tail. (20x30 that sounds familiar from somewhere). The airframe itself, just the Blue-FFF and R-Tech foam and a spritz of 3M-77 adhesive and 3 inch wide packing tape weighed only 104 grams. To represent the weight of the electronics and miscellaneous hardware I used a roll of pennies. Did you know that a roll of pennies weigh about 130 grams. Anyways my all-up-weight was 234 grams which is real close to the probable registration threshold of 250 grams. I have a 40 inch wingspan version where the foam air-frame only weighs 124 grams.
Between the wimpy catapult and 15 mph gusts I did not get very far with my experiment. I was lucky to get a reasonable Center-Of-Gravity figured out. I think. For an easy throw, it floats along very nicely. But for a hard / fast throw, it curves up, stalls, and nose-dives. It leaves me wondering if the Center-Of-Lift can change depending on airspeed. Or it might just be that darned gusty wind.
I think that I see something special in the Kline-Fogleman stepped airfoils and since I love to experiment I decided to do some experimentation to test some of my theories. In a earlier discussion BMatthews suggested that I build gliders for my testing. He also suggested building a system to get a consistent “Throw” so that flight times and/or flight distances could be compared. Good idea.
I spent last weekend building a catapult with a 30° slope, and ran out of weekend before I could try it out. During the week I decided that 30° was too steep and too tall, so today I modified it to be only 15° slope and not so tall. This had the added benefit of fitting into my car easier.
My catapult is based on 8 foot long twin rails, that are 3 inches apart in this version, with a 15° slope. I used 2x3 inch boards from Home Depot and some leftover plywood for the basic shape, and 1/4-20 carriage bolts and matching fender washers and wing-nuts for ease of re-assembly at the flying field. In this version the rails are 3 inches apart to accommodate my two HP-SuperFly's (EasyStar derivative) and my two Air-Hogs-Titan's. This rail separation will also work good with my experimental deltas once I add small “keels” to them. In my next version of this catapult I will probably use forks that hold the rails about 9 inches apart to accommodate planes with 8 inch propellers. The forks that set the rail separation are modular / swap-able. I almost forgot to mention that it uses a long bungee cord to accelerate the aircraft. The bungee cord started out life as a cargo net from Harbor Freight.
Here are a couple pictures.
I plan on trying it out tomorrow.
I think that I see something special in the Kline-Fogleman stepped airfoils and since I love to experiment I thought that I would build a tabletop-wind-tunnel to test my theories.
Well … I started out asking for suggestions for cheap telemetry, and, ended up getting a quick education in wind-tunnel design, and came to the conclusion that I would not get very far using any blower compatible with the 15 Amp 115 Volt house current in my garage. http://www.rcgroups.com/forums/showthread.php?t=2513381
HugePanic suggested that I setup my experiment on top of my car so that I could get 60 mph airspeed without the hassle of buying a motor plus blower with large cubic-feet-per-minute and then fine tuning the turbulence out of a wind-tunnel. I will probably get around to a car-top experiment later.
BMatthews suggested that I build gliders for my testing. He also suggested building a system to get a consistent “Throw” so that flight times and/or flight distances could be compared. Good idea. I liked it enough to start down this path next.
I see this the most feasable in the pharmacy segment. Small packs, light weight, urgent deliveries of meds etc .
I saw this and gave a response worthy of a Business Major
I totally agree with pharmacy deliveries. - From a regional hospital or pharmacy to smaller satellite hospitals and nursing homes. Everyday, nursing homes and small hospitals need something that they do not already have. Currently regional pharmacies need to own a fleet of cars/vans and hire drivers, usually to make once daily delivery routes, (I remember, order by 3pm and receive it by 8pm, the backup plan is a local pharmacy and local taxicab company).
The reverse would apply to medical lab-work getting picked up from outlying doctor offices and going to a central / regional medical lab. Again this is currently typically a once daily pickup route with the lab providing overnight service so that the doctor can deal with the answers the next morning.
Also I can see a lot of businesses wanting to get their afternoon small shipments to the FedEx terminal after the standard 3pm pick-up time.
So Yes, I can see a few commercial applications for drone delivery and pick-up service. Actually I see fast pick-up, so that you do not lose a cycle of once-daily service to be the most urgent business demand. So far I am not seeing the demand from the consumer sector.
Can any of you all think of any more high volume commercial needs for drone pick-up / delivery service.
Starting to get more interesting,
P.S. Someday it would be interesting and fun to place an order for hot pizza and cold beer and receive it by drone.
But I think the chances of ordering anything off the beaten path like "Rotor_Drone_Magazine" or "Model_Airplane_News" or a book like "Drones_for_Dummies", would result in a message saying "Not-Available-For-Drone-Delivery".
Recently the DOT/FAA commissioned a task force to make suggestions for how to implement national registration of “Drones” including traditional R/C-Airplanes, so that a crashed drone could be traced back to its owner, and among other things they recommended that anybody operating a drone over 250 grams be required to register as a “Drone-Operator”. In response to this situation many people in this forum are very unhappy about it and really going nuts about it. Meanwhile I am only a little unhappy about it and I am currently developing scratch-built-foamies intended to fit under this 250 gram threshold.
I am doing some catching up on my writing tonight. A few months back (April 2015) I built another plane, the JD-11, and it has some good potential, but it also needs some refinement / reinforcement. It is a slow flying Delta, has a 48” wingspan, 20” length of blue foam, 26” from prop-spinner to rudder. It has a 100 Watt power system, Blue-Wonder/HexTronik-24grams 3s/1500kv motor, one of my bamboo motor mounts, 12Amp ESC, 1,000mAh/3s/20c battery, 6x4 MasterAirScrew GF propeller, and last but not least a Lemon receiver with DSMX and stabilization and delta mixing all built in (works good with my newly upgraded 9X transmitter).
I got one of my buddies to maiden it, and he said that I needed to adjust my Center-Of-Gravity. Before building it I had studied COG for deltas, and found settings for beginner / intermediate / advance. Now I thought that COG meant the balance point between the front and back, you know 50/50 and make minor adjustments from there. Well I was quickly reminded that Deltas “need reflex” where the nose is up a little, most of the wing is down a little, and the Elevons (elevator-ailerons) point up a little. Apparently for slow flying a Delta, beginners should have a little more of the nose-up higher angle of attack.
Something else we quickly noticed was that the wings were bending upwards, not hinging at the root, but curving upwards trying to look like the bottom of a circle, not good for consistent control with those elevons. An easy fix for some carbon-fiber tube.
Last Thursday 3-26-2015, I got six flights on my latest plane, the JD-10. It was a chuck glider conversion, starting with an Air-Hogs-Titan and adding electronics. The star of the show was a Lemon Receiver featuring DSM-X + Stabilization + Delta-Mixing all in one small unit + a small satellite/diversity receiver. Once I got it airborne it worked good.
Other features were as follows:
1 – The Air-Hogs-Titan has wings that are both swept back and have dihedral, probably resulting in a strong self-righting dihedral effect.
2 – The As-Found center-of-gravity for the chuck glider before adding electronics was approximately 5-1/2 inches back from the leading edge of the wing root (~3/4 of wing root), and when adding the electronics I balanced the components to maintain the same center-of-gravity.
3 – After determining the As-Found center-of-gravity, I placed a piece of heat-shrink across the top of the fuselage so that I could repeat the balance point (see picture below). I have used this several times now and it works great for repeatably balancing a plane.
4 – I added left and right elevator so that I could use them as elevons (Delta). I also added rudder mostly for later use. Because I wanted to keep all of my wiring and servos on the fuselage and integrated empennage (tail), and because I wanted to keep the known-good wings clean, I did NOT add ailerons. Of course, these control surfaces used three servos, and I used 9gram servos because sometime in the...Continue Reading
Previously I wanted to use my Turnigy 9X transmitter to talk to a “Lemon Receiver with Stabilization”, and quickly learned that there was a channel assignment mis-match, which could be remedied with a firmware upgrade to ER9X, which required additional hardware to perform the firmware update, so I put in an order for the necessary hardware …
This afternoon I received the “USBasp Delux” from “9XRprogrammer dot com”. This is a kit containing an EEProm programmer on little circuit board that has a usb connector on one end and connects to a ribbon cable on the other end. This evening I soldered the ribbon cable to the prescribed pads according to YouTube. Then I downloaded a hex file, and downloaded an EEProm loader/programmer. And by carefully following directions on YouTube I managed to successfully update/flash the transmitters firmware to the desired ER9X which is supposed to be flexible enough to do anything that I want.
While I had the transmitters back cover off, I also installed a back-light kit resulting in a very big improvement to the readability of the LCD display .
Hey, I just noticed that I am on my fourth upgrade to this radio that I had been wanting for over a year.
But the good news is that my soldering is good and all of these upgrades have worked on the first try.
Now I am reading the ER9X firmware manual, light reading at only 46 pages, learning how to setup the first four models that I need.
Thanks for reading.
I am starting to like YouTube, the instructional videos are actually useful.
Where to solder in the transmitter and how to flash new firmware.
After receiving my Lemon DSMX Stabilizer Receivers I tried them out and promptly discovered a channel assignment mismatch.
Turnigy 9X - - - Lemon Stabilizer
Ch1 = Ail - - - Ch1 = Thr
Ch2 = Ele - - - Ch2 = Ail (Right Aileron)
Ch3 = Thr - - - Ch3 = Ele
Ch4 = Rud - - - Ch4 = Rud
Ch5 = Gyr - - - Ch5 = Reserved - Stabilizer On/Off
Ch6 = Flp - - - Ch6 = Aux1 (Left Aileron, Gear, Flaps, etc...)
Ch7 = Aux - - - Ch7 = Aux2
Ch8 = Aux - - - Ch8 = Reserved - Master Gain
With stabilization dis-abled I could move the servo leads around as needed, but when I wanted Stabilization and Delta output, all I got was junk.
I asked about this in the Radios forum and learned that the Turnigy 9X radio uses the Futaba channel sequence while the Lemon (and orange) receivers use the Spektrum channel sequence. And to fix this state of affairs I would have to upgrade the firmware in my Turnigy 9X radio to a non-default open-source firmware. And I would need to modify the transmitter with a usb programmer to do this. I now have the parts on order.
Looks like a minor delay before my stuff is fully capable of doing what I want.
In the mean time it is back to the older FlySky FS-CT6B system.
Somebody started a thread asking how many batteries people have. I replied with a number ( 26 total with 9 ready to be sold/traded/donated and 4 ready to be trashed). And I also added that your variety of batteries will be matched to the variety of the sizes / missions of your airplanes from Micros to Trainers to Warbirds to EDF's to etc …
Three weeks ago I ordered three of the Lemon Receivers with Stabilization and Satellite, and they finally arrived last night (2-11-20015 to 3-03-2015). I have been looking forward to getting these, I have several applications in mind.