I finished my version of the EasyStar, which I have dubbed the "GeekStar" in honor of the show's name "MyGeekShow".
I've got it as close as possible to the EasyStar; CG, Weight, Strength, Angle of Incidence on the Wing and Motor, Throws, etc. Everything I could think of.
Why re-build an Easy Star you might ask? Well, first of they cost $80 for the basic kit, and secondly, I want to be able to modify the design at some future point as I add weight, cameras, drone gear, etc. And the sooner I learn the skills the better. Why not star with the best airplane as your example?
As I work towards building the GeekStar (My Geek Show's version of the Easy Star) I decided I needed a better building technique. This week I built a demo/sample of the EasyStar's nose section to see if 3/4 inch EPS foam would be a suitible build material and to see if a "layered" building approach would work, and in both cases: Yes!
The thicker foam is very hard to cut out with a knife, I'll have to build a hot wire cutter, but when it's all glued together, it can build great looking shapes that are very strong and very light.
This week I flew and crashed my MTP3. I know, I know, I crash more than I fly sometimes!
I learned a lot from this experience;
1.) Rudder/elevator needs to be much larger, or keep it at a standard of 1/3rd of the wing area
2.) Don't expect control surfaces to work if they don't have any air going over them
3.) CG (at least for me) never really works at 33%, it needs to be more like 25% or even 20% on my clark-y airfoils.
4.) While seeking for a light aircraft is a great goal, having something so light with so much drag that when the motor turns off it practically stops mid-air, may be a bad thing. I donno, just something I'm observing.
Instead of fixing or making a MTP4, I'm going replicate the easy star as closely as possible and make a "geek star" (aka. mygeekshow version of easystar) that I will then improve/modify to work better for FPV/Drone objectives.
Successfully maiden'd the third version of my Modular Testing Platform. My eventual goal is to scratch build an airplane that carry and utilize FPV and UAV components, but I wanted to start small and basic first.
Overall it flew well, had plenty of power, and wasn't as "pitchy" as the last MTP, however I'm going to have to strengthen my motor mount or have some other total new solution to landing (different method, prop location, etc.) I may start relying more on my Easy Star which has well over 100 flights with zero crashes while I figure out this scratch building thing....
Nothing too crazy, just a simple test of my stock Easy Star's performance. The 7.4v 1200mha battery and the 450 Brushed motor kept it in the air at 3/4 throttle for just over 14 minutes. It was a very windy day, with steady winds 5-7mph and a few gusts of over 15mph.
Next episode I'll see how high I can fly it!
The MTP3 is almost done, just waiting on some electronics to come in the mail. Then I'll be able to see what my own creation/ LiPo/ Brushless can do compared to one of the best kits I've ever flown.
For my next airplane I'm planning on using a folding prop to reduce damage during landings (as my motor is mounted on the nose). The folding prop looked smaller (the actual blade-moving air portion) and I was also a little concerned about the folding blades becoming unbalanced or not fully extending.
I decided to throw three different kinds of props on my motor testing tower and find out what their performance really was. I tested them for amps consumed, watts required, airspeed (at about 1 ft. away from the prop) and of course, thrust.
The folding prop did just fine, and at least matched the performance of the others. I have no hesitation of using on my MTP3.
At full throttle flying straight, I got 62 MPH, in a steep dive it reached 79 MPH, and in a straight down deadly dive, it reached 92, after which the wing separated and the airplane was destroyed!
The MTP3 will be built over the next few weeks and will have new design features to protect against this happening again as well as other improvements.
This week I made improvements to the MTP2 and took it for some general flight maneuvers to get a better feel for its abilities, its turning into quite the platform! Don't forget, my end goal is to FPV and then drone this airplane to fly across the United States.
It's flight path was much more stable and direct, the control inputs were not as sensitive, and overall performance was improved.
I made the following improvements this week: -Leveled (set to neutral) the ailerons and elevator -Reduced the control surfaces themselves by 50% -Redesigned the motor mount to allow for better landings -Placed the motor closer to the center of drag (placed it on the top of the motor mount)
The belly landings are still destroying the motor mount due to the prop coming into contact with the ground during landing. I've ordered a folding prop in hopes that it will not sacrifice performance and allow belly landings without damaging the motor or airframe.
So I know this isn't exactly "DIY Drone-ish" as far subject matter, but I thought the interview was pretty interesting as Greg's approch to designing and testing new concepts and his RC Super Hero were so unique that it deserved to be shared.
Greg runs the YouTube channel "BornTaFly" and sells his models and PDF plans through www.RCSuperHero.com
The Modular Testing Platform 2 flies! It flies really well!
I had a great hand toss takeoff, a rough start as I figured out the control sensitivities and trim, some good cruise around time, and a perfect landing.
Any improvements you think I should make? Here is my planned list for the next episode:
-Motor mount location (to make it more inline with the center of drag)
-Landing nose design (to allow for softer landings)
-Smaller control surfaces (to reduce control over sensitivities)
-Tighter servo mounts (reduce servo play)
-Level control surfaces (both the ailerons and elevator are not level when the controller is neutral)
This week I completed the MTP or Modular Testing Platform II.
For electronics, I added the elevator and aileron servos and mounted the motor, esc, and receiver to the airplane without any trouble. (see links below for which one's I used)
I also completed my Clark Y airfoil, which was much more difficult and time consuming than my prior K2 airfoil, however I anticipate an improvement in performance. As I used Bluecore (aka Fan Fold Foam, Extruded Polystyrene) for the entire build, I noted that the difficulty in curving the top section over the front of the airframe was very difficult, to the point of almost snapping the foam and led to an close, but imperfect airfoil. I'll have to use more flexible foams in the future or discover an effective way to curve Bluecor.
I did indirectly add some angle of incidence on the wing, which as far as I know, will slow the airplane a little and add some natural lift effect.The new motor is heavier, but over 3 times more powerful, giving this a 1:1 thrust ratio.
Next week: the Maiden flight of the MTP II! I'm actually pretty nervous to fly it, the MTP II took almost twice as long to create as the first MTP, and has quite a few new properties I've never tried before.
I completed the MTP II (Modular Testing Platform) as far as I could while I waited to receive the new Motor and Servos I'd ordered. They came in the last day of this week, so I'll be completing the MTP II next week. There is a lot of improvements on this design/construction over the first MTP, some include:
-Minor fuselage improvements for better aerodynamics and strength. (including moving the wooden dowels to be apart of the construction instead of just sitting inside the fuselage.
-Improved airfoil: I got a lot of feedback that while the K2 airfoil was functional, I'd be better off with a more classic airfoil, so I built a Clark Y airfoil. I got the information for this wing from: http://www.worldofkrauss.com/foils which is an AMAZING site for airfoil research. You HAVE to go check it out. I gives not only the exact shape of each airfoil, but also it's flight characteristics. Very cool.
-Next, instead of using one of my radio's channel to control the rudder, I'm using it to control a set of ailerons, which will give me a lot more control and allow me additional roll stability options. I stole this idea from fellow YouTube user PeteDaws.
-I also used CA Foam Safe Glue instead of Hot Glue. In the past I'd had airplane literally melt in the trunk of my car due to all the heat, CA Glue won't fail due to that as once it's bonded, it doesn't let go. Also I found that the construction of the airplane was much more precise and clean. Weight also dropped by about 15 - 20%.
-Lastly, I ordered a larger motor as the last motor was too weak for this size of airplane.
So what do you think? Looking better? Any other improvements I should make before I make the maiden?
I started building the MTP II this week, but based on my experience and your feedback on hot glue's weaknesses, I decided to wait to put the pieces together until my CA foam safe glue arrives in the mail.
In the meantime, I wanted to do some some testing on my motor as many of you said it appeared too weak for the airplane. As I got started thinking of ways to test the motor, I realized how many different elements go into a motor/prop efficiency/power/thrust/etc.
So I built the Motor Testing Tower, a tower that allows the motor to mounted on top and while its running the tower simultaneously measures the force generated, the watts/volts/amps consumed, the speed of the air flowing from the propeller, and the temperature of the motor (or ESC, battery, etc.).
I was VERY surprised with the results, as it showed that my old brushed set up generated more thrust (9 oz) than my brushless set up (6 oz). After reviewing the data and the motor specs I am not surprised, the brushless motor is much smaller than the brushed motor, and was not designed for that prop size or the amount of watts that I was putting through it, no wonder it got so hot after a few moments of running that I couldn't touch it without being burned.
I ordered a larger motor yesterday that should be a much more appropriate fit for this airplane, and hopefully it will get here in time for next week's episode.
What do you guys think of the tower? Anything else I could add? I was thinking a RPM measuring device could also be added to complete the set up.
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I've been working hard to try and figure out this center of gravity deal. After enduring half a dozen crashes I finally got it right: I threw the airplane, the thrust was perfect, it was going just fine until... I pulled up and it went down. Thats right, my control surface orientation for my elevator was reversed. By the time I realized what had happened it was too late, and the MTP made its final landing, straight into the ground.
So if you've made changes to your airplane's control surface in anyway; your servo hookups, your control horn location, your transmitter settings, heck, every time you go to fly, just do a quick sanity check on your control surfaces, when you pull up, does your elevator go up too, etc...
I'm glad I made this mistake on a cheap airplane that could easily be rebuilt. I've got to experience these kinds of mistakes early so that as my models get more complex and expensive my simple errors will have been worked out my system.
I also learned that on a new model, put the CG a little nose heavy until you figure out where it should be, error on CG being t nose heavy. It appears that nose heavy is a lot more manageable than tail heavy, which is about as guaranteed to kill your airplane as it can get. I'm still amazing how much CG affects performance.
I also am falling out of love with Hot Glue. Its great stuff for a lot of reasons, I did entire episode on it a while back to prove that point. But, here in Arkansas, even when my model is in the trunk on my car, it gets hot enough (about 95 degrees Fahrenheit) to damage anything under some kind of pressure, where the hot glue will just fail.
I think I'll slowly move to some CA foam safe glue as I get a little better at not crashing everything I build in the first 5 seconds of my flight.
This week I took the Modular Test Platform (MTP) for it's maiden flight, I can't tell you how nervous I was to give it it's first throw, or how excited I was when I saw flying through the air! You all probably know what I mean.
I got 2 or 3 "OK" flights in (20-30 seconds) before it had gotten beaten up enough to not really fly anymore. With each crash though, I was expecting more damage, but those wooden dowels really add a lot of strength and rigidity, while the foam and hot glue give it some flexibility. Eventually, the motor section got so crushed that the motor was too unsecured to make additional flights.
The needed improvements are:
1.) Improve CG: at first it was tail heavy, causing the airplane to "high alpha" and not allow the wings to really generate lift. As I moved the battery toward the nose to shift the CG, things got better and better.
2.) Reduce control surfaces: even the smallest movement of my transmitter sticks would make the airplane almost lose control as it exerted a LOT of force. Either (or both!) the control surfaces need to be reduced in size or the throws need to be reduced.
3.) More power: the brushed motor, 10C NiMh x 7.2v battery, and 10 amp ESC set up has got to go. It was taken from a wild hawk, and while functional, the power system is heavy, weak, and inefficient. The new system will have a brushless motor, 20C 11.1v LiPo, and 30 amp ESC. I've already bench tested it and it has at least 5 - 6 times the thrust.
4.) Wing incidence: I also think adding a little angle on the wing will add natural stability and climb.
Next week I'll be making these and other improvements to the MTP. Anything I've missed?
I completed the airframe of my Modular Test Platform this week. It's core function is to allow me to test, repair, and replace each section individually, cutting down on prototyping cost and time.
The airplane itself is made from Bluecor aka Fan Fold Foam, and is supported by poplar wooden dowels. These serve two purposes: support the airframe by adding rigidity, and allow for each section to be removed and added as needed.
The wing is a Kfm2 airfoil, which has pretty good performance while being very easy to build. I added a little dihedral on the ends of the wing in the hope of gaining additional stability as this airplane, for the moment, does not have ailerons (which I can easily add later as this is modular!).
I'm still waiting on my Hobby King order to come in to replace a faulty motor/esc they sent me last time (I actually don't know what the EXACT issue is, it might even be my rx/tx) but when they come in I hope to complete the build and get it in the air.
In the end, this is all supporting my five year plan to fly an rc airplane across the United States. See http://www.mygeekshow.com/five-year-plan for the full details.
This week I started building my MTP or Modular Test Platform that will help me someday build a full/partial UAV that will cross all 3,000 miles of the U.S.*
I constructed the modular tail section that will be able to separate from the fuselage, nestled the servos in really good to reduce drag, and placed the control horns as closely to the pivot point to increase control surface range.
I tested my electronics: I took the Servo's, Tx and Rx from a crashed Wild Hawk RTF, and new 2200 mAh 20c batteries, 1,400 kv motor, 30amp Mystery ESC, and a 8x4 apc prop (all from Hobby King) and hooked it all up, then powered them up to see if all was well. And it wasn't!
My ESC/Motor set up was non-functional. I'm not sure which or if both are not functioning, and as this is my first brushless set up, I don't have other electronics to test it with. I checked all the connections to make sure everything was set up correctly, and made other efforts, but couldn't get them to function. I went ahead and ordered new parts to replace both, just in case, while I complete the airplane construction to stay on schedule.
I plan on completing it next week, maybe even making the maiden!
To see what I I did, check out the episode on YouTube above
*visit www.MyGeekShow.com for the full details of my 3,000 mile flight goal
To achieve my goal of flying across the country, I'll need a good grasp of flight dynamics. To do this, I'll need to test different configurations of wings, fuselages, tails, motors, etc.
So I've decided to build a MTP or a Modular Test Platform. Check it out:
