Joined Aug 2008
Originally Posted by Joe 1320
Good things come in small packages, or so I've been told. When it comes to airframes, that is rarely the case. If you fly R/C airplanes enough, you've probably figured out that the larger the airframe, the more forgiving the handling. In the case of the A-10 Warthog, the full scale airplane is not a speed demon, it's purpose is for close air support and attacking heavy ground targets. The twin engines provide lots of thrust. The airframe is made to take loads of punishment and carry a fair amount of heavy ordinance. I had a blast with my GWS A-10s. True to form, they weren't speed demons. They took lots of punishment over the years, some being held together with packing tape due to botched landings, incidental contact with trees, and all around abuse that takes it's toll on the everyday flier. I used to make attack runs down the drainage canal at edge of the my field, imagining that big gattling gun hitting the "dam" at the end of the canal, pulling up hard and slamming the throttle wide open for an impressive exit. This was done over and over with the same resulting smile on my face each time.
The problem with those GWS kits was their EPS foam. Breath on it wrong and it deforms or breaks. If the plane was built light enough, even the brushed fans gave it enough thrust for some decent fun. The problem is that "light" translates into "fragile". The fuse could turn to confetti on a hard enough hit, and the subsequent repairs make the plane heavier and heavier. I found it difficult to keep an A-10 looking mint. Eventually, my attention waned as I do like to keep my models looking decent. My latest GWS A-10 sat in the graveyard still able to fly, albeit barely. Not long ago I stumbled across a micro A-10 project that caught my eye. The prospect of a twin 30mm EDF Hog had me intrigued. My initial skepticism had been thrown a curve ball, this little airframe was going to be manufactured with EPO foam. Hot dog! I had lots of previous experience with flexible foams such as EPO. Several manufacturers had offered airframes in this type of material. Each company seemingly had their own formula. Some had Elapor, others had EPP, while another called theirs Z-foam. The principle is the same, the foam has more flex engineered into it's profile rather than the more hard and brittle EPS foam. The flexible foam not only was resistant to turning itself into confetti on harder hits, but the foam had exceptional abilities to disperse energy on impact. That meant that your individual componants like batteries, servos and receivers were better protected from crash damage and would likely survive to fly another day. This foam would be a huge plus in a micro airframe due to the fact that the small models usually were more twitchy and at many times suffered from less than smooth landings. I've seen EPP and EPO airplanes do a cartwheel and just bounce with little damage. This whole package peaked my interest.
The ELERC A-10 arrived via EMS shipping, however it was apparently subject to some rough handling. As soon as the box was unpacked, I could see that it was crushed on one end. I opened the box and was relieved that there was only a minor problem that would be fixed during the assembly. I was recently made aware the model is not in EPO foam, but a high density EPS. I was pleasantly surprised that the fans and motors were already installed as were the speed controls. The wing was packaged seperately with it's servo installed and alierons operable. In fact, all the parts fit together so well that it took 5 minutes to dry assemble everything for photos. That's a major plus for those with limited time for an in depth build. Out of the box, the fit and finish of the foam is decent. All the parts with the exception of the wing joint fit together with zero drama. The fit of the wing to fuselage joiner at the leading edge of the wing for, whatever reason, doesn't want to fit together correctly, but that's such a minor inconvenience considering how well this goes together like a snap-tite model. Glue will only make the joints perminant! So without even looking at the instructions supplied, it went together that easily. That in itself is the makings for a good ARF or RTF package. Now it's time to do a proper assembly and setup of this micro A-10, I'll be doing that over the next several nights, just as the average hobbiest would do when escaping from the day's work and pressures......using a few of those precious nights off to have fun building a new toy.
__________________________________________________ _______________You would think that this box that was wrapped in bubble wrap could survive in the hands of a payed courier? It looks like the box was shoved into a small space with little care. EMS used to be better than that.
The contents as packed with only one problem as a result of the box being crushed.
One nacelle mount is cracked. Actually, more like the foam beads seperated. It's quite an easy fix.
Here's the contents laid out for assembly. This version comes with the fans and motors already installed, the speed controls are located in the exhaust of the nacelles for maximum cooling. The servos are installed in the fuselage and wing, control rods and tubes are pre-routed in the fuse as well. The elevator is pre hinged, even the landing gear just pops into place.
Here's where the wing mounts in the fuselage, the wing uses a double pronged tang that fits in the front edge of the fuse joint, a screw retains the rear of the wing to the fuselage.
Some items that every modeler should have in their box of equipment are a Wattmeter, IR thermometer, and a digital scale. These three devices will go a long way towards taking some of the unknown out of the equation and help us plan on what performace one can expect from a power system.
The first order of business is to check the power system and determine a baseline performance. In order to choose the correct lipo, it's important to find out the demands of the motors and fans so after binding a spektrum receiver to the DX7 transmitter, the speed control's Y harness was connected to the receiver.
Initial throttle up was performed using a 1000 mAh 2s 15C lipo. The first reading showed a quick flash to 20.1 amps. Changing to a 1000 mAh 20C lipo showed an initial flash of 20.8 amps. Evidently the power system is well matched to the twin 12A speed controls so one could feel confident that wide open throttle could be used without much fear of overloading the speed controllers. As voltage drops, so does the amp draw. Under the load of the motors during a static test and using a 1000 mAh 15C 2 cell lipo, voltage dropped to 6.64V and 19.1 amps, so that's 126.8 Watts on a partially discharged battery. There is no doubt that a fresh high dischage lipo will elevate those numbers, however it is pertinant to know what kind of performance to expect a minute into the flight.
The speed controls are mounted in the nacelles just behind the motors and located in the airstream for the benefits of maximum cooling.
Next up was to check the static thrust. the fuselage was placed nose down on the scale, the scale was reset at zero. Any thrust generated by the fans is displayed in either ounces or grams of weight, since the thrust is measured in the same axis as gravity, the result is fairly accurate. Initial tests using 3back to back throttle ups resulted in a repeatable 105g of thrust with a lipo down to only 7.9 volts resting and 6.64volts under load. A quick thrust test using a charged lipo resulted in 125g of thrust. However, it pulled a whopping 23.9 amps. This setup is looking like a bit of an amp hog. It's also showing now to be barely within the continuous rating of the speed controllers. I would imagine that the fans will unload a little in flight and as the lipo discharges, the amp consumption will drop as well. Additional testing with a fresh lipo will be done after final assembly. That will be a more in depth test, but for now I have an idea of what to expect. I have a hunch that static thrust can be increased by smoothing the airflow out of the nacelles, it appears as though the speed controller wiring can be repositioned slightly and have some effect on airflow. We'll find out in the end, but for now we have a start.
The tail assembly was glued into place and the engines once again tested. The airflow exiting the engines flows directly over the elevators. Check out the video below and see the effect. Without the elevator control horn hooked up, the elevators are free to move according to the air current. The result is that the elevator is pulled upward. The reason is that faster air is moving over the top of the surface, and this will create lift.
That means that the motors will provide a certain amount of lift by pushing air over the horizonatal stab. The result will be a raise in the tail at full throttle. Once the elevator is hooked up, a certain amount of up reflex will be required in order to get balanced, level flight. This also means that there will be a certain amount of vectored thrust. Add to the equation the fact that the nacelles are above the neutral line of the wing, making a slight tendency to drop the nose as thrust builds, elevator up incidence will be set at about 15º up for the maiden.
__________________________________________________ _______________A few things need to be addressed on final assembly. The landing gear mounts pop out fairly easy and should be glued more firmly into place if landing gear are to be used. This is typical on ARFs and RTF airplanes as a whole. The method that holds the wing in place is decent, however with the wing fully against the wing saddle in the fuselage there is a gap between the plywood mount and the plastic wing retainer. The cure is to add either a layer of plywood or perhaps foam tape to fill the gap as the parts need to fit together and not be open or pulled together by the screw. It's not a good fit as it sits. This would allow too much flex at the rear and something will break free from the foam in a less than perfect landing. The load on the retaining joint needs to be better distributed. Aileron servo is hooked to the receiver, the wing is installed and the mount finished. The screw is installed and the control surfaces' movement is checked.
I just couldn't wait. Upon receiving a shipping notice that my lipos on order wouldn't arrive by this weekend, I knew I had a 1000 mAh 2s 20C pack that barely fits. Actually, it won't fit without melting out some foam on the underside of the hatch. After performing a little clearancing on the canopy, there is just enough room so that I could use one of my wife's hair bands to keep the canopy in place for the maiden. They are just the right size and don't cut into the foam. The motors were tested and the fans sounded sweet and so I conned my wife into putting on a coat and heading outside.
With my wife on the video camera, my nerves were heightening. Micros can be such and handful. The weather was cool, sky was clear, hardly any air movement so I put it on the tarmac and let it rip. The A-10 lifted off fairly quick, but as soon as it got it in the air I quickly found the elevator to be sensitive. I used standard rates on the transmitter. The response of the ailerons was pretty good. I might keep the rate but increase the throw. The elevator probably needs the most dialing in of the expo and rates. All that was not going to help me at the moment. This little hog was doing it's thing, I just needed to be very mindful and concentrated on the sticks. A few circuits were performed, some diving attack runs, a slow roll, a low speed handling test right off the deck and landed. I breathed a sigh of relief and smiled. It was an intense flight without the rates dialed in, but the bird looked great and handled decent in spite of the lack of transmitter programming. There was no time to attempt any trim adjustments, I'll do that on the subsequent flights as this 1000 mAh pack made the plane just a touch nose heavy. I'm going to wait for the proper lipos to arrive before making any changes.
Although in factory configuration the package is an amp hog, this little warthog behaves just like larger versions. It's a nice size to pop in the trunk for a mid afternoon diversion from the office or to pack in a small travel case on vacation. This bird can take off in any fair sized parking lot, it does however need some space to fly. This isn't a slow flying floater, it's got a little speed to it and speed means that it travels distance quickly. The semi scale landing gear held up to a little skip on landing when I cut throttle just a little too much.
Vvvvery nice flight ! Well done,Joe.
Previously,we worried about the thrust that would be weak ,but changed my mind since seeing your flight.
The 30mm ducted fan is ADF30-10
10200KV 8.4V 11.4A 96g(8 blades)
How do you like the more powerful new version of ADF30-10 for A10???:
8 blades rotor + new fan housing:
ADF30-100 about 12500kv 8.5v 14.1A 67800rpm(load),136g thrust
I think it should be a rocket