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Old Dec 30, 2010, 05:50 PM
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Mini-Review
ELERC Micro A-10 Warthog with 30mm EDFs

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.


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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.



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The contents as packed with only one problem as a result of the box being crushed.





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One nacelle mount is cracked. Actually, more like the foam beads seperated. It's quite an easy fix.



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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.


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8 blade fan, brushless motors pre installed.





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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.



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Tail surfaces and landing gear mocked into place, a dummy lipo in the battery tray and there she sits.




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add the canopy and here is the result.







So now the mock up comes apart, stay tuned for the next few nights as the real assembly is done. The minor issues discovered on the mock up will be taken care of during the assembly as well as a suitable visual scheme to finalize the build. I can't wait to be blasting down the canal..... gun blazing.....






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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.




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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.




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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.


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The speed controls are mounted in the nacelles just behind the motors and located in the airstream for the benefits of maximum cooling.



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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.

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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.


ELERC A-10.avi (0 min 8 sec)


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 15 up for the maiden.

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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.



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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.



ELERC A 10 Maiden Flight Video (2 min 59 sec)


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So for those wanting the excitement of making those attack runs, this A-10 fits the bill. It's small, lands and takes off in a reasonably small space if you have the skill. Is this a beginner's plane? The simple word is no. This is the kind of plane for someone with a little experience in EDF jets. For those already accustomed to the performance of a micro EDF jet, this one is quite roll stable and should be a joy on landing as a take offs instead of being forced to fly as the typical belly flopper. At some point I will remove the landing gear and try the hog as hand launched belly flopper, but for now the little A-10 will be parked in the hanger to continue the testing when the proper lipos arrive. It is nice to have semi scale landing gear for display purposes. So whether you decide to get the plug and play version or purchase the typical ARF airframe and use your own power system, this little "Hog" delivers good speed and manners for a micro jet.

This A-10 is a nice compromise between micro size and a larger airframe's handling traits. For an A-10 enthusiast or micro jet jockey, this is one that you'll want to have in your hanger. While I'm a little disappointed that the model was not made with EPO, The foam on this model is still flexible enough to absorb some punishment without snapping like a twig or turning into confetti on a bad landing.

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Subsequent testing with a fresh lipo showed that the two fans combined registered 155g of thrust. That's plenty of thrust for the airframe. After looking closely at the engine nacelles, I believe the ducts to have manufactured upside down. The bottom wall of the duct shoudl be on top and visa versa. The exit diameter also needs to be reduced in order to gain the most effeciency from the existing setup. Once the modifications are complete, the model should have reduced pitch sensitivity and reduced pitch change with the application of throttle.


Take a close look at the picture below. Note the engine nacelles and the thrust angle. There is an upsweep to the exhaust nozzles, that thrust line keeps the elevator out of the exhaust wash and offsets the normal nose down effect of having engines that sit above the centerline of the wing.



Now here's the exhaust end on the micro A-10. THe upper half and lower half have a different contour, however it appears as though it is backwards. Had the designer flipped the taper from the top half to the bottom, there would have been a more correct up thrust line. There may also be some merit in necking down the exhaust outlet size.




After playing around with a couple ideas, I settled on modifications to the exhaust duct using depron inserts. The goal was to reduce the exhaust exit diameter and create a touch of up thrust to offset the nose down tendency at throttle with the unmodified nacelles.

Inserts were cut from 2mm depron and put in the bottom half of the exhaust duct. The original design shows a thicker upper half of the nacelle, the bottom half was much thinner. This modification corrects that condition. The depon can be sanded either prior to installation or after. The contour of the inner lip was sanded smooth to provide a clean transition from the inner duct wall and over the the depron insert. The end result is a necked down exhaust diameter to approximately 28mm. The duct is not exactly concentric, but close. The insert directs the airflow slightly higher, in effect pushing the tail down rather than the airflow over the stab causing the tail to lift..... with a subsequent nose down pitch at throttle.

Cut the depron....



Roll it with a little heat and something to form it on



Installed in the duct and trimmed, then sanded to the proper contour.



I also opted for a larger control horn for the elevator for better leverage and feel.


Now it was time to test the results. I installed the 800 mAh 30C lipo pack, checked the flight control surfaces and just went at it. I hand launched the model and immediatly upon leaving my hand it performed a gentile climb out. I said to myself, "Man this looks really good so far." I performed a few circuits and every time I punched the throttle, the plane kept it's same pitch and it powered though all manouvers cleanly, including loops from level flight. The higher velocity of the exhaust gives a little more speed with less throttle and can even fly slower than a stock setup. The overall result should mean longer flight times as less throttle can be used, there is still a bit of a vectored thrust at higher elevator throws, but the biggest plus is that the nose down tendency is gone. The plane is much more forgiving and stable, it tends to fly just like larger versions. I went through a couple packs and did numerous runs against that "dam" at the end of the canal, the smile brought back some fond A-10 memories. This plane is a blast now and I highly recommend this modification if thrust tubes are not being used, it will make this a much more pleasurable plane to fly. One thing though...... this plane suffers from the typical A-10 power off drop. The nacelles block some airflow over the elevators when power is off so there is a loss of elevator effectiveness without the fans running. You must get used to landing with power on, you won't get very far by cutting power up high and attempting to glide down. The bird gets flown right down to the deck before cutting power. Remember that trait and you will have many fun flights ahead. Another trait that should perhaps be mentioned is that it won't roll all that fast, increasing the aileron throw just seems to make for a more twitchy model. This A-10 seems to respond best when flown a little more scale with relatively small aileron throw.

ELERC Micro A-10 after modifications (2 min 48 sec)



So in summary, When flown stock the performance is decent but is accompanied by a few qwirks. With some modifications, the plane performs like it's larger brothers, which for a micro...... is a bit surprising. Micros normally have touchy handling and are fragile in nature. This A-10 is now quite stable and robust enough to survive some impacts. Now it's time to do a little dress up and detailing!


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Old Dec 30, 2010, 07:20 PM
Life begins at transition
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Joe,
In your battery box, did yours have a divider around 3/4 the way back? It looks like it's missing, I'm wondering if you cut it out, it's not showing up in the picture, or if different versions are being made??
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Old Dec 30, 2010, 07:27 PM
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Joe,
In your battery box, did yours have a divider around 3/4 the way back? It looks like it's missing, I'm wondering if you cut it out, it's not showing up in the picture, or if different versions are being made??
I have no such divider. There are usually changes done during beta testing so there's no telling what changes have been made. I'll be taking up close photos during assembly to continue this review so we'll find out.
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Old Dec 30, 2010, 07:34 PM
Life begins at transition
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Hmm, interesting! I wonder if we've all been given slightly different versions, as a way of testing their changes 'one at a time', but all at once? clever!
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Old Dec 30, 2010, 07:42 PM
Team30 Micro EDF
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Are we all going to post separate threads for each of our builds? I thought we were going to use the thread Ozzi started to keep it all together in one place?...

I am sure Lee would prefer it that way.
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Old Dec 30, 2010, 07:48 PM
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Old Dec 30, 2010, 07:52 PM
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Quote:
Originally Posted by NitroCharged View Post
Are we all going to post separate threads for each of our builds? I thought we were going to use the thread Ozzi started to keep it all together in one place?...

I am sure Lee would prefer it that way.
I'm sorry, I wasn't part of that discussion.

I was simply doing a review of the A-10 and a build log. I'm sure there is no harm in keeping a Plug and Play review of the product seperate from other modifications thread. Honestly, I never dreamed of pulling a hijack and putting my review in someone else's thread. Besides, Lee enjoyed reading the review thus far so he must be happy.
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Old Dec 30, 2010, 10:07 PM
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Lee must be very happy. Lots of exposure for this great little model. Lets just hope it flies well. Have you had a chance to measure the output of the PnP power system yet?
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Old Dec 31, 2010, 12:53 PM
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Originally Posted by ozzi supercub View Post
Lee must be very happy. Lots of exposure for this great little model. Lets just hope it flies well. Have you had a chance to measure the output of the PnP power system yet?

That information was added to the review. Final numbers with a high discharge lipo have not happened yet. It looks like this little Hog is a bit of an amp Hog.
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Old Dec 31, 2010, 03:00 PM
Team30 Micro EDF
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The 8 blade EDF units need a minimum of 800mah 25C lipo's according to Lee. The lipo is supplied in the retail RTF version.
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Old Jan 01, 2011, 11:30 AM
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Originally Posted by NitroCharged View Post
The 8 blade EDF units need a minimum of 800mah 25C lipo's according to Lee. The lipo is supplied in the retail RTF version.
Even that might not be enough. I just tested them again using a fully charged 1000 mAh 20C pack and the draw peaked to a high of 23.9 amps with a sustained 23 amps after 5 seconds. Might really need a 30C pack or the lipo will be the limiting factor in power production, that will be hard on the lipo.
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Old Jan 04, 2011, 01:10 PM
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The video below shows lift being created by the exit air blowing over the horizontal stab. The result will be the tail being lifted. Once the elevator is hooked up to the control rod, a small amount of up reflex will be required to keep it in level flight. Elevator will also prove to be quite responsive with engines running.

ELERC A-10.avi (0 min 8 sec)
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Old Jan 04, 2011, 01:31 PM
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That vid really demonstrates it nicely. The elevator is very sensitive in flight.
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Old Jan 04, 2011, 02:14 PM
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That vid really demonstrates it nicely. The elevator is very sensitive in flight.
And if it performs like larger versions, airflow across the horizontal stab gets blocked by the motors during power off tests. Cut power and it will nose down unless larger control throws are used. Dual rates should help. I wonder if there is a way to mix elevator rates with throttle on transmitters? Any programming experts? A decrease in elevator rate as throttle rate increases might be a sweet program for an instance such as this. It will still work with the flip of a switch though.
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Old Jan 04, 2011, 03:46 PM
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Easier than mixing it out, I added thrust tubes, and the effect all bar disappeared. I was very happy with that, as the nose-down was a horrible handling quality.
My thrust tube sits about 1-1.5mm above the lower surface of the nacelle, and that must be just enough to clear the horizontal stab. Now I can cut the throttle, glide around, then punch it to max, without any massive pitching.

It is good to see though, exactly what happens with the stock nacelle. Maybe for the production run, shrink the exit of the nacelle? Requires a mould change, but should stop the airflow over the stab.
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