|Nov 28, 2011, 12:50 AM|
TECHone Hobby EPP Funfly ARF Build/Fly/Re-Build
I am relatively new to the hobby. My son and I have been hitting the simulator for a year or so and I have progressed up to a 4-ch RTF ultra-micro (PZ T-28), while my son is still trying to make the transition from simulator. He is pretty young and has difficulty with both orientation of the ultra-micro 3-ch we have (HZ Champ) and with any breeze.
First and foremost, a 3-ch park flyer sized trainer made from EPP my son can more easily discern orientation on and that will be a bit better in mild wind conditions than our current 3-ch UM.
A secondary objective is as a complement to my growth in flying skills: I aim to grow in building skills. Start with an ARF (this project), move on to a kit, and then, maybe, a scratch build.
Research & Reviews (plus Hobbyking Tuff Trainer)
I did a lot of research for an EPP fixed wing trainer. Turns out, ARF/PNP/kit EPP trainers are rare as hen's teeth and is mostly a scratch build proposition. Two presented themselves, though they really are the same model in the same way that every 1980s-era Chrysler/Dodge/Plymouth was the same K-car.
Those two models were the TECHone Hobby Funfly EPP (FF) and the Hobbyking Tuff Trainer (TT).
They differ in that the FF has old-school rounded trailing edges on elevator & rudder, while the TT's are straight. Also, the TT has evolved a bit and now can be had in 4-ch configuration with a bottom battery hatch.
Reviews for both could be charitably described as "mixed." The two main problems cited were control rods binding and stripping servos and being horrifically tail heavy. A weak firewall also has several mentions. In addition, the revised TT battery hatch is bemoaned in several reviews. The HK product page has a sampling of these reviews.
I would be remiss were I not to mention the http://flitetest.com/ review:
They also mention the how tail heavy it is and have a firewall problem.
Why would I choose to risk a purchase with such mixed reviews?
1. No other EPP high wing trainers I could find.
Vendors & Hardware
I bought the ARF kit and a few extras from 84hobby.com:
and gave 84 a short, sweet, positive review:
(Upshot: great to do business with, would gladly purchase from him again.)
I bought the power system from Grayson Hobby.
and also wrote a review:
(Upshot: hardware seems solid so far, but commo was lacking when most needed.)
Motor: GH2212-13, 1000kv, 47g---------------------------
I will make more posts later. My outline is below and I will reserve the first few posts for my log. Feel free to comment.
|Nov 28, 2011, 12:51 AM|
I received my ARF from 84hobby in short order.
I have experience with only a few examples of EPP used in RC aircraft, but the EPP on this model feels a bit...overcooked. Less "wet" and rubbery, more "dry" and brittle. Especially so relative to the examples of EPP packing material I have encountered.
Also, the factory glue joins were haphazard.
1. Wing was not glued all the way along the joinI used the flexible, rubbery, clear-drying canopy glue to reinforce the firewall and landing gear slot; CA (foam safe, throughout) with baking soda to reinforce the internal reinforcement; and combined CA/baking soda/popsickle sticks to sturdy up the servo mount (images later).
Assembly of the tail bits was trivial and I used CA & baking soda.
|Nov 28, 2011, 12:52 AM|
Control Rod Hades
Control Rod Hades
The servos sit in a servo bay behind the power system bay and push control rods through plastic tubes back toward the control surfaces (rudder & elevator).
I "dry fit" the provided control rods and found that the reviews were on target in that the rod had to bend sharply away from the rear tube exit toward the control horns and bound up on the tube and EPP. Nylon gears would soon wear out under the strain, in my estimation.
I decided to cut out some of the EPP foam to make the bends less severe.
Here are a couple images showing the results with the original tube at the far left side of hte cut (elevator side, rudder side similar):
I cut a bit more foam and ended up in the hollow where the tabs from the rudder and elevator assemblies resided. Then, I made a rookie error that cost me a good bit of time, but was quite the learning opportunity.
I had run out of my black-cap foam-safe CA and had picked up some new foam-safe CA with a white cap. I then applied the white-cap CA inside the hollow to sturdy up the internal tabs when all did not go as planned. It was like nothing was coming out of the bottle...I checked the bottle top cut I made and squeezed some more. I then realized that the white-cap foam safe CA is thin, while the black-cap CA I had been using was thicker "gap-filling" CA. The thin CA had been running all over creation inside, using capillary action like crazy...yes, CA got all up in the control rod tube and made a rough situation impossible.
I ended up buying new (thinner) piano wire & control rod tubing. Youtube showed me how to make a good Z-bend with linesman pliers. I replaced both sides and extended the tubing along the cut I had made, so less of the thinner piano wire would be unsupported on its way to the control horn. I secured the rest of the tube with white Gorilla glue and taped over it to keep the expanding PU glue in place.
I rather like the result and can live with the little bit of blue masking tape I was not able to pull out from under the tube:
|Nov 28, 2011, 12:53 AM|
Control Horn Purgatory
Control Horn Purgatory
I installed the control horns as instructed, with the holes directly over the joint/hinge. That went fine, though I am not enamored of using screws. I would have preferred longer horns shoved up through a slit on the foam and glued in place, a technique I will use on future scratch builds.
I bent the control rods on their way to the control horns so that they would not bind as they moved back & forth.
I started with the EZ Connectors in the holes closest to the control surface, which works for the rudder, not so much for the elevator. The lowest hole in in that control horn resulted in the horizontal stabilizer & elevator being yanked back & forth, rather than rotating the ruder on the hinge. I had to move it out to the farthest hole to get translate linear into rotational motion.
"E-Z Connectors," my tuckus. I am NOT a big fan of these critters. There is some sort of "Heisenberg Uncertainty Principle for RC Planes" at work, here. As I crank down on the EZ Connector, it will pull the control rod and/or rotate the connector in the horn. One needs a lot of hand strength and two needle-nose pliers/clamps to have any chance of success. In the future, for my scratch-builds, I will just use Z-bends and incorporate a U-shaped bend to facilitate minor control rod length adjustments.
I had to reduce the length of the rod, as it interfered with raising the elevator.
|Nov 28, 2011, 12:53 AM|
The servo platform was glued in with indifference and was not fully supported by surrounding foam. I shimmed it up with popsicle stick material and glued it all down more securely with CA.
I also had to shim the back end of the control rod tubes and glue them to reduce sloppy play in the system. I used some FF and a bamboo skewer, along with CA. I think I will eventually spritz some water mist down the remaining void space and hit it with White Gorilla Glue to more fill in the voids.
|Nov 28, 2011, 12:54 AM|
If I made any smart decisions that turned out to be inspired, I think it was my choice in power system. The reports of serious tail-heavy characteristics caused me to err on the side of more mass with regard to motor, esc, and lipo.
In the end, this worked to balance out the tail and I hit CG right on the nose.
I did 30-sec WOT ground tests with the 8x4 and 9x5 props. With the 8x4 GWSDD prop, the batt, motor, and ESC stayed cold. The 9x5 GWSDD prop caused the ESC and motor to get a little warm is all. I did not have a 10x5 prop to test, so I ran with the 9x5 GWSDD.
Using the 9x5 GWSDD prop, I have all sorts of power for 3-ch aerobatics and an awful lot of low-end grunt to get out of tight spots by the use of throttle. More on that later.
|Nov 28, 2011, 12:54 AM|
So, here is Version 1 of my Funfly. The field I fly at has a semi-rough turf/grass strip and I crafted new gear with larger tires.
|Nov 28, 2011, 12:55 AM|
Crash on Takeoff
Crash on Takeoff
The title tells the tale. I moved the throttle forward gently, it was off the ground by half throttle, and promptly flipped over to the left and pretty much exploded the nose. It was quite impressive. Take a gander.
It was really much, much worse than the photos can show, as there were incomplete fractures all through the fuse back to the landing gear. The motor mount firewall was broke and the wooden bit that holds the landing gear was completely yanked out. The landing gear axle broke.
I had mentioned earlier that the EPP felt a bit dry & overcooked. Given my experience with a subsequent EPP plane build, I think this EPP is not as springy as most.
|Nov 28, 2011, 12:56 AM|
Rebuild: Fuse & Firewall
I used CA, both gel and thin, as well as kicker in a liberal manner. I then used Scotch/3M Extreme Tape to help reinforce the front of the fuse back to the servo bay. No way hot glue or white PU glue could have been wicked into some of those fractures.
One note: I did rebuild the landing gear, but have not used it again, since the field is just too rough for a plane this small & light to ROG.
The old firewall, which I had reinforced with canopy glue, broke to pieces. I removed the remaining bits of (1/16"??) plywood and cut off the bit of overhanging foam. I then cut a new firewall out of 1/8" ply and glued it on with white gorilla glue.
I left off gluing back on the overhanging foam, as I knew I was going to muck with motor mount angle quite a bit.
|Nov 28, 2011, 12:57 AM|
The wing was indifferently glued together at the factory and the crash did not help the join. I decided it needed some serious help.
I glued the join with white GG and taped it down to prevent the GG from foaming out where it ought not to be. I then took two popsickle sticks and doused them in boiling water while applying compression to them. This allowed for them to bend and stay bent. I then GG'd them to the top of the wing, as both reinforcement and to help the wing keep its shape under the rubber bands.
|Nov 28, 2011, 12:57 AM|
Here is Version 2, along with the landing gear I don't use.
|Nov 28, 2011, 12:58 AM|
Successful Re-Maiden and Trimming
Successful Re-Maiden and Trimming
This time I dispensed with the landing gear and tossed it with my left hand. It needs only 1/3 throttle or so and then can quickly climb.
I place the battery on the right side of the ESC/batt bay and use 3.5mm connectors all aound (fuel hose covering connectors).
Right off, it climbed like crazy on half throttle. It also had a serious tendency to move off at an angle when I hit the throttle. I spent many flights trimming the control surfaces and shimming the motor mount this way & that. I ended up with zero side thrust and a healthy bit of down thrust.
How It Flies
Really, really well, once reasonably trimmed.
It is almost HZUM Champ-like in its self-righting ability when you go hands-off and zero throttle. Likely, it is as self-righting, but it generally doesn't have as much room (relatively, scale-wise) to self correct before the ground interrupts. It glides great and dead stick landings are a snap. You can glide it in and slide on its belly or do the usual flare, your choice. The 3M Extreme Tape is slick and takes a beating.
It does all the 3-ch aerobatics and does them well & snappily. I include inverted flight as well as outside loops. This is a bit much, likely, for a novice, so my dual rates tone it down to 60% with 25% expo. It can move pretty darn slow before stalling and then it drops nose rather than twists to the side.
It can handle some wind, but will get a bit carried away if the wind really picks up. I crashed it this way once (only broke the prop, it was pretty minor), when it got caught a bit in the wind and I fought to bring it back. The airfoil lifts like crazy and if you don't stay on the down elevator can get it it mis-positioned for the wind.
The 2212-13/1000kv, 20amp ESC, and 9x5 GWSDD prop are well-suited to the plane. It has a whole lot of grunt with the power system, but does not go too fast on WOT for the air frame. It will cruise somewhere between 1/4 and 1/3 throttle. It is very quiet relative to most the other park flyer electrics I have encountered. I tried a 10x4.7 GWS SF prop, but either the air frame or the prop made more noise and it did not fly as well. I will stick with 9x5. I use solely 1000mah lipos with C-ratings of 20C, 25C, and 45C. None of them get hot. The motor has never gotten even warm in this cool weather and the ESC has only gotten warm, even when I hammered it it a few flights. When the weather turns warm, I will cut some intake and exhaust vent holes, as there is only the hole behind the firewall at the moment.
My boy can see it a lot farther away and it is not as wind-sensitive. He has spent a bit of time on a buddy box, where I reel it in when he gets too close to the ground or too far away.
I was out on a nice day a few weeks back and a retired fellow flying a heli thought it flew quite well and he inquired about it, as he has not flown FW. He liked the power it had, combined with its glide characteristics, and thought he could quickly learn on something like it.
I bet that it could tote a considerable load, such as FPV gear, should I want to mount such. It has plenty of reserve power and flies straight & steady.
Conclusions & Lessons Learned
I am now happy with the result of my labors. I have an EPP trainer, park flyer sized, that flies well.
I learned quite a lot building this "ARF." Some of those things were skills, some of those things were how NOT to do things.
Here is what comes to mind as "word to the wise" sort of lessons.
1. Cheap ARF, RTF, PNP planes are to be avoided.
I had been spoiled by Hobby Zone and Park Zone RTF/BNF assembly quality. TECHone is not in that league. Starting from a dis-assembled kit and building properly and with care will save loads of time, when I buy another cheap kit. A cheap ARF is buying trouble, as you have to fix all their careless mistakes.
2. Removable "pinch" type landing gear is for the birds.
This is the second model I have had bust along this "feature." The addition of the cut, even if reinforced, leaves a weak spot. I have some ideas for alternate removable gear and will work that issue rather than use the supplied gear. Matter of fact, I will likely fill in mine with white gorilla glue and re-cover with Extreme tape.
|Dec 31, 2011, 11:56 PM|
Where are you at with yours?
I bought my FunFly from 2DogRC. It was easy to put together and I ran across most of the issues you have identified. This bird is tail heavy beyond belief and has a really distinct down thrust on the motor mount.
Take Offs are an absoulte nightmare as the airplane is just almost impossible to control. Once I coax it to altitude and throttle way back it becomes more stable - but not anything close to what I expected. I've watched the YouTube videos and have now idea how they were able to get it to ROG so well.
I like the looks and I really don't want to trash it - but I believe that it is grossly over powered even with a 2s. Running a 8x4 prop.
I would like to know how your maiden flights went.
How did you solve the tail heavy issues?
Are you going to go full 4-ch with ailerons?
Looking forward to hearing about your experiences.
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