OK, if I keep modifying these ARF's like this the folks at Brodak's are going to get CHEEZED! However, its like cooking; you get a little of this and some of that, you wonder how it might go together and... GOULASH!
This story starts back at this year's fly-in. I got a chance to fly John Paris' (actually Frank Carlise's) Super Clown with the Brodak electric system in it. The experience was eye-opening and a power system followed us back home. Discussions with Mike Palko indicated he was pessimistic about using the power system outside of its intended use, however, we were convinced that the power available would handle a larger, draggier bird and set-out to find a test bed. Upon further review, we came back to an Oriental. Dad had one nearly RTF, seemed
like the fastest way from there to here was to "borrow" that bird, gut it and stuff the electric power package in it.
So that's what I did. Also blunted the leading edge, shortened the flaps, and sealed the hinge lines - like the OTHER Oriental I am flying - see that post for details.
Anyhow, the key to this mod was adding a nose ring off the end of the existing engine mounts. To this some lite ply side panels were added then aggressively shaped so the cowl would fit over them. Finally, the fiberglass cowl is glued on with silicone seal, tying everything together and reinforcing it all. Purpose built this could have been
lighter and stronger. Because the cowl is glued on, the existing cut-out in the cowl (for the slimer engine) was made symmetrical and the engine installs from underneath and slips forward to the firewall.
The Brodak battery ALMOST fits perfectly in the tank compartment. If the wires came off the front instead of the side corner (or if the fuse was a tad wider), the battery would fit on the mounts where the tank normally sits. However, the web between the mounts, then the mounts themselves were removed and the battery easily fits to the top of the fuselage. Lots of room for airflow too. A hole was cut in the rear bulkhead to channel air out under the wing, and two holes cut in the top to vent heat there.
The engine controller, timer and arming switch were a bit more perplexing. Besides this is a test bed and it is better to make FUNCTIONAL installations rather than pretty ones. That's my story and I'm sticking to it. Desire was to get the controller where it would cool. The timer and arming switch pretty much have to be exposed to
power up the system. Anyhow, the ESC was siliconed into a hole cut in the tank, uh, I mean battery hatch, the timer up on the fuselage side where it can be seen and activated, and the arming switch on the side.
Several folks have posted that their best luck came with the 9x4.5E APC prop - so that's where we started. Sounds small, but historically there is precedent. Folks like Kostecky & Gierke used to use 9-6 three blades
on larger/heavier birds than the Oriental. I rationalized that their 3 bladers running around 8k-9k "filled the disc" about the same as the 9" 2-blade at the expected 12k output. My flight with the Super Clown also demonstrated that the little flatter pitched prop had a LOT of recovery in it if the bird got stalled.
Going in I was more afraid of TOO MUCH speed rather than too little. The Brodak system is purpose built and not tunable - so any tuning would have to be with props, aerodynamics, and line length. The SLimer Oriental flies on 63' lines so thats were we started.
Test flight showed lap times around 5.0 sec ON 63' LINES, with LOTS of power to do anything! Near end of run it slowed down quite a bit, and shut off on cue at 5 minutes. Opened up the fuselage and discovered the battery had ballooned! Second flight started off around 4.8 sec lap times and got (I think) a low voltage shutdown short of 5 minutes.
In an effort to slow down the bird and maybe lighten the battery load, my brother Arch the "propellor artist" tricked out the 9x4.5 by narrowing the blades substantially. Got us a couple tenths of a second lap time, so we went extreme. Flight 4 was with a stock 9x4 PowerPoint wood prop. Starting lap time was 5.3 sec - about the same as the LA40 Oriental! Then a bout 1.5 minutes into the flight the motor gave a shut down signal. Then did it again at roughly 1 minute intervals until it finally shut down at 5 minutes. Discussion with John Paris indicated he had a similar experience and determined the ESC was bad, so we got a replacement. BRODAK STANDS BEHIND THEIR PRODUCTS!
Figured we had it nailed, but subsequent flights showed the thrust was just too far off to accept, so went back to the modified APC.
My plate is full and my experience lacking, so the bird was packed up and sent home with my nephew Archie, the RC Electric pylon racer. A couple days later he calls and says all the smoke got loose from the charger! So he used his Hobbico charger. Took it out to fly, set the timer for 6 minutes and did a full pattern. Reports more than enough power & duration. Second flight like the first except he added a few extra laps here and there. He has a Triton on order and a box of alternative new props to try. The Triton will really let him see ho hard he is working the battery. Figure if we can get it flying on a 4 pitch with diameter to suit we'll pretty well have it licked. As it is, Archie reports (and I concurr) that he would not be afraid to take it to a contest.
Summing up, we are able to EFFECTIVELY fly the 47 oz bird with the stock Brodak system using a modified APC prop. If we can do some more prop tweaking I think the system will be pretty much good to go!