|Feb 12, 2012, 06:17 PM|
Eflite UMX Gee Bee R2
Picked mine up today at my favorite LHS. Brought my 10CHP & a freshly-charged Hyp 240 2s pack with me. Spooled her up in the shop & OCP kicked in. Spooled her up a second time & everything was fine. I did a bit of testing, and felt confident that it wasn't going to happen in flight.
It was windy & gusty, but I just couldn't wait to get the maiden in, as we're heading back into the deep-freeze, with 20-30 MPH winds until Sunday. Hopefully, I'll be able to shoot some hatcam video at the club field Sunday afternoon. Fortunately, my LHS is located right next to a large movie theater with a huge asphalt parking lot.
I mounted my homebrew Hyp 240 2s pack about 6mm or so from the front of the battery tray, with the wires facing aft. I lined her up into the wind, and rolled into the throttle. She got a bit tail-happy from the P-factor as the tail came up (as a Gee Bee should), but it was easy to compensate with rudder. That made me laugh a bit, as it reminded me of the videos I've seen of the full-scale plane on takeoff. I let her build up some speed on the mains, then eased the stick back. She climbed out with authority. I leveled out & checked the trim. None was needed, as she was flying straight & true. She felt slightly nose-heavy, though - so I'll move the pack a bit further aft next time. I brought her around for a WOT pass. She picked up speed quickly, and there was a fair amount of Doppler shift as she went by. I was surprised at how fast she is, given the huge nose & undercambered wing. She seems to be faster than my Sbach w/5030, but I'd have to fly the planes back-to-back to make an accurate speed comparison.
I did some loops, rolls, KE, inverted flight, and vertical climbs. She tracked well through all maneuvers - despite the gusty conditions. Particularly impressive - considering the u/c airfoil & short-coupled airframe. Thrust-to-weight is definitely better than 1:1. She had no problem executing huge, round loops, and extended vertical climbs are effortless, albeit very non-scale looking. She can climb straight up for at least a couple hundred feet right from takeoff, if commanded to do so. However flying a scale Gee Bee in that manner just doesn't look right to me. Despite the built-in aileron differential, rudder is required for decent-looking turns (again, as it should be with a Gee Bee). I found the stock control rod positions to be about right for scale-like flying & pattern-style aerobatics. It was very apparent to me that she does not like to be flown around at half-throttle or less. She is much, much happier when flown up on the wing. In fact, she is happiest when flying at or near WOT - just as any good racing plane should be!
I decided to shoot a few approaches to get a feel for how she handles at lower speeds. AS3X is definitely your friend when she's not 'up on step'. She will slow down, but slow is not her forte. Of course, she's a racing plane, so one would not expect her to be happy just putting around at UM T-28 speeds. Power-off, she is pretty much a brick with control-surfaces (as a Gee Bee should be). She comes in noticeably hotter than my Sbach without SFGs - despite the u/c airfoil. I didn't carry enough power all the way down on my first approach, and the landing was pretty crappy. Plus, there was a crosswind. On my second approach I carried a fair amount of power all the way down, and set up for a full-stall three-pointer. She started getting a bit squirrelly just before touchdown, and then settled-in with a thunk. I must have been right on the edge of stalling before she got into ground-effect. I rolled into the throttle, and went around for another try. This time, I came in a bit flatter & hotter. I flew her all the way down, and didn't cut the power until after the mains were planted. She rewarded me with an absolutely perfect, scale, two-wheel landing - tail still flying as she went by! She rolled out straight as an arrow. I let the tail come down on its own. As I taxied back, I found myself laughing out loud, and grinning from ear-to-ear!!
It was getting dark, so I had to call it quits after one flight.
The plane looks great on the runway & even better in flight! There is plenty of detail for scale buffs to enjoy. I did notice that the wingtips are quite delicate, however. They will not fare well if they make contact with a hard-surfaced runway. In flight, she looks very scale - nearly indistinguishable from the full-scale version at times. She is even fast enough to look scale during WOT passes.
This plane wants to be flown. She is not happy with a passive pilot who waits for things to happen, and then reacts to them.
To fly & land comfortably, the Gee Bee definitely needs more room than the Sbach or Beast. I was planning to fly her at our indoor spot this Sat night - but after the maiden, I wouldn't I'd want to fly her in there unless we have all three soccer courts & everyone else is grounded while I fly.
She flies nothing like the Beast 3D or Sbach, which is a very good thing! I love those planes, but I bought a Gee Bee because I want to fly a Gee Bee. If I want to fly an unlimited aerobatic ship or sport-plane, I have a few from which to choose. Even with AS3X, there is still plenty of personality here. But not so much that a true intermediate pilot would feel intimidated. However, the Gee Bee is definitely not your next plane after mastering the T-28.
It is very nice to see that they didn't completely tune the 'Gee Bee' out of the Gee Bee. They gave her enough Gee Bee personality so her pilot will never mistake her for another plane in the hangar, but they tuned out the worst parts of her infamous nasty side. I think they struck a good balance between realistic flying behavior and pilot-friendliness.
Of course, I only have one flight on the airframe, so my thoughts may change. But I'm impressed!
EDIT - 2/12/2012:
Here's some hatcam footage I shot this morning at the club field. First flight was with the stock 5.25" x 3.5" prop & the second flight was with the GWS 5030. I'm using the same homebrew Hyperion 240 mAh packs that I use in my Beast 3D & Sbach. Due to the 5030's thinner hub, a spacer is required. An Sbach prop spacer works perfectly for this.
With the stock prop, I'm getting 4:40 to the 80% discharge point on my Hyperion 240 mAh packs. With the 5030, I'm getting 5:30 to the 80% discharge point. Seems like the vertical is better with the 5030. Not sure which one I prefer, though. I'll need to get some calm-wx flights in to figure it out.
EDIT - 2/15/2012:
Just got back from testing RCBabbel's Hyperion 320 mAh 2s pack with the GWS 5030 prop! All I can say is WOW!! I have found my favorite pack/prop combo for this plane!!
The Gee Bee's gargantuan gaping maw simply swallows the portly performance pack. Surprisingly, getting the CG right was easy! In flight, the 320 pack's added performance more than offsets the extra weight. She might come in 1-2 MPH hotter than before, but I really didn't notice the extra weight during slow flybys or when landing. On an aggressive flight with lots of WOT, I'm getting 7 minutes to the 80% discharge point!
For those who fly indoors or outdoors in tight quarters, the extra weight of the 320 pack may be noticeable. For most pilots, however, a Hyp 320 2s pack & GWS 5030 prop will unlock the true performance of this bird!
See RCBabbel for plug & play Hyperion 320 25c, Hyp 450 25c, and Thunder Power 325 65c packs: http://www.rcgroups.com/forums/member.php?u=54990
Check the pic below to see where I mounted the pack. I flew another flight with it all the way back, but the CG was too far aft for good wind penetration.
EDIT - 2/24/2012:
Here's a comparison between a Hyperion 450 & 320 2s 'BabbelBatt'.
Compared to the 320 mAh pack, the 450 seems to be a bit faster. Vertical performance seems to be slightly better - despite the extra weight. With the 450 as far back as possible, the CG is about 23-24 mm aft from the LE - just a bit forward of the recommended 26 mm. Sustained KE suffers a bit, and it takes a bit more down-elevator for level inverted flight. Other than that, she flies just fine. The nose stays up in turns & it doesn't drop excessively when the throttle is pulled back. Also, there is still plenty of elevator authority for a power-off flare.
I think the Hyp 450 is an excellent choice for those who want maximum power & endurance, and are willing to sacrifice a bit of sustained KE performance to get it. Also, the extra weight makes the 450 an excellent choice for flying in turbulent conditions. It's a keeper, for sure!! Check the pic below to see where I mounted the pack.
Static RPM testing
Here's some static RPM data with the GWS 5030 on the Hyperion 240, 320, and 450 mAh 2s packs. EDIT - 6/20/2012: Added Thunder Power G6 325 mAh 65c 2s Babbelbatt static test data. The THP 325 only has 5 cycles on it, so its performance should improve after break-in. RPM taken under natural light with a calibrated optical tach, 20 sec into each run on a freshly-charged pack:
Elevation: 910 ft AMSL
Temp: 70 F
Prop: GWS 5030
-------------- RPM ---- Thrust (g)* - Speed (MPH)**
Hyp 450 -- 12980 ----- 161 ----------- 36.90
THP 325 - 12800 ----- 156 ----------- 36.36
Hyp 320 -- 12600 ----- 151 ----------- 35.80
Hyp 240 -- 12240 ----- 142 ----------- 34.80
*Calculated using the GWS prop spreadsheet
**Calculated pitch-speed. Prop slippage and in-flight unloading not taken into account.
Going by the above:
EW ------- 88.24g
Hyp 240 -- 14.46g
Hyp 320 -- 18.80g
THP 325 - 20.80g
Hyp 450 -- 25.28g
--------------- AUW -- Thrust/weight -- Wing-loading
Hyp 240 -- 102.70g ----- 1.38:1 ------- 7.21 oz/sq ft
Hyp 320 -- 107.04g ----- 1.41:1 ------- 7.51 oz/sq ft
THP 325 - 109.04g ----- 1.43:1 ------- 7.65 oz/sq ft
Hyp 450 - -113.52g ----- 1:42:1 ------- 7.97 oz/sq ft
Note that the Thunder Power 325 65c pack provides the best thrust-to-weight ratio.
|Feb 19, 2012, 04:25 PM|
Joined Aug 2011
I'm thinking of going from a Parkzone UM Pole Cat to the Gee Bee R2. Is it a good next step? I can fly the Pole Cat pretty well - flips, rolls, some inverted, take offs, landings, etc. what are your thoughts? I want a more stable yet faster plane...
|Feb 19, 2012, 11:35 PM|
Hope that helps!
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