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Old Sep 17, 2014, 09:38 AM
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Originally Posted by Altbob View Post
OK, I'm convinced to get a new set of mounts and replace the CF with metal wires, epoxied in.

Of course, as Joel rightly points out, that means the damage in a bad landing will just occur somewhere else - in this plane the likely spot would be for the landing gear or spats to crack off if the wings don't break off at the roots and/or the fly wires are made snap proof. Oh well. Ideally the spats would be attached with magnets so they could break free by design and be snapped back on afterwards.

Until I can made some of these improvements I think the best plan might be to just turn inverted and glide the GeeBee to a stop on its back. Unfortunately I don't have a paved runway anywhere where I'd want to fly this little UMX, but as Joel says, I have a heck of a "backyard"

Since they really only work in tension and not compression I would just CA some strong black thread in place of the rod.
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Old Sep 17, 2014, 09:51 AM
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East Bethel, MN USA
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Speaking of the landing gear struts - I broke one in half just from a rough crosswind landing on asphalt. The rigidity of the foam is not an asset in this case.

Joel
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Old Sep 17, 2014, 12:51 PM
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Agreed Joel. I'm actually on my second UMX GeeBee (got the first one years ago, full price when it first came out, got the new one a month ago for $65!) The last one I had got the crap beaten out of it regularly, and it was pieced back together from fatal crashes several times. Both wings ripped off, ailerons bent, nose crushed on top and bottom more than once, battery tray ripped clean off, engine broken free from it's mount, removable hatch mangled and bowed due to the use of CA accelerator (possibly because I sprayed too much on), landing struts cracked in half, spats utterly crushed and rebuilt several times, every CF rod replaced and reglued more than once...apparently I am a glutton for punishment because I am now ready to do it all over again!

In the end, I made my old UMX GeeBee all but indestructible with carbon spars on both wings, carbon strips straightening out the ailerons, tape and glue reinforcements on the gear and fly wire connection points and a sturdy balsa wood battery tray added inside, not to mention a lot of foam filler and red paint to keep it pretty. But it became heavy in the air and acrobatics became impossible, in part I think because the motor was wearing out. I couldn't even generate enough power to do a loop without going into a power dive first. After the last crack up, caused by not being able to get out of an inverted low pass due to insufficient power, I decided it was time to search for a second hand model and reboot the whole thing. I got lucky and found a brand new one that someone was unloading here on RCGroups!

So long story short, I am a far better pilot now and I tend to crash a whole lot less...but I still crash from time to time because I have a penchant for pushing my skills to the bleeding edge. I've already replaced the stock prop with a 5030, but I also want to reinforce the new plane a bit in the most vulnerable and fragile places. Without going overboard and adding too much weight as before, under the theory that my crashes from here on out will be less of the catastrophic variety and more of the mundane, "oh well, I broke a CF rod" type. I am still thinking that putting those CF wing spars on is a good idea. The wings on this plane are eggshell fragile, and that's one repair that is hard to do without ruining the look of the plane. With the spars in place, the flywires really do serve only an aesthetic purpose, so maybe thick black thread is all that I need?

At any rate, I bought the set of hardpoints from Amain Hobby as suggested, as I have little real hope that I will be able to reuse the mounting hardware from the old plane, even if I use a pin vise to try and hand drill out the CF remnants - a job that would likely take many hours and leave me with pin holes in my bloody fingers.

I hope someone out there appreciated my typing all that out - sorry to bend your ears, but who else am I going to ramble on to about this stuff? My wife just rolls her eyes
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Old Sep 17, 2014, 02:23 PM
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Australia
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Hey I have one of those roll her eyes wives as well! Could you tell us
more about your wing spar mods, I have a standard Gee Bee and like
the idea of strengthening those flimsy wings. Thank you......
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Old Sep 17, 2014, 02:52 PM
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Sure Peter. I just cut them off the old UMX GeeBee to install them on the new one. I'll take some photos when I do it. It's incredibly easy.
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Old Sep 18, 2014, 02:59 PM
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Here you go! I described the whole process in the photos so I won't repeat everything here. Just keep in mind that I messed up by using a semi-transparent scotch tape and should have used the better clear plastic tape, so the mod is a little uglier than the last time I did it

Frankly the tape is just "belt and suspenders" - if you epoxy well, the extra tape reinforcement may not be necessary. I felt it was worth doing anyway, if only to smooth the surface over the CF rod and reduce drag. Frankly the drag from the under-wing aileron servos probably far exceeds this mod and it's virtually irrelevant. The whole mod probably weights less than 2 grams. Heck, I doubt it tops 1 gram... Hence the fact that this is about 1/2" ahead of the CG has no effect on flight characteristics that I can detect.

I may have to hide the whole thing with red paint at some point, just to pretty up the undersides of the wings.
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Old Sep 18, 2014, 03:22 PM
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Great mod well described thank you, I to do tumble landings as I have only grass to land on. Don't have a spare Gee Bee to will have to chase up some CF bars, great way to add strength without much weight, thanks for sharing!
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Old Yesterday, 08:46 AM
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Kokomo, Indiana
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Interesting discussion on reinforcing the Gee Bee. Good to know about

I was wondering how the propeller from the UMX Pitts would fly the UMX Gee Bee so I installed one, as shown. I am quite happy with the gained efficiency. I had felt the need to fly at 60% and higher throttle with the GWS5030 for decent loops from level flight, quicker rolls, etc. The larger diameter of the prop from the Pitts let me drop this to right about 50% throttle with the same flight characteristics. Toward the end of the flight I did bump up the throttle closer to 55% to maintain loops as the battery voltage started to sag. The flight time was at least one minute longer with this prop; before my voltage monitor circuit killed the motor. I land dead stick onto grass This change is a keeper.

Please note that my Gee Bee has had the ESC replaced with a Plush 6A to eliminate the OCP, and has a Turnigy 1811-2900KV motor for greatly reduced noise.
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Old Yesterday, 08:57 AM
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United States, IL, Waterloo
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Quote:
Originally Posted by Altbob View Post
Here you go! I described the whole process in the photos so I won't repeat everything here. Just keep in mind that I messed up by using a semi-transparent scotch tape and should have used the better clear plastic tape, so the mod is a little uglier than the last time I did it

Frankly the tape is just "belt and suspenders" - if you epoxy well, the extra tape reinforcement may not be necessary. I felt it was worth doing anyway, if only to smooth the surface over the CF rod and reduce drag. Frankly the drag from the under-wing aileron servos probably far exceeds this mod and it's virtually irrelevant. The whole mod probably weights less than 2 grams. Heck, I doubt it tops 1 gram... Hence the fact that this is about 1/2" ahead of the CG has no effect on flight characteristics that I can detect.

I may have to hide the whole thing with red paint at some point, just to pretty up the undersides of the wings.

Nice mod with little weight added, I like it!
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Old Yesterday, 11:54 AM
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Quote:
Originally Posted by CorvetteC5 View Post
Interesting discussion on reinforcing the Gee Bee. Good to know about

I was wondering how the propeller from the UMX Pitts would fly the UMX Gee Bee so I installed one, as shown. I am quite happy with the gained efficiency. I had felt the need to fly at 60% and higher throttle with the GWS5030 for decent loops from level flight, quicker rolls, etc. The larger diameter of the prop from the Pitts let me drop this to right about 50% throttle with the same flight characteristics. Toward the end of the flight I did bump up the throttle closer to 55% to maintain loops as the battery voltage started to sag. The flight time was at least one minute longer with this prop; before my voltage monitor circuit killed the motor. I land dead stick onto grass This change is a keeper.

Please note that my Gee Bee has had the ESC replaced with a Plush 6A to eliminate the OCP, and has a Turnigy 1811-2900KV motor for greatly reduced noise.
This is very interesting, especially since I just updated to the GWS5030. Isn't that Pitts prop the same pitch as the original prop Eflite supplied? I did think the 5030 a little short in diameter to clear the big nose of the GeeBee, but I'm trusting by what I've read and made the switch...
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Old Yesterday, 01:57 PM
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The Gee Bee prop is 5.25" x 3.5", whereas the Pitts/Yak prop is 5.75" x 2.5" - so they're quite a bit different. The 5030 is a lot more efficient than the Gee Bee prop (at least on the 3000Kv motor), but the Pitts/Yak prop seems to be much improved. It's a far better match for the 3000Kv motor than the Gee Bee prop.

That said - 3000Kv/5043 combo really hauls tail on 2s in the Beast, Pitts, Sbach, and Yak. It's way, way faster than any of the other viable 2s UMX motor/prop combos in those airframes. In fact, it's within a couple MPH of the 2300Kv/5043 in the Sbach on 3s! (In the aforementioned airframes, the 2300Kv/5043 is the fastest UMX motor/prop combo that can be operated with reasonable reliability on 3s, using the newer 2s bl UMX bricks that have the upgraded 4.9A ESC.) Problem is, the Gee Bee came with an early version of the EFLU4864 brick that only has a 3A ESC. It can't even handle the Gee Bee prop reliably, so the 3000Kv/5043 on 2s isn't an option. However the current EFLU4864 brick handles the 3000Kv/5043 combo on 2s without hitting OCP.

Joel
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Last edited by turboparker; Yesterday at 03:10 PM. Reason: Clarification
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Old Yesterday, 02:17 PM
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Got a link for ordering a UMX Pitts prop?
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Old Yesterday, 02:31 PM
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Altbob,

HH sells replacement props for all of their UM/UMX planes, but the 5.75 x 2.5 is currently on backorder: http://www.horizonhobby.com/products...er-EFLUP575225

However, I'm not sure if the original brick with the 3A ESC will handle the 3000Kv/Pitts prop combo reliably. According to HH engineering, they pushed the current brick close to the limit with the 3000Kv/5,75" x 2.5" prop combo in the Pitts & Yak.

CorvetteC5,

What are you getting for current @ WOT on a freshly-charged pack with the Pitts prop? Also - how does the 1811-2900KV compare to the 3000Kv in terms of current requirement with a given prop? Based on your experience, do you think the original brick will handle the Pitts prop without hitting OCP @ WOT on a freshly-charged, low-IR pack?

Joel
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Old Today, 09:10 AM
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USA, CA, Chula Vista
Joined Sep 2004
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Quote:
Originally Posted by CorvetteC5 View Post
Interesting discussion on reinforcing the Gee Bee. Good to know about

I was wondering how the propeller from the UMX Pitts would fly the UMX Gee Bee so I installed one, as shown. I am quite happy with the gained efficiency. I had felt the need to fly at 60% and higher throttle with the GWS5030 for decent loops from level flight, quicker rolls, etc. The larger diameter of the prop from the Pitts let me drop this to right about 50% throttle with the same flight characteristics. Toward the end of the flight I did bump up the throttle closer to 55% to maintain loops as the battery voltage started to sag. The flight time was at least one minute longer with this prop; before my voltage monitor circuit killed the motor. I land dead stick onto grass This change is a keeper.

Please note that my Gee Bee has had the ESC replaced with a Plush 6A to eliminate the OCP, and has a Turnigy 1811-2900KV motor for greatly reduced noise.
I am really interested in the Turnigy 1811-2900kv motor as my Pitts motor just died and HH are refusing to replace it as plane was purchased in May of this year. New motor is $30. What mods were necessary for the Turnigy motor? Would the stock ESC work for this motor?
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