Airbusdriver74

Hi Mike,

wow! Great video. Amazing how you fly the GeeBee. On the photo it looks like you have CARF's latest version, is that right? Have you flown it without the I-gyro as well? I'm considering to install one as well, but not everybody here is enthusiastic about gyro's.

stefan

RichardGee

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The only area in which I found the gyro very helpful was on take off. However, this could be more ME than any issues with a gyro.
I generally DO NOT like the "feel" of a plane flying with a 3-axis gyro... I feel "disconnected"
IF taking off and landing on grass, I wouldn't even consider adding a gyro, but for asphalt or other hard surface, it can help with ground handling.

Airbusdriver74

Thanks for sharing your experience richard

EQ1

Greetings!
Being an enthusiast concerning the R2 I've read this thread from post #1. I've got my own CARF R2 and was facing similar problems like others. Well, being an aerodynamicist I have some assumption why this baby behaves so badly. Therefore, I am planning to do some thorough flow simulations along with flight mechanic calculations in order to confirm my theory in a scientific way and to improve the flight characteristics of this aircraft based upon this.

Well, maybe someone asked himself what the cause of the crash of Hannes' R2 was. Of course, he is an experienced pilot and flew his aircraft quite a while. As I said, mine did exactly the same and I think I know the cause. In order to make the results even more scientifically valid, it would be very helpful, if as much as possible people from this forum could provide me with their TOW and RPM with prop size. I will then compile all the information and post the results here along with my aerodynamic findings. What do you think? Anyone interested?

Have a nice day!
Olaf

RichardGee

My Feedback: (156)

Olaf,
As you may already know, the Gee Bee R models were designed and tested (in a wind tunnel) by Pete Miller back in 1931. He was an aeronautical engineer and his Gee Bee design was one of the first aircraft to be modeled and then tested in a wind tunnel. His calculations were extremely accurate as he predicted the top speed to be 298 mph... and the full scale Gee Bee R1 was clocked at just over 296 mph. There are many factors about the design of this racing plane that I do not understand, beyond the obviously exaggerated outline of the massive fuselage and short wing and tail. As Delmar Benjamin experienced, it is unstable in pitch and yaw, yet this cannot be blamed on an improper CG, as the "perfect" CG still renders the airplane unstable... he described the airplane's stability as "divergent." I believe the CARF model has even more problems than the full scale Gee Bee owing to an inaccurate outline of the vertical fin, however, I understand this has been corrected in the newly revised kit..?
The model behaves very poorly if using a large diameter, low pitch prop.. again, I am do not fully understand why, but have theorized about gyroscopic effects and P-factor.
The model does not require more than 100cc to perform well, yet requires substantial nose weight to balance, hence the recommendation of a 150cc sized engine.
That said, engines in that size range (up to the Moki 250) are said to be "over-powering" or "over-speeding" the model.... but you couldn't prove that by me. I find the performance on a 150cc to be ideal.
The videos I have seen of the Moki powered Gee Bee's appear to be powered properly, but I can only imagine the landing demands by increasing nose weight by 50%+!

I encourage you to explore the aerodynamics of this aircraft and share your findings on this blog. I've no doubt most Gee Bee fans would be interested in learning more...

Lifer

My Feedback: (1)

It's been a while since I have studied aerodynamics, but I believe the symptoms of the Gee Bee R-2 is a "low polar moment of inertia." Check it out and see if it matches your experience.

EQ1

Richard,
thanks for your interest and encouragement. Yes, I know about the history, but my interest is concerning behaviour, not performance. And I have never seen any statement about predictions about that. So, I could of course tell you about my assumptions right now, but this would render all results to something arbitrary, because every information coming in after that would be influenced by my statements. Again, please let me know about your specific configurations, i.e. TOW and prop/revs, maybe the number of flights or statements about flight behaviour. Definitely, I will give anything of my findings back. I am interested to see this airplane flying beautyfully. And this is just an aircraft and physics do neither lie nor change ;-)

@Lifer
Well, the polar moment of inertia is a structural/mechanical thing, which really does not apply as being low in the case of the R2. The diameter of the fuselage is really large, i.e. moreover the pmi. It is the resistance against torsion.

Hope to discuss things further with you.

Have a nice day
Olaf

Lifer

My Feedback: (1)

Actually, it's the effect of the design on stability characteristics, unless things have changed over the last 30 years or so.

EQ1

Are you talking about structure/aerodynamic interactions? I doubt.

Shall I? Maybe. (Longitudinal) Stability of an aircraft means that it creates a counteracting moment to a disturbance of the AOA. Increased AOA, e.g. due to gusts, will lead to a nose-up moment. A stable aircraft would react with a nose-down moment in order to decrease the disturbance. Thus it is stable. Stability depends on several things, like the lift derivative of the wing and the vertical tail, as well as the fuselage and the engine (thrust line). You can setup an equation for all the components for the overall moment, build the derivative d_cm/d_alpha and try to find the c.g. where this derivative is negative (counteracting) enough (around -0.8 to -1.0 per radian). But: This is OK for the R2, this is not the culprit.

Lifer

My Feedback: (1)

Actually, I think that's what I just said, in about 20 words. I believe that you need to always get in the last word, so go ahead. I'm not in RCU in order to argue and try to prove something, I'm here for enjoyment and to learn. Fire away, I'll graciously give you the final word!

EQ1

O yeah, thanks for that. May I remind you that you never ever gave any valid information? Just buzzing words ... And yes, listen to me and you will learn ;-)

EQ1

Ok guys (and possiblly ladies). This kind of conversation was not my intention. Just had the feeling to get things right. If still someone is interested I will stay to my promise.

RichardGee

My Feedback: (156)

I have flown the original CARF Gee Bee at 36 pounds, 157cc, spinning 28x14 to a 32x10. The 32x10 created major handling problems. The aircraft would not track straight at any speed.
I have flown the CARF Gee Bee at 30 pounds, 120cc, spinning 26x14 to 29x10S. The 29x10S handled very poorly; very similar to the 32x10.
I have seen the plane flown at up to 40 pounds with seemingly no ill effects other than a slightly higher landing speed.

Large diameter, low pitch props tend to make the airplane "crab".... it constantly wants to travel slightly sideways for every 10 feet forward. This tends to be speed-dependent, as the rudder will be trimmed for straight flight at full throttle, but the trim changes when the airplane is slowed. Smaller diameter, bigger pitch props help eliminate this.

At 30 pounds the Gee Bee becomes very "floaty" on landing when in ground effect. However, the airplane still stalls very suddenly when slowed too much. When it stalls, it simply sinks and the elevator becomes totally ineffective.

Every Gee Bee R2 I have flown has a unique rudder idiosyncrasy in that rudder deflection causes the nose to pitch down. This obviously creates problems when lining up on final, yet trying to maintain a steady glide path.
After 60+ flights on two CARF Gee Bees, I never felt as though I was in complete control of the airplane.
However, I never crashed the airplane as a result.

EQ1

Thank you very much Richard, this is a lot of really helpful information. Just a question: did you observe any tendency of the a.c. in a turn, lets say 45 degrees or more, to roll more than expected?

RichardGee

My Feedback: (156)

Not totally sure what you are asking, but I can say that in a 90 degree bank, the Gee Bee would appear to be "skidding"... meaning, it was drifting away from the point about which it was turning, almost as if the wings were not "biting" like one would expect. The faster the turn, the more up elevator would be required to maintain the arc of the turn and not allow the plane to drift away from the center of the arc. This is totally unlike most other aircraft that tend to stay in a bank and turn as long as elevator is being applied. If the Gee Bee was placed in knife edge, it would pull towards the gear, such that UP elevator was required to maintain heading. This mimics what the plane does when banked over and turning.

EQ1

Hm, yep, something like that. Ouch, it is difficult to ask questions without implying the answer. Well, did you observe any difference in banking behaviour dependend on the TOW? (I almost gave away my assumptions ...)

RichardGee

My Feedback: (156)

I cannot be absolutely certain as this was never a characteristic I was acutely observing between light and heavy Gee Bee's, but if memory serves me correctly, yes, the heavier the plane, the more it wanted to pull towards the gear in a 90 degree bank.

mikepq

My Feedback: (6)

I have the older version. The first 1/2 of my maiden flight was with no gyro.. as soon as I dialed in some gain it instantly made it very stable. I now have 9 flights with a Radar Gun Still recording at 132.9 MPH top speed.. I am trying to get faster, but I don't think it's going to .. Super fun to do full throttle low passes.. LOL!!

EQ1

Mike, the gyro was applied to the ailerons or the elevator? What was your TOW?

Thanks
Olaf

dirtydingus

Hey guys, anyone have a good clear picture of the graphics that go on the cowl of the Gee Bee? (7-11). Repainting my GB in the original paint scheme and would like to get the graphics as accurate as possible.
Thanks
Jim

mikepq

My Feedback: (6)

My Gyro is set up for all 3 Axis.. Rudder, Elevator, and Ailerons... I do not know that exact weight, but the CG is sitting at 74mm and it works good there.
19 flights and counting.

mikepq

My Feedback: (6)

https://www.google.com/search?q=Gee+...0R2%20graphics


Jim, check out this site for the graphics.

Doesn't Kirby graphics do a kit for the R-2?

rexmexx

Hi Stefan,

is there any news about your R2? Have you flown it so far? I am rebuilding my very old Fiberclassics Version and havent flown it for years.
If you like you can also reply via PM in german.

Is there maybe anybody else who has flown a newly built R2?


BR

Airbusdriver74

Hi Br

My GeeBee is still waiting for its maiden flight. I'm waiting till the solo shot 3 camera is delivered to me but they keep on postponing the release of it. When I have that camera I can track the entire flight which might help me making adjustments after looking back the video.
Do you still have an original fiberclassics? COOL!!!
Of course when I made progress with mine I'll keep you updated here. At the moment I'm considering installing a multiplex wingstabi in it.....
Stefan

40GeeBee

Did they remove the off set in the rudder that they had in old version? I have been going to remove that out of mine, which I haven't done yet, just siting in the middle of my garage for the last 5 years!