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Happy New Year Richard!
You stated your weight is reduced with all these mods you did, well, what is is?

Has any one every thought that the horizontal stab and rudder might be too small, some body just built a GB QED up Washington and they stated they made the fin and rudder bigger and it flew great.http://www.rcuniverse.com/forum/atta...mentid=1952982

Isen"t that a good looking airplane?

Quote:

Originally Posted by 40GeeBee (Post 11697972)

Happy New Year Richard!
You stated your weight is reduced with all these mods you did, well, what is is?

Happy New Year Paul!

The ready to fly weight is 14.7 kg. However, as I now must add a substantial amount of nose weight, all the weight savings is moot (i.e. a waste of time and energy other than having learned even more about this fascinating airplane :)
My CG, although the same as before with the 3W157, is too far aft for stable flight.
I must add nose weight until I can again achieve stability.
I do not not know what the final weight additions will total.

Quote:

Originally Posted by RichardGee (Post 11697728)

Jaz,
Either I was flying your plane… or you were flying mine on Sunday, as I posted 3 horrendous flights with my “newly redesigned and lighter and more scale Gee Bee”…

What you describe is identical in every respect to what I experienced on Sunday, as well as on MANY other previous flights prior to my recent changes. My plane handled exactly the same as when I had switched from a DA150 to a DA100 (in my first GB) and the CG was at 80mm.
What is worse (for me) is that all the work I had to do to compensate for the removal of nearly 4 pounds of engine in the nose (3W157 to a DA120), paid NO dividends – the handling actually went in the opposite direction! Disappointing?? You bet!!

Post mortem, it has been suggested that perhaps what WAS the accepted CG (73mm – 76mm) is no longer valid on my aircraft, as the nose has grown in length by 5cm (scale cowl). This makes sense and is something I will have to correct and test.
However, as you did not lengthen your Gee Bee, I have to assume you are balancing it within the accepted “norm?” If so, I can only attribute the ill-handling to what I have always suspected on this airplane, and that is the twisted vertical fin. It isn’t so much the fact that the fin LE is offset left (for yaw to the right); it is more that the fin has an airfoil that imposes the exact opposite effect of the offset. Stand over the tail and look down at it and you will see what I mean. With the unwanted and non-scale addition of an airfoil, the vertical fin’s effect on the aircraft is totally speed-dependent and (IMHO) results in an UN trimmable flying thing (like your shopping cart analogy).

That said, there ARE pilots who have managed to program the perfect level of rudder mixing with the throttle such that they have been able to neutralize the fin’s “enigmatic” affects :) This requires patience, many flights, and the ability to analyze exactly what is happening with the aircraft’s yaw at every speed; remembering what you want to change in the pits, re-testing, WHILE keeping your airplane in one piece throughout the trial and error testing flights… no small feat!!

However, even WITH the perfect amount of mix, what then results is a Gee Bee which is constantly exhibiting instability in pitch, as rudder deflections create negative pitch reactions (nose down). I was once sure this was simply an aerodynamic anomaly unique to the Gee Bee… but have come to believe this is actually gyroscopic procession – exactly what happens with cyclic inputs on a helicopter – caused by the Gee Bee’s short tail moment’s lack of leverage.

- Gyroscopic procession is the imposition of force 90 degrees from the axis of force, which is why changes in yaw result in the nose pitching down. I can only assume that IF our engines were spinning clockwise, the affect would be the opposite, with yaw deflections creating a nose-up reaction. And that, boys and girls, is about the extent of my aerodynamic understanding! :)

Since you stated that you have re-checked everything, what is your current CG? And how are you checking it? Do you have something accurate like an EZ Balancer?

Thanks Richard, there sure is some real info to think about in all this!

Looking at the flight video it visually appears much better than the first flight but under full throttle only with maximum right rudder mix offset as well as my own stick adjustments. It is when I brought it back to half to 2/3 throttle that it appears to lose a lot of its tracking. Whichever way it was a real handful that did not feel right.

The motor dome offset is the only thing that has not been checked so when I get a little bit of time I will pull it apart and check it.

I was getting a little anxious with it during the latter part of the flight due to a few times the engine sounded like it momentarily faltered or dropped RPM. It only seemed to be when at half throttle not under acceleration so will have to look into that as well.

When I get the video cut into a watchable point will post it.

Oh all up this Gee Bee weighs 16.3kg

http://www.rcuniverse.com/forum/atta...mentid=1953008
http://www.rcuniverse.com/forum/atta...mentid=1953007

Here it is, my second attempt to tame the beast.

Pity about the landing which caught me out!

Jaz

https://vimeo.com/83117444

Quote:

Originally Posted by 40GeeBee (Post 11697986)

My 70" 30cc R2 has a much bigger than scale horizontal stab and it flies like a trainer compared to the CARF model. though if I had the choice I would prefer it would be more scale like the big R2.

http://www.rcuniverse.com/forum/atta...mentid=1953040
http://www.rcuniverse.com/forum/atta...mentid=1953042

Just an observation, but it looks like it has left thrust, or needs more right thrust. It appears to be yawing left all the time evidenced by it's responses when knife-edged.

Well, here is the maiden of my “new and improved and lighter DA120 powered Gee Bee”…
It now has a scale cowl, which is 2 inches longer and helped in balancing with the diminutive and light DA120. There is certainly NO shortage of power, as most of this flight was at part throttle. IT also has Zimmermann canisters, which really help the DA to breath.

Directional stability was about as bad as I have ever experienced with the plane :confused:

Subsequent flights with a much more forward CG also proved to be equally disappointing. It is possible my propeller – a Mejlik 29x10S – is creating too much disturbance around the tail and causing much of the directional instability. I plan to try a Menz 26x14… but first need to find and BUY one :-)

My landing speaks for itself - no harm done, except to the ego…

Just when you think you have this airplane under your thumb... it can and will rise up and bite ya!! :mad:

http://www.youtube.com/watch?v=wszPO_S4ovQ

Wow Richard,

that plane looks like it flies like mine, good job on staying on top of it. Let us all know how you go sorting it out. One thing for sure it sure has plenty of go-go. It looks no different in performance to any of the bigger engined Gee Bee's that come up on the videos.

I pulled mine apart a few days ago and checked the engine offset. The motor dome is about 30deg out with not only right but a bit of up thrust as well. Am going to get a new motor dome and dial it in with a digital angle meter.

Jaz

Quote:

Originally Posted by kittykatjaz (Post 11705496)

Thanks Jaz. Before using my new motor dome, I checked the angles with a digital incidence meter to make sure I was installing the dome with ONLY right thrust and no down thrust. I found the factory markings (what you would normally use to line up the "top" of the dome with the fuselage top panel line), to be OFF by about 20 degrees. I am very confident mine has only right thrust via the dome. I am hopeful a completely different prop will have the desired affects... I also have a trusty 3W157 to go back to IF my little experiment proves to be a bust :cool:

I simply LOVE the plane too much to ever give up on it... but I must admit that since my first flight with a CARF Gee Bee in February of 2009, I have waved the white flag of surrender MANY times :D;)

Hi Richard,
I been checking all these videos and I am coming to the conclusslion that all these models are being landed to slow, this is not a floating aircraft it has to be flown into to the ground. Watch Delmar when he landed his airplane, he was coming in hot. That is what happened on your last video, you were trying to float this airplane in and it is no a floater, as soon as the wheels touch down they acts like a brake and over goes the airplane! I saw Delmar fly this airplane about 15 times and he never flip it on its back. You can make this airplane as light as you can and that problem will always be there.
Paul Steiner

Here my latest flight video from season 2013, I love the handling of the plane**

Do not forget, you have to fly it all the time...

http://www.youtube.com/watch?v=cRU0jDBHXtQ

Quote:

Originally Posted by 40GeeBee (Post 11706869)

Paul,
In general, I agree with you. However, what Delmar does with the full scale, and what we do landing the model are two very different experiences. I too witnessed Delmar fly the Gee Bee R2 replica many times from 1994 in Watsonville until his last U.S. flight in Visalia, CA. I am well-aware of his experience with aileron reversal on landing #6 when he slowed the aircraft and attempted to 3 point it.
When Delmar wheel landed this plane, he did so at a minimum of 100 mph. The aircraft would use up about a quarter mile of runway to execute a full-stop landing, or about 1320 feet. One third of that distance is 435 feet.

Most of us are NOT good enough to set this plane down on the numbers and then use up most a 600 foot runway getting it slowed down! To do so requires such a high rate of speed on landing that the slightest deviation from going straight ahead WILL result in a ground loop, dragging a wing tip, or a tumble. Certainly there are exceptions when one of us is lucky enough to execute everything perfectly, but frankly, I am NOT that good.
Grass is FAR more forgiving of directional deviations on take off and especially in landing, as well as supressing the landing speed and roll-out by at least 50%.
I have landed this plane many times on grass, asphalt and now our new field's Geotek mat runway and I can tell you that Geotek is the most unforgiving of the 3

So, I agree with you in principle on the problem of getting too slow - and this is something I always fight, but it is a natural tendency when landing on a hard surface runway.

IF you would like to come out and show me how its done, you are welcome to take the sticks!!

Quote:

Originally Posted by 40GeeBee (Post 11706869)

Hi Paul,

Videos can be quite deceiving with the actual speed the plane is travelling at. Just watch any car race on TV compared to seeing it live. On the last video I posted, the speeds I was coming in was waaaay higher than any other plane that I fly. It was quite surprising to see in the video how much slower it looks. Unfortunately my strip is surrounded by trees, the approach from the left where it is level has tall trees, the approach from the right has tall trees on top of a hill. So on top of the high approach speed I have to drop quickly, attempt to level off then get back onto the strip before running off the end into the scrub. In reality I should of gone around again. It was a difficult approach especially with that other gas plane buzzing around resulting in me not being able to hear the Gee Bee's engine and I was starting to get a little anxious with everything going on. But that's the game we play when flying these aircraft.

This plane is one hell of a handful when the higher speeds start to wash off and the elevator quickly starts to lose its effectiveness, more so if the setup is not perfect which mine is not yet at. If you are lucky enough to get everything perfect or are the best pilot in the world then it looks easy but god help you if you are outside that fine line of perfection in both skills and Gee Bee setup.

Jaz

Great flights Hannes and the Evolution sounds like its running without a hitch...any issues on the engine?
Good Job Man:cool:

Thank you!!

The engine runs great, love it**

Seeing light at the end if the tunnel

http://www.youtube.com/watch?v=k0xeIccyKhc Yesterday's second flight... I think I have this angry little airplane just about under control, resulting in a happy Gee Bee and a happy pilot ;)

http://www.youtube.com/watch?v=k0xeIccyKhc

What did you do that improved it so much?

Quote:

Originally Posted by Lifer (Post 11715479)

What did you do that improved it so much?

Reducing weight by 10% was an improvement, but not quite as much as I would have thought. However, where I really went WRONG was my initial prop choice... a Mejzlik 29x10S. This prop was wonderful when the DA120 was on the nose of a slow, draggy, LONG, 146" span Hempel Decathlon, but a disaster on a fast, short-coupled, tiny tail-feathered Gee Bee. The gyroscopic precession effects of that huge prop were creating havoc with directional stability as the reaction to pitch and yaw corrections were directionally 90 degrees ahead of the directional change. In flight, the airplane felt UNTRIMMABLE - and it WAS:(
Switching to a Mejzlik 26x14TH reduced the GP affects by a factor of 10. Combined with some throttle / rudder and aileron / rudder mixing, the airplane is MUCH-improved.

Although it should not be necessary to mix rudder with aileron, I am convinced that engine dome right thrust is excessive for a DA120 and so the airplane is fighting another dynamic that can be compensated for with rudder, but only corrected by reducing engine right thrust. I CAN do this, but then of course my prop shaft no longer perfectly aligns with the front of the dummy radial... .and WHAT is more important? A good LOOKING Gee Bee or a good FLYING Gee Bee?:cool:

Of course, the BEST thing to do - to get both - is simply replace the DA120 with an Evo 7 (like Hannes) and completely re-re-re-do ALL my internal modifications for the resultant CG shift... then I can have looks, sound, AND performance!

I suppose, however, to truly LOVE this plane, one must have a personality similar to Delmar's.... like Delmar, "I get bored EASILY and have to get in and MIX IT UP!" Which is why I have flown this plane with: DA100, DA120, DA150 and 3W157CS; CGs from 66mm to 80mm from the leading edge; Props of every size; two elevator servos, one elevator servo, with and w/o a gryo; long gear, short gear; 31 pounds up to 36 pounds; ... and I cannot say with certainly that I have in fact arrived at PERFECTION... perhaps that's a good thing, as perfection can be BORING:D

I have never experienced perfection. Perhaps in the next life.....

I have been flying the little Gee Bee R-2 that Great Planes marketed a while ago. Many, many flights and no damage. Lower pitched props so the engine can wind up, plus it acts as an airbrake when idled. Also, I have set up a down elevator-to-flap mix, without the flaps, of course. For me, an airplane that has a tendency to dive at idle, easily overcome with a little up-stick pressure held constantly, makes for a better landing. Holding down elevator seems un-natural, but pulling a variable amount of up to control the glideslope seems easy and natural.

It's not in my budget to get the CARF R-2, yet. I sure appreciate you sharing your experience, and learning curve in any case! One of these days......