The forward portion of the rudder over the fin is still there just 2.25" shorter. There is still 1.75" of rudder remaining above the fin even after modification which should serve as an adequate counterbalance. I'm not sure aerodynamically what the change has done to the amount of force on the rudder but it could be possible that it has actually taken some load off due to not having to fight all of the coupling (pitch & roll) issues that used to exist? Somebody smarter than me would have to figure that one out. I am using a Hitech 5645 on the rudder with a 4-40 push rod. This servo has 133 oz. torque and also should be adequate.

Just wanted to let everyone know I flew my UCD for the first time Sunday. Awesome plane. I'm a newbie at advanced aerobatics, but this is a very stable plane that I immediately felt comfortable with. And what a floater! It doesn't want to land. I'm running an OS .91 Surpass with a 14x6 APC prop. If I went to a 15x6 or a 15x4, what differences would I see?

I sincerely doubt that the UCD was originally designed as a "balanced" rudder. More like 'It looked about right, and should sell a bunch'. If it had been designed correctly in the first place, do you think there would have been all of the cross coupling?
I fail to see how a closed loop has more torque than a single push rod . A closed loop may take some of the backlash out of the system. I think that you will find that torque is force*distance, unless you reduce the distance that the rudder is moving the torque will be the same. Just my 2 cents worth.

APC 15X4W @ 9800 will let you hover @ 1/2 throttle & pull out better.

Firstly, I don't see a great amount of coupling with my UCD. Overcontrolling the rudder will often cause unwanted pitching.
Secondly, I never said that using a pull-pull will give you more "torque". I just recommend it for the reason you mentioned (reduce backlash).
Lastly, True! Torque = Force * Distance. But an unbalanced control surface (cause by snipping off top of the leading edge of the rudder) vice a balanced control surface will require more "Force" to move an equal distance, thus requiring more Torque.

My UCD3D seems to have a good bit of coupling requiring aileron and elevator to hold...

However, a friend maidened his this past weekend with a YS-91 and a 15x6...

He said it has no coupling at all... he just flipped it over and bled in rudder and it held true... Watching him do them supported what he said... I didn't see him "catch" it in anyway.

An interesting point is that he said he was flying only on the low rates and balanced per the manual.

I have heard of others too having similar experiences.

I wonder how this can be other than perhaps there are some differnces in setup... maybe aileron differential, throw combinations, etc...

It's neat to see a mod that helps it for some, but I'd like to know why some are experiencing it badly and others midly or not at all...

Has anybody considered what the proper aileron neutral position should be with this plane? Maybe this is causing some of the coupling. I am going to enable the flapperon setting on my radio this weekend and try altering the neutral position with it to see if the coupling can be mixed out this way without causing unwanted pitch variations with speed.

Where do you have your CG set at?

The shortened rudder definitely helped my UCD a LOT with the coupling issue.

I had previously added a dorsal strake in front of the fin in an attempt to get more side area above the stab, which did help a bit, but the short rudder has had a much bigger effect.

Here's a pic of mine:

Typically, once the CG is set you set the aileron neutral by putting the plane in a vertical, power off dive. If the plane pulls to canopy, drop the ailerons, if it pushes to the gear, raise the ailerons.

Changing the neutal from the above setting may fix the KE problem but the plane will be out of trim.

My plane only has slight roll coupling is KE, wants to keep rolling to inverted. Easily mixed out.

sea157:
hroachen, supertiger, searchen and fixwing i love your all appoarch. ......

This plane Rocks.
Marc from RCU myself and others Sunday, had a nice day flying..
When I saw this plane fly WOW.
I really love this plane , I might have to sell all my Helli, and get back into full plane mod again...

Has anyone gotten one of the 46 versions yet? I have been around several of the 60-91 sized and really wasn't interested. Now, however, I am really interested.

Got it on order at the LHS but no word yet.

[QUOTE]Originally posted by geoharry
[B]Typically, once the CG is set you set the aileron neutral by putting the plane in a vertical, power off dive. If the plane pulls to canopy, drop the ailerons, if it pushes to the gear, raise the ailerons.

Changing the neutal from the above setting may fix the KE problem but the plane will be out of trim.

Geoharry,
Please correct me if I am wrong, but it seems to me what you stated above is incorrect.

If the ailerons are dropped, that causes more drag on bottom of wing and the plane will pitch toward the canopy. You will need to raise the ailerons to correct of pitching toward the canopy.

And if the ailerons are up higher that will great more drag on top of wing, and make the plane tuck toward the gear. To solve that problem you will need to lower the ailerons.

m.gramling,
your deductions from above terminology appears backwards. Drag would normally cause a tuck towards the drag, you describe the effect as reverse from that. Also, I don't think you can really talk about raising and lowering both ailerons very small amounts as creating drag, but rather as changing the wing incidence, which will bring the plane out of trim. Applying spoilerons or flapperons to the wing on a plane has different effects on different planes, all depending on tail moment length, CG, wingincidence placement, etc, etc. Most tail heavy planes (the way we like them the best) will tuck, as if the ailerons were used as elevons, a short tail moment plane much more so than a long t.m. plane like the UCD.
Hey, all testing is allowed here, so why not just go out there and do some flying, turning them aiilerons up and down with the knob on the TX, flipping it inverted, flying knife edge, seeing what it does, and report back here.
Most RC model planes, especially the purpose designed and built funfly planes like these will react different from plane to plane, engine to engine, set up to set up. The main thing is to just go out there and fly the snot out of it, playing with setting, CG, thrust angles, etc., that's what makes it fun.
DKjens

I keep seeing teasers for this 40 size UCD. It's in the toledo pictures, many people are talking about it, and I just opened the newest issue of MAN! and there it was!!! Does anyone have any idea when this thing will come out?!? Did Great Planes say anyting at toledo?

thanx,
matt

Were did you see the pic's?

This must of been answered , but did not see it.
What servo set up are you using and why?
What engines , so on so forth.
Thanks for your time..

whats the top speed of theese things with an os 91fx?

we don't fly the ucan at top speed we try to fly it as slow as possible and still do all the aerobatics so the 91fx is used for it's power and not speed.

o ya i know i was just wondering.

ZG77_OzZ

If you mean the original UCD

Standard servos all around except high torque on rudder, that's the minimum (what I have) you can go up from there.

I have a Magnum xls .91 (2 stroke) plenty of power and cheap ($150) or for more money try the Saito 100 (same power or less as .91 from what I've seen).

how much clearance is on the bird for the bigger props? can this bird hold an 18"?

Don't know off hand but my 15" prop is not even close to the ground. I can lift the tail high enough to get out of the hold-down with the engine running. I can measure but 18" should be fine.

I like the YS 110, it is coming out soon.
My Fury has a YS and its a great engine.
I probley will go with the 9202 , and a digital on the tail.
Did some reading on this, I am glade you replayed on what you have..
I like the hop up parts that Marc from RCU did to his plane...
His Reviw was helpful as well..