Len Todd

I set the CG in the middle of the spec range with the large E-Z Balancer. The nose wheel comes up off the ground when sitting on the pavement. If I put the canopy on, the nose wheel just barely stays on the ground. When landing into the wind, the plane wants to pop up in the air and bounce around as I try to get it to settle.

I am thinking I need to add more weight to the Nose. So, ... what is a good CG setting that actually works well? Or, ... Maybe I need more Down Elevator to offset the flaps. Any more DE seems a bit excessive.

And sorry, I did not get a chance to roll it over and see which way she goes when inverted. Still trying to get used to the thing. But checking the CG when inverted is the next goal. Not much flying time even with the wing tank. Just start to get comfortable going so fast and then the timer goes off and then got to think about landing.

ravill

My Feedback: (11)

Well, with the classic flash if you had too much flap or if the CG was at all on the rear side, it would porpoise really bad. Like REALLY bad. So, too much flap?

Ruizmilton

My Feedback: (29)

I use 232mm as the CG, 75mm landing flaps, about 2mm down elevator, make sure elevator trim on this setting is on a down attitude, hold nose up with elevator stick all the way to the stall, land on the mains always, make sure about the down elevator trim, otherwise plane could become airborne again, this because it is so light on the nose wheel that anything on runway (stones, bumps)can make nose jump on roll out

paulhat

Hi Len,

What CG measurement are you running at the moment?
The UF is naturally light on the nose wheel but not to the point where it sits on its tail. I would say that if its sitting on its tail a mistake in CG measurement has been made.
I would re- adjust to 225-230mm and see how that goes.

Paul.

Dave Wilshere

What is not said is what gear, what legs. The UF was designed with a main leg that trails quite some sitting in the ground. People chop and change gear without considering this. In the U.K. 98% use the stock gear and we don't see these issues.
Flying qualities and ground handling were based on the product as designed as a package.

Len Todd

Good Point Dave. I am using Prolink gear with trailing links. Guess this is where the Xicoy CG scale would come in handy. Eh?

I was really concerned about the light nose. I think I am going to move some components forward to get it to the point where I am confident it will at least stay nose down at least when sitting on the ground. Then I'll take a look at the CG again.

Guys, ... Thanks for the recommended CG and Flap to Elevator settings. They will give am a good point of reference to start from.

I did set the flaps up exactly like the manual's addendum. I was coming in on landing flap only cause there was a 20-25 mph crosswind. I know dumb eh? But, the winds have been horrible for weeks and it was time to fly.

I suspect the CG because of the light nose and the Down Elevator are the culprits. It was still ballooning up a small bit when the landing flaps were applied. Not a lot, but maybe too much with the winds we were experiencing. I am used to the Sprint, which is set up so that once it is on the ground, it stays on the ground. Sprint to UF is a big leap.

Canadian Man

My Feedback: (1)

My UF with prolink gear sits on tail with canopy off. Wont go there by itself but if I push tail down it will stay.
With Canopy on it will drop nose but it's still light.

Inverted takes a little stick to keep it going straight.
When flying on grass it's not an issue at all. Flying of pavement need to hold off the deck till it's slow enough.

Springbok Flyer

Hi Len,

My UF flies like the proverbial *****cat: cg 215mm from wing LE at fuselage joint with wheels down (Prolinks). Ailerons 10mm up and 12mm down with 5mm crow on full flap. Elevator is 13mm up and 15mm down, with down compensation for flap 2.5 and 5mm. Flap is 28mm take off and 75mm landing. I use 15% expo on elevator and 7.5% on ailerons. Rudder is 40mm both ways.

On my Xicoy cg balancer my cg position is 45mm in front of the main wheel axle position and the nosewheel is 815mm in front of the mains. The weight altering position is 1000mm in front of the mains. BTW I have a KT140 in it and no wingtanks, only the two saddles and the fuselage tank. I fly for 6 minutes from wheels up to wheels down. It weights 10.14kg dry.

Cheers,

Jan

scoeroo

My Feedback: (9)

Light on the nose wheel ....interesting
What about with all tanks full ?
What axel offset to the rear are you running ? ?

i3dm

My Feedback: (51)

sitting on the tail without canopy is the perfect CG for me to do long rolling manuvers
thats how i setup mine.

Dave Wilshere

Again...when people post, please give all the information like what gear/legs. With a CARF set and lots of trail, most would find that unflyable since that's another 25mm (inch) back...

i3dm

My Feedback: (51)

Mine is stock airtech struts and wheels.
we fly several this way with the CG - perfect.

Len Todd

The GC was initially set at 222 mm from the trailing edge. Today, I moved the batteries forward and I had a small weight in there in front of the steering servo that I also moved as far forward as possible. I fly with two 2s 2000 Mah LiPos for the Pbox and Gear and a 2700 Mah 3S LiFePo4 for the Turbine. So, ... all the batteries are light.

I now have a CG sitting at 28mm in front of the Main's axle centers. The plane will sit level w/o the canopy and the nose wheel will come down and stay down by itself, unless the plane is sitting on the tail, then it stays on the tail. But any time the tail is off the ground, the nose will come down by itself. This measures out to be a CG 248 mm from the trailing edge or 235 from the leading edge. Given that the Spec is 220-225mm from the trailing edge, per the Manual's addendum, the plane should now be nose heavy. If necessary, I can move can batteries back and set it as far back to 225 mm w/o any froggin' around.

Doubled up on the DEs when flaps are in. Will get measurements of the changes for both settings tomorrow. Ran out of time. Had to solve some elevator flutter on the Giant Extra. It looks to me like the servos are just plain worn out enough to cause some oscillations. Replaced the 193 oz-in with 333 oz-in servos. Hopefully the wind will die down tomorrow to try things out. Weather report said 40-50 mph gusts here today, ... again. Last night was out flying in 25-30 mph winds. But, ... I stuck to the planes that I knew were spot on. Even then, almost lost the Pitts in a crosswind when landing. PITA.

Len Todd

Is your 232mm measurement from the front or trailing edge?

Len Todd

There is less than 5 mm offset from the strut to the axle.

When the tanks are full, it is a little bit heavier on the nose. But not much. I need to get a Xicoy CG scale. Just need to figure out if I want to flip for the control surface attachments too.

Dave Wilshere

The UF balance is measured from the fuse/wing break line back! If if I understand what you have written above you are tail heavy. Talking about the balance from LE and TE is just confusing, 230mm back is what you want. There are pictures on the UF thread in several places.

if you have moved all the cells forward you must be forward if where you were!

Dave

Len Todd

Thanks Dave. I read the Addendum wrong. I interpreted it to be 220-225 from the back wing/fuse joint. So much for late night reading. I went back and reread the addendum and you are correct, as you already know. So, ...

At 235 mm back from the front wing/fuse joint, I am still a bit tail heavy. I can still move the second battery forward. Maybe that will get me to within spec. Maybe even go back to the 5700 Mah 2S LiPos for the turbine, if more weight is needed.

Once again, Thanks Dave for following thru on this thread.

Len Todd

Well the CG is now 222 mm from the front wing/fuse intersection. Just moved the second Rxer battery up in the nose. Given that the CG during the maiden and subsequent flight was > 1" rear of the designated spot, I guess I am lucky to still have the plane given the winds I flew it in. Also, the Plane sits nicely on the ground now.

I set the Flap DE to 3 degrees for Take-off Flaps and 6 degrees for Landing Flaps. I previously set the Flaps themselves per the spec. Probably stick with the Landing Flaps for a while as 3 3/4" seems like a lot of Flap. We have 3800' of runway.

Again, Thanks Dave!

Ruizmilton

My Feedback: (29)

IMPORTANT! This is ​​​​​​​from the front edge of the wing center section, NOT the leading edge at the wing/fuselage joint,

ravill

My Feedback: (11)

Yeah, my classic flash HATED being tail heavy.

Len Todd

Thanks for all the help guys! I think I have it correct now. Will double check it when the Xicoy CG gear gets hear early next week. It will give me a chance to learn how to use the scale.

Dave Wilshere

Don't be scared to adjust it to suit your thumbs now, you are in the ball park, but 222mm may be a little nose heavy for nice aeros.
Flap, even with a long strip you still want drag, lift will just lead to floaty, skippy landings. Turbine idle thrust will have a huge affect on this, but for me...more drag the better.

Enjoy

Dave Wilshere

Don't be scared to adjust it to suit your thumbs, now you are in the ball park, but 222mm may be a little nose heavy for nice aeros.
Flap, even with a long strip you still want drag, lift will just lead to floaty, skippy landings. Turbine idle thrust will have a huge affect on this, but for me...more drag the better.

Enjoy

Springbok Flyer

222 is not too nose heavy - it will do any aero you wish.... but I agree get more drag on those flaps.