TOYMAKER

My Feedback: (6)

OK for all you trim experts. I am not a bipe expert sooooo please chime in if you can.

My GP Ultimate w/DL 50 w/Vess 22a prop and balance at 1" in front of rear holddown bolt on top with wings off. On initial flight had to have several clicks of left aileron and about 6 clicks of down trim. It also needed a little side thrust added. I added about 1 1/2 degree downthrust and 1 degree side thrust and then flew several flights. Side thurst OK and up/down thrust seems OK on level flight when powering off it will fly level till it loses flying speed and uplines are good. I cant explain the aileron trim as wings seem to be unwarped. Here is my delima. On inverted segments especially on a 45 up line it wants to point the nose up even higher however on level inverted flight the plane requires a touch of down. Invert snaps are very quick as compared to upright and have a tendancy to over rotate.

The incidences are thus: Engine -1.5 degree to (stab +.5 degree at leading edge). Top wing -.5 degree, Bottom wing 0 degree. wings relative to stab or thrust line
AUW is 15lbs 2 oz.

Does this sound indicative of being tail heavy(my first inclination). Would reflexing the ailerons up/down help with some of these trim issues? It does pull to the belly on knife edge and wants to roll with the rudder. Even with the down thrust I still have to carry a noticable amount of down trim.

Thanks

Wayne

nitro wing

My Feedback: (1)

You may want to bring the upper down to - 1,maybe -1.5.
This is a just a shot in the dark,others may have better ideas.
I would asume that the stab and bottom should be 0.
Leave the engine thrust until you can correct the other behaviour.

gadix

My Feedback: (2)

i had the same problem on GP pitts!

align the engine as counter to the way you see/feel the aircraft pulls - nothing more you can do there
**** you must akign bottom wing to rear stab and top wing to bottom one accordingly!!!!!
use a incedence meter to make it accurate.

good luck

TOYMAKER

My Feedback: (6)

It is rather difficult to change the incidence on this airplane unfortunately. If we establish the bottom wing as zero then the stab is +.5 at leading edge, top wing is -.5 and engine thrust is -1.5.

I'm still leaning toward a more forward c.g.

Wayne

nitro wing

My Feedback: (1)

The bottom wing should shim easily to match the stab?
The stab is mounted permanent or is removable? 0.5 0r 1.0 degrees can be a huge adjustment.
Hope it can be worked out.The CG is easiest to adjust.
How about aileron travel? are they in sync? No droop on any? Measure in degrees,each one.
How does the plane behave in a long clean entered dowline,without power?

Tired Old Man

My Feedback: (1)

It's tail heavy. The amount of down trim required in the beginning indicated that. The pitching up more when inverted verified it. That down trim became up trim when inverted, pushing the tail down... Move the cg forward about 1/4" to start, and adjust until it cleans up. The added down thrust is a bit on the heavy side and may have created a pitching moment with the addition of engine thrust. More than 1 degree total would have been the high side for down thrust. 1/2 of a degree would have been more in line with what might have been needed. This is something I would change back before changing the cg. Side thrust is likely just fine.

The bottom wing incidence is fine. The horizontal stab incidence should match the bottom wing. The top wing anywhere from negative 1/2 to 1-1.2 degrees is good.

For the roll check to see that the bottom wing is dead level with the fuselage and that the span between the wings is equal-equal at the leading and trailing edges for the entire span. If you are running a negative top incidence allow for the difference in that space between the leading and trailing edge. The leading edge will have less space than the trailing by about 1/8".

Performance bipes couple in both pitch and yaw. Nothing you can do to avoid it. CG location effects the amount in either direction. You're answer here is in using transmitter mixes or get real good at hand flying the couples in knife edge and rudder intensive maneuvers.

gadix

My Feedback: (2)

i found it easy to do the incedence:

1. level the AP on a stand - use an eye bubble on the horizontal stab
2. attached the bottom wing - see waht the difference from the stab. - to correct u can use shim under the wing bolts or make the wing locking wood pin holes bigger so you can "wabble" the wing to get the correct position - this is for a one fix wing! for a 2 parts wing it is much easier just enlarge the pin whol;es to getthe correct incedence
3. to align the TOP W to the lower one, use shims onder the 2 stabs and enlarge the locking screw hole, this way u can "play" with wing all arround to get the most correct position to the bottom one.

hope it helps

TOYMAKER

My Feedback: (6)

After reviewing the answers and thinking about it last night I believe I will take out some of the down thrust. Increase the lower wing incidence +.5 degree to get it even with the stab. Fixing the lower wing is just a matter of shimming the trailing edge. This will give me about -1. degree on the top wing and zero on stab and lower wing then if its still to sensative I can move the c.g.

Thanks for the responses.

BTW the DL50 has been about as perfect a running engine as I could ask for. Solid as a rock and after 1.5 gal. it has settled in nicely. No burble on midrange and throttles up nicely on the Vess 22A . I may go to the 23A after some more run time and after I switch to synthetic oil.

Smooth Flying...

Wayne

greyfoxx

Say Toymaker!

I'm watching your post with a great deal of interest seeing as how I'm ready to check the CG on my new Great Planes Ultimate with a Copperhead Venom 45cc engine on the front. I thought that based upon a post in an earlier forum, I too would start with the CG at 1 inch in front of thecenter of the rear bolt on the cabane, using the wood carrying handle per the instructions on that post. I sounds like I might want to move that CG forward perhaps 3/16 to 1/4 of an inch, at least for the first few flights and until I get a good feel for the plane (my first bipe and gas powered model).

One thing I have learned in life is that, "Experience is a hard teacher. She always gives the test first, and the lesson some time later!"

Thanks,

Phillip

gadix

My Feedback: (2)

"Experience is a hard teacher. She always gives the test first, and the lesson some time later!"
OH YEH!!!
and sometime it just cost lots of $$$$$$$
HA

greyfoxx

If we're lucky, it will only cost us $$$$$!! Only if we're lucky GADIX.

Phillip

Tired Old Man

My Feedback: (1)

The engine thrust line was an easy flight check. If the nose did not pitch up or down with the addition of power the engine vertical thrust line was correct. If the nose pitches down with added power and up when power is removed then it would have too much down thrust. The opposite for up thrust.

That was one of the reasons for the cg call. Add the zooming upward when rolled inverted and you have everything you need to make the call for a very tail heavy plane. Been there with a few of my own.

Unequal decalage with a bipes wings will always generate a roll. Too bad it's not available anymore but Harry Higley wrote and published a book called "Bipes" quite a few years ago. What a wonderful information source for correctly setting up large and small biplanes.

TOYMAKER

My Feedback: (6)

Thats where I started with the balance. I doesn't fly like its too tail heavy or at least I have been carefull enough to be aware of it at all times. It slows down quickly and needs power on the landing. It doesn't land like its too tail heavy. But a cg change is the easiest thing to work with at this point. I just got a note from Todd Blose (accomplished FAI and IMAC competitor) and he said the Ultimates like to fly with -1 to -1.5 degrees in the top wing. He said try that first and then see if the down thrust is OK.

I'll keep everyone posted as soon as I can put up another flight

Wayne

3DAP

I have a Aeroworks 27% Ultimate and started out tail heavy and had a few other issues as well. After talking with Pat Roy about it, I got my incidences at .5 to -.5 on wings as he recommended and got cg so level flight was hands off and inverted flight required a touch of down. In a forty five degree upline Bipe would hold its heading with out much down at all. Once I got all that dialed in I programmed in roll and pitch coupling (back stick and opposite aileron) on left and right passes. Now knife edge slices thru the sky with ease. Thankx for the help Surfer


3DAP

nitro wing

My Feedback: (1)

My reasoning for Incidences stemmed from flights of an EF tak 54.
I had 2 degrees positive incidence in the stab.
This caused quite a pitch down on maiden,took 4-5 clicks up to correct,but the plane was squirrely and a Devil to fly cleanly,especially in 3D and aerobatics
Once I had the stabs fixed I could concentrate on CG adjustments.Its pretty good now.

Tired Old Man

My Feedback: (1)

And all that time I thought I was giving him some great advice developed from the accumulated experience of about 30 bipes in building an set up brought forward from an original Andrews Aeromaster to present day muscle bipes. I never realized that a lack of personal competition experience negated all the rest.

Seems I wasted both of our time.

nitro wing

My Feedback: (1)

You've had 30 Bipes?Have you had a chance to fly or play with a BME Pitts Challenger?
I cant find much info on it at all.

Tired Old Man

My Feedback: (1)

Haven't done the BME version. The Challenger Pitts (Indy products, pre-Horizon) is pretty much the same plane as the original Oracle Pitts. Pitts fuselage with Ultimate wings. Flys like a Stinker but lighter. Wild and crazy aerobatics but not designed for 3d. A little better roll precision than a straight Pitts. The bigger they get the better they are.

In about 38 years of rc you get the chance to do a bunch of bipes if they're you're thing. I've always had a fondness for bipes. They do some things in a manner no other plane can. Tumbles being one of them if they are heavy enough.

TOYMAKER

My Feedback: (6)

Pat,

Please dont take my comments wrong. I have competed in pattern competition for many years and ha many hours of trimming mono planes. I do know what c/g can do and have concidered your thoughts on that. I do also know that wing incidence on these bipes is very important especially the Ultimate an area I have limited knowldge. Todd Blose info is also valubale too as he has had several Ultimates and they all flew well. The incidences are obviously off on my plane and I will correct that and check the c/g also. My first inclination was the c/g. And through discussion with several people on and off this list the incidences seem to be an issue also.

I truely appreciate your comments and hope you continue to chime in.

Cheers....

Wayne

TOYMAKER

My Feedback: (6)

OK here is what I have done and how it has worked out. Original setup out of the box was this: Stab +.5 degree, bottom wing zero, top wing -.5 degree I then added 1.5 down thrust. to counteract the down elevator trim. This did not work.

Then...

First attempt I set the bottom wing zero/zero to stab thus giving me zero stab, zero bottom wing and -1 degree top wing. Went and flew. It was better on the knife edge and half the down trim went away.

Next I took out half the down thrust as I was still getting a pull to the belly on up line. And it still had a slight pull to belly.

I went home and took out all the down thrust and left it at stock setup except for an addtional degress of side thrust. I added another -.5 degree on the top wing and moved the c/g forward .25 inch. So curent setup is zero/zero stab and lower wing, -1.5 degree on top wing. This took out all the down trim and I now have a level elevator. The up lines are near perfect and the 45 degree inverted up line is now locked in. It takes a some down elevator to fly level inverted. HOWEVER it now will not flat spin like it did before. So I am going to set the c/g back to where I originally had it. I will have to report back on this after I change it back.

So it seems getting the wings all in the correct incidence has helped and corrected my issues. I had to quit flying early toady as on of the stock DL motor mounts broke. I should have replaced them on installation but according to Bob at DLUSA he said they should be good when mounted properly. Perhaps shimming them for the down thrust put stress on them. Any way I am installing aluminum stand offs that DL offers now with the lastest edition of the motor. The DL engine has performed flawlessly for me so far... knocking on wood.

Thanks everyone,

Wayne

TOYMAKER

My Feedback: (6)

I moved the c.g back to its original location that I started with. Now the plane will flat spin and snap well. So increasing the incidence has cured all most all off the issues I had with this Ulitimate. The first though was a c.g. issue but further invesigation and trim changes proved otherwise.

I have ended up with zero/zero on stab to bottom wing and -1.5 degrees on the top wing, stock downthrust, added 1 degree rt thrust.

Plane flew great today, tracks well and does most everything that I could ask it to do.

Thanks to all that responded.

Wayne