Knife Edge Problem
 

I flew my Funtana yesterday for the first time and I noticed in knife edge it pushes toward the belly quite hard.
Is it normal for this kind of model...since it has a high stab location?
CG @ 5 3/4
OS 70
Servos: 5 x 3004

RE: Knife Edge Problem
 

Maybe the wing and stab incidence is off? It's typical for these planes to have some type of coupling. It just depends on how it was built from Hanger 9. You can usually add mixing (a little up elevator with rudder) to fix that but not if it's really bad. Possible the engine thrust could affect it too.

Here's a test for proper engine thrust: Pull a vertical line 100 feet in front of you. Do it on a day with little to no wind. Make sure the cross wind is hitting the side of the plane if there is any. Watch the plane. If it pitches towards the wheels, it needs a little less down thrust. If it pitches towards the canopy, it needs less up thrust. You should be viewing the side of the plane as it's going vertical. You can do the same thing for left right-thrust but pull vertical at the end of the run way and view the top of the plane. Make sure the wind direction is following the runway (left or right). And of course make sure your rudder is centered and don't move it during the test.

Joe

RE: Knife Edge Problem
 

The Funtana is not famous for it's knife-edge abilities.Fly it and work with it,adjust your CG,but I doubt you will ever have superiour knife-edge with it.It does however do well in aerobatics where knife-edge is required in a combination of moves.

RE: Knife Edge Problem
 

Almost every bird I have owned pulls to the belly (12 various 3D birds). On every plane I own I put a little up in both ailerons. This creates some washout (which is good) and will keep the bird from pulling the belly.

RE: Knife Edge Problem
 

Cool, I can do that with my flap knob on my tx. Is it good to have that in all aerobatics or just the KE?

Joe

RE: Knife Edge Problem
 

Up ailerons( spoilerons) is often used to correct a rocking problem in Harriers and other stall manouvers.not used throughout the entire aerobatic envelope
Most pilots use some "up" mixing to neutralize this behaviour in knife-edge

RE: Knife Edge Problem
 

I will try this to see how it works on KE, but in my radio (6EXA) when I use flaperon mix it reduces the servo travels to 60%.
Another sugestion is to put a litle up on both ailerons adjusting the links, right?

RE: Knife Edge Problem
 

When I mentioned up-mixing,I was referring to the elevator,combinded with rudder deflection.I usually "stick" it out in my aircraft and rarely run mixes,but I am sure someone on here can give you better details on how to properly set it up;)

RE: Knife Edge Problem
 

I have a funtanaS 40. CG is good - trims neutral - level flight go inverted need just a touch of down to maintain altitude, Vertical dive test - wants to tuck to belly a touch....lowered flaps to strighten that out , KE-Pulls HARD, I mean HARD to the belly...takes a ton of up to keep it anywhere near straight. The thrust of the motor (UP/DN) is virtually at 0. Fly straight and level at full throttle and then to idle..shows a gradual decent. When flying at idle and go full power it stays level. Mixed elev into rudder on KE switch but it wants to roll out. The wing incidence is set by H9 and the h stab Incidence appears to be true to the wing. Other than the KE it flys good. This prob makes a slow roll difficult when you attempt to use rudder at the 1/4 and 3/4. Any help would be appreciated.

Thanks
V

RE: Knife Edge Problem
 

My Funtana used to tuck to the belly real bad in knife. It'd end up snapping out by the time you got enough correction on the elevator. Later on I had the wing dowels chew themselves out so I sleeved them with 10mm alloy tubing. When I opened out the holes in the bulkhead I filed away at the top of the hole only (towards the canopy). This gave about 1mm of extra wing incidence. It almost completely cured the tuck. I have 10% up elevator mixing with full rudder. One other thing I did was to reduce the rudder movement a bit. It was almost touching the elevators at full deflection before. Mine will hold a steady, no hight loss, knife for ever at half throttle now. Hope this helps you out.

Gez

RE: Knife Edge Problem
 

fun4vincer, You mention at the start "my CG is good". Mine will knife edge good at 1/2 power with about 20degrees deflection. I mentioned your CG because mine will climg hands off inverted. Do you know what your CG is in "


David

RE: Knife Edge Problem
 

Try here....

http://www.nsrca.org/technical/trimming/trimming.htm

Angus

RE: Knife Edge Problem
 

I used that trimming chart to get this far....CG is 5 1/8 behind leading edge...At first...hands off it would climb when inverted but I added some nose weight(did the same thing in KE before adding weight), after adding weight just a touch of down to maintain level inverted. Do you think I should add more nose weight? Trimming chart says add more nose weight if it tucks to belly. Have a pull - pull ready to install but Im not quite sure exactly how im going to do that without using a pully(not real interested in that) or having the wires come out about 6 inches in front of the H stab to provide straight shot. Anyone done that yet? After checking again my engine thrust is about 1 or 2 degrees up. WOWBAGGER...that is exactly what happens to me, by the time you correct with the elev it snaps out....I would like to try some other options before changing the holes but I really appreciate the input. In a power off vertical dive did yours tuck to the belly?Thanks again for the help.

Appreciate the help

V

RE: Knife Edge Problem
 

V your CG is 1&1/4" in front of mine. Maybe your flying style is a lot different from mine? Mine wont 3-D at less than 6-1/4" and then it needs to burn some fuel.

IMHO some of you are wasting your time trying to use conventional wisdom on this plane. It is simply a different animal. I may get slammed for this or called an idiot. So be it. But I know what made mine come to life. The first flight at an AFT CG is nerve racking. Once it was airborn however the nerves were gone. This plane is made for one thing 3-D. Trying to trim it like a sport plane just will not get you were you need to be. Once again IMHO


David

RE: Knife Edge Problem
 

if i was you do as i do. I have a JR PCM 9X a very powerful system all agree. forget all about mixers and mixing up ailerons learn to fly by skill not by computers it is far more rewarding and you will become a better pilot for it.

RE: Knife Edge Problem
 

I can try that...im not opposed to anything..I just started where the manual said to.

Thanks
V

RE: Knife Edge Problem
 

You will a much better pilot if you