Su-26M Knife Edge

[Smitty]

Is anyone else having a real bad coupling problem when you do a knife edge with the PAU Su-26m. Mine pulls real bad to the landing gear. I have tried to catch it right off the bat, but it is impossible to do a really straight knife edge and trying to do a snap while in a knife edge and return to a knife edge is a waste of time. Any help and I would be real thankful.---Smitty

 

[Jetpainter]

Is anyone else having a real bad coupling problem when you do a knife edge with the PAU Su-26m. Mine pulls real bad to the landing gear. I have tried to catch it right off the bat, but it is impossible to do a really straight knife edge and trying to do a snap while in a knife edge and return to a knife edge is a waste of time. Any help and I would be real thankful.---Smitty

It could be tail heavy or a thrust and or incidence issue. I solved mine on my Pilot edge with a mix.

Find the Peter Goldsmith trimming guide and go through it. It can be very helpful.

 

[Terryscustom]

It's a scale plane, you need to balance how you like it and then learn how to do KE mixing. I had mine mixed for hands off KE as well as straight up and dowe lines. Amazing after mixing. Once you learn to KE mix all your planes it will make you a better pilot

 

[Smitty]

Ok, thanks for the input, The plane when rolled inverted at a 45 degree angle indicates it is a tad nose heavy. The plane fly great other than the knife edge. I will figure it out.--Smitty

 

[BalsaDust]

Yup what terry said. My Carden cap 232 wouldn't KE for crap at first but after some mixing I got it dialed in pretty good. I started with one mix and worked from there concentrating on fixing one problem at a time.

So first I roll into KE and work on my aileron mix. I noticed when I applied left rudder the plane wanted to roll back to the belly. So to correct it I think I ended up with a 3% right aileron to left rudder mix. I then went KE the other direction with right rudder resulting in the same % mix of 3% left aileron to right rudder.

OK so now its holding in knife edge so I can start to work on the pull to the belly while in KE. this was worse that the roll to the belly I had so I think I ended up with a 5% up elevator to left and right rudder.

Hope that helps.

 

[Terryscustom]

Ok, thanks for the input, The plane when rolled inverted at a 45 degree angle indicates it is a tad

Ok, thanks for the input, The plane when rolled inverted at a 45 degree angle indicates it is a tad nose heavy. The plane fly great other than the knife edge. I will figure it out.--Smitty

Rudder to Elevator / Aileron is a mix that's already in pretty much ever radio out there, you just need to look at it to figure it out. First step is to set the CG to where you want it, CG plays a roll in amount of coupling but has zero to do with getting rid of it. ALL aerobatic planes have some coupling to the gear and likely a slight roll to the gear as well.

The Sukhoi is a very short plane, very scale, scale wing placement and a round cowl which all play a roll in the coupling. Yet you will notice it flies like it's on rails. Mix it little by little after you get your CG. For something that pulls like the SU, start with about 6% up elevator to rudder. Double check that the elevators go up slightly with both left and right rudder applied. DO NOT put it on a switch, it always needs to be active regardless of what some on the web will say.

When you are done, likely the values for right and left will be slightly different, don't worry about that. Next pay attention to the rolling that may happen, likely you will need a tad of rudder to aileron for hands off KE flight.

Try to do this on a calm day or with light winds going down the runway so it does not effect you.

 

[Jetpainter]

Several of my airplanes will try and roll out as well as pull. My JR 11x has the mix for rudder to elevator and ailerons so the set up is easy, and like Terry said when the mix is set up right it does wonders. Nice stable knife edge as low as your nerve will allow.

I have mine on a switch and never turn it off. I've been meaning to take the switch out of the mix just keep forgetting.

 

[babathehutt]

Rudder to Elevator / Aileron is a mix that's already in pretty much ever radio out there, you just need to look at it to figure it out. First step is to set the CG to where you want it, CG plays a roll in amount of coupling but has zero to do with getting rid of it. ALL aerobatic planes have some coupling to the gear and likely a slight roll to the gear as well.

The Sukhoi is a very short plane, very scale, scale wing placement and a round cowl which all play a roll in the coupling. Yet you will notice it flies like it's on rails. Mix it little by little after you get your CG. For something that pulls like the SU, start with about 6% up elevator to rudder. Double check that the elevators go up slightly with both left and right rudder applied. DO NOT put it on a switch, it always needs to be active regardless of what some on the web will say.

When you are done, likely the values for right and left will be slightly different, don't worry about that. Next pay attention to the rolling that may happen, likely you will need a tad of rudder to aileron for hands off KE flight.

Try to do this on a calm day or with light winds going down the runway so it does not effect you.

I have my knife edge mix on a switch—the "On" switch! I agree with leaving it on. It takes the bad tendencies out of the rudder and will make your rollers, knife edges, and turns more true.

 

[Smitty]

Think I solved my problem on the knife edge thing, turns out I was putting too much rudder in as soon as I rolled to a knife edge, yesterday I just rolled to the KE and then put in what was needed and the plane handled KE real good. Didn't need near the amount of rudder that I thought I would need.---Smitty