Radio mixing for knife edge
10-31-2004, 10:24 PM
#1
Member
Thread Starter
My Feedback: (1)
Join Date: Sep 2004
Location: Advance,
NC
Posts: 41
Likes: 0
Received 0 Likes
on
0 Posts
Radio mixing for knife edge
Hi All,
I tried searching the site and viewing topics in the radio section with no luck so I hope this the right place to post this. I have been flying a Morris Hobbies Topcat and a H9 Texan for a couple of months, and this week I added a H9 J-3 Cub with a Satio GK.56. Every mag review of a 3D plane mentions knife edge flight and "coupling" between the pitch and roll axis. They often state that you can progam a mix to aviod this or just fly and manually trim it out. What I am unclear about is what mix are they referring to and what two surfaces do you adjust? For example I have a Mix set up for my J-3 cub that adds 40% rudder to the Ailerons to make scale like turns. When you push the right stick to the left, it adds a little left rudder. Very simple, it works very well and that plane is very easy to fly. But on a 3D plane how do you create a mix that allows you to fly straight knife edge that does not affect normal stick inputs when your flying the plane around? For example, My topcat will fly knife edge with full throttle and full rudder and I can direct it its path by using the elevator to bank it toward or away from the pit. If I set up a mix, like the magazines talk about what am I attempting to do? And also what happens if this mix is active all the time and I am doing 3D stuff and tossing the plane around? On the cub its simple because its a Sunday flyer and never on its back or vertical. I just want to learn how these mixes work to see if I am flying my Topcat to its potential. BTW- I have a Futaba 7CAP and a O.S. .46AX on my plane with a APC 12.25x 3.75 prop.
Here is a link to my Train website, but there are two PLave videos on the link bar on the left.
[link]http://www.circledscenicrailroad.com[/link]
I tried searching the site and viewing topics in the radio section with no luck so I hope this the right place to post this. I have been flying a Morris Hobbies Topcat and a H9 Texan for a couple of months, and this week I added a H9 J-3 Cub with a Satio GK.56. Every mag review of a 3D plane mentions knife edge flight and "coupling" between the pitch and roll axis. They often state that you can progam a mix to aviod this or just fly and manually trim it out. What I am unclear about is what mix are they referring to and what two surfaces do you adjust? For example I have a Mix set up for my J-3 cub that adds 40% rudder to the Ailerons to make scale like turns. When you push the right stick to the left, it adds a little left rudder. Very simple, it works very well and that plane is very easy to fly. But on a 3D plane how do you create a mix that allows you to fly straight knife edge that does not affect normal stick inputs when your flying the plane around? For example, My topcat will fly knife edge with full throttle and full rudder and I can direct it its path by using the elevator to bank it toward or away from the pit. If I set up a mix, like the magazines talk about what am I attempting to do? And also what happens if this mix is active all the time and I am doing 3D stuff and tossing the plane around? On the cub its simple because its a Sunday flyer and never on its back or vertical. I just want to learn how these mixes work to see if I am flying my Topcat to its potential. BTW- I have a Futaba 7CAP and a O.S. .46AX on my plane with a APC 12.25x 3.75 prop.
Here is a link to my Train website, but there are two PLave videos on the link bar on the left.
[link]http://www.circledscenicrailroad.com[/link]
10-31-2004, 10:45 PM
#2
Senior Member
My Feedback: (1)
Join Date: Oct 2004
Location: Warrenton,
OR
Posts: 153
Likes: 0
Received 0 Likes
on
0 Posts
RE: Radio mixing for knife edge
I'm going to be interested to see what the knowledgeable folks have to say here. I have a Venture 60 that I mix in some up elevator to the rudder for doing knife edge to keep it from turning to the belly when doing knife edge. I have the mixing set up to be activated by a switch on my 6XAS. I'm like you, I don't know if this should be activated all the time or just for knife edge. I have noticed that without the mix being activated that when I give a rudder command in straight and level flight that the plane dives so maybe it would be appropriate to have it activated at all times. Or maybe the dive is a sign of other setup problems?
Jim
Jim
10-31-2004, 10:55 PM
#3
My Feedback: (1)
Join Date: Oct 2004
Location: Champaign,
IL
Posts: 34
Likes: 0
Received 0 Likes
on
0 Posts
RE: Radio mixing for knife edge
The mix they are refereing to is this.
If you plane is in knife edge and it flies without any aileron or elevator correction to keep it straight you need no mixing.
If you can fly horizon to horizon without any elevator or aileron corrections to keep it in knife edge then you plane is fine and doesn't need any mixes.
My 3D foamy will pitch slowly to the belly in knife edge requireing about 10% up elevator, I still have control of the elevator like you do with the rudder of your Cub even with the mix engaged.
Anothe one of my planes required the slight amount of up elevator, but also needed 7% aileron because the plane would roll slightly with rudder and try to level out.
I have the mix on at all times as it makes the plane fly better. In other words my plane will pitch down slightly regardless of what manuver I am doing when using rudder, so the slight up elevator mixing makes the plane act only in the yaw axis when using the rudder for hovering, hammerheads and of course knife edge.
Hope that helps.
Matt
If you plane is in knife edge and it flies without any aileron or elevator correction to keep it straight you need no mixing.
If you can fly horizon to horizon without any elevator or aileron corrections to keep it in knife edge then you plane is fine and doesn't need any mixes.
My 3D foamy will pitch slowly to the belly in knife edge requireing about 10% up elevator, I still have control of the elevator like you do with the rudder of your Cub even with the mix engaged.
Anothe one of my planes required the slight amount of up elevator, but also needed 7% aileron because the plane would roll slightly with rudder and try to level out.
I have the mix on at all times as it makes the plane fly better. In other words my plane will pitch down slightly regardless of what manuver I am doing when using rudder, so the slight up elevator mixing makes the plane act only in the yaw axis when using the rudder for hovering, hammerheads and of course knife edge.
Hope that helps.
Matt
11-01-2004, 05:02 AM
#4
Senior Member
Join Date: Jan 2003
Location: Eagle River,
AK
Posts: 942
Likes: 0
Received 0 Likes
on
0 Posts
RE: Radio mixing for knife edge
Well I will fly a knife edge at different speeds and AOA I just use LOTS AND LOTS of practice and you should be able to fly it out without mixes.
11-01-2004, 11:15 AM
#5
RE: Radio mixing for knife edge
I think the question about having the mix on a switch or not depends on a couple things. First are you flying sport or 3-D? Second what kind of plane is it? For example....I use a mix to knife edge on a Goldburg ULT. It is also on a switch. Most of the time the plane flys the same with the mix on or off. The exception would be doing a hammerhead or hovering. Doing one of these manuvers with the mix on won't happen. The down ELEV mixed to the rudder will pitch the plane out of the manuver. The other example would be the Funtana .40. The mix has to be flown in with this plane. I tried setting it in the radio but the %of mix changes with speed. A full throttle knife edge only takes a little ELEV correction. A high AOA knife edge at low speed (harrier style) takes no correction.
I wish I could give you a better answer. What it boils down to is every plane is different. You will just have to try some different %s and tinker with it. Start out with the mix on a switch. After it's fine tuned you will know if you need it left on the switch or not.
BTW on the 7C can you assign which switch does the mixing? On the 9C i like to use the trainer switch to try out new things. That way if you get in trouble you can just let go.
David
I wish I could give you a better answer. What it boils down to is every plane is different. You will just have to try some different %s and tinker with it. Start out with the mix on a switch. After it's fine tuned you will know if you need it left on the switch or not.
BTW on the 7C can you assign which switch does the mixing? On the 9C i like to use the trainer switch to try out new things. That way if you get in trouble you can just let go.
David
11-01-2004, 11:34 AM
#6
Senior Member
Join Date: Apr 2003
Location: London, UNITED KINGDOM
Posts: 2,235
Likes: 0
Received 0 Likes
on
0 Posts
RE: Radio mixing for knife edge
mix rudder to elevator to correct pitch changes (ie without the mix the plane will tend to turn towards its belly or canopy when in knife edge), and mix rudder to aileron to correct roll changes (ie without the mix the plane will tend to roll to the right way up or inverted when in knife edge).
The problem is that for the amount of mix needed may change depending on the amount of rudder used at any moment. I set up my rudder throw to maintain KE at half throttle on low rates, and set up the mixes for this, as this is likely to be when I do long KE passes.
I dont bother changing the mix for high and 3d rates, it is unlikely to help.
As for whether it should be on all the time or not, that is a personal preference thing, but for me I have it on all the time. The idea is that I want ailerons to only roll the plane, elevator to pitch the plane, and rudder to yaw it.
The problem is that for the amount of mix needed may change depending on the amount of rudder used at any moment. I set up my rudder throw to maintain KE at half throttle on low rates, and set up the mixes for this, as this is likely to be when I do long KE passes.
I dont bother changing the mix for high and 3d rates, it is unlikely to help.
As for whether it should be on all the time or not, that is a personal preference thing, but for me I have it on all the time. The idea is that I want ailerons to only roll the plane, elevator to pitch the plane, and rudder to yaw it.
11-01-2004, 02:36 PM
#7
RE: Radio mixing for knife edge
If you want the mix to work at all rudder travel, you'll need to use multi-point mixes. many fun fly & 3D planes will knife edge pretty well at low throttle movement, but for high or full rudder like in a knife edge loop on the bottom, the plane tends to pitch down so you need a different amount of mix.
Most 8/9 channel radios have a 5-point mix. You'll need to set it up linear to start with, the curve on the graph will be a straight line. Try knife edge at various rudder amounts and see if you need more elevator correction or not. Adjust from there.
Of course you need it on a switch, you don't want to be snapping and flat spinning with the mix on-at least I don't.
Most 8/9 channel radios have a 5-point mix. You'll need to set it up linear to start with, the curve on the graph will be a straight line. Try knife edge at various rudder amounts and see if you need more elevator correction or not. Adjust from there.
Of course you need it on a switch, you don't want to be snapping and flat spinning with the mix on-at least I don't.
11-01-2004, 05:44 PM
#8
Senior Member
Join Date: Apr 2003
Location: London, UNITED KINGDOM
Posts: 2,235
Likes: 0
Received 0 Likes
on
0 Posts
RE: Radio mixing for knife edge
ORIGINAL: Ed_Moorman
Of course you need it on a switch, you don't want to be snapping and flat spinning with the mix on-at least I don't.
Of course you need it on a switch, you don't want to be snapping and flat spinning with the mix on-at least I don't.
.My view is if the amount of mix needed is such that it will impact other manouvers, such as spins, stall turns etc, then you need a better (ie more neutral) plane [&:].
11-02-2004, 08:54 AM
#9
My Feedback: (4)
RE: Radio mixing for knife edge
I sort of had the same opinion, if you need to do that much programming on the radio, then maybe you need a better plane. Then one of the TOC guys I fly with once in a while did some trimming on my 35% Carden Extra 300S - and did I change my mind real quick after flying it once he was done. I would now say that I will spend the first hour of air time trimming out a plane via the Tx programming - and what a difference it makes. Nobody has an issue with using the trim tabs to make a plane fly straight and level - why not use the power in our Txs to make the plane fly the way you want in all conditions - knife edge - 3D - spins .......
Dan
Dan
