Elevator control horn leadouts

[Chris Fretz]

So after using this site for a wile now an finding out I needed to fix some of my airplanes. 25 some odd years ago I built all my airplanes thinking I needed 60+ degrees of elevator deflection. (I still look at 20 degrees and think that just doesn't seem enough, guess old habits are hard to break)  So one of them I was able to move the pushrod to the inside hole on the belcrank to fix it.  The others I'd rather not cut into just yet so I've been extending the control horns to get into the 25 degree range. My question is there a point were you have to much leadout movement to tone down the elevator deflection? One of them has much more than 45 degree belcrank movement which I have a pretty long control horn making the leadouts moving a lot for full deflection movement.

[Chris Fretz]

If you have over 45 degrees of elevator, you in essence have air or dive brakes....  20 flap and 35 elevator are about the max you will ever need. too much and the plane will stall and make for a horrible pattern if it  doesn't crash first. Based on some videos posted on here, a small video camera showed about 10 degrees tops. Any degree of movement will or should immediately start the model in a different path. More travel of the control surface only makes the maneuver extreme and out of sorts. Even in combat.

Some set up the controls for 1 to 1 or less. Let's hope the top flyers come on and give a better explanation.

When I said I have more than 45 degree of movement I ment on the belcrank itself not the elevator. I've made extensions on the control horns to cut the degree of elevator movement down to suggested amount of movement on here. Now I'm asking if excessive leadout movement will cause problems with the handle an wrist movement.

I've seen my airplanes do horrible patterns so this is why I'm trying to fix them.

[Perry Rose]

Wider line spacing at the handle. It's a balancing game between the handle spacing the c/g point and control surface deflection to get it where you want.

[Chris Fretz]

Ohhh yeah I didn't even think about adjusting there as well.

[Steve Helmick]

I've personally looked at some of Paul Walker's planes. His controls are very slow, allowing a wide handle spacing. Leadouts travel A LOT. I am somewhat surprised that his elevators move as much as they do, but as you have found out already, you really can't use all of that, except in dire emergency situations. At least, that will slow down the plane and result in it hitting the ground at a lower speed. That would be a good thing if you were to have a line break, I suppose.

I haven't questioned Paul on the reasoning, but when he flew my plane (last Spring?), he was a bit apprehensive about how little the elevators moved. But he said it flew ok, and didn't suggest any trim changes (which is unusual). Yeah, he flew it a lot better than I can. Paul is 11 time NATS Open winner, a past World Champ, and has many high placings at the WC. Hopefully, he'll become a repeat Champion in Perth this month!  Steve

[billbyles]

<snip> Paul is 11 time NATS Open winner, a past World Champ, and has many high placings at the WC. Hopefully, he'll become a repeat Champion in Perth this month!  Steve

Not to nitpick, Steve, but he now has his name on the Walker Trophy 12 times (just FYI.)

[Steve Helmick]

Bill...Are you sure? I could be wrong, of course. I am short of enough fingers and toes, that's for sure.    Steve

[Mark Scarborough]

Bill...Are you sure? I could be wrong, of course. I am short of enough fingers and toes, that's for sure.    Steve

Its 12 Steve,, I was there this year, well last year

[Chris Fretz]

I've personally looked at some of Paul Walker's planes. His controls are very slow, allowing a wide handle spacing. Leadouts travel A LOT. I am somewhat surprised that his elevators move as much as they do, but as you have found out already, you really can't use all of that, except in dire emergency situations. At least, that will slow down the plane and result in it hitting the ground at a lower speed. That would be a good thing if you were to have a line break, I suppose.

I haven't questioned Paul on the reasoning, but when he flew my plane (last Spring?), he was a bit apprehensive about how little the elevators moved. But he said it flew ok, and didn't suggest any trim changes (which is unusual). Yeah, he flew it a lot better than I can. Paul is 11 time NATS Open winner, a past World Champ, and has many high placings at the WC. Hopefully, he'll become a repeat Champion in Perth this month!  Steve

How much degree of motion would you say your airplane has that he had flown?

[Howard Rush]

So after using this site for a wile now an finding out I needed to fix some of my airplanes. 25 some odd years ago I built all my airplanes thinking I needed 60+ degrees of elevator deflection. (I still look at 20 degrees and think that just doesn't seem enough, guess old habits are hard to break)  So one of them I was able to move the pushrod to the inside hole on the belcrank to fix it.  The others I'd rather not cut into just yet so I've been extending the control horns to get into the 25 degree range. My question is there a point were you have to much leadout movement to tone down the elevator deflection? One of them has much more than 45 degree belcrank movement which I have a pretty long control horn making the leadouts moving a lot for full deflection movement.

What you have is good.  Here is how I'd approach the problem:
1. Have the bellcrank rotate as much as possible and put the CG in the design location for that airplane. 
2. Then provide control horn length that gives just enough control to turn the tightest you'll ever need to turn.  You can find this length experimentally. 
3. Then adjust the handle spacing until it feels comfortable. 
4. Proceed to the Walker trim process, http://flyinglines.org/walkerstunt.html

The purpose of 1-3 is to give the greatest ratio of leadout travel to control surface movement, which gives the maximum leverage over control loads.  That minimizes the effect of control line stretch, and allows you to fly accurately.  It's particularly a big deal if your airplane has flaps.   This process does not involve trading or compromising among CG, control deflection, and handle spacing.  CG determines control throw.  CG and control throw determine handle spacing. 

[Steve Helmick]

How much degree of motion would you say your airplane has that he had flown?

Well, if you hang it from the up line, maybe 30 degrees, but from the handle, I'd say under 15 deg. for sure, maybe 10 degrees of up. It's an OPP...(Other People's Plane)...I didn't build it. I'm not sure that it has a 4" bellcrank, but I would hope so. It's heavy, but flies ok otherwise. Biggest current problem is not enough ground clearance for 11.5" prop diameter, which is what it needs. I'd like to use more diameter, maybe, or at least try more diameter.

Carbon props are pretty expensive when you destroy two on consecutive flights, even if those are a couple weeks apart. Nothing wrong with a full inch of ground clearance with the plane level, wheels on ground, IMO. This is a problem with having a CF landing gear that's built into the fuselage and isn't either adjustable or removeable!  Steve