78'' Extra

[RKEstes]

Thank you. It's a 3 1/2" CF from Troy Built Models. It has a very beefy backplate. I ordered another 4 inch for my 88" Edge.

 

[Enterprise]

Could you guys share what happened? I have mine setup per the manual but I am using longer 1 3/4" arms and 70mm turnbuckles (stock are 60mm) I'm getting tons of throw without getting even close to binding or any geometry problems.

Daren has the video of the event.

I setup the elevator servos with the spline aft per the manual (my issue)

I then used 2" arms and noticed on the bench that when I did a full up to full down, the momentum would swing the arm into a cam over. I backed the end points down to not even get close to this happening. Before this I had tried 1.5" arms and the 1.75" position. I think I remember getting this problem on the 1.75" setting as well.

Anyways the day I first flew it, it was stupid windy. After a waterfall, the wind hit the top of the elevator, and pushed it into a cam over. The plane was not flyable with 1 full down stuck elevator half. I tried to pulse the servo to get it to reset, but it was pretty low. In retrospect I should have just pushed down till it was heading skyward, and tried to recover some more. Instead I fought it to the ground and it broke the fuse literally in half.

We then looked at Daren's, his was setup with 1.5" arms and the spline forward, which makes the situation not very likely to occur. If I had only reversed the servo in the pocket, I think I would have been fine.

My re-kit is finally going to be here tomorrow. I wish I could say I have a bunch of spare parts, but a lot of the plane was damaged including the canopy and cowling. In the end I deviated from the manual with the longer arms, but I think the issue would have been worse with the shorter arms. Just a cautionary tale and a expensive lesson in servo geometry.

 

[dth7]

Daren has the video of the event.

I setup the elevator servos with the spline aft per the manual (my issue)

I then used 2" arms and noticed on the bench that when I did a full up to full down, the momentum would swing the arm into a cam over. I backed the end points down to not even get close to this happening. Before this I had tried 1.5" arms and the 1.75" position. I think I remember getting this problem on the 1.75" setting as well.

Anyways the day I first flew it, it was stupid windy. After a waterfall, the wind hit the top of the elevator, and pushed it into a cam over. The plane was not flyable with 1 full down stuck elevator half. I tried to pulse the servo to get it to reset, but it was pretty low. In retrospect I should have just pushed down till it was heading skyward, and tried to recover some more. Instead I fought it to the ground and it broke the fuse literally in half.

We then looked at Daren's, his was setup with 1.5" arms and the spline forward, which makes the situation not very likely to occur. If I had only reversed the servo in the pocket, I think I would have been fine.

My re-kit is finally going to be here tomorrow. I wish I could say I have a bunch of spare parts, but a lot of the plane was damaged including the canopy and cowling. In the end I deviated from the manual with the longer arms, but I think the issue would have been worse with the shorter arms. Just a cautionary tale and a expensive lesson in servo geometry.

Better not to watch it again! Matt's explanation is accurate. I just wouldn't be too obsessed with getting "sick" throws til you fly it and see what you need. I'm surprised what I get out of it with what I consider "high" rates not sick.

 

[RKEstes]

Thanks for posting that guys. Just checked mine to make sure there is no way the elevator can cam over like that.

 

[ryan_m]

I'll have to check mine as well. I mounted the servos with output shaft to the rear, and had also ordered the longer 70mm turnbuckles, discovered that there was no way to use the turnbuckles with the servos mounted as they were, they were too long. Was too lazy to flip the servos around, and left them that way and used the stock ones. Perhaps I should go fix it now...

 

[dth7]

Holy crap Matt. You've started servo panic in EF 78 Extra World! Just kidding guys. This is why we love this forum. When someone hears or learns something important it gets passed right along. Occasionally with some humor! Haha.

 

[bryanb]

checking mine, too.

 

[ryan_m]

I definitely noticed the possiblility of doing the same thing, on full down elevator it wouldn't have taken much to push the servo arm over to the other side.
put the 70mm secraft turnbuckles on, flipped the servos so the shaft is to the front, and it looks much better now. Glad I did this before I had any problem! Probably could have just reduced throw some, but I tend to like a lot of down in my planes. And since I had the parts on hand...
what the heck.

 

[Enterprise]

I thought the reduced throw would work, but do a hard maneuver with 25 mph gusting winds, and you get what happened to me.

 

[bryanb]

I definitely noticed the possiblility of doing the same thing, on full down elevator it wouldn't have taken much to push the servo arm over to the other side.
put the 70mm secraft turnbuckles on, flipped the servos so the shaft is to the front, and it looks much better now. Glad I did this before I had any problem! Probably could have just reduced throw some, but I tend to like a lot of down in my planes. And since I had the parts on hand...
what the heck.

Where did you get your 70mm turnbuckles?