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Elevator stop issues

R

rrd1_99

Active Member
Hung the elevators tonight and hooked up the F790 pushrod to the bellcrank and elevator horns. Problem is, the horns contact the F712 bulkhead before the "up" elevator stop and the "down" stop barely lets them get below level. This is a QB, so the down stop was already installed, and I built the up stop per plans. I'm getting just over 20 degrees of up travel and 4 degrees of down. I would say the fix is to cut the down stop out to allow more travel and build another up stop out of 1" instead of 3/4" angle and cut it down to the whatever dimension makes it work correctly. Anybody else have similar issues?

Roger
-9A slow QB
La Grande Oregon
 
Same travel

Doesn't change anything. It's definitely the elevator horns hitting the F712 bulkhead that stops up travel and the QB down stop limiting down travel by contacting the horns. I saw in the old RVator book where the -3 sometimes needed the horns trimmed to allow full up travel. I also know I have seen figures for proper up/down travel in degrees, but I can't find them anywhere now of course.

Roger
 
The limit specs for the -9A are on instruction page 15-2 (Max. elevator Up/Down = 30/25 deg., Min. Up/Down = 25/20 deg.) This is important stuff and obviously should be resolved. Something is off in your setup. Double check everything (QB or not) against the plans. Is the horizontal stab mounted at the correct height? I think I have heard of a F-711E down stop not being fabricated correctly on a QB.
Next stop, call Van's.
 
Thanks guys

I emailed Van's on Friday, but with OSH this week I'm sure they will be a bit understaffed.

The F711-E down stop being "oversized" makes sense, as it would allow for removing material to get the correct travel limit. The up travel issue is a bit more baffling to me. I have checked-double-checked ad nauseum the whole setup and can't find any thing out of place. The fore-aft position of the HS is dead-on with respect to the F711(?) attach bars, the shims are installed under the front spar attach angles.

Anyway, I'm sure there will be a reasonable fix for it. Thanks for your input!

Roger
 
Okay, so I'm a big dummy....

But at least I figured it out by myself so no one got the pleasure of pointing out my lack of brain activity.:p

When you measure the angle of deflection, you shouldn't just lay the digital level on the top elevator skin. Instead, you should measure the angle of the CHORD line! Duh!

The good news is, now I have 27 degrees of up travel without the stop installed and 16 degrees of down travel with the QB stop installed. I will have to build a new "up" stop from 1" stock to prevent the horns from contacting the rear bulkhead and remove some material from the "down" stop but at least this makes sense!

Roger
-9A slow QB
 
Good deal. Isn't logical progress satisfying?
Hey, I've done that little brain psych myself when measuring surface deflection.
 
rrd1_99 said:
But at least I figured it out by myself so no one got the pleasure of pointing out my lack of brain activity.:p

When you measure the angle of deflection, you shouldn't just lay the digital level on the top elevator skin. Instead, you should measure the angle of the CHORD line! Duh!

The good news is, now I have 27 degrees of up travel without the stop installed and 16 degrees of down travel with the QB stop installed. I will have to build a new "up" stop from 1" stock to prevent the horns from contacting the rear bulkhead and remove some material from the "down" stop but at least this makes sense!

Roger
-9A slow QB
Click to expand...
Roger,

To my way of thinking, you can use a digital level on the top surface of the elevator. Lets say you rest the level on the top surface with the elevator in the neutral position and it reads say, 7 degrees down. Push the elevator down and if the new reading was say, 28 degrees, then you would have 21 degrees down travel. When measuring the up travel you would have to add 7 degrees to the reading.

Fin
9A
 
Yeah, that would work also...

Finley Atherton said:
To my way of thinking, you can use a digital level on the top surface of the elevator. Lets say you rest the level on the top surface with the elevator in the neutral position and it reads say, 7 degrees down. Push the elevator down and if the new reading was say, 28 degrees, then you would have 21 degrees down travel. When measuring the up travel you would have to add 7 degrees to the reading.

Fin
9A
Click to expand...

as would "zeroing" the digital level with it on the elevator skin. What DOESN'T work is moving the elevator to full travel, then laying the level on it and reading the number as "deflection angle". Simple geometry problem easily solved on paper, easily screwed up by me in practice.

Roger
 
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