Help! RV-9/9A down elevator stop location?

[alpinelakespilot2000]

Just confirming: where is the down (forward) elevator stop on the RV-9/9A? I understand it to be flush with the fwd edge of the opening in the aft deck (and immediately under the flange cutout on the HS spar).

The problem is that my elevator horn weldments are still about a 1/4" from that location when the fwd moving control column hits the top of the seat rib cutouts. I know that opening the seat ribs more is a common issue, but I have no idea how much I'll need to open them up in order to get that last 1/4" of travel on the horns. Before I start hacking away at the seat ribs, I just figured I should confirm that the down stop is where I think it is. (FWIW, pushrods are to plans length with the center fuselage bellcrank in the vertical position at elevators neutral.)

Am I right in the location of the stop and that opening up the seat ribs more is the only solution?

Thanks.

 

[cln1owner]

Steve,

What's the forward angle of the sticks in the neutral position?

 

[Steve]

I'd measure the amount of elevator travel you have now before trimming any metal in the plane. The spec is in the preview plans.

 

[RVbySDI]

I can only reply with what I did on my airplane. The only way I was able to get the aileron rods to not hit the seat ribs was to take a Dremel tool to the seat rib openings in that area. I cut quite a substantial amount of material out of those seat ribs. Perhaps someone else will chime in with another method but this is how I ended up handling the issue.

 

[alpinelakespilot2000]

Steve,
What's the forward angle of the sticks in the neutral position?

Angled just slightly forward. I know it's not supposed to be straight up. Since the length of the fwd pushrod is exactly per specs with the bellcrank vertical, I think I'm right on regarding the stick angle but haven't seen any specific number of degrees it's supposed to be.

I'd measure the amount of elevator travel you have now before trimming any metal in the plane. The spec is in the preview plans.

My up and down travel is right in the mid-range of the specs without the sticks connected, so I'm good there too.

Both are reasons that I think it must be the seat ribs... I just wanted to make sure that I was correct in assuming that the fwd and aft edges of the rear deck opening were indeed the locations for the up and down stops.

Please keep the suggestions coming though, and if anyone has pictures of their seat ribs showing what they look like with proper clearance, I'd love to see them! I'll try to take a picture of mine today and post them.

Thanks for the help.

 

[Don]

Section 15-2 of my manual has the specs for what the travel should be for all of the control surfaces. Unless Van's has changed it (or I misread something), the maximum up/dn travel is 30/25 degrees and the minimum up/dn travel is 25/20 degrees. I hesitate to recommend what you do but in my case, I was able to achieve the travel required by adjusting the length of the control tubes. It seems to make sense to me to do that before you start cutting away at the seat ribs.

 

[cln1owner]

If there's room with the rod end bearings it might only take one or two turns, of added length on the forward push rod, to make up that 1/4 inch.

How much it will change the angle of the stick is unknown. I would think a forward angle on the stick would be more confortable than a straight up, so if it moves the stick too much, I'd cut the ribs... maybe a combination of both.

 

[alpinelakespilot2000]

Section 15-2 of my manual has the specs for what the travel should be for all of the control surfaces.

Yes, thanks Don. As I mentioned above, I'm right in the middle of those specs, so I'm good there.

If there's room with the rod end bearings it might only take one or two turns, of added length on the forward push rod, to make up that 1/4 inch.

Yeah, Nate, I was thinking that there's no reason the bellcrank has to be straight up, so my next step was going to be to see if, by chance, I can get some significant travel by lengthening the forward pushrod just a little bit. Then the only question will be whether my crotch or seat gets in the way of full up travel. Did you rig yours yet when you fit the empennage?

Will still try to get a pic posted later tonight to see how mine compares RVbySDI Steve or anyone else who had to trim the seat ribs.

 

[alpinelakespilot2000]

Checked things out at the airport and figured out what I had already figured out the first time I installed the empennage a couple years ago but since forgotten.

Lengthening the forward pushrod an extra 3/8" did in fact allow for the extra 1/4" of forward travel I needed on the elevator horns without the control column rubbing the seat ribs. However, lengthening the pushrod, in turn, allowed the shaft of the fwd rod end bearing to bind on the "clevis" of the control column before the elevator reached its UP stop going the other direction. Definitely not good and, in fact, worse than my original problem!

What I found instead was that splitting the difference, an extra 3/16" on the pushrod plus removing about 1/32" from seat rib, had the exact same effect as lengthening the pushrod by 3/8" without the binding on the rod end bearing or seat rib. Now the column just touches the seat rib as the elevator horns hit the down stop and the rod end bearing just barely avoids binding on the control weldment clevis. Thus, the trimming the seat rib seems to offer the biggest bang for the buck. Tomorrow I will take off about another 1/32 on the seat ribs if possible and this should get me back to the pushrod length indicated in the plans and allow for full elevator travel with no binding on either the seat ribs or fwd rod end bearing.

Here's my original 1/4" of down elevator travel needed:


And here's the rubbing of the weldment before I removed about 1/32" (by about 3/4") on the top of each seat rib cutout. I think I still have room to trim them some more:


Hope this helps someone else.

 

[Rupester]

Angle of neutral stick position

When I was rigging the control column, I called Vans and asked about the recommended neutral stick position. They instantly responded, "5 degrees forward tilt". I set it there and it helped with the seat rib interference.