Shim the vertical stab spar?

[Scott Will]

Was adjusting the rod end bearings on the rudder the other day. After I put the rudder on, I can see how the gap between the VS and rudder grows towards the bottom. It's because when we drilled the VS to the fuselage, the lower spar portion wasn't fully contacting the aft bulkhead.

Anyway, the rudder swings freely but I'm not sure I like the gap? What would you do? Shim the vertical stab spar? I dont know how much I'd have to shim it but by looking it looks like about 3/32 would do the trick. The bolts take all the load... so maybe some large washers underneath?

Or would you just leave it alone and not tell anyone?

how it is

maybe shim?

 

[RV_7A]

Scott,

What I did (and what Vans tells you to do) was ensure that the rod ends in the rudder were adjusted so that they were perfectly in line and screwed to the depth specified by Vans. Then bolt the rear spar of the VS to the rear bulkhead. Then raise or lower the front of the VS so that the 3 hinge brackets are also in line with one another, clamp and drill the front plate where is attaches to the HS. The rudder should fit and allow you to drop all 3 bolts in without any prying ot tweaking. This will ensure that there is no bind when you move the rudder. Doing this will close that gap at the bottom as long as you have the rod end adjusted per the plans.

-Jeff

 

[pierre smith]

String.......

Hi Scott,
Jeff's correct but the way we aligned ours was to adjust the upper and lower rudder hinges to provide the same gap upper and lower and THEN with a string down thru all three hinges, adjust the center one to align with the other two.

 

[Scott Will]

Well all the bolt holes are drilled... so I have to live with what I have.

Maybe I can do what Pierre recommended... adjust the top and bottom for an even gap and let the middle one fall where it may. Besides, it looks like my upper one is a little tight. There's no binding as it is, though.

- Scott

 

[RV_7A]

Scott,

I highly recommend replacing the front mounting plate. Align and redrill. Its not hardly any amount of work and you will be happy you "did it right"

The white plate shown here will need replacing since you already drilled it misaligned. Once replaced you raise the VS spar and this will push the top hinge aft and give you the alignment needed.

-Jeff

 

[Jim Percy]

Scott-

Are you sure the gap doesn't grow toward the bottom because the width of the VS spar/ rear bulkhead also grows toward the bottom?

At any rate, what's the harm in trying the easy fix first? Just back out the top bearing, say 1/2 turn, and move the bottom bearing in by the same amount. They are equally spaced from the center so you should be able to leave that one alone. You can test the bearing alignment by putting polts/pins in the top and bottom, then checking that the center bolt falls into place easily. Keep an eye on the alignment of the counterbalance arm too- as you narrow the bottom gap, the CB arm will probably angle up in the front.

The way I see it, if you make a new plate or add a shim you'll still have to adjust the bearings a certain amount.

My 2 cents-
Jim

 

[rvbuilder2002]

First verify whether you have a problem with the vertical stab position. Remove the rudder and place acarpenters level or other long straight edge against the back of the the three sets of hinge brackets.
It should contact all three showing the the hinge points are all aligned. If they are not, this must be corrected. You can adjust the rod ends on the rudder, to fit the V. stab even if the hinge points are miss aligned but it will be tweeking your rudder. This is the cause of rivet hole cracking in a lot of RV rudders.
Also, as already mentioned in another post, the gap on the rudder is not constant. The rudder and vertical stab vary in thickness from top to bottom but the F-712 bulkhead is a constant width. This causes the gap to vary from the top to the bottom on the fuselage. This might be part of what you are seeing since it appears that your rudder counterbalance arm is parallel to the top of the vertical stab.

Scott

 

[Steve]

I fitted my -9 rudder last week. The -9 instructions say to verify the top gap is constant (where the rudder swings over the VS). Adjust the rudder rod ends to make it happen.

Steve

 

[Scott Will]

started from scratch

Last night I verified that my hinge brackets were not in perfect alignment. One was off by 1/16" when placing a straightedge along the brackets.

Drilled off the old front attach plate F-781. Even though I have a new one on the way from Van's I made a new one from scratch using thicker material, .090. This even helped bring it tight against the HS. I made it longer on the bottom so it sits flush against the aft deck and makes the brackets all fall in a perfect line now. Cool.

I readjusted the rod ends to where Van's tells you... and I guess I still have that optical illusion because the gap grows at the bottom. But at least it swings freely. (it did before but now even more so).

Where holes have to go... make new one because edge dist on bottom is getting smaller

New one from thicker stock

Haven't drilled it yet... looks like I have to move my holes over some.

 

[RV_7A]

Steve- You must have misunderstood the instructions. No where does it say to adjust the rod ends to make this happen. You adjust the rod ends to the depth Vans specifies. Then checking their aligment (if you choose) with a straight edge and make tiny adjustments on either the top or bottom (take your pick) to get them perfectly in line with one another. Just like Scott (RVBUILDER2002) mentioned, the Gap between the VS and Rudder is not the same from top to bottom due to the taper in the width of the 2. When the Rudder goes to full deflection in either direction, the gap will close evenly top to bottom and the VS skin will not come into contact Rudder.

Scott Will is doing a great job addressing his issue well. Post those pics Scott!

-Jeff

 

[David H. Milliken]

rudder to Vertical stab gap

Hmmmmm... This will be my first reply on any subject so I'll see if I post this correctly!

Make sure you are using the dimension off of the big prints as the smaller 3-ring binder instruction have been revised for the bottom bearing dimension. My page 8-18 in the 3-ring instructions called for the bottom bearing to be 1 3/64" but this dimension has been changed by Revision R2 to 1 1/16" on drawing 7 of the big prints. (This maybe has been corrected since my publication date of 7/15/04 for this page) This smaller dimension is more in line with reality. As has been pointed out already, the rudder gap is in fact not consistent top to bottom with the rudder in neutral but gaps should be fairly even with the rudder at its left and right limits. That, along with a consistent gap at the counterweight-vertical fin should make a satisfactory install.
Dave Milliken
RV7 - Fitting wings

 

[Scott Will]

Does anyone have any pics of where the end/tip of the vertical stab should be in relation to the turtle deck?

Good catch on the bearing dimension, David. I hate optical illusions!

 

[Steve]

Jeff,
You're correct. The instructions say to set the rod bearings to the dimension on the print as a starting point. Then make further adjustments until the rudder swings freely. I'm at work and don't have the book in front of me but the instructions do say the gap (bottom of rudder CB arm and top of VS) should be even (paraphrased).
The vertical gap will, of course, vary due the taper on the VS and the rudder.
Steve