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Vertical Stab position

amaris

Well Known Member
I'm placing the VS on the fuselage. With using a straight edge to check the hinge alignment, it still seems you can have those in alignment but have too much lean forward or aft. Is there a measurement for that or is it purely keeping those in alignment? Is it 90 degrees to the aft deck or anything?

PS, someone mentioned to not trim the forward spar until fitting. Yep, I should have looked at that gotcha before trimming the called out measurement. I have to fab a new plate now.
 
A Friend

A friend put his vertical on with a slight lean forward. The hinges lined up, but the front plate was riding on the lowest vertical rib and had a gap to the spar. This wasnt noticed till after the spar and plate were matched drilled. He had to trim the plate so it would sit flush to spar and not on fib of rib flange. I checked his edge distance before riveting and all was good. Check the plate fit is flush to the spar at the top side before drilling; dont be this guy.
 
Fishing line

Ideally the hinges should be perfectly aligned in both dimensions and 90 degrees to the longerons.
I used some really thin fishing line and weights. Conical shaped weights worked best. They sit in the top hole perfectly centered. Another weight at the bottom to add tension. Works like a plumb bob. When you have the string centered in all the hinges, it's good.
I also had to make a new plate and it took a lot of playing with position before the line centered.
 
I've had to stop for the day. I can't seem to get the line centered and also touching the back of the rear bulkhead. It needs to tilt rearward and when I do, the gap at the top by the longeron where the bracket attaches is out 1/4".
 
VS position

I've had to stop for the day. I can't seem to get the line centered and also touching the back of the rear bulkhead. It needs to tilt rearward and when I do, the gap at the top by the longeron where the bracket attaches is out 1/4".

I had to make a new attach plate. I made the mistake of cutting per plan.

Try different positions. In front of the plate. Behind the plate. When you start getting close, try shims. It took me what seemed like forever then suddenly it just started to fit and the string hung perfectly in the center. You git this. Build on. :D
 
Larry, thanks for always giving me encouragement. I've got someone flying up next week to help with the canopy, so hopefully, I can make a little headway with this too.
 
Still not working...

I've checked everything, the fuselage is level in both directions. When I get the fishing line centered in the holes on the vert stab, I have to lean it back to the point there's a gap of .067 at the top of the fuselage where the attach bracket goes. Pictured here. Does anyone have thoughts on what I could be missing?


 
Clamps

Probably the wrong advise, but try clamping the VS stab to the bulkhead so it's flush and align the string again.
The other suggestion is see if Vans will allow a shim.
 
That feels like I?m adding preload to the rear spar. I?ve emailed vans to see what they think.
 
Allen, from what I remember, and I could have it wrong. I thought you were supposed to start by clamping to the bulkhead. Then the forward attach plate is positioned. I?m not quite at that point yet, but close.
 
To follow up:

1st off, my rear spar wasn't straight which caused my misalignment issues. Not sure why I dind't think to check that in the first place! A straightedge held from top to bottom had the bottom recessed about 1/8". I thought, let me add a tiny bit of bend back to the spar/doubler to get things into alignment. That worked, but of course those spars with the bent flanges don't like bending. The flange puckered out about 1/16" similar to when you flute a rib.

So, I spoke to Kevin @Van's. (He's always great to talk to). That spar doesn't have a need to carry much foreward/aft strength, so it's not an issue if that puckered. The design load is side to side on that and the front spar/plate is the strong piece for the forward/aft movement. He said from there, any small gap left next to the W-712D elevator stop can be clamped out and drilled. Some pre-load isn't an issue. He also said the rod end bearings can adjust out any slight alignment issues so not to worry that much about it, just make sure the whole thing is plumb and square to the fuselage.

Lessons: when building the vertial stabilizer, besides the obvious as others have said, don't trim the 5/8" off the forward spar until you're ready to bolt this thing together. Also, make sure your rear spar and doubler are straight before riveting those together. It'll make life less interesting when you get to the assembly stage.

My 2 cents, YMMV as they say.
 
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