How Vertical is Vertical Enough?

[MK77]

Hi fellow RV'ers,

I'm in the midst of final assembly of the RV-7 project I took over from a previous builder. I'm mounting the empennage right now.

Like many of the sub-assemblies that I thought were finished and ready to bolt together, upon closer look it appears that the VS to fuselage assembly may not be quite to the level of accuracy that I would like.

1. I have the HS mounted. I temporarily installed the VS and measured the distance from the top tip of the VS to the tip of each end of the HS. Naturally, these measurements should be equal to indicate a truly vertical VS. Here's what I'm reading:
Left HS tip to VS = 66 5/8 inches
Right HS tip to VS = 67 1/8 inches

Total delta is 1/2 in. So my question is how far off can this be without a dramatic effect to the flight characteristic? I know perfect is ideal but that's going to take some real re-work. The rear VS spar is well centered in the rear bulkhead. If I take out all but the bottom bolt in the rear spar, I need to push the VS rear spar all the way until it's hitting the right side before I get equal measurements.

2. The hinge line is not perfect. The top hinge bracket is aft almost a 1/16". Ideas on how to fix this?

Thanks!
Matt

[rvbuilder2002]

The half inch lateral dimension is not really a problem.

The 1/16" off on the hinge line is a problem and has to be fixed.
Redoing the fwd spar attach is the only way to fix it.

[MK77]

Originally Posted by rvbuilder2002

The half inch lateral dimension is not really a problem.

I was hoping you'd say that! I did the math and it's less than 0.5 degrees so I figured it was probably ok.

To fix the hinge line, is the only way to remove the F-781 attach plate from the spar, replace and re-align?

[BillL]

It has been a bit since i checked mine, but you know the VS is rotated to the right, right? You said "tip".

I certainly don't want to second guess Scott, but you might want to recheck.

Correction: Uhhhhh - yeah - the other right. Like Bret Says. Never go by memory alone when old, recheck. A couple of discussions added.

http://www.vansairforce.com/communit...t=16865&page=2

http://www.vansairforce.com/communit...ad.php?t=82731

[bret]

Originally Posted by BillL

It has been a bit since i checked mine, but you know the VS is rotated to the right, right? You said "tip".

I certainly don't want to second guess Scott, but you might want to recheck.

Don't get this backwards, double check but I think the leading edge of the VS is mounted to the Left.....

[6 Gun]

I think you are right Brent , but I mounted mine center and it flies feet off in cruise.
Bob

[MK77]

Yep, I measured the offset and the correct value called out in the manual is there, 1/4" to the LEFT so I'm good with that. The measurements I was concerned about were from the top of the VS to the HS tips. Manual specifies they should be equal.

[rvbuilder2002]

Originally Posted by MK77

I was hoping you'd say that! I did the math and it's less than 0.5 degrees so I figured it was probably ok.

To fix the hinge line, is the only way to remove the F-781 attach plate from the spar, replace and re-align?

The best way to fix this would be to redo the fwd spar attach.
Another alternative would be making a shim to bolt between the bottom of the vert stab spar and the fuselage. This would effect a number of other things though (non standard shape to rudder stops, etc) and it would be difficult to get the hinge line exactly straight so it would not be the method I would choose.

[StuBob]

Pardon the newbie question, but how do you know it's the vertical rather than horizontal that's out of alignment?

[Mel]

Originally Posted by StuBob

Pardon the newbie question, but how do you know it's the vertical rather than horizontal that's out of alignment?

The horizontal should be leveled with respect to the main wing spar carry-thru.