Little or NO edge distance on Rt. posterior wing spar

[cleve_thompson]

Last week I was having a time getting the drift pins to fit in the front spar and because of good advise was able to overcome that obstacle. Now I have a new and more frightening one. We fitted our wings on the RV 9A Friday and checked the sweep, triangulation and incidence and found them to be RIGHT on. Then we checked our edge distance on the rear spars and found that on the left, we had several mm's of spare distance. However, on the right, we find that there is at best NO extra edge distance and in fact, I think we may be several mm's short in the medial-lateral plane (inboard-outboard/horizontal plane) It is so questionable that I don't feel secure enough to go ahead and drill them. The Posterior wing spar doesn't rest against the fuselage and in fact stands off a centimeter or so. In the horizontal plane we are fine.

Any suggestions?

 

[Mel]

If I understand correctly, to get proper amount of edge distance, you would have to sweep the wing back slightly. A VERY SMALL amount of sweep back is acceptable as long as both wings are the same. The other option would be to replace the attach fitting on the rear spar with a longer one..

 

[cytoxin]

The Posterior wing spar doesn't rest against the fuselage and in fact stands off a centimeter or so. In the horizontal plane we are fine.

Any suggestions?

i know this may come across as a elementary thing but you are measuring from the center of the hole, right? its not really a centimeter is it ?
also a chalk line on the floor is much more difficult to use with 4 plumb bobs than a tightly pulled string.

 

[szicree]

a chalk line on the floor is much more difficult to use with 4 plumb bobs than a tightly pulled string.

I found a line on the floor next to impossible. Much easier to tie a string to a couple of cinderblocks and stretch it taught. Then you can move the line instead of the plane.

 

[cleve_thompson]

Mel,
Our sweep is perfect now. I think that sweeping the wings back some, as you suggest,would give us more edge distance. How much sweep could we accept? I wonder if one wouldn't have to move the wing tips a great deal to move the rear spar even a fraction? I am so afraid that the drill will wonder that I would not be comfortable with no room for error! I don't know what you mean by replacing the attach fitting on the spar. We are using a quick build so breaking the wing apart is frightening!

Cytoxin,
We are using a string and 4 plumb bobs to measure sweep. I was talking in mm.'s not fractions of an inch because it is easier for me to think in the metric system. We are measuring from the middle of the planned hole. BTW, as a retired surgeon, your users name intrigues me. How did you come to using a name commonly associated with chemotherapy?

 

[sportpilot]

rear spar attach

Here is a picture of what Cleve is Talking about. The black line on the left represents the edge of the wing spar hidden behind the fuselage attachment. The red circle is NOT exactly the edge clearence radius, but is laid over the photo as an approximation. The little dot in the center is exactly where we want to drill the hole. Maybe this will help visualize our problem. I hope it dosent confuse the issue.

Rear wing spar attach bolt hole clearence is 5/8 radius

 

[13brv3]

From the picture, it doesn't look like it could possibly get any better than that. How big is that circle? The RV-8 I just did called for a minimum of 5/8" from the center of the hole to any edge, and I'm guessing that's the same for a -9. If that's the case, I can't believe you don't have plenty of clearance now.

Cheers,
Rusty

 

[Kyle Boatright]

Are you certain, I mean completely certain that you established a true centerline on the fuselage and have the wings perpendicular to that centerline?

If the centerline isn't true, or your wings are not perpendicular to the centerline, you could have one wing with a slight foreward sweep and another with an aft sweep. The wing with the forward sweep *might* exibit a too-small edge distance on the aft spar bolt....

Just something to double and triple check before you do something extreme.

 

[videobobk]

I had to file a small amount off to keep from getting forward sweep, so I find it difficult to understand how this could happen, but obviously it has. DON'T DRILL! I know this sounds impossible, but the only way I could see this happening is if the front spar isn't in all the way, either. Is it possible you have the front pins in the wrong hole? Excuse my asking, but at this point, I'll bet you would like to find something simple to explain the problem. IAEF, call Van's. This shouldn't happen on a QB!

Bob Kelly

 

[cytoxin]

Mel,
Cytoxin,
your users name intrigues me. How did you come to using a name commonly associated with chemotherapy?

had a little affair with it once a month for a year to stop a little disease known as necrotising vasculitis. all is well now or so it would seem.. anyhoo if the spar pictured is yours it looks low on the trailing/aft edge. has the plane been leveled and spacer/level put in exactly the correct spot.. (for incedence) something is a miss here unless you over trimmed the spar.
ADDED] i also had to remove some rear spar to prevent having fwd sweep