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Outboard LE fit to spar

rjcthree

rjcthree

Well Known Member
Everyone, I searched this topic on the -9 forum and came up with zip. The -7 forum had a hint of it, but nothing I can use . . .

I'm fitting my outboard LE, clecko'd to ribs, to the main spar. Bottom of the wing matches up nicely, holes align like we've been spoiled to expect.

The top does not line up. The LE holes are about half a hole diameter forward of the pre-drilled spar holes. Way too far off.

I've spent about two hours, moving around ribs and whatnot, measuring and inspecting. The cause that I find is that the wing spar web is not flat - it rises to the center (between upper and lower flanges). It's out of flat by 0.030-0.040" at each flange max, tapering to half that as you go outboard.

Anybody else see this? How'd you beat it? I only see two ways to fix this, adjust the LE ribs (difficult without really messing them up) or do a little reforming of the spar web for flatness - my more likely option - using a form top and bottom and big wood clamps(controllable, repeatable).

Thanks, Rick 90432
 
Hi Rick - I just did this on both my wings with no problems. Are you fitting the LE to the spar in the jig? If so, make sure the spar is level at both ends of the jig and that the sag is removed in the center (use a jack or something).

It sounds to me like you have a twist and/or sag going on. I was amazed by how much you could move the spar around in the jig. I wouldn't remove any metal from the spar to make it fit.

Good Luck
 
You've probably checked this, but are the spar-contacting flanges on each rib bent to 90 degrees? Some of my ribs took a fair bit of adjusting.

It's been a long time since I was at this stage, but I do remember some struggles getting this area aligned as well. I mostly remember having trouble getting the skin to settle down onto the ribs enough. (I have seen some people pull the skin down with straps, however I did not do this and I'm not sure it's a good idea.) Are your LE skin-to-spar holes lining up or are those off too?
 
Dave, thanks for your response, it sounds like you're about the same place I am. Anyway, my wing panel has less than 1 mm of variation in it- it is not warped or out of plane. Just for giggles, I just induced about an inch of warp into the panel (you're right, it moves in the frame a lot) just to see, and I can almost fully correct for the out of alignment vertically- almost - but it induces a horizontal offset. No joy here.

I had not planned on removing any material, just tweaking the spar web flat. If you remember mounting your tie-down bars, I bet you remember them not being flush when the upper and lower bolts were tightened up. My spar is like that at all but the most outboard LE rib stations.

Rick 90432
 
Paul, my LE to spar holes are the problem, the evidence of the issue, if you will. They are out by a half-hole diameter. Leaning on it doesn't get me too much closer.

Rick 90432
 
One thing I forget to mention - all my rear skins fit very well, inboard, outboard, top and bottom. If I were facing a warp of some kind, I would expect them to be off too. They aren't.

I'm still working my bowed web theory.

Rick 90432 :confused:
 
rjcthree said:
If you remember mounting your tie-down bars, I bet you remember them not being flush when the upper and lower bolts were tightened up. My spar is like that at all but the most outboard LE rib stations.
Click to expand...

Hi Rick - I'm 90% sure that my tie down bars were perfectly flush with the spar web... Your theory may be accurate...
 
update

Everybody who's been watching this, thanks for your help.

I tweaked the spar web to flat, and while that helped, it didn't solve the issue.

I am going to post in the general construction area, to see if anybody from the other areas may have faced/solved this.

Rick 90432 :mad:
 
Update

Along with Ken Scott at Van's we've been measuring and whatnot, pictures, etc. The spar web was in play, and is corrected, but the primary issue appears to be how the W-909's were bent. The skin CL hole measurement from the most aft rib hole to the spar hole is 1 1/8", which is correct per Ken, when clecko'd to the spar, the same distance in the rib/spar joint is 1 3/16", which is long, resulting in my mismatch. New W-909's are on order, hopefully that will be the end of this. And hopefully Van's will credit the parts. This is the third part issue I've had, where parts weren't right.

Rick 90432 :(
 
LE fit issue

Hi Rick

Wish I had seen this earlier. Same problem with my RV 8 wing. Took a bunch of head scratching to figure out that some of the ribs were mis-bent. Fortunately, I got it figured out before I riveted them all on. This is not the first issue I have had with mis-bending. Also an elevator skin that was slightly off. The CNC machine cuts the part and puts the holes in exactly the right position. The problem lies in getting the piece properly on the bending brake. 1/16th off and the part just don't fit.

Glad you sorted this out. Wish I had seen the thread sooner, might have saved some head scratching.

Regards,

Michael Wynn
RV 8 Fuselage
San Ramon, CA
 
Solved . . . no. Work around, Yes.

If anybody actually reads these things, here's the wrap up:

I rec'd my new nose ribs. They were better formed than my first set. This did not unsatisfactorily deal with the spar to LE skin hole mismatch, but took care of about half. I adjusted the rib flange that meets the spar to compensate for the rest. It's now drilled, ready to come off the frame.

In case you were wondering, the range of the total 'warp' in my wing panel is right at 1mm across the panel. Straight enough, I think.

I invented an easier way(for me) to get the ribs into the LE skin, after struggling with about three others. It goes like this: LE skin on a table, with the LE facing you, bottom down, with the forward most holes off the table edge, lightly clamped. Install the first two cleckos in the TOP of the skin/ribs. Roll one side into alignment with the bottom holes, put in two bottom cleckos, roll the other side in, same thing, roll a center one in, then work out to the rest from the center. After putting a few more top side cleckos, I moved the whole mess to the cradle, and it came together nicely.

Rick 90432
ACL/Knee reconstruction Tuesday! :eek:
 
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