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Left wing outboard top skin to spar mismatch.

High_Flyer

High_Flyer

Well Known Member
Hi,

I've fitted the top skins of both wings last night.
On the left wing, the outboard skin prepunched holes do not line up with the prepunched holes in the spar channel.

Everything fits just fine except for the 15 most outboard holes.

P1040847.jpg


P1040848.jpg



Here is a close up of one of the holes. They are all about the same:

P1040849.jpg


You can see that the misalignment is almost half the diameter of the holes.

I've tried both skins on this spar with same result. Both skins fit just fine on the other wing (or spar). I've tried everything I could think of, no luck.

I'm afraid that if I drill as it is I will enlarge either the hole in the skin or in the spar, ending up with 8 shaped holes, which is no good.

Any suggestions please...

Alain.
 
Hello Alain,

I certainly wouldn't match-drill anything on that wing panel until you can get the skin aligned and clecoed on correctly. Since both skins fit well on the other spar, is there some sag or twist in the problem spar that might cause the holes to be misaligned?

Can you cleco the skin to *just* the spar and not the ribs or rear spar? If you can, you might be able to pull everything into alignment by starting at the front spar and clecoing down to the rear spar.

If there isn't any sag or twist in the wing box and you can't get the skin clecoed to just the front spar, you might try checking the prepunched holes in the spar to see if they have consistent edge distance and spacing. If they are, then something is probably still out of alignment. If they aren't, it's time to call Vans.

Hope this helps!

Dave
 
High_Flyer said:
Hi,

I've fitted the top skins of both wings last night.
On the left wing, the outboard skin prepunched holes do not line up with the prepunched holes in the spar channel.

Everything fits just fine except for the 15 most outboard holes.

I'm afraid that if I drill as it is I will enlarge either the hole in the skin or in the spar, ending up with 8 shaped holes, which is no good.

Any suggestions please...

Alain.
Click to expand...

If both skins fit the same then I would guess the skins are punched wrong in that area or the spar. Have you checked the fit with the other spar?

CALL Vans Aircraft!
 
Both skins fit well on the right spar.
I've tried everything to align the holes, tried to cleco only on the spar and not the ribs, nothing works.
It seems to me that the left spar has been misdrilled on the last 15 holes, since the problem is the same with both skins on the left spar and both skins fit well on the right spar.
Waiting for an answer from Vans, i'll keep you guys updated.
Alain.
 
One solution would be to ask Van's for a skin that's un-punched at those 15 holes (if they have the flexibility to accommodate that) or completely blank and use a strap duplicator to drill the skin to the structure.
 
aulamborn said:
One solution would be to ask Van's for a skin that's un-punched at those 15 holes (if they have the flexibility to accommodate that) or completely blank and use a strap duplicator to drill the skin to the structure.
Click to expand...

Exactly. It appears the spar was mis-drilled. Perhaps you could work with Vans to take actual measurements which they could compare with the engineering model.

If it turns out to be the spar, the cheapest and least painful option for both parties is for Vans to acknowledge the mistake and ship a skin that is un-punched at those locations. I'll bet they can accommodate.

Drilling as-is is inviting disaster.
 
You could take the measurements of the hole spacing on the spar in question and compare them to the other spar, just as an additional check.
 
If you have not already tried.....try starting with a cleco in the middle of the skin and then fasten with clecos in every second hole as you work equally towards the tip and root.
 
Answer from Vans and more...

Here is the answer I got from Vans, and what I've replied:

From Vans:
How does the leading edge cleco onto the spar? Does that have the same mismatch or is it OK? I presume you have tried clecoing th eparts together in a different order to se if that helps.

It looks like the holes are mostly offset laterally, not fore and aft? If so, it looks like the spar or punch press may have slipped slightly during the punching process, rather than it being a variation in the bend, which sometimes makes an offset fore and aft.

It's possible that the easiest way to fix this is to add a doubler under the rivets that will have elongated holes, so they are sandwiched between the good holes in the skin and doubler. I actually wouldn't worry too much about having elongated holes on that small area where the wing is relatively lightly loaded.

Vans



My reply:
The spar is perfectly level, I've checked this many times.
I've measured the distance between the holes. Please refer once again to the new attached pictures.

P1040853.jpg


P1040857.jpg


Counting the holes from tip towards root, the distance between all holes is about 55/64, but between holes 15 and 16 it is 58/64, a difference of 3/64 or about half the prepunched hole diameter, and that's exactly what I'm seeing visually.

That seems to confirm that the holes in the spar have been mis-drilled between hole 15 and 16, and this misalignment is carried on for holes 15 to 1. As you're saying these holes are offset laterally..

Further to this, I've just been trying to fit the bottom skins and same problem there. The right wing is just fine, but the left wing same problem on the bottom skin, same number of holes.

I have not made the leading edge yet, but I'm suspecting the problem will be the same for the left leading edge skin..

Are you suggesting to match drill these holes (60 holes in total, 15 for top skin, 15 for bottom skin, 15 top and 15 bottom for leading edge) using the skin as a guide, which will make the holes in the spar elongated, and add a doubler in the "inside" of the wing, to have the spar sandwiched between 2 layers? May I also use 1 size bigger rivets there, Size 4 instead of 3??
 
hmmm

Just my opinion here, if you try to match drill through the skin holes into the spar. The drill will go to the spar hole,because its thicker, leaving you with an elongated hole in the skin. Try to measure holes carefully, and you may be able to go up on the size rivet and not have any elongation. To me that would be best. If you are dealing with 3/64ths, I think one rivet size up should fix this problem. Hope this helps. Only thing is make sure that you are able to keep the proper edge distance with an oversize rivet hole.

bird
 
I don't know if I know the best way. How hard would a new spar be at this point? I know I wouldn't use any kind of doubler, that doesn't sound right. Leading edge and bottom are that way too? I guess if I wanted to save it, I'd put blank rivets in the spar holes and pick up a whole new rivet line in between. Yuck. If the skins weren't all pre-punched ... sucks.
 
aerhed said:
I don't know if I know the best way. How hard would a new spar be at this point?
Click to expand...

I'm in France, that would be an expensive option.
And all the ribs are already riveted on the spar, so I would have to drill many rivets out to get the ribs back.
Maybe have new skins with unpunched holes at this location would be easier and cheaper. I'll see with Vans.
I'm leaving for work for a week away from home, I'll pick this up when coming back.
Thanks a lot for all the inputs.
Alain.
 
High_Flyer said:
...Maybe have new skins with unpunched holes at this location would be easier and cheaper...
Click to expand...

This is what I'd do if it occurred to me. Ask Van's a new skin without prepunched holes on the spar line and match drill them using the spar as a guide. It looks like the perfect solution.
 
Another option woul be to procure a sheet (half sheet) of the .025 alclad locally, duplicate the size and match drill all the holes except the bad ones using the skin you have now. Cleco it in place and back drill through the spar holes.

Another issue to consider is the leading edge skin, does the mismatch affect this as well?

Doug Gray
 
If it is a miss-punched spar then Van needs to fix it?

It appears from the info provided that the spar web may have shifted slightly in the punch press. If this is true then Van needs to fix the problem with your parts. However since you already have progressed to this point the simplest solution is as follows:

1. Van cuts new skins (if not already in hand for RV-6/8) and doesn't pre-punch the holes.

2. Van ships the new skins out to you.

3. You line up the new skins on your bench with the pre-punched skins.

4. You match drill the holes in the new skins using the old skins as your guide. Remember not to drill the set of holes that didn't line up.

5. Place you new skins on the spar and back drill using the spar as a guide.

It won't take you very long to drill the holes. Any other solution would be unacceptable to me.

Van parts sometime don't come out right and they don't know it. They have acted responsibly in the past and I believe they will in this case.
 
I have to agree with Paul. There's a mistake here with the spar. Intentionally producing a line of shoddy holes is not an acceptable answer. I'd have to demand new skins. And as you said, the leading edge skin will have this same problem.
 
Further to my previous posts, I have now tried the bottom skin and the leading edge skin, with the same problem on all 3 skins on the left wing.
That's a total of 60 holes (2 rows of 15 on top, 2 rows of 15 on bottom) on the outboard part of the spar, between the last 2 ribs, that have been misdrilled.

Pmerems said:
It appears from the info provided that the spar web may have shifted slightly in the punch press...
Click to expand...

I believe that's exactly what happened, and in the first response I got from Vans that's what they said as well.

Pmerems said:
...If this is true then Van needs to fix the problem with your parts. However since you already have progressed to this point the simplest solution is as follows:

1. Van cuts new skins (if not already in hand for RV-6/8) and doesn't pre-punch the holes.

2. Van ships the new skins out to you.

3. You line up the new skins on your bench with the pre-punched skins.

4. You match drill the holes in the new skins using the old skins as your guide. Remember not to drill the set of holes that didn't line up.

5. Place you new skins on the spar and back drill using the spar as a guide.

It won't take you very long to drill the holes. Any other solution would be unacceptable to me.

Van parts sometime don't come out right and they don't know it. They have acted responsibly in the past and I believe they will in this case.
Click to expand...

I've sent an email to Vans yesterday suggesting exactly that. Waiting for an answer on monday I hope.
I believe from what I've read about them that Vans will do what they can to help. However it may be a be costly as the parts have to be shipped to France. I don't know how that will work out...

Hopefully this will be resolved soon.

I'll keep you guys updated...

Alain.
 
My advice is to not touch the spar and work only with the skin. I think the best thing to do is get a new skin and redrill. I live in basel switzerland and if you need any help please let me know.
If that is close to you I can help. I plan to start building a rv7 next year. I work for a vip aircraft company as a b1 mech which we do all checks and outfitting. We have a great sheet metal workshop here and will help you as much as i can to sort this out [email protected].
 
Last edited:
If there is a definite mistake in the drilling of the spar i would be request that Van's send a new spar. The cost to Van's is not the issue the issue is you paid for a perfect spar. Your not that far along and it would be. Better to address the issue than to find out later that the skins do not line up with the leading edge skins or that this causes a warp in the wing after you have spent hundreds of hours working around a doubler fix
This should not even be a discussion for Van's they could fed ex a spar to you in a couple of days and prepay to have that one shipped back.

Smilin' Jack
 
One last item
I would drop plumb lines from the spar to the rear spar, you can be level in the length of the spar and still have a twist caused by having a rib installed wrong or the reinforcement plates installed wrong. Check all your construction so far
Jack
 
Solution underway

I have now returned home and could talk on the phone to Scott at Vans support and we found a solution.
As suggested in earlier posts on this thread, Vans will make new skins for me, unpunched at the location of the problem and ship them to me soon. When the skins arrive I will simply match drill the skins to the spar.

Apparently from the discussion I just had, when drilling the spar at the factory they have to reposition the spar to punch these 4 rows of 15 holes and what probably happened is that the spar slightly moved and the holes have been drilled slightly offset, unoticed by the people at Vans. But Vans is so far very helpful and as written above will do what they can to correct the situation.

Thanks a lot to all of you for all the answers and suggestions.

I'll update this when the new skins arrive.

Alain.
 
Update

Hi everyone,

Update on the previous posts:
I have receive the replacement skins, unpunched at at the location of the bad holes in the spar.
All good for the top and bottom skins, however the leading edges skin is a right one instad of a left one... Talked to Vans support sent email and they will send yet another one.
It will take time, but eventually the problem will be solved.
I have to say that the support at Vans is very good, everyone I speak to is very helpful, and they are doing what they can to solve the issue. The replacement parts have been sent at no cost to me.

Whishing everyone a merry Christmas and a "RV filled" happy new year.

Alain.
 
Alain,
That is great to hear! I am glad that a solution in on the way. You and I are roughly at the same place in the build. I know how frustrating it is to have to slow down for something out of your control. Ultimately, you'll feel better with this solution rather than the doubler.
 
Problem solved

HI,
Glad to report that my problem is now solved.
Vans sent me new skins, unpunched at the location.
Remember the 1st try was only half good as they sent me correct top and bottom skins, but a right leading edge instead of a left one. Second try they sent ma the correct leading edge, now all I have to do is match drill from the spar to the new skins.
Thanks everyone for all the posts to try to find a solution.
Alain;
 
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