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Spar damage on initial fitting?

claycookiemonster

Well Known Member
The wings have been successfully hung for initial fitting and one has been removed. Upon removal, there is clearly some slight damage to the aft surface of the spar there. There is also a "rubbed" spot on the center section which looks like the culprit. There is no damage of any kind on the front surface of the spar.

This is a bit more than just rubbing off the anodized coating. There is a bit of a tactile sensation there. Maybe the thickness of a sheet of paper?

Given the tight fit, and the struggle to get the alignment right, I'm not totally surprised this happened. I'm not sure how else we could have inserted the spars.

I guess I'm hoping for reassurance on this.
 

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I'm sure this is not the first time it's happened to someone. I recall there is a comment in the construction manual about rounding off and tapering any sharp rubbing edges before inserting the wings. You could still do that for when the wings go back in. The limit of any gouging is generally 10% of the material thickness I believe. I think you should be OK, but verify with Vans because it's obviously an important part.
 
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There were some gouge marks on my spar from initial fitting of the wing. I lightly sanded down the gouge marks to remove the stress riser only, not the big area. Lightly prime the gouge area with zinc chromate. Don’t use too much because the extra thickness of the primer will bind the spar again since there is almost zero clearance left.

When you are ready to mount the wings permanently, clean everything well with acetone. Clean the bolt holes with pipe brush. Lube everything before installing.

If you mount the wings only one time and never remove them, do you know if there are gouge marks? 😉
 
I'd contact Van's about this.

Perhaps a decent lubricant will help next time. Ages ago, I remember that the BD-5 specified lanolin for this job. They said that it was the only thing they knew of that worked. Back around 1975, that was.

Dave
 
The limit of any gouging is generally 10% of the material thickness I believe. I think you should be OK, but verify with Vans because it's obviously an important part.

Except for spars. The “manufacturer” is the only authority, which is you technically. However, I believe the intent is whomever engineered the spar, which is Vans.
My bet is they will tell you to clean them up, prime, and build on. The most critical part of the machined spars are the tight tolerance thru bolt holes. None of the damage affects the holes and very little material was “lost”.
 
I'd contact Van's about this.

Perhaps a decent lubricant will help next time. Ages ago, I remember that the BD-5 specified lanolin for this job. They said that it was the only thing they knew of that worked. Back around 1975, that was.

Dave

+1 on Vans contact. May ask to sand smooth.

I made a spreader to help prevent this. Long thread, two nuts and washers inside. Measured with digital caliper. It helped a lot
 
Clay,
I had the same happen to mine. Round the edges before reinstalling and use plenty of grease next fit. I called Vans and they said getting the required edge distance before drilling the rear spar was more important. I would clean them up with scotch brite and prime before refitting.
 
Thanks all. Good idea to check in with the Mother Ship. Also, good recommendation to sand off any irregularities. We did grease the alignment pins, but not the spar/center section interface. Lesson learned for final assembly. Thanks.
 
Let me give you the professional stress disposition I have given 1000's of times on air transpor( airplanes to maintenance.

  • "break sharp edges" and/or blend smooth removing minimum material.*
  • No sharp edges (maroon scotchbrite pad on rotary tool works well if you are careful and controlled). Get some scrap and practice, other wise hand work it (SLOWLY) under GOOD LIGHT. and magnification.
  • Final Surface finish 63 rms (root mean square) accomplished with fine (light grey) Scotchbrite pad and is as smooth or smoother than original finish,
  • Measure depth of material removed and note here: _____________ Max depth is x.xx. if depth is great reconvene with Engineering.
  • Prime with (spec) and pain (spec) to match as required. (Note you removed clad so you need to use corrosion protection)
  • Demine what caused the issue and correct it before installing spar in center section.
  • Reassemble structure

* Minimum material removal means do not make it deeper, wider or longer than needed to remove damage and make smooth. in general 20 to 1 blend ratio for deeper gouges. Say you have a sharp 0.010 gouge (I think yours is much less), you would have 0.4" wide blend, or 0.20" each side of damage as you blend out.

If you are in an area of where fastener sits you may NOT want to blend there, adjust the blend ratio, say 10 to 1. In extrema cases (which your is not) may need to blend around the hole or spot face the land where fastener seats. Do not do this. It is just an example for much larger and deeper damage at edge of hole. This is typical of corrosion repair, which you are no where near. However if damage is across a fastener hole it will be a little more tricky and require more time and careful blending to remove damage and maintain flat landing for fastener.

In general aircraft are designed with rework allowable expressed in percentage of total thickness (example 10%) or actual dimension (0.030"). NOT SAYING THIS IS ALLOWABLE, JUST EXAMPLE for transport category planes with thick metal, not sheet metal. In the case of Air transport planes there is a SRM or Structural Repair Manual with allowable damage. In this cases call Van's.

I'm sure Van's Aircraft will say scrap the spars and buy a new wing kit... Ha ha. Kidding. You are doing the right thing by asking. Eye balling it this will have zero point zero zero effect on the over all strength of the wing. Another way of saying it, this is not the weakest or most critical part of the wing for any flight load. The wing roots are overbuilt intentionally. Van's did not cut the margin of safety to the bare minimum. However we can not allow damage or be cavalier about it. It always has to be addressed. During the manufacture of large jets you might be surprised how many Booboo's there are. They are all documented, addressed and recorded and those records or rejection tags and dispositions go with the plane. Yes in a few cases for big screw ups sections of fuselage or whole wing were scrapped. Rare, but it has happened.

I recommend you find out what is scratching the spar. You may have some issues in your center section to address before plugging them back in.
 
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Damage

Yep it’s totally ruined, best thing to do is sell it for scrap. But there is a bright
Side. I’m flush with bitcoin money and I’m willing to give you twice what
Aluminum it selling for. But ya gotta act quick, because those flying cars that
are coming out any day now and everyone knows there gonna make conventional worth penny’s on the dollar!!
 
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