Spar damage on initial fitting?

[claycookiemonster]

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.

[abuura]

Keep going...inevitable result of fitting the wings and then removing them.

[PaulvS]

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.

[PhatRV]

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? 😉

[David Paule]

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

[Taltruda]

I believe the instructions have you lather it with grease..

[JonJay]

Originally Posted by PaulvS

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”.

[BillL]

Originally Posted by David Paule

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

[Maxrate]

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.

[claycookiemonster]

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.