Main spar ding

Probably nothing but I thought I would throw out some pictures for everyone to weigh in on. While match drilling the tanks I accidentally dinged the spar "block" with my #40 bit. I dressed it out and estimate it only to be 1/32" deep. I know Van's probaby doesn't expect us to be able to build these airplanes with no dings occasionally but then again it is the spar.



Thank's

You have nothing to worry about there, build on!

Mark,

I would file it down more. Prime it and move on.

I would also consult Van's about it too.

Does not look bad but let VAN's make the call.

My .02

Blend, alodine, touch up with paint and move on.

I have a spar ding in my airplane too (bucking bar slipped when solo riveting)...consulted Van's, they said sand, prime, move on...and so I did.

More blending

While I don't think you're going to need a new spar, I would blend that much more gradually than you currently have...perhaps an inch on either side of the gouge...and of a depth to make all of the original gouge disappear. There are two things that cause me concern:

1. This is the most highly loaded part of the spar (right near the root)
2. The gouge is going crosswise across the bar. The same gouge in a spanwise direction wouldn't be nearly as bad.

I learned quite a few years ago that it's better to have less material, and a smooth transition than to have more material with a sharp transition. I've actually seen a fracture progress through a series of holes until it went around one particular hole before resuming the hole to hole progression. Closer inspection showed the crack went around that hole to go to a sharp (reentrant) corner that happened to be nearby. So, having a stress riser (the sharp corner) was actually weaker than having missing material (the hole in the plate). Stress risers can be very serious.

Also call Van's. Their word should be final.

Blend it more

Hi Mark,

Doesn't look that bad to me, as the other guys have said, I'd blend the damage a bit more to improve the blend radius, 20-1 radius is the norm. alodine 1200 then prime. If you can measure the blend area and depth to within .000" (3 decimal places) depth, length and width, send that to VANS I'm sure your in the clear.

Cheers,

Forgettaboutit... not an issue.

Another question

After fixing a small ding, is it acceptable to use rattle can primer or is alodyne required on the spar?

Skyking902001

Your choice... either will work just fine.

skyking902001 said:

After fixing a small ding, is it acceptable to use rattle can primer or is alodyne required on the spar?

Skyking902001

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I did exactly as Van's told me to do on mine...sand, prime, move on. No alodine, but you can if you want. I didn't.

I'm waiting to hear back from Van's monday before I dress it anymore, but a local AP friend looked at it and said as many others that the correct way to fix this is to make the area look almost like a shallow ditch around the damaged area, just deep enough to remove the drill bit marks. The radius needs to be about 1/4" each side of the marked area with a very gradual blend. I just hate to take that much material off the spar! Man, my hide is sitting almost over that area!!

Thank's for the input..

The stress concentration factor for a V-notch is 6, and that particular V-notch is located in a highly stressed component subject to cyclical loading.

Do not use a file. You want to blend it out, then polish to eliminate any scratching. You can do it best with aluminum oxide sandpaper and your thumb, or appropriate 3M Roloc disks in a small right angle die grinder.

DanH said:

The stress concentration factor for a V-notch is 6, and that particular V-notch is located in a highly stressed component subject to cyclical loading.

Do not use a file. You want to blend it out, then polish to eliminate any scratching. You can do it best with aluminum oxide sandpaper and your thumb, or appropriate 3M Roloc disks in a small right angle die grinder.

Click to expand...

good info!

cjensen said:

I have a spar ding in my airplane too (bucking bar slipped when solo riveting)...consulted Van's, they said sand, prime, move on...and so I did.

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Not repaired, at least not in the photo above. You must blend deep enough to remove all trace of the notch. See the gouges still remaining above and below the hole? Same stress factor as the original, untouched notches.



Plenty of books on this subject, but you really don't need to look any further than your Vans builders manual, page 5-2, last paragraph....remove all trace of the scratch, 600 grit final finish.

Hey Dan, from where do you have these numbers? Kay

DanH said:

Not repaired, at least not in the photo above. You must blend deep enough to remove all trace of the notch. See the gouges still remaining above and below the hole? Same stress factor as the original, untouched notches.

Plenty of books on this subject, but you really don't need to look any further than your Vans builders manual, page 5-2, last paragraph....remove all trace of the scratch, 600 grit final finish.

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True, but these marks are in the web which is loaded much less and primarily in shear (rather than tension / compression), so the application is far less critical than the spar caps.

Good illustration, Dan.

KayS said:

Hey Dan, from where do you have these numbers?

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Memory, but a look on my shelf finds the factors for notches and holes in Fundamentals of Aircraft Material Factors, Charles Dole. I used the standard 3X for a hole for the half hole round notch, a reasonable aproximation.

mcencula said:

True, but these marks are in the web which is loaded much less and primarily in shear (rather than tension / compression), so the application is far less critical than the spar caps.

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Sure. I just pointed out "the repair that is not a repair" because it's seen so often in the field.

DanH said:

Sure. I just pointed out "the repair that is not a repair" because it's seen so often in the field.

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Absolutely Dan...I did sand a bit farther, and had it "approved" by our mechanics here where I work, and Van's. That's the last picture I had of it before it was primed.

On the subject of spar damage I think it’s important to ask Vans, although I would assume at this one they would most likely just say sand and prime.
I also had issues with spar damage during the building process. First picture shows the result of me letting the U- channel get to low while drilling above the center section. I realized my mistake before it got worse than this. The picture shows damage of the fuselage top forward spar (picture taken from above). This was a sand, prime and move on issue.



The other had to do with shipping damage of the QB wings where the wing crate had a rough treatment during shipping. Somehow the screws holding wings during transportation broke and the subsequent movement of the spars against the broken screws made scratches inside the sparholes of the right wing that made it a replacement issue. It was not first a replacement from my written description of the damage issue but later “up close” pictures of the damage made vans engineers call for a replacement of the entire quickbuilt wing (pictures below of right wing). Therefore I think the lesson also is not just to consult vans but also make sure to show some good quality pictures of the damage to help them in the decision on what actions needs to be taken. My left wing also had one 2 mm deep scratch just outside the edge of one of the large sparholes which due to location and direction was a sand and prime issue.





Vans wanted the right wing back for testing. I think they wanted to make sure it did not end up flying on another RV-8 somehow.

Final results

Here are PIC's of the final result if my spar ding. As per Dan H. suggestions I started out with a 220 grit aluminum oxide sandpaper instead of a round file and removed all the tooling marks. I then finished the "ditch" out with a 600 grit wet/dry sandpaper to blend it all in. The result was that all tooling marks are removed, the area has a gradual blend to it and I only had to remove 1/16" of spar block at the deepest measurement. My A/P friend and Vans said that this was the correct way to repair the damage and would not sacrifice much if any of the strength of the spar. I now only have to prime the area to finish the repair.

Thank's for all who weighed in.

PS. Vans has it right there in black and white......."Remove the clecoed tank assembly from the wing, and drill all the rivet holes to final size. (Doing so off the wing prevents accidentally drilling the spar)".

Wow - that looks good, great repair.

WOW!!! I Mean WOW...

Maxrate said:

Here are PIC's of the final result if my spar ding. As per Dan H. suggestions I started out with a 220 grit aluminum oxide sandpaper instead of a round file and removed all the tooling marks. I then finished the "ditch" out with a 600 grit wet/dry sandpaper to blend it all in. The result was that all tooling marks are removed, the area has a gradual blend to it and I only had to remove 1/16" of spar block at the deepest measurement. My A/P friend and Vans said that this was the correct way to repair the damage and would not sacrifice much if any of the strength of the spar. I now only have to prime the area to finish the repair.

Thank's for all who weighed in.

PS. Vans has it right there in black and white......."Remove the clecoed tank assembly from the wing, and drill all the rivet holes to final size. (Doing so off the wing prevents accidentally drilling the spar)".

Click to expand...

That is one of the nicest repairs I've ever seen!!! GREAT job.

An acceptable job....there are no optional lesser quality levels. This is the minimum.

I'll pull G with you on that repair Mark.