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Interesting countersink

M

MercFE

Well Known Member
Worked on countersinking all the required spots on all the HS and VS spots earlier this week. After a lot of studying and practicing the process, I was able to get the micro stop set up to be the right depth and went to work.

All of the countersinks came out great... Except one. I can't tell you what I did, nor can I tell from looking at it as the impression of the cage didn't move. But, it appears that I got the countersink to walk somehow, leaving a perfectly oval hole in an HS-902 spar.

The location of the errant hole is right in the middle of the spar, in what will be the lower edge.

I sent an e-mail to Vans support, but haven't received any response yet. Work has interfered with trying to call them. I'm leaning toward needing replacement, but I'm hoping for some miracle cure. Hoping to prime over the next couple days and start banging rivets this weekend.

So, figured since Vans hasn't helped yet, I'd get an idea of what others here think.

 
Looks like you have room to just add an extra rivet on each side of the 'oops' and build on. Fortunately it's on the bottom so not as visible. Doubt a re-do would be required.

Chris
 
Chris,

Be honest with you, that's exactly what I'm hoping. Guess I should dive into the AC to figure out the spacing and see where I could fit them in.
 
Try this...

measure the longest part of the hole and see if an oversize flush rivet would fit. then drill so hole is round and HAND Countersink,
this would allow for proper spacing, and not sacrifice any structural integrity.
 
Spar fix

YellowJacket RV9 said:
Looks like you have room to just add an extra rivet on each side of the 'oops' and build on. Fortunately it's on the bottom so not as visible. Doubt a re-do would be required.

Chris
Click to expand...

I agree with Chris but Vans is the final word. They may recommend a doubler be added on the inside spanning the bad hole and the one either side. Holes spaced equally between the bad hole and the good holes either side should fit. Edge spacing is 2 x diameter of the hole?
You may consider making a guide from a piece of scrap. Cleko it behind the holes so the pilot has a good hole.
Also, try and hold the cage so it doesn't spin when it touches the part. A small shard stuck on the guard can easily leave a nice circle to buff out.
 
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bad hole

The idea is to carry the load through the rivet into the spar in shear.
Not just fill the hole. It is critical that the holes be under the upper limits
for the diameter of rivet you are using so the load is transmitted in a uniform manner. It looks to me like you are at 2X diameter from the edge. I think a double is called for and not knowing the design loads or whether it is inboard or outboard on the spar, CALL Vans. Remember the lower spar sees more tension than compression.
 
Just replace it

Man, that part is 21 clams plus maybe 10/20 bucks shipping. If you had called yesterday you would have had it by this Friday. You'll have plenty of opportunity to repair parts later on in your build when structures have been assembled and you screw something up. Why debate, speculate? Practice on this damaged spar, use it for spacers, setting microstop depths. These are some of your first parts. Try to achieve very high standards early on and if that involves replacing some parts, so be it. You want a miracle cure.....40 dollars :)

Victor
Id be more than happy to come on up and spend a little time with you guys in your shop just to make sure you are off to a solid start. :Add note, I did all the sheet metal at Maywood Middle School and the new science wing addition a couple of years ago. Also are you the Victor that knows John Ridge from Emerald Aire?
 
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Agreed about replacing it, if the price is right. Still good idea to learn about the different repair possibilities.

Hopefully, I might be able to find some time to actually call Vans today. Depends on if my scheduled flight actually goes or cancels here soon.

Greatly appreciate the offer to meet any other Vans guys in the area. Joined the EAA chapter in Puyallup recently. Quite a few Vans builders in their chapter.

As for knowing John Ridge, I'm not that Victor. LOL

AlphaCharlieBravo said:
Man, that part is 21 clams plus maybe 10/20 bucks shipping. If you had called yesterday you would have had it by this Friday. You'll have plenty of opportunity to repair parts later on in your build when structures have been assembled and you screw something up. Why debate, speculate? Practice on this damaged spar, use it for spacers, setting microstop depths. These are some of your first parts. Try to achieve very high standards early on and if that involves replacing some parts, so be it. You want a miracle cure.....40 dollars :)

Victor
Id be more than happy to come on up and spend a little time with you guys in your shop just to make sure you are off to a solid start. :Add note, I did all the sheet metal at Maywood Middle School and the new science wing addition a couple of years ago. Also are you the Victor that knows John Ridge from Emerald Aire?
Click to expand...
 
Marteck said:
Remember the lower spar sees more tension than compression.
Click to expand...

That's true for the wing, but not the Hstab. It is typically pulling down on these airplanes so it's in compression.

A doubler will fix this quite easily and not be that obvious since it is on the lower side. I'm sure VANs can give you the appropriate details.
 
I finally learned that you could search for parts on the Vans online store. Being only $21, and needing some other stuff anyways, it makes sense to go ahead and order the replacement.

I fully believe that the mistake is repairable, but I'm sure this will be amongst my cheapest mistakes in the build.
 
It's kind of a shame it has to be fixed... it really is a beautifully done oval shape. (Almost like it was done on a mill!)
 
MercFE said:
All of the countersinks came out great... Except one. I can't tell you what I did, nor can I tell from looking at it as the impression of the cage didn't move. But, it appears that I got the countersink to walk somehow, leaving a perfectly oval hole in an HS-902 spar.
Click to expand...

Victor, take a close look at your countersink cutter. I think you will find that the fluted or cutting portion of the cutter extends down onto the pilot/tip. If the material you are cutting is thin enough, and you introduce enough of a side load, the pilot itself can cut and allow the hole to oval out. A scrap piece of metal, clamped to the underside of the flange will provide more material as a guide.
 
Definitely listen to what Vans has to say and follow their advice, but when I spoke to them about a similar fault in my early building, I like the advice they gave me. They said "Don't forget what you are building. You're building an airplane". So when I screw something up, I ask myself whether replacing parts is critical for the safety and performance of the plane, or is the real issue cosmetics and the warm fuzzies I may get from seeking perfection.
 
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