What is a double margin threaded drill bit? Not familiar. Thanks.
http://i58.tinypic.com/1h858k.jpg
Is this is not a more desirable configuration for transferring load from the horizontal plane to the vertical plane? Seems like a relief like the one in the SB only serves to concentrate the load at that location.
Hello everyone,
A quick tally on the numbers so far listed on this thread:
Cracks found- 5
No Cracks - 40
11% so far on finding cracks in the hs
I will be checking my 6a tomorrow to report back.
Thanks
John
When the numbers stack up, I suspect we'll find the statistical chance of a crack was increased by notching toward the neutral axis, due to loss of section modulus.
Dan, I was thinking the same thing. Except this isn't about statistics. It's about increased stress in the spar member where it has a reduced area, due to these reliefs....When the numbers stack up, I suspect we'll find the statistical chance of a crack was increased by notching toward the neutral axis, due to loss of section modulus. I don't have the exact height and thickness handy. Ballpark would be a stress increase of 30~40% with upper and lower notches 5/16" deep, given a spar center section height of 4"~5 " and thickness of .030"~.040".
ke the one on the left in the illustration. Full height would be like Tom's (post 26) or Paul's (post 36). Some who did cut notches ...
Anyone else given any thought to their procedure? I think technique will matter in this repair and any suggestions could prove invaluable.
I noticed in a lot of the photo's that where cracks exist even the slightest roughness or bend in the relief seems to be. I have zoomed in on most of the photos even including the one in the SB and you can see the roughness. Am I seeing something that is not there.
I would be interested if Vans comes up with a revision to this service bulletin down the road and offers a different fix.
Jack
Pulled the fairing and at first look thought I was home free. One piqued my interest a little though so more cleaning and buffing and macro photography and the lower right relief had a crack about 3/16th of an inch. But, it's a crack.
In the really blown up photo you can see the relief was no smoothed and polished as well as it could have been. The other three were smooth and no cracks.
I'll fly some and when the parts are available I'll comply with the SB. The safety of the air frame is not in question as it stands right now.
1900 hours, lot's of acro, some grass.
205HP, CS.
Really hard to see any crack here but as I looked really close I could see a tine hair line running across the relief notch, which didn't look rough until I really macro'd and blew it up. see below
Here is a really zoomed in clear shot of the crack... a lot of work over a little crack..
Yes, I see that the bottom rivet is not set correctly, but thanks in advance for pointing that out..
I at least have not lost my sense of humor over this
In these pictures the flange of the spar does not set flush with the skin and the skin looks pulled up just a bit. I wonder if this condition is putting a possible load on the flange exist on the other aircraft that have found cracks?
Pulled the fairing and at first look thought I was home free. One piqued my interest a little though so more cleaning and buffing and macro photography and the lower right relief had a crack about 3/16th of an inch. But, it's a crack.
In the really blown up photo you can see the relief was no smoothed and polished as well as it could have been. The other three were smooth and no cracks.
I'll fly some and when the parts are available I'll comply with the SB. The safety of the air frame is not in question as it stands right now.
1900 hours, lot's of acro, some grass.
205HP, CS.
Really hard to see any crack here but as I looked really close I could see a tine hair line running across the relief notch, which didn't look rough until I really macro'd and blew it up. see below
Here is a really zoomed in clear shot of the crack... a lot of work over a little crack..
Yes, I see that the bottom rivet is not set correctly, but thanks in advance for pointing that out..
I at least have not lost my sense of humor over this
I don't hear any serious questioning of Van's Aircraft. As for the speculation, conjecture, and discussion - well, this is an Internet discussion board!...With out close inspection of many examples and test data any speculation is not of much value.
... I assume (?) I can do the inspection and log book entries myself...
Just more data-I don't hear any serious questioning of Van's Aircraft. As for the speculation, conjecture, and discussion - well, this is an Internet discussion board!
We were talking about this and wonder if the correlation is the notches