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11-29-2012, 08:28 PM
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Join Date: Feb 2010
Location: Perth, Western Australia
Posts: 1,647
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As Tony said...
Vans were aware of the step when they did their investigation and clearly don't consider that it needs any correction. If you try to remove it, you are more likely to create a problem. In fact, the plus side of having a step is that you have a little extra thickness in that area to distribute the bolt tension, and that's not a bad thing.
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rgmwa
RV-12LR 912ULS
120346
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11-30-2012, 04:06 AM
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Join Date: May 2010
Location: Spring Hill Fl
Posts: 734
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OK AS IS
Robert
I see this in a different view
The high point narrows the point load and increases the shear potential
However van's has solved this problem by adding a bolt at each side to share the tension and move it to the flange of the U-Chanel.
So I agree Vans were aware of the step when they did their investigation and clearly don't consider that it needs any correction.
Quote:
Originally Posted by rgmwa
Vans were aware of the step when they did their investigation and clearly don't consider that it needs any correction. If you try to remove it, you are more likely to create a problem. In fact, the plus side of having a step is that you have a little extra thickness in that area to distribute the bolt tension, and that's not a bad thing.
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11-30-2012, 05:42 AM
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Join Date: May 2008
Location: Arlington, Texas
Posts: 127
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Steps amd cracks
For RV2002Builder, I have steps at all 4 outboard bolt hole locations and I have 2 cracks on the right side forward hole and 1 crack on the left side forward hole. There was no washer contact from the bolt hole to the flat part of the C-section at any of the 4 bolt hole locations.
As Peterk posted I have the kit and have started the repair. I have done a fit check of all the parts and everything fits very well. A slight interference between the forward part of left hand saddle and a rivet which was identified as a possibility in the SB for earlier kits. With help, we have straightened out the wrinkles and clecoed the doublers in place. All the current holes line up without any problem and the doubler pulls up tight against the existing skin without any visible gaps.
Glad to see some light at the end of the tunnel. Even our Texas weather is cooperating so working conditions at the hangar are comfortable. Bob Kibby N712BK "still on injured reserve but recovering"
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11-30-2012, 06:13 AM
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Join Date: Feb 2010
Location: Perth, Western Australia
Posts: 1,647
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Quote:
Originally Posted by joedallas
Robert
I see this in a different view
The high point narrows the point load and increases the shear potential
However van's has solved this problem by adding a bolt at each side to share the tension and move it to the flange of the U-Chanel.
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Yes, the front half of the doubler is basically beefing up the channel web and helping to spread the concentrated load from the problematic front bolt more efficiently, and generally reduce stresses. Roughly the same as if the web in that area was thicker to start with. It's also providing more bearing area for the AN5 bolt shank, but that's probably a secondary consideration. The aft part of the doubler is mainly along for the ride, because that's not where the problem is.
Anyway, that's just my interpretation, and I don't want to hijack the thread. I'm happy to leave all the analysis to the real aeronautical engineers at Vans and see how Tony progresses with his installation. Just waiting for my parts to arrive now, so I can do the same. It's also clear from looking through the documentation that this exercise took a LOT of engineering time, effort and money, so thanks again to Vans and to Scott for all his input.
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rgmwa
RV-12LR 912ULS
120346
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11-30-2012, 07:18 AM
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Join Date: Dec 2008
Location: Lacey, WA
Posts: 1,365
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Actually, it's cold in Tony's hanger and he wants to fly on any of the good days we will be getting this Winter. Look for updates from him on the S.B. install in the Spring.
There should be good posts from Kibby and others in the warm southern climates  .
Tony
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Tony
E-LSA RV-12 ULS
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11-30-2012, 11:16 AM
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Join Date: Nov 2011
Location: Hansville, Washington
Posts: 536
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Quote:
Originally Posted by rgmwa
Vans were aware of the step when they did their investigation and clearly don't consider that it needs any correction. If you try to remove it, you are more likely to create a problem. In fact, the plus side of having a step is that you have a little extra thickness in that area to distribute the bolt tension, and that's not a bad thing.
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The bigger question for Vans is why is there variation in these hole pockets? Some have no steps, and those that have steps, have steps of varying dimensions. For a machining operation on a piece of Primary structure, this is clearly unacceptable. Very hard for me to fathom how this could happen in the first place, and also how it could pass post-machining inspection. This variability makes defining the problem and the solution that much more difficult.
And yes, I say this (reluctantly) as having been Director of Quality Assurance for 10 years at Boeing Commercial Airplanes.
I myself wouldn't touch adjusting the step with a ten foot pole.
Bob Bogash
N737G
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11-30-2012, 12:07 PM
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Join Date: Jul 2005
Location: Hubbard Oregon
Posts: 9,035
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Quote:
Originally Posted by NASA515
The bigger question for Vans is why is there variation in these hole pockets? Some have no steps, and those that have steps, have steps of varying dimensions. For a machining operation on a piece of Primary structure, this is clearly unacceptable. Very hard for me to fathom how this could happen in the first place, and also how it could pass post-machining inspection. This variability makes defining the problem and the solution that much more difficult.
And yes, I say this (reluctantly) as having been Director of Quality Assurance for 10 years at Boeing Commercial Airplanes.
I myself wouldn't touch adjusting the step with a ten foot pole.
Bob Bogash
N737G
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The center section C channel on an RV-12 is made from an aluminum extrusion.
When you purchase raw aluminum extrusion, the specified dimensional tolerances provided by the manufacturer are quite large (at least compared to rolled aluminum sheet stock).
The channel would have been prohibitively expensive if every single part received surface milling on all sides during production.
Consequently, when the pockets are milled using the bottom surface as a zero reference, any variation in the extruded thickness will cause an equal variation in the pocket alignment.
It can not be said for certain that this explains 100 % of the dimensional variation at the bottom of the pocket, but it is certainly a lot of it.
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11-30-2012, 12:26 PM
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Join Date: Jul 2005
Location: Hubbard Oregon
Posts: 9,035
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Quote:
Originally Posted by Bob Kibby
For RV2002Builder, I have steps at all 4 outboard bolt hole locations and I have 2 cracks on the right side forward hole and 1 crack on the left side forward hole.
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I stand corrected.
I rechecked my information and found that their was only one airplane that had aggresive cracks that required an additional re-enforcement (beyond what the S.B. provides), where there was also a step.
Quote:
Originally Posted by Bob Kibby
There was no washer contact from the bolt hole to the flat part of the C-section at any of the 4 bolt hole locations.
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By flat part, I assume you mean the main web of the C channel, because even if there is a step at the pocket location, there is still a flat at the bottom of the milled pockets at the location of each bolt hole. Just in some cases it is not as large as the full foot print of the washer (but it still is flat).
Just to reiterate...
A stepped surface under the washer had nothing to do with cracks in the channel. The cracks were caused by excessively loose bolts. Most of the airplanes that have any cracks, had no steps under the washers. In some of these cases, the washer pounded a recessed depression into the C channel (because the bolt was loose).
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12-01-2012, 06:18 PM
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Join Date: Nov 2008
Location: Gloversville, NY
Posts: 1,587
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Received my SB kit today.
Inventoried, it's all there. Congrats and thanks to everyone at Van's for providing what appears to be a well engineered improvement. Sure is nice to get such a complete package, so we don't have to chase down the necessary parts on our own.
Serial # 176, about 100th to fly.
__________________
John Peck, CFII, A&P, EAA Tech Counselor, Flight Advisor.
?Master Pilot? Award, UFO Member.
RV-12 N37JP 120176 Flying since 2012.
One Week Wonder Build Team, OSH 2018.
VAF paid through 10/2019.
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12-02-2012, 08:32 PM
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Join Date: Dec 2008
Location: Lacey, WA
Posts: 1,365
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JB finishes upgrade w/picture album
JBs completed upgrade:

John Bender completed his SB 12-11-09 MLG Upgrade and has posted a picture album in Piccasa:
http://www.vansairforce.com/communit...0&postcount=98
John,
Hope you don't mind, a post in this thread will lead searchers for SB 12-11-09 to your pictures.
Tony
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Tony
E-LSA RV-12 ULS
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