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  #11  
Old 08-05-2021, 09:18 PM
seagull seagull is offline
 
Join Date: Dec 2019
Location: San Bernardino
Posts: 402
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Did you follow the link I posted, is that the e screw you think it is?

It's possible my builder did an upgrade and countersunk the panel screws. Possibly the original kit is button head that you noted.

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Last edited by seagull : 08-05-2021 at 09:35 PM.
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  #12  
Old 08-06-2021, 12:04 AM
Mich48041 Mich48041 is offline
 
Join Date: Apr 2008
Location: Riley TWP MI
Posts: 3,237
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Seagull, plan's page 29A-11 dated 2013 calls for AN507C632R8 screws which are flat head countersunk SS.
My original plans dated 2008 call for AN515-6R8 to hold the instrument panel.
I am the only one using MS35206-228 which are an improvement over the AN515-6R8.
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Last edited by Mich48041 : 08-06-2021 at 08:13 AM. Reason: corrected typo
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  #13  
Old 08-06-2021, 07:04 AM
Ezburton Ezburton is offline
 
Join Date: May 2017
Location: MD
Posts: 106
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Quote:
Originally Posted by StephenMiner View Post
After quite a few oil changes and taking the cowling off and putting back on numerous times, a few of the screws are stripped. I contacted vans to get replacements but they want to know the part numbers for the screws. I am having a hard time finding the screw part numbers for the RV-12 (everything on the top and bottom cowling). I am not the original builder. Any ideas what all the screws part numbers are along with the washers? Any help is appreciated!
I had the same problem on my Long EZ and now Velocity, but they were flat head SS screws. I use a powered screw driver for putting in and taking out. In/out half a dozen times and I had to throw them away or risk not being able to get them out again.

A few years ago I switched to torx 100 deg flat head SS screws and haven't stripped one since. They do however sublimate when they impact concrete and must be replaced.

I haven't looked for pan head ones, but I am sure they are out there.
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  #14  
Old 08-09-2021, 10:15 AM
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rcarsey rcarsey is offline
 
Join Date: Jul 2012
Location: North Brunswick, NJ
Posts: 273
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Quote:
Originally Posted by rvbuilder2002 View Post
This is the screw specified in the KAI.

The un-threaded portion of the shank reduces wear on the cowl and enlargement of the holes (important on the RV-12 in particular since the fiberglass is not very thick).
I have to check the KAI when I get to the hangar (apparently I've been using wrong 6 screws for the front of the upper cowl for awhile now).. but wouldn't this logic also apply to areas such as the wheel fairings (holding the two halves together).. and possibly to other areas such as: 8 screws holding on the lower cowl's nose leg plate, 4 screws holding on the lower cowl, or the screws holding on the wheel fairings to their mounting brackets?

I'm guessing that the factory just hasn't seen the wear in those areas at this time ?
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  #15  
Old 08-09-2021, 11:19 AM
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DaleB DaleB is offline
 
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Location: Omaha, NE (KMLE)
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Quote:
Originally Posted by Ezburton View Post
A few years ago I switched to torx 100 deg flat head SS screws and haven't stripped one since. They do however sublimate when they impact concrete and must be replaced.

I haven't looked for pan head ones, but I am sure they are out there.
McMaster has 18-8 stainless Torx round head screws.

Where'd you find the 100 degree Torx flat heads?
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  #16  
Old 08-09-2021, 11:20 AM
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rvbuilder2002 rvbuilder2002 is offline
 
Join Date: Jul 2005
Location: Hubbard Oregon
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Quote:
Originally Posted by rcarsey View Post
I'm guessing that the factory just hasn't seen the wear in those areas at this time ?
That guess would be correct.

You also need to keep in mind that vibration influence and other factors varies with different parts of the airframe. Screw style is a factor as well.
In cases where flush screws can be / and are used, the smooth surface of the screw head is baring on the fiberglass within the countersink. This is not the same as screw threads baring on the interior sides of an un-countersunk hole.

Another main difference with the larger wheel fairing screws is that if the fairings are installed per the plans, the brackets have a net fit to the molded in pockets on the wheel fairing that restrain movement. The primary work of the screw is to just hold the bracket in place within the pocket.
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  #17  
Old 08-27-2021, 10:03 PM
Charlie12 Charlie12 is offline
 
Join Date: Oct 2014
Location: Port Orange FL
Posts: 53
Default cowling screws

Scott is speaking from the factory so I am hesitant to disagree, but my KAI (p. 38-07) says AN526C832R8 and that is all I have ever used. I just had the cowling off for an oil change last week.

Washer head AN525 has an unthreaded portion of the shank and threads in bearing against the edges of a hole has always been considered ill-advised in structural design (it was specifically forbidden when I worked for the Air Force) so this type screw makes sense but that is not what is called for in my KAI. Maybe it was a revision to the KAI after I finished building?
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  #18  
Old 08-27-2021, 11:05 PM
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jrock836 jrock836 is offline
 
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Quote:
Originally Posted by Charlie12 View Post
Scott is speaking from the factory so I am hesitant to disagree, but my KAI (p. 38-07) says AN526C832R8 and that is all I have ever used. I just had the cowling off for an oil change last week.

Washer head AN525 has an unthreaded portion of the shank and threads in bearing against the edges of a hole has always been considered ill-advised in structural design (it was specifically forbidden when I worked for the Air Force) so this type screw makes sense but that is not what is called for in my KAI. Maybe it was a revision to the KAI after I finished building?
Scott addressed the confusion in the below linked thread..

https://vansairforce.net/community/s...=193497&page=3
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  #19  
Old 08-29-2021, 02:54 PM
Charlie12 Charlie12 is offline
 
Join Date: Oct 2014
Location: Port Orange FL
Posts: 53
Default screws at front of upper cowling

Scott says AN526 screws are "not what is recommended" and I don't disagree with the choice of AN525 instead, but... I have never received any communication from the factory recommending to change them. If it is important we should have received some sort of service bulletin. I think I will switch to AN525 but I have not experienced any problem yet with the AN526 screws. Live and learn.

Later: As a sanity check I just looked at the latest KAI cowling drawings posted on Van's website. RV-12 KAI, page 38-07, still says use AN526. The more recent RV-12iS KAI, page 37iS/U-12, says use AN525. I will probably change to AN525 next time I take the cowling off.
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Last edited by Charlie12 : 08-29-2021 at 03:23 PM. Reason: new info
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  #20  
Old 08-29-2021, 05:05 PM
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rvbuilder2002 rvbuilder2002 is offline
 
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Location: Hubbard Oregon
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Quote:
Originally Posted by Charlie12 View Post
Scott says AN526 screws are "not what is recommended" and I don't disagree with the choice of AN525 instead, but... I have never received any communication from the factory recommending to change them. If it is important we should have received some sort of service bulletin. I think I will switch to AN525 but I have not experienced any problem yet with the AN526 screws. Live and learn.

Later: As a sanity check I just looked at the latest KAI cowling drawings posted on Van's website. RV-12 KAI, page 38-07, still says use AN526. The more recent RV-12iS KAI, page 37iS/U-12, says use AN525. I will probably change to AN525 next time I take the cowling off.
Charlie,
There is a big difference between potentially safety of flight details and a rolling product design improvement.
Many design improvements have been made over the 12+ years that the RV-12 has been active. If the design change didn’t concern flight safety, then they got disseminated via Kai revisions. Those changes aren’t done on a monthly basis so it can sometimes take a while for it to happen with an update of an overall section. This one somehow fell through the cracks but is part of our collector for that section when the next update happens.
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Opinions, information and comments are my own unless stated otherwise. They do not necessarily represent the direction/opinions of my employer.

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Hubbard, Oregon
Van's Aircraft Engineering Prototype Shop Manager
FAA/DAR
RV-6A (aka "Junkyard Special ")
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