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Cowl Attach Screws - page 45-25

iamtheari

Well Known Member
The plans on page 45-25 details A through C call for the following screws to attach the cowl:

Side hinge pins: 2 x AN526C832R6
Air inlet: 4 x AN525-832R8 w/ 5610-18-31 washer
Bottom aft edge: 6 (RV-14A) or 4 (RV-14) x AN525-832R8 w/ 5610-18-31 washer

I can't find the AN525-832R8's anywhere in the packing list for any of the kits. There are 4 AN525-832R9's in bag 3213 but, other than that, I don't see any AN525-832's at all.

Edit to add: The spinner attaches with AN526C832R8's through 5610-18-31 washers. The finishing kit comes with 18 of the AN526C's in bag 3219. Should the plans for the cowl attachment say AN526C832R8 instead of AN525-832R8?

What am I missing?
 
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The AN525's are washer head screws with some unthreaded / smooth shank.

The smooth shank is the reason they are specified. When a plain screw is used, the threads act like a file under the vibration influence that is present and slowly enlarges the hole in fiberglass.

They are not specified on the spinner because it is a bit more of a appearance decision and they do not tend to wear the holes like happens at other locations on the cowl.

I have no explanation for why you can't find AN525's in the hardware packing lists for cowl installation. I suggest a call to Van's.
 
The AN525's are washer head screws with some unthreaded / smooth shank.

The smooth shank is the reason they are specified. When a plain screw is used, the threads act like a file under the vibration influence that is present and slowly enlarges the hole in fiberglass.

They are not specified on the spinner because it is a bit more of a appearance decision and they do not tend to wear the holes like happens at other locations on the cowl.

I have no explanation for why you can't find AN525's in the hardware packing lists for cowl installation. I suggest a call to Van's.

Thanks, Scott. It's really helpful to know the reasoning behind the hardware selection. I'll call Van's to ask about clues where the AN525's are hiding.
 
If I recall correctly they are abbreviated and might be listed as AN525-8R8 or something like that
 
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If I recall correctly they are abbreviated and might be listed as AN525-8R8 or something like that

That was the answer. I saw those in the packing list and did a quick search on my phone to see if they were the same as AN525-832R8. What came up was a series of references to a #8-36 thread on the 8R8. For example: https://military-fasteners.com/screws/machine+screws/AN525-8R8

The otherwise wonderful Standard Aircraft Handbook doesn’t have a chart for AN525 as it does for so many other AN part numbers, including AN526. So it isn’t any help.

The AN525-8R8 in the Finishing Kit, bag #3218, are apparently #8-32 thread. Kevin from Van’s wrote back right away this afternoon to tell me that all #8 screws are 32 threads per inch. I don’t know if that’s true in the wild, but it seems to be true in the RV-14 kit.

Onward and upward for me. I hope this thread serves posterity for the next guy who gets paranoid about AN525 screws as I did today. :)
 
Section 5 in the construction manual has a hardware identification chart that You might find helpful.
I have often found the charts in section 5 helpful for fluid fittings and figuring out which blind rivet I found spilled on the floor. I didn't have any luck finding any information about AN525 screws there, though. I am fully capable of having overlooked that information.
 
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