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Horiz stab to fuse bolts

T

tomcostanza

Well Known Member
Hi,

I'm looking at DWG-27A (upper right corner) at the bolts that go through HS-714, F-798 shim, F-714 aft deck, F-710C spacer, and F-710B angle (whew!). The plans call out a -10A bolt, but I need 3-4 washers to keep the nut on the threads and tighten everything. A -7A seems like the correct length. Am I missing something, or are the plans wrong?

Thanks in advance,
 
As long as the rules are met

Tom,

If you can put a -7A bolt through there and still see some grip (unthreaded part of the shank) showing on the other end, then go for it.

There are many places that the plans call out bolt or rivet lenghts that are not quite right. There will also be slight variations from one aircraft to another due to material and construction tolerances, etc. Consider all hardware callouts on the plans a first guess that needs to be verified or adjusted as necessary for your airplane. A good reference on how to select and install the right hardware is the Standard Aircraft Handbook, ISBN 0-07-134836-0 (see section "Installation of Nuts and Bolts").

-Roee
 
But then again, maybe you are missing something...

FWIW, I just checked on my airplane, and it takes a -10A bolt with two washers. On mine a -7A bolt doesn't show any grip, so it would be too short.

A difference of 1-2 washer thicknesses is pretty significant on this structure, so you should probably check your airplane carefully against the plans before proceeding.
 
Including the washer, I'm measuring .628" of grip length needed in this application. The -7 bolt has a .500 grip length while the -10 bolt has just about .630" on the one I measured. It's possible you may need another thin washer to keep threads from bottoming out here.
 
roee said:
Tom,

If you can put a -7A bolt through there and still see some grip (unthreaded part of the shank) showing on the other end, then go for it.



-Roee
Click to expand...

Absolutely NOT!!! If you can put a -7 in there and still show some grip length, you're missing some 1/8" thick structural piece! Pretty important when it comes to keeping the tail on!
 
Just add up the pieces

You have four pieces of 1/8" material which equals .500". F-714 is .040" and a washer is .063" for a total of .603" minimum! No way a -7 bolt with a grip length of .500 is going in here! An extra 3 washers takes up a slack of .189"; You are definitely missing something here! Sorry for all the posts, but this is serious.
 
captainron said:
Absolutely NOT!!! If you can put a -7 in there and still show some grip length, you're missing some 1/8" thick structural piece! Pretty important when it comes to keeping the tail on!
Click to expand...

Easy fella. I agree, Ron. Please see my second reply, immediatly following my first reply. If it is indeed a two washer difference, that is a pretty big discrepancy, and that may indicate that something structural is missing or of incorrect thickness.

But I stand by my original remarks that (given the structure was fabricated correctly) there will still be slight variation and the hardware ultimately must be fitted correctly to your structure.

In this particular case, on any of our airplanes, if you take Van's hardware callout literally and use just one AN960-10 washer as specified, the nut will bottom out on the thread, and the HS will likely depart the airplane.
 
roee said:
Easy fella. I agree, Ron. Please see my second reply, immediatly following my first reply. If it is indeed a two washer difference, that is a pretty big discrepancy, and that may indicate that something structural is missing or of incorrect thickness.

But I stand by my original remarks that (given the structure was fabricated correctly) there will still be slight variation and the hardware ultimately must be fitted correctly to your structure.

In this particular case, on any of our airplanes, if you take Van's hardware callout literally and use just one AN960-10 washer as specified, the nut will bottom out on the thread, and the HS will likely depart the airplane.
Click to expand...

Sorry Roee, I didn't realize that post #3 was you again. I worry about builders not really checking these grip lengths and just torquing to spec not realizing that the nut is just bottoming out on the bolt shank and leaving the structure loose. I had an experience involving this after an A&P worked on a Chieftain I was flying many years ago and caused an engine failure in-flight.
 
Yup!

Thanks guys. I DID miss something. A bonehead mistake, but only a few rivets to re-do. Used the wrong stock for the F-710 angle. I'm sure I would have found it eventually (after the tail fell off), but the fix would have been much more difficult by then.

Thanks again to all.
 
I don't think any of the rest of us have made any mistakes:D so beat yourself about the head and shoulders and get back to work. Don
 
I don't think any of the rest of us have made any mistakes so beat yourself about the head and shoulders and get back to work. Don
Click to expand...

Will do Don.

As John Wayne said, "Life is hard. It's harder when you're stupid."

Seriously, it never ceases to amaze me what a wonderful community this is. If everyone were as helpful, considerate, and encouraging as this crew, the world would be a much better place.
 
I think posting was a great thing for you. So what if you missed something, you realized something was wrong and sent out to find out what. Good job.
 
Yep, but as others have mentioned, even when you fix it you'll probably need two washer on there. I certainly did.
 
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