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Old 11-27-2019, 04:33 AM
mturnerb mturnerb is offline
 
Join Date: Apr 2015
Location: Jacksonville, FL
Posts: 1,647
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Quote:
Originally Posted by rvbuilder2002 View Post
Review Section 5 in the construction manual regarding shop heads on rivets.
Pay particular attention to the Referenced MIL Spec for rivets. The minimum and maximum shop head size is much broader than "Must be exactly .5D thick and 1.5D in diameter.

Something else to keep in mind.....
With the experience level that most people are at when building the empenage, 9 times out of 10 if a removal is done, the rivet hole will get messed up and the second installation attempt will be even worse than the first.

I'm not saying that a rivet should never be removed. Just don't do it without serious contemplation. Especially early in the project with a lower skill level.

Experience is helpful here for sure - you start to get a feel for which rivets look "right". I find this part of Section 5 particularly useful in this regard:

"One of the common calls we get is "I had to drill out a bad rivet and now the hole is oversize. What do I do?" Sometimes this is done multiple times in the same hole and now the hole is so large that the builder has to use a bolt and nut instead of a rivet. To relieve the anxiety sometimes associated with an imperfectly set rivet and to avert potential problems arising from ill-advised attempts at repair, (not to say 'never repair a rivet'), guidance in the form of an excerpt from the Alcoa Aluminum Rivet Book, dated 1984, is provided here.


"The standards to which driven rivets should conform are frequently uncertain. In addition to dimensions and perfection of shape, inspection is concerned with whether the drive head is coaxial with the shank (not "clinched") and whether there is excessive cracking of the heads. It has been determined that even badly cracked heads are satisfactory from the standpoint of static strength, fatigue strength and resistance to corrosion. (Poorly set and cracked) rivet
heads were tested in tension to determine how well formed a head has to be in order to develop full strength. The tensile strengths of all the rivets were within five percent of the strongest. The test indicated that minor deviations from the theoretically desired shape of head are not cause for concern or replacement. The second rivet that is driven in any one hole [is] likely to be more defective than the first because the hole is enlarged and [the] rivet will be more likely to buckle and form an imperfect head. Tests have shown that very small rivet heads are sufficient to develop the strength of the rivet shank, even when the rivets are subject to a straight tensile pull....where a large head is not needed for appearance, smaller sizes of drive head should be used to decrease the required driving pressures."
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