HFS
Well Known Member
I haven't had occasion to need these (yet), but Paul Dye's article in KP got me thinking about how to make a direct "drop in" Pop sealed end blind rivet to assist in this dreaded repair.
What I came up with was a combination of a little lathe work + cold working the remaining head into a -3 AN (100* angle) flat head. So it now becomes an "Oops" rivet: -4 body with a -3 flat head.
On my (old - 1981) -4 plans, before the rear baffle was turned around (allowing bucked rivets instead of sealed blind rivets), the callout was for Pop AD41H (universal head) for the rear tank baffle to rib flange & tank skin to rib joint would logically be AK41H (flat head). For the rear baffle to skin joint, the callout was for Pop AK42H, because the combined skin thicknesses warranted it.
I made a "die" set for the cold re-work of the head on these Pop sealed end rivets,
and have made enough of them to send "samples" out around the country for evaluation.
I have also undertaken pull-to-failure shear tests for these modified rivets to see how they compare to the design allowance of AN426AD3-3/3.5 rivets in shear, with .032 dimpled skins. That number is 217 lbs. All my coupons failed above that number - so probably not much joint strength compromise in using one or two of them for leak repair.
An "immersion" test is, and will be, an ongoing device moving forward to validate the use of these rivets for "weeping" rivet syndrome.
While I was at it, I also began to modify open ended Avex blind rivets to be replacements for the "smoking" rivet, whose replacement resists bucked rivets.
If anyone has need for either of these styles of modified rivets (only where there is really a need), I'd be glad to send one or two out, if doing so would help in those "testy" repairs.
Just PM me if you (really) need one.
Thx - HFS
What I came up with was a combination of a little lathe work + cold working the remaining head into a -3 AN (100* angle) flat head. So it now becomes an "Oops" rivet: -4 body with a -3 flat head.
On my (old - 1981) -4 plans, before the rear baffle was turned around (allowing bucked rivets instead of sealed blind rivets), the callout was for Pop AD41H (universal head) for the rear tank baffle to rib flange & tank skin to rib joint would logically be AK41H (flat head). For the rear baffle to skin joint, the callout was for Pop AK42H, because the combined skin thicknesses warranted it.
I made a "die" set for the cold re-work of the head on these Pop sealed end rivets,
and have made enough of them to send "samples" out around the country for evaluation.
I have also undertaken pull-to-failure shear tests for these modified rivets to see how they compare to the design allowance of AN426AD3-3/3.5 rivets in shear, with .032 dimpled skins. That number is 217 lbs. All my coupons failed above that number - so probably not much joint strength compromise in using one or two of them for leak repair.
An "immersion" test is, and will be, an ongoing device moving forward to validate the use of these rivets for "weeping" rivet syndrome.
While I was at it, I also began to modify open ended Avex blind rivets to be replacements for the "smoking" rivet, whose replacement resists bucked rivets.
If anyone has need for either of these styles of modified rivets (only where there is really a need), I'd be glad to send one or two out, if doing so would help in those "testy" repairs.
Just PM me if you (really) need one.
Thx - HFS
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