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<< Lancair Builders' Mail List >>
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Posted for Brent Regan <Brent@regandesigns.com>:
Ted Stanley writes
<<There is an error in Chapter 8 page 8-29 showing the assembly of the aileron
pushrod ends. Hopefully it was nothing but a typo, but a dangerous one. This
page shows using AN470A4-24 rivets. WRONG ! The correct rivet is an
AN470AD4-4.>>
First, I believe Ted meant to call AN470AD4-24 as the correct part #.
Second, IMHO there is not a significant difference if you used D or AD rivets here. The assembly instructions call for the use of Loctite when assembling the rod ends. The shear strength of Loctite is 3000 to 5000 PSI and the area of the rod end adapter is 1.77 square inches giving a pullout force of 5310 to 8850 pounds (depending on the bond gap).
Compare this figure with the shear strength of the two -4 rivets. Their area is 0.0122 square inches X 2 rivets X 2 places = 0.049 sq in x 10,000 PSI = 490 pounds for the A rivets or 1472 pounds for the AD riv
ets. The difference is 17% in total strength between the A and AD rivets. This is inconsequential when you consider that there would need to be a 1000+ pound force on the stick to fail this joint. I would seem that the rivet is not the primary structural element in this joint.
The rivets are there to hold the joint together while the Loctite cures and you would likely find that a -24 AD rivet is near impossible to properly head in this application.
I know that the first argument to this is "What happens if the Loctite fails?" to which I would recommend you take a long look at your airplane and ask yourself "Is now a good time to loose faith in adhesives?"
Compliments of the season.
Brent Regan
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