SPA recommends Cherry pulled rivets or Aircraft rivets. Not all suppliers use the same naming structure. The most common Cherry rivet nomenclature is broken down as follows.
**NOTE – You cannot use 5052 Aluminum rivets as the sheer strength is not high enough
Rivet Material |
Mandrel Material |
Head Style |
Type of Rivet (not always used) |
Rivet diameter in 32nds of an inch |
Rivet maximum grip length in 16ths of and inch |
B= 5056 Aluminum C= Stainless
Do NOT USE: A=5052 Aluminum M=Monel S=Steel U=Copper |
S=Steel C=Stainless
DO NOT USE: A=7178 Aluminum |
P=Protruding L=Large C=Flush |
S=Structural Q=Cherry Q Rivet (self-plunging) |
3=3/32nd inch diameter hole
4=1/8th inch diameter hole |
1=1/16th (.063) 2=1/8th (.125) 3=3/16th (.1875) 4=1/4th (.250) 5=5/16th (.3125) 6=2/8th (.375) 7=7/16th (.4375) 8=1/2 (.5)
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To determine the proper grip length of a rivet required you add up the thicknesses of the metal being attached.
Some examples for selecting the proper rivet regarding grip length are:
Example 1 – When attaching a rib to a skin, if the skin is .020 and the rib is .025 the total thickness is .045 and the rivet to use would be a #1. Example would be BSC-41.
Example 2 – When attaching a .025 rib to a .1875 spar stiffener and a .032 spar channel the total thickness is 0.2445 making the rivet to use a #4.
**NOTE** - SPA LLC tested a great deal of rivets before settling on the ones chosen for the prototype. We used flush/blind rivets on the skins where aesthetics are in question. Where the rivets were not seen we used protruding heads such as BSPS-42 or BSPS-43 according to grip length recommendations. The recommended rivet for flush/blind for skin to rib attachment (except the fuel tanks) is the BSC-42 from Aircraft Spruce (ACS). Although it falls ever so slightly out of the typical grip range length, it produces tight joints and almost no stem pulls. When testing with the protruding head BSP-41 we experienced a high number of crack on the back side of the rivet, so we chose to recommend the BSPS-42 and were happy with the testing results. We recommend that any rivet you choose that you do a number of test installations verifying you result in a tight joint and minimal/no stem pulls.
