Team SPA

The aircraft offered by SPA are designed for blind rivets.  There is the option to use aircraft rivets on the wing, tail and rear fuselage skins - but blind rivets will be required on the forward fuselage.  Understanding rivets and performing test rivet sets to determine tool settings to get the proper set is paramount when building a metal airplane. 

Here is a link to some good information from renowned designer and engineer Chris Heintz on the pros and cons of blind rivets versus aircraft (AD) rivets. 

Chris Heintz on Solid Rivets

Chris Heintz on Blind Rivets

Here is an excerpt from the Panther builders manual on rivet explanation and options.

Most of the rivet options on the Panther build are open and interchangeable. There are some rivets requirements are not optional and are duly noted on the plans. If the plans indicate “or equivalent” then the builder has the option of the rivet called out or an equivalent strength/grip length rivet according to the rivet manufacturer guidelines.In general the builder can choose from:

• Protruding head pulled rivets

• Flush/countersunk pulled rivets. 

• Flush solid aircraft rivets- MS20426AD3 (ACS calls them AN426AD3) (only for attaching skins)

**NOTE – You cannot use 5052 Aluminum (A) rivets as the sheer strength is not high enough

**NOTE – SPA highly recommends only experienced builders use solid rivets for attaching skins.If you are planning to use solid rivets for attaching the skins on your Panther please make sure you are well versed with determining the proper grip length for the rivet application and that you have the proper tools for the job.There is a great deal of online and printed material on the proper procedure, please make good use of this.

** NOTE - Regarding rivet options for hinge:The side of the hinge that attaches to the control surface will be a protruding head rivet, EXCEPT for the trim tab (depends if you are using countersunk or protruding head rivets on your skin).The side of the hinge that attaches to the main structure will use the rivet type you are using on the skin, and length according to rivet length guidelines.

**Note - some builders prefer stainless steel rivets on the hinges for the additional shear strength.

Rivet guidelines:

• Rivet length is determined by the rivet grip guidelines of the rivet chosen. Please follow the guidelines of the rivet manufacturer.

• If the rivet is specified on the plans then use that rivet or the equivalent strength/grip length.This is not optional.

• If aluminum is attaching to steel then a stainless steel rivet is required. 

• Closed end rivets are used on the fuel tanks.

• Rivet installation orientation – In general you should attempt to place the factory head against the thinnest metal.IE – when fastening .1875” to .032” the factory head lays against the .032”.This is not always possible, but should be practiced as a general guideline when it is.On the plans occasionally the rivet orientation will be shown or noted.This typically for ease of assembly or adequate access for the rivet puller.(The factory head is the preformed head that sits against the rivet puller.The other side is called the shop head.)

Understanding Pulled Rivet Nomenclature

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.

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.