Most of the blind rivets called LP4-3, that are actually Gesipa GSMD41-43APG PolyGrip rivets (.039-.197 Grip) with shear strength of 162 lbs. (720 N) and a minimum tensile strength of 236 lbs (1050 N).
CS4-4 is countersunk Gesipa GSMC42-44APG (.059-.256 Grip) with the same strength – with shear strength of 162 lbs. (720 N) and a minimum tensile strength of 236 lbs (1050 N).
Priming (corrosion protection)
RV-12 is primarily build of 2024-T3 Alclad aluminum sheets.
Many people argue whether it is necessary to prime internal parts of the airframe.
Manual does not mandate for priming alclad parts. Anyway a lot of people prime everything inside the plane.
I plan to stick to the manual. If manual does not call for priming I wont do it.
Vans use alclad for a reason. It already has thin pure aluminium protection layer. Not much. about 2.5 – 5% of the sheet thickness, but it is there. (Alcoa Al-2024techsheet.pdf, MIL-A-8625F (paragraph 126.96.36.199)).
Priming often requires scratching the surface to improve the primer adhesion. It seems kinda pointless to remove one protecting layer in order to apply another.
I saw 40 years old planes with no primer inside and no corrosion. I saw 3 years old planes with some corrosion under the primer. I guess the issue of corrosion is more complex than just applying a barrier layer on the aluminium sheets.
RV-12 does not seem to be designed to spend nights outdoors. It needs a hanger. Hanger would significantly reduce the risk of corrosion along with other important things.
I don’t think the lifespan of a plane like RV-12 can exceed 20-30 years. I’m sure properly maintained and stored alclad built plane will not develop major corrosion issues within the timeframe.
There are two options
1. E-LSA – aircraft should be build strictly per plans. Some modifications allowed after certification. So one cannot change engine, fuel system and probably avionics during the building process without manufacturer’s approval. The plane is treated pretty much like factory build aircraft. Some certification details are here: https://www.casa.gov.au/sites/g/files/net351/f/_assets/main/rules/1998casr/021/021c41.pdf
and here https://www.casa.gov.au/sites/g/files/net351/f/_assets/main/rules/1998casr/021/021c42.pdf
Pros of E-LSA certification
– Resale value may be higher because the new owner can perform all (or most) of the maintenance themselves and also the owner should comply with all the manufacturer’s AD
– most expensive option to build the aircraft. You cannot use cheaper engine, avionics etc without approval of the kit manufacturer.
2. E-AB – aircraft can be build any way the builder wants as long as the SAAA technical counsellor finds the design and building techniques adequate and safe. Details are here: https://www.casa.gov.au/sites/g/files/net351/f/_assets/main/rules/1998casr/021/021c04.pdf