I'm not particularly superstitious but I give blood to all my vehicles. My theory is if I give them little amounts regularly, they won't demand great amounts all at once. I manage to skin a knuckle or cut a finger or stab myself as Pierre has done, and I make sure the blood is smeared inconspicuously somewhere on the vehicle. On the exhaust is a favorite location but the RVs have blood on the airframe (the -10 is difficult because I have to make sure it's over primer; I don't trust it on alclad). As I said, a silly superstition but I have never been seriously hurt in an accident (no broken bones yet for this old man) even though I risk life and limb on motorcycles. Only one aircraft accident so far, but the RVs seem satisfied as well.