Hinges under stress - mechanical engineering type question

Peter Dohm asked, quite reasonably
What are these hinges supposed to hold???

The spar. I'm thinking about the possibility of considering the
feasibility of investigating a folding wing. The spar would have a
hinge installed top and bottom. To fold the wing you remove the
bottom pin. GW of the aircraft in mind is ~1500lb. It would need to
be able to take 6 g's, hence my concern about strength.

The sailplane may have used standard piano hinges, but it was about
500 lbs, and probably not stressed for more than 3 g's.