I am very new to aircraft structures so excuse me if my questions dont make too much sense, anyway here goes:

1) I understand that the spar is a structural element that extends the entire length of the wing, it carries majority of the load experienced by the wing. From my googling, I have seen different shaped spars, some are like circular rods while others look like rectangular beams? Is this correct or am I confusing it with some other part of the wing?

2) What does "box-spar" mean? does the box refer to the box that also includes the ribs, etc?

2) How are "hobby" spars made (I mean not for a passenger aircraft, but lets say for a smaller UAV) ? Are they wrapped around one male mould and then pulled off after curing? Are they hand wrapped around the mould? (I am interested in techniques that arent too expensive)

3) From what I have read, I have seen Invar and steel moulds being used, this is quite expensive. For a more economical option, could I use a foam tool?

4) I have read about sacrificial tooling but havent quite been able to understand it. Could it be considered for making a spar?

Thank you!