Might be a dumb question really, but would a King/Prince/Herald on a chariot get a Look Out Sir save from a cannon ball? And how many chariots would need to be present to give the save?

Of course they do! You'd need at least 5 rank & file chariots to get it.

not counting the champ. but do you need 5 or 3?

Sadly, a TK on a chariot needs 5 other chariots alongside to get LOS (6 total chariots in the unit).

Similarly, a champ on a chariot requires 5 rank and file chariots (not including himself and any characters) to get a LOS. While one could argue that 6 rank and file chariots (7 total) are required for a TK LOS if one of those chariots is a champ, the rule and wording on page 93 was written for the champ, and not a character per se. In the characters ruling a TK chariot + 5 rank and file chariots should provide LOS, even if one of those 5 chariots is a champ. But the wording as written on page 93 can make this arguable.

If the LOS rule for TK chariots was only 3 rank and file models, I'd easily put Arkhan in one. For now, he's on foot.

The Champion is not a "Rank and File" model, so sadly there is nothing to argue about that...

Really?? Page 93 >> "Unless a champion is slain by a direct attack, then he must be the last rank and file model to be removed as a casualty."


How does "...he must be the last rank and file..." not mean that he's rank and file?

Huh, I really need to double-check stuff before posting in the future... Since I was wrong on that I would assume that the champion would indeed be part of the "5 or more" models required for a LoS for a character, since as you quoted he is a rank and file model.

Unrelated (mostly), wounds normally flow from the unit to the Champion if he's the last one standing, what happens if he is/was in a challenge the same turn?

So you need 5 rank and file chariots for LoS? Even though we only need 3 chariots to form a rank? Seems crappy but I guess it makes sense because even Ogres need a Look Out Gnoblar to reduce the number...