For John, BLUF: You should build one. Nothing to see here; just move along.
From the Beeb we have "Warwick Castle trebuchet fireball 'sparked boathouse blaze'".
A blaze thought to have been caused by a fireball which was launched from a trebuchet at Warwick Castle has destroyed an historic boathouse.Regards — Cliff
Sparks from the projectile are believed to have ignited the blaze.
About 300 spectators were watching a demonstration of the weapon, described as the "world's largest working siege machine", when the thatched building caught fire on Friday evening.
"No-one was ever at any risk," a castle spokeswoman said.