Gus and Ethelred spend evenings, before the sun sets, working on making a miniature ballista. The old cross bow from Telosh is where they start. Studying how it work, how wood bolts are best made. Once some form of mastery of the machine is in hand they take it apart. Study each piece, how it is formed, shaped and what it’s purpose is. Then they put it back together. This is repeated again.
Then they take it apart one more time. This time they work to replicate the parts, but twice the size. Fashioning the part from wood, rope and sinew.
After a week Ethelred feels like it will be possible, but still difficult to make a much larger ballista.