Best made in a paddock with plenty of room for hurling and a tractor with a loader will make it easy to get the throwing arm onto the support frame.
Step 1: Prepare Materials
Detatch roots from trunk
We used a couple of blue gums, a fast growing eucalyptus (Eucalyptus globulus) approx 10 years old.
We cut the following:
Main arm 10.5m long
Legs 2 x 3m long
2 x 3.5m long
cross arm (pivot) 2m long
For cross bracing we used 1 by 5m length and 2 x 2.5m lengths.
(multiply by 3 for approx lengths in ft)
(note the chaps, face mask and safety helmet used when felling tree are omitted by model pretending to fell tree)
After cutting timber to length, find a good location for building the treb and set out timbers. Starting with legs, lash the tops of each 3m leg to a 3.5m leg leaving enough overhang at the top for the cross arm (pivot) to sit in. I had some help from my kids who had practised lashing at scouts with this step.
Step 2: Set up Frame
Outrigger style cross bracing is a better solution. Lay a long pole (approx 5m) on the ground in front of the legs and fix to legs by lashing or heavy duty coach bolt. Then lash or bolt cross braces between the pole and the legs.