A great video from two guys building an i550 sportboat showing their plywood scarf jig. It’s an update on the circular saw plywood scarf jig described in the Gougeon’s brothers’s book. They are using a Festool TS55 but you could use any modern track saw in the same way. Just clamp the track to the jig.
The scarf joint jig is at an angle of 80 degrees and the saw is set at 6 degrees - making for a combined angle of 86 degrees.
There set up is a lot simpler than the Gougeon’s.
The Gougeon’s original scarf jig:
The Poozle Trap jig: