A lot of people get hung up about scarfing joints, but their fears are mostly unfounded. They are a simple joint and they work very well even if they are not done perfectly. When scarfing planks, a 6:1 ratio works well as it is big enough to provide a big glue area and to get a nice smooth join with no kinks. The ratio 6:1 simply means that the length of the joint is 6X the width of the timber. In my case the timber is 19mm wide, but round that to 20mm X 6 = 120mm. Draw a line 120mm from the edge and then join the corners. Do the same for the other piece to be joined. I like to cut mine with a Japanese pull saw (Dozuki) as they are fast and accurate. Then just to even things up clamp the two pieces tother like in this pic and give them a few licks with a block plane. That’s all.
Here are the panel pins I like to knock in (just a couple of mm) and which are then snipped off close to the surface. When the two halves are brought together, the pins provide the grip to prevent the joint sliding apart when under clamping pressure. (Epoxy is like liquid ball bearings!)
By the way, the chinelogs are 19X45 strips of Paulownia.
This pic is a ring-in. It shows the rudder case all cut and ready for assembly after it gets sealed with epoxy. The bolt holes are all drilled. Some of the bolts will need to be installed during the glue-up. The infill and cheek supports are Hoop pine.
Ciaw for now :)_