Scribing a collar into a truss
Our current job is a large detached house, which consists of four cross-frames, each of which with a unique curved collar. I just thought it might be interesting to relay the cutting process.
It starts with a curved timber that has been ‘slabbed’ This allows us to carefully select the best section, following the grain, which we mill our horizontal edges from. A specialist saw is used to rip the curves, effectively a chainsaw on a base plate.
Once cleaned up a little, the timber is laid upon the truss and plumb-bob scribed down into position. This technique is one that has been used for centuries. The mortice on the rafter is marked to precisely match the tenon on the collar.
The joints are then cut and timbers assembled. Now this truss can have the studs laid upon it and once again scribed together.
***update 9th October***
We finished the final cross-frame and here you can see wall the studs etc scribed to the collar. Note that this is actually a different truss.