Roubo Joinery Bowsaw Prototype – Frame

With the stirrup system finalized for anchoring the saw plate it was time to move on to the frame.  Armed with some extra-dense 5/4 white oak I dove in.   I wanted to make sure the frame was both simple in construction and beefy enough to withstand the stresses of tensioning such a robust plate.

The overall structure couldn’t be much simpler — two vertical arms connected by a crossbar that was inserted as an unpinned mortise-and-tenon into the arms.  Once I had the dimensions and proportions where I wanted them I used my mortiser to cut the pockets in the arms and sawed the tenons on the crossbar.

Then I moved on to the housings for the stirrups.  It was a simple matter of laying them out against the base of the arm, removing the material so that the stirrup fit neatly, then sawing a slot for the plate to go through.

With the arms and crossbar cut to length and fitted together, and the stirrup housing made, I sawed the curved shape of the arms on the bandsaw.

I assembled everything together just to make sure the parts all worked together before moving on.  I really was pleased with the manner in which it all fit together.  It seemed a little beefy, but I had not put it to work yet.  Besides, it is considerably easier to make elements smaller ex poste than to make them larger.  It made me recall on of my Dad’s favorite quips in the shop, “I just don’t understand this.  I’ve cut it twice and it is still too short.”

With rasps and spokeshaves I shaped the arms to be more congenial to being hand held.  Once it was far enough along to give it a test drive I assembled it completely and strung the top with multiple strands of linen cord for tensioning, found scrap stick (a practice spindle from the writing desk) to act as the windlass paddle, and it was ready for the race track.  I’d added a small vanity flourish at the top of the arm so I just knew it would saw like a banshee.  I cranked up the tension until the plate twanged like one of Stevie Ray’s guitar strings (before he broke it) and lit into a scrap of wood.

And it did saw like a banshee.  Made from concrete.  It was so heavy I actually grunted when picking it up to use the first time.  Somehow I had to hog off a gob of mass or otherwise it was a two-handed-only tool, and I wanted something that could be used with one hand.