If you don’t remember the teacher from ‘Ferris Beuhler’s Day Off’ the title is not at all funny, it’s barely funny if you do remember the movie:-) Anyway, I got a chance to work on the birdsmouth joints Paul ( Shipwright) recommended for making my hollow mast prototype. Once I’d fabricated a zero clearance dado blade insert I did a couple of test cuts and then ran my 10 boards through for my trial glue up.
I had cut a pronounced taper on the boards figuring that a large taper would be harder to glue up. Well it was a bit awkward, I had hoped to do a dry run but couldn’t quite manage that. Then I realized after looking at all my boards and seeing during the dry run that I would not be able to close the mast, that the angles of the birdsmouth joints had been cut wrong. So I took my shoes and socks off ;-)and divided 360 by 10 ( using the simple formula recommended by Paul to calculate the angles depending on the number of segments used) and somehow got it in my head that I had to set my saw at 30 degrees as the complimentary angle to the 36 degrees I needed. I still can’t figure why 30 got stuck in my head:-( So the prototype didn’t come out as intended. I didn’t take a picture of the open side but it was about one more board width too open.
I did learn a lot about the work flow and that I am going to need to figure out a process to actually do a glue up. My trick of using masking tape and the just rolling the segments up worked well on the mitred joints of my first attempt but doesn’t work with the birds mouth joint because of the material behind the cut joint. The use of the dado blade worked very well. I may still try the two cut method that Paul described just to see which method is better. When I realized I’d cut the boards wrong I figured I’d still glue the boards together just to see what I would get. Because I would not be able to bungie cord the segments together I used hot glue to stick em together. I’d made a sufficient number of mistakes and tried a bunch if new things so I think I learned a lot. Which I guess is the point of a trial run:-)
-- "Checking for square? what madness is this! The cabinet is square because I will it to be so!" Jeremy Greiner LJ Topic#20953 2011 Feb 2