Sunday, March 22, 2015

Observations on Birdsmouth Spars

Building birdsmouth spars using the modified birdsmouth technique (asymmetric V-notch) requires paying closer attention to details than I did this past week.

The scarf cuts in the milled-to-size and notched pieces didn't match up properly due to the asymmetric features of the notch (and my inattention to that detail when making the scarf cuts.) Fortunately, the pieces are long enough to let me recut them. (And if you have the luxury of having full length lumber available, good for you!)

Using less than perfect "Select" grade lumber meant dealing with a few knots in the staves - and I figured I could just flip/flop staves end-for-end to stagger and/or separate the knots. But, wait… because that notch is asymmetric, it isn't possible to flip/flop the staves end-for-end as doing so changes the orientation of the notch. I'll insert a plug to reinforce the area with the knots. (If I'm not happy with this yard when it is completed, I'll build a new one.)

Using a jig to cut the scarfs on the table saw was, once the jig was built, faster and easier than using a router with a jig to cut the scarfs.

Cutting plugs for the spars on the table saw is easier than I expected it to be (remember, I have been using a table saw for less than a year and I am still learning.)

Assembling the staves for a dry fit is tricky and frustrating. That (trickiness and frustration) can be minimized by using stands/supports to hold four or five staves together while adding the last three or four staves. I can only imagine how much fun assembling will be with everything lathered up with epoxy...

CVG DF is much nicer lumber for building spars than "select" grade lumber from a big-box store. Two years ago I purchased two 20' pieces of CVG DF, intending to use them for the main mast. However, moving those 20' pieces from where I was to where I am meant having to cut them to a more manageable size. So, those two pieces are being used to build the main boom and mizzen mast. I'll order new material for the main mast. (I bought the select grade lumber to experiment building birdsmouth spars, figuring if it didn't work, I didn't "waste" the DF on the experiment.)


  1. Bob - I agree, if you're going to need to scarf pieces together to get full length, and then arrange them to stagger whatever knots you have left, it's better to do all that before cutting the notches. For dry assembly I found a couple zip ties held things together well. You can put one end together and secure it and then move to the middle and do the same. -- Dave

    1. Thanks, Dave. I need to remember patience is a virtue. I'll try zip-ties for dry assembly. - Bob