I glued up the birdsmouth mast for the Herreshoff Biscayne Bay 14 I am building over the weekend, and I am a bit surprised at the ease with which it flexes. The mast is 21' long, keel stepped, and stayed. The timber is Sitka Spruce. At this point it is 8 sided.

My initial impression of the flex came from how much flex the unsupported length flexes, if I clamp the spar to my bench at deck height. I can easily move the head of the mast 3 inches without much force. Maybe that isn't much over the 18 1/2 foot unclamped length.

Naturally, and more realistically, there is a lot less flex if I put another clamp at the point on the mast where the stays will be. Once I do that there is a quarter to half inch of easy flex in the top 5' of the mast, and a lesser wiggle in the opposite direction in the middle of the mast.

I realize that Capt. Nat generally designed light masts, and this design calls for a hollow mast of more traditional hollow construction with what seem to me very thin walls. The birdsmouth spar I have built has thicker walls than the design.

I also realize that a traditional rig often will have a decent amount of flex. I understand this isn't some super rigid, taut modern rig. I'd just like a reality check that the amount of flex here is reasonable, as this is the first hollow wood spar I have built. I figure that if I am going to do something like add material to the mast, it will be a lot easier to do so while it's still 8 sided.