Hello Frank
The drawing you attached is very interesting.
However, I am not convinced that Mary Ann's mast #100 has been constructed in that way.
The original SA masts are hollow, constructed using the "birds mouth" technique.
I can see why HM would devise a simpler method of construction, and also why they would plan to have the hollowing in the main body of the mast, in order to get nearer to the weight of the SA masts.
However, I managed to [color="Red"]
push[/color] the aerial cable for my VHF through the mast. If the mast was hollowed as the drawing suggests I think it would have "bunched up" and jammed in the widened section. I suspect that my mast at least has a 15mm x 15mm square hole only throughout the length of the mast.
This suspicion is reinforced by the weight of the mast, mine weighs 27 Kg without any fittings.
If anyone can be bothered to find the density of Douglas Fir they could calculate what the weight should be for both a solid mast and one built according to the drawing.