Be very careful when you make the top curved bit. The pics don't show it, but the davit curves inwards from just above the screw, and then both narrows and bends more so that the eye in the end is vertically above the boat lifting hook. In addition, the whole thing tapers in all dimensions! Not an easy thing to make. Really, as far as making one is concerned it isn't all that much removed from the Quadrant davit. Take away the actual "quadrant " bit and put a hinge pin at the outer edge, then the principle is really just the same. So if you can find some front or back views of a quadrant davit I think you'll find that the top bits of the 2 sorts are near enough the same. When I had loads of the things to make for "Norseman" I used perspex and using a power file did the tapering bit, and sort of melted the top curve with a gas torch until it fitted my wooden template. Took ages!
I'll have a bit of a trawl for mor info. Cheers. BY.