Thursday, July 26, 2012

Davits.....Part 2

     As the design process unfolded, one of my goals was a very robust and rigid dinghy support system. I did not want something hanging off the back of my boat that would come loose in the first storm. Most of the davit systems I see on smaller boats are retained with 4 screws and a small bracket, mounted right at the trailing edge of the swim platform.

     In place of these thin, stamped brackets, I machined my own pair out of a 3 inch diameter piece of 316 stainless steel bar stock. I cut it into 2 half cylinders, and machined the resulting pieces to through-bolt to the swim platform, from the trailing edge. On top of each bracket, I drilled and tapped a 3/8" - 16 through hole, to secure the trailing edge of the new davit assemblies.

     To mount the forward sections of the davits, I decided that I did not want to penetrate the swim platform in any way. Every penetration is just one more area for water to intrude into coring, and it adds to the maintenance load too, since core penetrations should be re-bedded every 5 years or so. Fortunately, there are several openings in the swim platform already, where the 4 elliptical drains are screwed down. I made up a couple 316 stainless steel backing plates, out of 1" x 1/2" x 12" 316 stainless, and along with some 3.5" long flat head stainless cap screws, screwed the davit arms down. The swim platform is effectively sandwiched between the davit arms and the backing plates, making for a very strong structure that required drilling no holes in the top of the swim platform. The finished davit system looks like this:

This is a mock-up assembly, before final sanding and polishing of the stainless. Once the dinghy enters the picture.....

     One person can load and unload the dinghy, although it is easier with two people. In the next post, I will show the final elements of the davits, and a modification I made, to help keep the dinghy in place.

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