I missed my chance on a 27 foot hull last winter and so looked at what was in my back yard and decided to run what I have. With the uncertainty in the world, I did not want to build first then sail. I wanted to go water camping this summer. So one step at a time.
The hull in the back yard is an old Fiberform deep V 21.5 feet long. A trailer boat. The original running gear is broken and parts for it are hard to get. It was removed and replaced with a small, 7.5 hp two stoke. This did give it a slight bow down waterline but I reasoned this would actually help it at hull speed. The top slab of the birthday cake was removed and part of it was used to make a quarter berth. We used it thus for camping for a week at the beginning of July. The biggest problem was rocking.
I had been thinking of adding a mast and sails anyway and did not want to put a centreboard in as I had just finished sealing the bottom of the hull by removing the through hulls so, off centre boards (David is from Alaska so maybe off center boards would be the correct spelling). I noticed that in David's video about "traveling off center boards, it was mentioned that they were water filled so I decided mine would be hollow as well. Because I only had about a month till my wife had her next set of holidays, I chose simple, cheap and quick. I purchased two 5 pound lead weights which were close but not quite heavy enough as the bards floated 4 inches or so high of the mount points.
Wood is not cheap these days but I tore down a shed last winter and still had some of the frame around. I decided that one sheet of plywood would make two boards that were 2 x 4 feet in size. I used a simple 2x4 (1.6ish x 3.5ish for real or 4 x 9cm) for the main frame. It ran top to bottom about 8 inches back from the leading edge and had a 1 inch thick strip attached to the bottom 2/3 for a thickness of about 3.5 inches. the front was 1.5 inches wide and the trailing edge was just under 1 inch. I basically laid these on top of a 24 x 48 inch piece of plywood, laid the other plywood on top and glued and screwed the whole thing together. The whole thing was painted and then I set about working on the mounts.
Because the side of the boat has some flare, the top needed to be close to the hull and the bottom held away from the hull so I used a 2x4 (rough full size) on edge as well as spacers on the boards themselves. The top mount was a 1/2 inch pin of ready rod with four nuts and lots of washers to sandwich a backing plate on both sides of the hull and then the board with a set of jamnuts last. The bottom was a single lag screw which should have had ample length to hold into the lower block but the epoxy had not help as well as hoped and so the lag screws seemed to go in but when we got to our first anchorage it was obvious they had not held. We removed the boards and removed the spacers (1 inch) and remounted them. They were now canted inwards towards the bottom but because we were not heeling that was ok.
Results: Even with the bottoms not properly held there was a marked difference in the rocking motion, waves on the beam were more up and down and less rocky. When the bottoms were properly fixed it was even better. off center boards make good stabilizers too. This may seem like weak construction but we had 25 knot winds complete with the waves that means. We managed to anchor a bit close to shore and they held through that too (we didn't run into the ground just settled on it). It was a success for sure. I can't wait to add a rudder and a mast for next year and to try a better version of the off center boards... I think I ended up with plywood that has interior grade glue as there was some de-lamination :) And I would like to wrap the lead and trailing edge with cloth too. I want to change the mount so that they can swing up as well.
As for the hull, while I could add a piece to the back to round it off for easier movement through the water. I think in the long run looking for a sailing hull would make more sense. This was quite cramped for four adults (and dog) even for 10 days camping.