Sunday, July 19, 2009
Whenever I think of a keel I think of a sailboat. My trawler has a keel under and adds a considerable amount of structure to the boat. The bottom of the keel ( keel shoe I think) is 3/8" plate, the sides are 5/16", the length of the keel is 20', the height is 50", and it's width is about 18". The rudder bears on the keel shoe and the prop shaft exits the boat through the keel. The keel provides protection for both the prop and the rudder.
I built the keel on the shop floor then used my skid steer loader with a sch. 80 pipe extending the forks for the machine to maneuver the keel into position. Once I had the keel assembly under the boat I used floor jacks and bottle jacks to lift it into place and get it aligned with the marks on the bottom of the hull plating. Once I was satisfied with the alignment I welded both the inside and outside of the keel before putting on the starboard side plate. Before I put the starboard plate I blasted and primed the inside again. I know I'll burn through some of the primer during the final weld up but I just didn't feel right covering that up without putting some paint on her.
Having such a large structure of the boat existing with burnt primer had always bothered me while I was building the keel so I made provisions to make the keel an air tight structure. After I installed the stern tube I air tested the keel to 7 psi. Air testing and repairing all the pinhole probably added a day to building of the keel, but I feel much better knowing it is air tight. My thinking is that by being air tight rust and corrosion will have a hard time getting started.