There's a link at Seahorse Marine's website to an earlier boat with some pictures during construction of what Mike describes and some profile drawings of the hull. I'd like to share my thoughts on this method of construction to possibly stimulate some discussion of general passagemaker boat design. My intention is not to be critical, only to share ideas. (Opinions are like ....) The long box keel will provde a rigid structure on which to support the vessel and will provide excellent directional stability. Some would argue that this long keel would limit fast steering ability down the face of a big wave. The shape of the keel will also have some effect here. A sloped or wedge shape keel will provde additional drag, which is a good thing in this situation. I believe that a sloped keel also has an advantage over a keel that is parallel to the waterline in the event of a grounding. Lot easier to pull a weight downhill than on a flat surface. The .250" material on the bottom seems a bit light to me for a few reasons. When the paint gets rubbed off there won't be much metal for the inevitable corrosion that will occur and may require replacement over the life of the vessel. The transverse floors placed every couple of feet also shouldn't extend all the way to the bottom plate. The plate is thick enough to span the few inches of width. If the boat is grounded on a sharp rock, what could have been only a long crease may now become a puncture at each of the hard points at the floors. Now on the inside of the boat, that entire space will have to be sealed airtight to prevent corrosion. It doesn't have to be painted, but it must be airtight. Mike mentions lightening holes but I don't know why this small weight would matter. Does bouyancy really matter? Possibly tankage is planned. Is there any ballast in the keel? On a metal boat a hollow keel is also perfect for an engine keel cooler or tankage. Seems to me like a difficult keel to build, especially to weld on the inside on the deep end. You'd have to lay it on one side to weld the remaining inside or be hung upside down by your feet. I took a different approach on my own boat starting with a wide flange steel beam 14" wide x 14" deep x 20' x 90 lbs.ft. The flanges are .750" thick and the web is .410". I cut 8" out of the web and welded the halves back together. The sides of the beam between the flanges are covered with .250" plate. It's also tapered to about 6" at each end in plan view. The resulting void in the beam is also baffled and is utilized for the engine keel cooler. The thickness and weight of the beam provide structure, ballast down low, and corrosion protection. On top of that I placed additional keel sides and floors to make a wedge shaped keel. There are three sealed voids with welded tops and access and one open which makes a sump under the engine. Two of the voids are partially filled with ballast and more may be added if necessary. I'm toying with using the remaining void, which the shaft log passes through, as a keel cooler for my hydraulic system/get home engine. The get home was not in the original plan and I am adverse to seawater cooling. John Crowley