Thanks to all for the replies. I found the answer to my question from Ray Hunt and Associate (the designer of the boat). They were very helpfull and took the time to actually go back to their old drawings... They hull lamination schedule is as follows: Hull topsides: 5 layers 1.5 oz. chopped strand mat (CSM) and 3 layers 18 oz. woven roving (WR) Hull bottom: Topsides laminate plus 1 layer CSM and 1 layer WR. Keel stub and bilge area in way of keel: Bottom laminate plus 2 layers each CSM and WR. From what I looked up, it seems that this is pretty much the same schedule than that of larger boats with a reputation for having a very strong hull. To clarify what I wrote about making the boat unsinkable: The volume of the bilge under the cabin sole is small. Most of the volume of what I call the bilge is located underneath the settes, under the beds of the front and back cabins, and in the engine room. It is easy to waterproof and divide up the volume under the beds and the settes by adding mini bulkheads. The top flat portion of liner that supports the cushions can either be cut off and replaced with some plywood, or plywood can be added directly on top of the liner. You must do away with the rectangular cutouts. To keep an access to these storage areas, screw-type waterproof deck plates (I have seen some up to 8inch diam.) can be fitted instead of the cutouts. If he boat is ever holed, the water would be contained between the mini bulkheads. The volume located between the mini bulkheads for which you do not need to gain access can be filled with packing peanuts for increased safety. I also agree that the addition of bulkheads under the front bed is needed for offshore cruising to stiffen up the hull. Glassing to the hull the wood members that hold the back cushions of the sette does not hurt either. The engine room can be waterproofed in the same way as the rest of the hull. I would keep access from to the engine room from the back room. A hatch with clamps coulf be fitted to allow access. Also, I would not adventure for some major offshore crossing without fiberglassing some heavy duty hatchboards to both of the companionways, and adding some large diameter drains that would direct the water to the sides of the hull via some through hull fittings. The front hatch and the windows may also need some reinforcing/replacement. Overall, I think that it is very possible for the O'day 37 to be made unsinkable. It sails well, its underbody is appropriate for cruising (the fin is quite long and it has a large skeg), and the hull is strong. Even if the bak cabin is not comfortable while underway it provides a great storage and a separate shower (most cruisers spend most of their time at anchor anyway). I think that this boat can become a capable offshore boat with not so much retrofit work. I also plan on replacing my old diesel with an electric motor. With 4 dedicated batteries the motor will have a 2 hour autonomy at near hull speed. While sailing, the prop will rotate and the motor will become a generator. 3 hours of sailing will yield 1 hour of motoring. If longer periods of motoring are required, a small diesel generator can be added to supply enough power to keep feeding the motor. For those interested in that, check out www.ecycle.com They have a neat and http://www.mindspring.com/~jimkerr1/sebebts.htm