Highest Utility for lowest T.C.O. DYI sailboat

[misanthropicexplore]

I know that in the real world, buying a used sailboat would be cheaper than building one, and building from established plans is cheaper than having new ones made, but I'm very curious about this as a thought experiment.

Boat is 2500 to 5000 lbs displacement at full load, or about 18-25' long if you prefer. (Small, but not record setting small, just modest)

The most important feature is a safe, small, solo boat for full time, blue water cruising in many different weather conditions and climates and coastal cruising. Appointment is very spartan: bucket or composting toilet, no running water, single burner stove, single kerosene or LED lantern, Yuloh/oars rather than motor. Limited standing room, or perhaps full standing room only in under a removable cover clipped in at safe harbor. So better than tent camping, but it's only for the slightly masochistic or monastic, yet actually meant to be lived in, not camped in for a short period.

It would be self built in the U.S., <1000 hour build time for amateur.

What overall has the best highest utility (for being used the way mentioned) for the lowest total cost of ownership? Heavy displacement steel, like a Tom Thumb? Ultralight displacement skin on frame like an umiak? Glassed plywood (like...everything else) Monohull or multi? Shoal draft for more anchorages or deep keel for better stability? Cheap rig that is replaced regularly or expensive rig that needs little maintenance? Long term cheaper to make a very heavy hull, light rig, and spend more on provisions, or cheaper to make a fast boat and spend less on provisions? (Assume 25-50% of time spent underway).

 

[messabout]

Glass over ply like everything else, aluminum maybe, steel no way. Skin on frame in blue water..........don't even think about it. The longer the boat the better. Even a 25 footer would be pretty miserable in a storm at sea or a long calm spell in the doldrums. Cats in that size range can do Transats, possibly faster than a mono but less commodious in every way. If you are to spend extended time at sea then your safety and comfort is a real factor. If a blue water boat then a keeler is practical. A keeler can let you get some rest at sea if you have moderate weather and functional self steering gear. In wild weather you ain't gonna' get any rest. You will need nav gear and weather gear and lots of water and provisions when you get into the big water. Davy Jones don't give a damn for your poor carcass so be prepared with the best gear and skill and a good and reliable boat.........

A boat with a 20 foot datum water line would need a mid section area of about 7.5 square feet if you are to have a displacement of 5000 pounds. You would really like to keep the length width ratio DWL/Bmwl as large as is reasonable, but the mid section will need to be pretty fat to get that amount of area in the midsection.............If the boat was built like a square chined box......... you are not advised to build it that way.... lets say it aspect ratio was something like 4 ( 20/5) you would be giving away some potential speed but have a better range of stability..you are not going to build it the box like way.... It could be 6 feet wide at the waterline and have 15 inch draft not counting appendages like a keel. Or you could have 4 foot beam waterline and 22.5 inches of immersion. Neither of those would be the right way to build a blue water boat.

I mention all this stuff to suggest that a good and appropriate design is not just a matter of drawing on a cocktail napkin. Get a credentialed designer to do it or find a current design that satisfies your needs. As is often said here; A sound used boat of proven ability can be bought for less money than you would need to build your own.

I will defer to my better informed forum brethren (and sisters) for further commentary.