|Doesn't show furnishings, but this is a good, strong start|
Building for Blue Water
I want to be clear... I have zero blue water experience, don't particularly want any and am NOT a naval architect. What follows is a bunch of amateur musings. Please take following assurances with a grain of salt and practice due diligence!
I'm often asked about taking TriloBoats offshore. In a nutshell, I don't see why not if they are built for it and competently handled.
That being said, I doubt they'd be the best choice if purpose built for the briny deeps. Wide barge bows and transoms (unless SKROWLed or brought to a point a la NZ SCOWS) could be uncomfortable in big water confused seas. Still, a number of blue water sailors I respect have said they think they'd do fine with only a few days of slow going in certain conditions. And once you're back 'longshore, I think they're hard to beat.
At the less expensive, DIY end of the spectrum, I'd likely choose a MacNaughton SILVER GULL, Benford DORY or Bolger ADVANCED SHARPIE. Of course, I'd fiddle with the designs - mostly regarding keel and rudder arrangements - but these are good, proven starting points.
Building for blue water, I think entails extra robust construction. But really, not a whole LOT more. Or rather, inshore cruisers shouldn't generally be a whole lot less, to my mind.
Where glue can fail and a nail can pull, double-ended fasteners are as secure as it gets (bolts, clench nails, rove and rivet and double wedged trunnels). Plank and frame joined by these should be thick and hard enough to resist pulling the ends through. Tape n Glue joints are strong and waterproof.
Pete Culler's dictum was "Nail where you can, screw where you should and bolt where you must." For taking a boat offshore, consider promoting everything up a notch. Note that bolts are expensive while the other double ended fasteners are not. Time, however, can be money.
NOTE: A non-cargo box barge can be a very light displacement boat for its footprint as it makes the most of its dimensions. This means it rises over, rather than plows through a wave. Skitters rather than absorbs a blow from a sea. Most of the sea stress is in the lower couple of feet of side, and fore and aft. The hull is a girder, as are interior furnishings which can be bonded structurally with an eye to longitudinal and side reinforcement. Rubrails, guards, eaves and the like can also be structural in support of the side panels. Modern glues create a virtual wood sculpture of the hull. All considered, a very strong yet lightweight hull can be built without the heavy frames and scantlings of traditional construction.
I like strong, doggable, centerline hatches (furthest from water in a knock-down), stout windows (they can be large, but with sea-going shutters to reduce their exposed surface) and 360deg, waterproof ventilation (a round turn in a vent hose is an easy solution).
Myself, I like retractable lateral resistance and rudder on an ultra-shoal draft hull. This leaves little to 'trip' on in a broach. This is controversial, and harder to arrange on the dories as designed.
I'd build a stout junk rig, able to take (running and removable) stays (these generate strong downward forces when sails are full of wind, and cantilevered masts are not generally designed to take that). UltraHighMolecularWeight Polyethelene rope (Dyneema, Spectra, et al) is about as strong as steel by diameter... even going oversized leaves a light, low windage rig.
I'd incorporate stormsails into the upper working sails, with lighter lowers. Since they'd be stayed, I'd go for maximum junk spread of sail. Maybe have some light-wind drifters for the metaphoric doldrums.
I'd like good anchor gear to include sea anchor and drogue set-and-retrieval (I'm a Jordan Series Drogue fan wearing both hats).
I've waffled about offshore cooking/heating fuels for years, with no real results. I like solid fuel stoves (wood and coal) but those can be scarce. A diesel drip can be added to the firebox as can a gas cooker (propane or LNG). A single burner gimballed stove can be chosen that burns a range of liquid fuels or exchange with a gas burner. A Retained Heat Cooker would be a real plus. Basically, one or two multi-fuel gizmos cover a lot of possibilities.
That's about it. Pretty much the same list for adventurous in- and 'longshore sailing. We can count on wood heat and duck out of the really bad stuff. Inshore, seas seldom reach the 'walking mountain' stage, anyway, and then only with fair notice.
Make good decisions!
Here's a selection of posts touching on this subject: