I'm going to get conversational and ramble here, no apologies. These are difficult times and this is as good an alternative as any to "whistling loudly" in order to reduce anxiety and induce thinking about other things.
Arne - interesting photos. There are plenty of ways to skin a cat and I have no doubt the boats you refer to were sound and good. Richard Hartley was adamant in the use of truss frames and advocated not using transverse rods in the armature of all his smaller boats, including the South Seas. I guess the one in your photo was either not a Hartley, or it was a larger vessel as I can see the transverse rods (on a 45 degree angle). Personally I followed Brian Donovan's school of thought which was placement of longitudinal rods along the diagonals, transverse rods on an angle, structural floors and structural sole, and building over wooden temporary mould frames. In his writings and in his lectures, Hartley was totally one-eyed about his construction design and methods, which were based on his past experience as a wooden boat builder.
(As a digression I once heard him justify his permanent truss frames by analogy with a canvas-covered canoe, and the fact that it would collapse if you took out the frames! He was not an engineer and he seemed to have a hatred of engineers, especially academics. I have seen him engage with Morley Sutherland (an engineer ferrocement pioneer) about these matters and feathers were very ruffled on both sides. That said, his designs worked reliably all around the world. A little-known fact is that, including his catalogues, he was in his day New Zealand's best-selling author.)
And he was adamant about using the 2-shot method. Yet to talk to Richard personally on a one-to-one basis he was a really nice guy, kind, helpful and always willing to discuss. None of his ferrocement designs had any visual beauty in my view - except perhaps the RORC series, to a degree - but I commercially fished for 10 years out of a modified Hartley South Seas and got to like it. (We took a sledge hammer to it, chopped a metre off the stern, smashed off that ugly semi-clipper bow then repaired the damage. We shortened her down to 35' to avoid the survey regulations, and she was a better boat for it. It served me well and paid for itself many times over. The old transom (which must have weighed half a ton) is still lying in the mud down here in the mangroves. I will put photos and all that story up on my website later when I get time.)
The Lone Gull turned out to be a superb longliner, I wouldn't have changed a thing more. The black longliner, Heidi Lisa, on the left, in the fishing basin photo, is a Hartley Coastal 32. (Man, could that thing stand on its stern and pitch, when bucking a head sea. Did a lot of miles and caught a lot of fish though).
Paul, thanks so much for those brilliant links. I am absolutely gutted now that I have gone too far in meshing up my current project with steel mesh, and commenced the plastering. I would rip it all off and use basalt fibre but there are about 7,000 or 8,000 staples holding the mesh down! (I used a battery-powered staple gun, burned out the first one, dropped the second one in the tide and I'm on my third. Brilliant device.)
One of the links Paul gave me shows basalt rod, it appears to have better (memory) characteristics than semi-high tensile steel for using in a conventional ferrocement-type armature layup. Two directionally opposed layers should fair themselves up nicely.
I would say a one-off BFRC hull along conventional FC lines would be feasible, and also being potentially stronger/stiffer it might be possible to move away from the double-compound curvature and look at hard chine models.
Female moulds, gell coats and mortar with chopped strands sprayed onto a layer of mesh would probably be the shot for commercial production.
I've got 45-year old tested ferrocement sheathing specimens here and I'm going down that road personally, for this somewhat extreme hull design. I have done it on a round bilge launch, but although the sheathing was satisfactory the result was not, so I don't recommend it generally, unless sheathing an old worn-out hull that would have to be scuttled otherwise, in which case it can sometimes be "just what the doctor ordered", depending on hull shape, displacement etc.
Basalt fibre would have been lighter, stronger, and a cinch to apply as a sheath - and I would have considered stopping the the sheath at the boot top. Food for thought. Too late for me now.
Marcus reckons he will pick up the baton. Some day.