How did the old timers design hulls

Why don't you try to show some evidence for these utterly untrue claims?

There was no significant "appearance of narrow ports" as distinct from mooring buoys when yacht design changed from the "classic" long keelers. Boats had always been getting into small harbours and needing the manoeuvrability to do so.

Anyone who knows their boat design history knows that the light displacement fin keelers, came in during the 1890s, well before marinas existed. It is therefore utterly wrong to claim that classic yachts were "killed" by "narrow ports". Cowes, for example, is a "narrow port" and it was used by both "classic yachts" and light displacement fin keelers. Classic boats were not "killed" by anything - they are still alive today.

If one defines a "classic yacht" as a medium long keeler with attached rudder, then it is untrue to claim that they were killed by a "conspiracy" formed by agility in tacking. It's just not true. The early designs with fin keels and separated rudder came about largely as a result of the desire to reduce wetted surface. I challenge you to show actual evidence to prove your claim.

The "classic yacht" with long keel and attached rudder was eclipsed in racing by the rise of lightweight fin keelers after the length x sail area rules were created. It then returned to racing with the International (Metre) and Universal Rules that penalised light displacement in the pre WW1 era. The longer keel and attached rudder then dominated until the 1950s and 1960s.

There was no change to "narrow harbours" in the period when the fin keelers were penalised before WW1. Your claim is simply untrue.

The earliest influential cruiser/offshore racer types to move away from the "classic yacht" style were boats like Zeevalk, Hoot Mon, Nocturne, Miranda, and perhaps the 410, 210, 11o and Flying 15. Nothing indicates that their appearance had a single thing to do with "narrow harbours". For example Uffa wrote at length about the Flying 15 design and he did NOT mention "narrow harbours" or fast tacking. The port facilities in Sydney did not change to "narrow harbours" before Payne designed Nocturne. No mention of the inspiration behind Zeevalk, Hoot Mon or Miranda mentions "narrow harbours" or short tacking.

Where is the evidence for your claim?

There is plenty of actual real information about why fin keels took over. No one who was writing about their arrival in English mentioned "narrow harbours", and fast tacking wasn't really a major issue.

 

at times keel length was taxed in france and beam and flare were taxed in england

 

especially in the 1980s

fat man in flares in the 1970s - Search Images

 

Herreshoff designed hulls by carving a half model into the 2oth century. Offsets were taken using a high accuracy machine.