Inspired by the Arabian dhows?

The similarities with the wineglass shape of the Viking ships have been mentioned.
However, although the Song dynasty was around the same period as the Viking age, I would rather guess that the builder of this junk has seen and been inspired by the Arabian dhows.

As for length to beam ratio, my last boat Frøken Sørensen’s l/b was only 2.7. She had a pointy bow, and wide transom, but thanks to her exceptionally big rudder, with a thick and perfectly streamlined section, there was never any control problems, even though the cb. was sitting quite far forward.
Generally, the bigger the ships, the higher the l/b ratio, both in the West and the East. Those huge treasure ships used in Admiral Zheng He’s fleet appear to have been outstanding in every way, even in China (armchair guess...)

As far as I have understood, many (most?) Chinese vessels, big or small, had big rudders, which did second duty as a second cb.

Arne


PS: The l/b of Slocum's Spray was only 2.59...
Spray (sailing vessel) - Wikipedia

Anonymous wrote:

Congratulations, John! This is very interesting, and I look forward to seeing details of the hull form and construction, when you're ready to publish them.

For comparison, the L/B ratios of SibLim are 2.78 overall and 2.71 submerged body at rest, so in the same ballpark as LeFang. However, I didn't use a modern 'delta' wide stern waterline shape, and neither Annie nor Frank are reporting excessive weather helm. The hull cross section is very different, though, wineglass for LeFang and 5-plank for SibLim.

Thanks David! for giving me confidence in my Song dynasty beamy hull. 

John 

Anonymous wrote:

Congratulations, John! This is very interesting, and I look forward to seeing details of the hull form and construction, when you're ready to publish them.

For comparison, the L/B ratios of SibLim are 2.78 overall and 2.71 submerged body at rest, so in the same ballpark as LeFang. However, I didn't use a modern 'delta' wide stern waterline shape, and neither Annie nor Frank are reporting excessive weather helm. The hull cross section is very different, though, wineglass for LeFang and 5-plank for SibLim.

Bonjour

Following the "Classe Mini"  the other racing boats are nowdays evolving with less stupid forms than the "delta". They discovered that with a more "rectangular" shape the boat would have less heel tendancy and would alloy more canvas for a given wind and ballast.

After an era where the racing boats were acting like submarines by passing through the waves, they discovered that, with very light hulls (especially in the forward part) and big sail area , it was more efficient to surf on the waves.

The bow now have more and more volume with mast and keel well aft. Some racing rules (IMOCA for instance) limit the width of the bow.  

The industrial cruising boats are following that tendancy because it allow to have much more roomy boats for a given length. As they are much to heavy with small sail area, they are banging in the waves... it is not that important, as they, most of the time,  stay in harbours and only a few sail offshore.(but it is an other story...)

An interresting offshore racing class (same races are round the world and go round Cap Horn !), less extreme than the "Classe Mini" , also dedicated to single handed or two man crew is the "class 40". The lenght is limited to 40' (12,19m) and the width to 4.5m (length to width ratio of 2.7). The last hull shapes are almost rectangular with a round bow. 

"Classe 40" class-rules

Eric

Anonymous wrote:

Anonymous wrote:

THE MYTH OF BEAMY HULL​​

Modern sailboats occasionally exhibit LOA/BEAM ratios below 3, but their widest sections typically lie toward the stern, lifting out of the water when heeling upwind. Experienced sailors recognize that asymmetric underwater hull of a heeling boat generates weather helm—a hydrodynamic force that increases with beam. A wider hull thus produces stronger weather helm, demanding more CE adjustments on the sail to maintain balance.

Bonjour

Thank you very much ! I'm very excited and waiting for more! 

The "classe mini" is an offshore racing classe dedicated to single handed racing. The length of the boats is limited to 6.5 m and the width to 3m. A length/ width ratio of 2.1. They are almost rectangular and very fast, downwind.  

classe mini website

They would be wider if the rules would allow it.

The most recent ones are scows with very round and nosy hull. They are very powerfull and some are fitted with foils. 

Eric

Thanks Eric, 

I read about this cute round bow mini transat boat, but never aware that her length/beam ratio is 2. 1.  Thanks for giving me confidence on my beamy hull. I also noted a benchmark called ＂Capsize Ratio " which warned designer to keep the length beam ratio above 3. 

John 

So cool, congratulations John! I like it very much.