Last updated on 6 April/97
The science and technology of the EAST outside of the notice of the invention of the compass has been little noticed in the west. A Cambridge historian, Joseph Needham has tried to overcome this. His life work, the Science and Civilization of China has made a big impact on the west.
The Chinese were great sailors and had reached Madagascar 100 years before Vasco de Gamma by long range sailing across the Indian Ocean after traversing the Chinese Coast. The ships were multi-masted and had excellent up-wind ability. One hundred years after the visit by Chinese ships, the natives of Madagascar were not impressed by the relatively smaller ships sailed by Vasco de Gamma.
There is no clear explanation as to why the Chinese didn't explore further. Many explanations are offered including... they didn't find anything that excited them. Everything was better at home. It is known that the Emperor made a law which forbade the building of large long range ships after the Madagascar expedition. It was said that the emperor was jealous of the fame gained by Cheng Ho, the leader of the expedition. [I named my former sailing dinghy after him.]
Sailed on Whitewater with safety. Boats had bulkheads which divided the boats into watertight Compartments. As long as some compartments were not holed, the boat would maintain enough floatation to land safely. This innovation was noted by the English visitors and adapted by the British Navy and hence to the rest of the world. In sport sailing the watertight compartments are a innovation that has been required of small boats in the last few decades only. No such requirement is required of the larger boats. I've raced in a 5-meter yacht that was swamped by following seas and promptly sank in San Francisco Bay.
High Efficiency. Fully battened and with leading edge unencumbered by mast. Controlled for optimum pitch as a function of height. This is necessary because the wind has a higher velocity at the great heights because of the shear with the water. Consequently, the apparent wind direction varies with height. Modern yachts attempt to control the sail pitch for the different heights but were not successful until the C-class catamarans used wing sails with adjustments that varied with height. The multiple sheets attached to the trailing edge of the fully battened sails permitted control with modest equipment. Sailing Upwind and with tacking was the norm at an early time historically.
The wind velocity increases with height.eg for a 10 knot wind in average sea conditions, the wind velocity is 5.4K at5 ft, 6.8 K at 13ft, 8 K at 32 feet and then gradually get to 10 K at 100ft. For a yacht sailing at 3 K, the wind "seen" by the sail [ or by the sailor] is shifted in velocity. The apparent wind is the vector sum of the true wind velocity and the boat velocity. For a Dragon Boat, the apparent wind is shifted by 3 degrees between the top and bottom of the mast on a close hauled course and is shifted by 12 degrees in a reaching course. Although racing yachts have gadgets to help put the proper twist in the sail, the accuracy that is achieved is far less than with a sail using full and multiple battens with multiple sheets. [Please read the section on the vector addition of velocities in your physics text.]
Figure showing addition of wind and boat velocity vectors to
obtain apparent wind.
Figure showing the twist of the sail of a racing yacht [vintage
1960's] while sailing a reaching course. Note that the twist is
far greater than the desired twist for optimum performance.
The mutliple sheets that control the sail of 20th C Chinese sailing ships were of quite small diameters compared to the sheets of Western boats. This is because the balanced rig required only small forces to control the pitch. When the sail in ENTIRELY trailing the mast, the sheet must take the full force of the sail. In the balanced rig, the wind helps to turn the sail. [also see balanced rudder]. There is a lot of finesse here.
Fully Balanced rudders and with finistered holes for maximum control with least resistance and with less force necessary from coxain.
A sketch from the 11th C of a working boat. The rudder is a balanced axial rudder. The rudder is very large and adjustable in height. It acts as a keel and so can be adjusted to optimize the keel for the ambient conditions.
A beautiful example of a balanced axial rudder that conforms to
the hull for high hydrodynamic efficiency.
Permitted making upwind much more efficient. See the boat made from bamboo poles.
A rowing boat model from the Han dynasty (-200BC). This uses a
steering oar plus oars of the modern western type. The steering
oar predates the axial and balanced rudders. The have a high drag
plus they require a lot of work on the helmsman to keep control.
The control is much worse with this type of rudder so that the
danger to the boat and crew are much greater.
High hydrodynamic efficiency as well as continuous action.
Might well have served as an inspiration for Bernoulli's
invention of the water screw (propellor) which happened after
some inventors had tried to make a motor driven scull of the
Chinese type. The hydrodynamic efficiency is a result of the
setting into energy more water but at a lower velocity. The
kinetic energy of the water is 1/2 mv^2 so adding velocity
extracts a big price!!. 
The Chinese scullers used these very large powerful sweeps to
propel the boats with a continuous figure eight motion. The
angular change of the blade to accomodate the multi-directions
was accomplished automatically by a ball joint arrangement on the
pivot of the sweep. Modern racing rowing boats do achieve a high
hydrodynamic efficiency with LIFT by utilizing large angles that
the oars sweep through. Please see the chapter on scull.lift.html.
Lug Rigged boats with flat bottoms and hoistable axial rudders. These came to Europe in the 16th C and spread rapidly. There is much speculation that this was adapted from the Chinese boats but with the loss of the battens and the multi sheets.
Josephe Needham, Science and Civilization in China, Vol IV:3. Cambridge University Press.
This is an epic work of multi volumes by Needham. It is also the first [and maybe only] serious systematic study of Chinese Science and Technology.
Pearl diving in Ming Dynasty, 1600's. Use of masks and air tubes and wet suits? The divers are clothed to keep warm but, of course, neoprene had not been invented. However garments of a close weave would keep water trapped and hence have an insulating effect which would permit divers to stay longer and hence be more productive.
