The Medieval Period
These medieval boats closely resembled the Viking boats of about 350 years before, and would have been used to ferry people around the coast of England. The boats used the clinker built style to construct the hull, which was a traditional Northern style at the time. The vessels were flexible also to allow them to move in the high seas and did not break up and sink. The difference between the boats was that these boat adopted a more defensive strategy by building light wooden towers on the deck fore and aft of the boat to give the crew a better vantage point when under attack and for look out. After this period this was commonly seen on most ships. Over the next century more sea worthy vessels were made with stronger hulls and a greater load capacity.
The steer board was very effective to begin with, but when the vessels soon became larger and heavier, the steer boards therefore also became larger and deeper which affected them when entering a key or harbour. The German cogs quickly developed a vertical extension to the keel, which allowed the first stern hung rudders to be used. These were easier to use and more effect for the larger vessels. These early boats also used a single square sail to power them. This was common for boats in the northern waters, however in the Mediterranean waters a Lateen (triangular sail) was being used. These were more effective for sailing windward, but tacking through the wind was more time consuming. These sails were first incorporated in to the boats of the northern waters in the fourteenth century, when they were used to improve performance and to enhance aesthetics of the square sails. The sails were still made out of nature materials, which had the tendency to stretch when wet.
Tall Ships Period
The tall ships were originally masterfully designed ships used for war. In the eighteenth century these vessels were very stable and heavy. The typical sail area would have been about 16,000 ft made from a material called Flax. This material was the earliest woven sailcloth, but was soon changed to American cotton and then to Egyptian cotton. These heavy boats were usually made abroad where good use of the native hard woods could be made. These woods were almost as strong as English Oak, but less dense so they had high buoyancy. It was also reported that an early form of lamination was used to strength the hull of the ship. After this period triangular sails were then moved to the mainsail, when simpler rigging techniques were used and better materials were developed, one of these materials was Nylon, which was first produced in 1938. This material is light and durable, but has less resistance to stretch. Nylon was quickly moved to use in Spinnakers, as the stretch does not affect the boats down-wind sailing.
Mid Fifty’s Revolution
The next large development was in the nineteen fifty’s when a polyester fibre was manufactured. This advance in the construction of synthetic fabric has improved the operation of the sailing vessels, by decreasing weight and increasing strength. The first synthetic fabric used was called Dacron® and was originally woven; this fabric was ideal for the mainsail because of its resistance to abrasion, UV resistance, and its higher flex strength and finally low cost.
The material also had a broad range of variable properties and the following factors affected the quality and cost of this yarn. The best quality and most desirable yarn would have a high tenacity (see glossary) and high modulus, however this would also be the most expensive. The compromise involved in choosing the right yarn also depends on the creep (long term stretch) and the ‘weaving quality’. Another variable property of the sailcloth is its yarn content. This varies with relation to the aspect ratio, this is the luff length divided by the foot length. Lower aspect ratios require a more even weave most often with fibres of similar Denier (weight of 9, 000 m of the fibre). The tightness of the weave is also a factor that changes for different sails. The smaller Denier must have a tighter weave. The sails can also be toughened with a finish, for example a resin, however these usually hold the sail shape so after extended use the sail changes shape.
Also in the 20th century we have also seen the mast change from a single piece wooden upright to Aluminium. This is a much stronger materials and can easily be produced by extrusion moulding. The development also saw a variety of new materials that could combine to make the first composite sails. The advantage of these sails was that the properties of different materials could be combined to make an excellent sail with the perfect assets. Exemplars of these materials were Kevlar®, Twaron®, Pentex®, Spectra®, Mylar®, Vectran® and Carbon Fibre, however these materials are used in the lamination process to enhance the strength and capabilities of the sail.
From both graphs above it is possible to see that the most useful material for sailing is the PBO (Zylon®), because of its high modulus, surprisingly it is higher than Aramids like Kevlar, and its high flex strength. The disadvantage is that the material is far more expensive due to the marketed profits. Carbon Fibre another liquid crystal polymer has similar properties, but again is expensive. From looking at the comparison graph above you can also notice that no material has all the correct properties, which supports the idea of having laminated sailcloth to create a superior cloth.
2002 and Beyond
The sail-racing world today is the leading development body for sailing performance, all the component designs are accomplished using computers, these are then computer generated and tested even before production starts. The companies spend millions on development projects and keep their plans strictly secret. This attitude however has allowed the sailing industry to experience the best developments in the history of sailing. For example the most professional racing boats use carbon fibre masts as these bend more and have super strength, because of the individual strength of fibres. These masts are also aerodynamically tested to achieve the best design. The hull design has also transformed to reduce turbulence in the water and cut the boats drag; this has been achieved by reducing the weight of the hull and the shape of the hull. The latest hull is a composite of Kevlar, foam and epoxy, which is baked in a huge oven. The strength of the hull is maximised by using strong structural designs like the honeycomb structure. The rig on racing yachts has also changed dramatically and is due to change even more drastically over the next decade due to better manufacturing methods. The most superior sail fabric on the market today is the 3DL sail (3 dimensional laminate), which is made of one panel and many laminates, which are moulded into the perfect dimensions using computer controlled hydraulic lifters. The usual process of sail design is where the sail is designed on computer or paper and is then divided into single panels, which stitch together to form the sail shape. The stitches used in this technique, help promotion stretching and weakness in the sail. A single moulded sail will be more accurate with less variation between sails produced the sail will also be stronger and lighter; it has also been shown that the sail holds its shape for longer. This sail also has the ability to use the best materials and combine them to form an amazing sail. The 3DL sail usually combine PBO, Kevlar and Mylar to give a strong sail which has a high U-V resistance and resistance to stretch.
Since the introduction of this sail, the construction method has dominated international Grand Prix sailboat racing and all the Whitbread race finishers used this sail. The yachts involved in the America’s Cup race all spend about £2.5 million on sails alone and the top ten all use 3DL sails, which on average have a lifetime of 100 - 500 hours, this shows how competitive and determined the teams are to win these races.
However the sailing developments discussed so far are development on the conventional design for a sailing yacht. As well as introducing these new innovations to the sailing world, a new sailing world has been born on this planet and in Space; these include Land yachting, Solar sailing (concept) and Speed sailing.
Sailing Faster than the Wind
In the past sailing has sometimes been considered very relaxed and recreational, however with the current rate of development the speed of sailing is seen to change a great deal. The newest yachts are so well designed that they are extremely sensitive to the wind so are able to catch the wind more easily. Due to this the boat have become so fast they are starting to create their own wind so are travelling faster than the wind. In terms of Physics this is due to vector addition when the boat is on its optimum course usually across the wind, not running in the direction of the wind. This improvement has led boat designers to design and build a totally new design of yacht that is built to harness this resource. The most successful design was built by ‘Yellow Pages’. This boat currently holds fastest speed on water under sail. The boat reached about a maximum of 86 km/h after 18 minutes of sailing. The sail leans into the wind and when it is caught the cockpit at one side of the yacht is lighted out of the water. This design has reduced the weight of the boat, as it is able to exploit the new composite materials. The design also means the boat has reduced the drag and turbulence of the hull, by making it thinner and longer. The sail is tall and rigid, very similar to the wing of an aircraft. This design has a number of advantages along with the extra speed. The first is that the boat is very stable so it can withstand a greater force from the wind; it is also very easy to keep on course and needs little human response to gusts of wind to keep it sailing to the greatest efficiency, however this all comes with the disadvantage that the boat is a one tack boat and handling any turn is difficult. The sail rocket is another example of the same design, but on a smaller scale. The same ideas have been used this design should be introduced to the market in about 7 years. Not only have we been setting records on land but we have also been busy sailing on land in an adapted vessel.
Land Yachting
The sea’s condition on a particular day often decides the safety rule on whether sailing is possible with out to greater risk. This has directed the world of sailing on to land, which seems much better; because there is no water drag so higher speeds can be recorded. The land yacht has three wheels, with the front one in control of the steering, via pedals. The sail is similar to a wind surfboard so is fully battened. The vehicle has no brakes to reduce weight and increase suspense involved. The wheels and like mountain bike wheels for maximum grip and strength, still with these wheels the little yacht is usually very unstable.
A variation of the land yacht is the ice sailing yacht, this is even better suited to sailing, because the ice has very little friction and so the yacht travels extremely quickly. With these yachts the power required from the sail is less so the sail is more yacht looking as you can see from the picture. The craft again uses three skates with the forward one steering.
Sailing to Mars
Sailing used to be a means of travelling on water, but the latest discoveries have opened the option for solar sailing. This will be a spacecraft with a large, lightweight mirror attached to it that moves by being pushed by light reflection. The light to push these sails could come from the sun or a laser that could be built. A giant mirror would be used because according to James Clerk Maxwell’s theory, particles that are reflected exert twice the force on the sail or object. In order for these sails to be powerful enough to create a decent amount of thrust the sails will each need to be kilometres wide. This is obviously not a problem due to the space. At Earth’s distance from the Sun’s power is the equivalent of 1.4 kilowatts per square meter. A square sail with each side 1 kilometre with this power would generate 9 newtons of thrust, which is enough because there is no noticeable friction in space to slow the craft.
The advantages for this idea include the following: any space missions could last for longer as the space craft would not run out of fuel, as it would not use as much, the craft could be lighter so it would be easier to enter space and the space craft would need less maintenance.
This could mean that the satellites could move around more for specific needs, for example to Mars and back a few times. This would in the long run save the space exploration teams lots of money and time by diminishing the number of different rocket missions that take place across the world. The sails would also be reusable to the extent of a couple of launches depending of their time in space. There would be less maintenance apart from repairs from debris collisions and normal wear and tear. With specific view to helping colonizing another planet the sails could be melted down and used to help build permanent shelter.
The idea still has a lot of development to be considered, for example the reflected radiation must be ensured not to focus the light on the craft or it will be heated and destroyed. The sail also only allows the craft to travel away from the sun so a sailing technique in space will have to be developed, perhaps using rockets to help stay on course. The sails will also need to be rigged so a mechanism will have to be designed to fly the sail and lower the sail when re-entering a planets atmosphere.
Over view
I have now reached the end of my report on the progression of the boat’s design, I have looked at how sailing became part of our lives and the issues that have enabled sailing to remain part of every day live. The path of the sailing boat has not been a smooth progression and there were areas when development slowed down and then of the other hand when production sped up and boomed in the late 19th and 20th centuries and is still developing at the same rate for the every ready world today. Sailing is the same as many technologies I feel and it only takes confidence in investment to encourage the market to bloom, however the one constraint we have is the demand shortage for developed sailing yachts. This alone has been responsible for the cut in working sailboats, because of the advent of the engine. I feel this report has also exposed the other roots that sailing has to offer like leisure curses and racing, which still remain popular today. Also bringing the sail to land yachts and skating yacht has increased demand for investment in the industry.
From the knowledge and experience I have harnessed I feel there are a few points that should be commented on from a fresh perspective in view of maybe shedding new issues for discussion in the broad industry.
Firstly I would like to explain the compromise between the controllability of the boat and the power from the sails. The sailing world shows both to the extreme from Norfolk Broad sailing yachts with excellent handling to the ‘Yellow Pages’ record breaker for the quickest boat. Since humans will always want to go faster the next area for development will probably be a boat that is a similar the design of the Yellow pages’ boat, but one that is able to tack. This would open a new class of racing boat and I feel it would be popular as the races would be faster and unconventional. This may also help develop areas of hydrodynamics for other water going vessels.
More particularly I would expect the range of composite materials to expand and ranges such as North sails’ 3DL sails to become more durable so they will be incorporated into the every day sailcloth class. This would improve the speed of leisure cruising.
With sail also comes an ethos, this atmosphere in my opinion is very discriminate against the people who live in land with no easy access to large inland lakes or the sea. I feel the yacht clubs are too expensive, maybe not to those who live on the coast that can make use of the facilities like free boat hire and races. The clubs do not allow for those go every other weekend by making the prices cheaper. This means many inland residences are not attracted to sailing, because it is too expensive. If the clubs were cheaper and boat storage was cheaper then the market would be over double.
Bibliography:
Sources:
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This site has a glossary of all the names used in sailing. This was especially useful when it came to understanding the parts of the sail and the tests involved in rating a material.
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This site has details on the 3DL sail. This was a useful page because the material is very new so there was little information on it.
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This site has a brief history of rigging and masts from the 1900 to the present day. This was useful in the early section of the project.
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This site has an incite into the evolution of the Viking ship and again was useful in the first section of the project.
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The site had a few pictures of tall ships and their origins. There was no real mechanical data.
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This page provided the details of the manufacturing processes.
- Channel 5 program: BIG STUFF. This programme was useful as it showed me the scale of production and the cost involved. They also talked about the processes they use when making the sail, this involve the CAD programme and the curing process.
Appendix
