Origami Construction of Displacement Hulls
Fully round metal hulls, as are typically formed over a frame, have the least shape limitations of any popular metal boat building technique. However, achieving a fair result using this technique is beyond the skill and budget of many builders. Thus builders use chined construction to minimize costs, time, and skill requirements.
Chined boats by their nature have shape limitations. Many boat owners do not like chines, regarding them at best as a necessary evil. As a result, designers go to considerable length to blend the chines into the hull and make them less noticeable. This further restricts the shape of the boats as compromises between performance, appearance and comfort are made.
Origami is an adaptation of chined construction, to further improve on the cost advantages of chined construction, while minimizing the objections people have towards chines. To understand the difference between chined construction and origami construction, consider the garment industry.
At one time clothing was built over a frame – a human body, wooden or wire frame. Today most garments are sewn on the flat to speed production. Men’s clothing is typically built with seams – chines in boat building terminology. The result is a “squared off” look, similar to a chined hull. Women’s clothing makes use of “darts” to achieve a rounded look. This does not limit the shapes available. Some might suggest it improves them.
This is the basis of origami construction:
Many of the early origami boats were designed using paper cut-outs and similar techniques and suffered from shape limitations that persist even to this day. This has turned designers, builders and owners away from origami because the boats are perceived as being rather crude and limited in shape.
However, in the mid 1980’s Gary Noble Curtis published an article on a mathematical solution to origami which formed the basis for our own work. Gary is a well know structural engineer and in talking to him it became apparent that shape limitations are not an inherent limitation of origami - rather they are a limitation of the technology available to work with origami.
Since that time we have developed tools and techniques to eliminate much of the guess work in developing new origami designs. This allows us to take just about any chined hull or round hull and turn it into an origami "clone". Typically the resulting origami hull looks better than the chined hull and can be hard to distinguish from a round hull.
Conversion to origami isn’t push-button technology. Similar to conventional boat design it requires a practiced eye and many hours of work to create a new origami design. However the results are well worth it in terms of appearance and construction savings, with an average conversion costing about $2000.
Shape limitation do remain in origami. Canoe sterns and concave bow sections are a challenge. In general, modern hull forms are easier to convert than some of the more traditional, wooden boat derived shapes.
How do origami hulls perform? Many people rate them superior to chined performance as the rounded fore and aft sections result in a cleaner entry and exit. The darts amidships improve roll damping and tracking as compared to fully round designs, with a slight increase in wetted surface. Whether this is an improvement over fully round designs is open to debate.
Our recommendation to anyone considering building a chined hull would be to convert the hull to origami. Unless the boat has specialized requirements or a complicated superstructure, conventional chined construction should in large part be a thing of the past.
If you require a full round hull for appearance, consider converting to origami. Multi-dart origami especially can deliver the look without the cost. If you require a full round hull for racing or luxury, build using conventional framing.
What is the future of origami? Origami shines best when building simple, functional boats on a budget for cruising and weekend handicapping. It is an ideal technology for amateur builders and cost conscious, low volume professional builders because it yields a fair hull with a minimum of time and effort.
Both the amateur and professional benefit from the reduced skill level required to achieve a fair result. Less experienced workers can perform a greater portion of the building without sacrificing quality. Low volume professional builders can compete with the high volume builder because there is no need to build specialized jigs or other such structures that must be amortized over multiple boats.
Greg Elliott spent the better part of 20 years cruising offshore with his wife and 2 children aboard their steel yacht, “Lazy Bones”. He has been building boats for 45 years and designing and building origami boats for 20 years. He holds a BSc in Mathematics and Computer Science.