About the Designer: John Marples and Jim Brown have collaborated for over twenty years in developing the world-class line of SEARUNNER MULTIHULLS. Jim's sense of design paired with John's technical expertise has produced more then thirty sail and powerboat designs for both commercial and private use. These designs have evolved from their more then 50 years of combined multihull experience - on the drawing board, in the boat shop and at sea.
More than 2,000 clients worldwide have produced thousands of sophisticated seafaring vessels for a variety of uses from their designs. Their drawings provide the simplicity and clarity necessary for efficient construction by ordinary craftsmen.
As a mechanical engineer, John Marples has more than earned the title of "Design Virtuoso". He was trained at California State Polytechnic University and has drafted more than 20 sail and power vessels ranging from 7 to 64 feet. And, he has built five vessels over 20 feet, including two U.S. Coast Guard certified passenger catamarans.
John Brown is recognized by the world sailing community as the author of numerous magazine articles and books about trimarans. He is also an instructor at Wooden Boat School in Brooklyn, Maine. Jim has been designing multihulls since the 1960’s, following his association with trimaran designer, Arthur Piver. He is also the inventor of the Constant Camber construction method. He is best known for his work on the SEARUNNER Trimaran Series. Recently, he designed the WINDRIDER 16, a radical, roto-molded trimaran for Wilderness Systems. His sailing experience includes five Pacific Ocean crossings, racing, cruising and deliveries for a total of more than 30,000 combined, blue-water miles. http://www.smalltrimarans.com/r/John-Marples-on-Constant-Camber-Audio.html About the Builder: Dave Sharp served in the military, Air Force and Army, for twenty years. During that time, he attended many training courses including electrical systems and motors. He attended Flight Engineering School where he learned electrical systems, electronics, jet and reciprocating engines, aircraft structural repair, etc. He was also an instructor in Air Transport and a Logistic Specialist. During his military career, he became a Licensed Radio Technician. At the same time, he earned a license as an Air Conditioning and Heating Technician and later opened his own custom cabinet shop.
After retiring in 1998, he opened a Fixed Base of Operation where he worked on aircraft and also taught at an A&P (Airframe and Power Plant) school. He and his wife, Laura, also owned and operated an airport café. When his lease ran out, Dave began installing Radar Systems on boats for Raymarine. And, later he began re-wiring Coast Guard Boats. After that, he put his Radio License to good use by installing and working on Radios and Microwaves for the Coast Guard.
What is Constant Camber? The Constant Camber design takes advantage of the engineering concept of "egg shells". This engineering concept is used in virtually all molded plastic toys, aircraft, cars, etc., where a very strong, rigid structure is needed. The curved shape is strong because it exerts even pressure, or horizontal as well as vertical forces, to resist any outside force.
Constant Camber panels are molded in a compound, curved shape. The layers are cross-laminated to improve the strength of the panel. When the wood strips are laid in a diagonal format, they can resist incredible torsional stress, which is a major factor in hull design.
Because of their strength, Constant Camber hulls require less internal framing, such as stringers, leaving more living space. And because they, require less internal framing, more weight can be used in the skin. Therefore, Constant Camber hulls are generally thicker, which gives them greater damage resistance. These hulls tend to have superior flexing resistance.
Designing the Mast: As an aircraft mechanic, Dave could not get used to the idea of using force to push a boat along in the water. A round mast caused way too much drag. The whole idea seemed outmoded, archaic and inefficient to him. He felt a mast should be strong, yet flexible and light weight. Above all, it had to create lift not drag!
At first, he began to look up winged, rotating masts on the internet. But, at that time, they were too expensive and no one was offering plans for the home-builder. So, he decided to design one himself. This brought into existence the business, "Mast Production".
He decided to combine his aircraft experience with his boat building experience. So, he designed the mast using light-weight, wooden ribs and stringers, a plastic spar along with a curved, cold-molded skin that was made out of wood, fiberglass and epoxy.
Although the mast could not be a-symmetrical like an airplane wing, which generally flies upward with flaps that spoil lift when one wants to go down again, he could make a symmetrical, tear drop shaped mast that would rotate in either direction to create uneven pressure or lift. This design would allow the wind to pull, rather than push, the boat through the water.
For a spar, he decided on a continuous, 4” diameter spar that was strong and durable as well as light weight and water proof. Then, he filled this with foam so that it would add extra floatation in the event that the boat should become capsized. There are also three smaller, conduits for electrical wires and halyards.
The mast rotates and cantors on a 4-½” ball joint much like a socket ball joint of a human shoulder. The mast system is also hinged at the base for self raising and lowering.
The aluminum mast head is covered with an aerodynamically-shaped, fiberglass cap to reduce drag. The mast head incorporates the radio antenna, the weather gathering equipment and the halyard sheaves.