Shark 24 keelboats racing upwind

Sailboat – a boat propelled partly or entirely by sails. The generic term covers a variety of boats, larger than small vessels such as sailboards and smaller than sailing ships, but distinctions in the size are not strictly defined.

  • Traditional sailboats are monohulls generally rely on ballast for stability, and usually are displacement hulls. This stabilizing ballast is generally around 30%.
  • Multihulls rely on the geometry and the broad stance of the multiple hulls for their stability, without any form of ballast. Multihulls are designed to be as light-weight as possible, yet maintain structural integrity. They are often built with flotation chambers with sufficient buoyancy to remain afloat.

Keel – the backbone of the hull. On a sailboat the word “keel” is also used to refer to the area that is added to the hull to improve its lateral plane. The lateral plane is what prevents leeway and allows sailing towards the wind. This can be an external piece or a part of the hull.

Many people enjoy racing their sailboats. This requires engineering to design and build specialized boats and equipment.

What’s the problem?
Team Concise’s Forty1Design (video 1:40) – at the start of the 2014 Round Britain and Ireland. The boat is designed to sail very fast.

  • Ask – What are the conditions the boat will sail in? How long is the race? How many people will be onboard? How strong are the winds?
  • Imagine – What are some existing boat designs that go fast in these conditions? What other designs used for boats can be adapted for these conditions?
  • Design, Build – How is the boat constructed? What materials are being used? How are pre-made hardware fittings secured to the boat’s hull?
  • Improve – What testing can be done before the race to determine if changes or improvements can be made? Can changes be made to improve performance as wind and sea conditions change during the race?

That’s engineering

  • directional stability – stability of a moving boat about an axis which is perpendicular to its direction of motion.
  • Stability – the tendency of a boat to return to its original direction in relation to the oncoming water when disturbed (rotated) away from that original direction.

If a boat is directionally stable, a restoring moment is produced that “pushes” the boat (in rotation) so as to return it to the original orientation, thus tending to keep the boat oriented in the original direction.
Engineering ideas

  • floatation, buoyancy, lateral stability, leeway, structural integrity, upwind, downwind, spinnaker, jib, mainsail, Genoa, ballast, displacement hull, planing hull, capsize, momentum, righting moment, torque, axis, perpendicular, motion, rotation

Do It
Challenges for you to work on…

  • Build a sailboat that is powered by the wind.
  • Using toy boats, experiment by making changes with sails, wind and waves.
  • Design your own wind-powered sailing vessel. Using simple, colorful, and recycled materials, design and build a model vessel to achieve the optimal use of wind power. Find a hull and sail configuration that moves across a water track in the fastest time, or carries the largest cargo of treasure. Follow the engineering design cycle. Apply your knowledge and understanding of wind power, buoyancy, displacement, friction, and lift to your sailboat design.