“Load” Testing
“Speed” Testing
Types of Hulls
Hull - the watertight body of the boat that
separates the load from the waters
Plane
Waterline 
Draft
Flat-bottom
Flat-bottom
Positive Aspects
Negative Aspects
• Stable
• Planes high (shallow draft)
• Can carry heavier loads
(if distributed properly)
• Slow moving
• High Center of Gravity
(can tip easily)
• Must be loaded properly
(equally distributed)
Flat-bottom
“V” Bottom
“V” Bottom
Positive Aspects
Negative Aspects
• Faster
• Planes lower (deeper draft)
• Less stable
• Lower Center of Gravity
(does not tip as easily)
• Must be loaded properly
(equally distributed)
“V” Bottom
Catamaran
Catamaran
Positive Aspects
Negative Aspects
• Faster than Flat bottom,
slower than “V” hull
• Planes higher than “V” hull,
lower than Flat bottom
• Carries more load than “V”
hull, less than Flat bottom
• Less stable than Flat
bottom, more stable than “V”
hull
• Medium Center of Gravity
• Must be loaded properly
(equally distributed)
Catamaran
Tri-Hull
Tri-Hull
Positive Aspects
Negative Aspects
• Stable
• Fast
• Carries more load than
traditional “V” hull designs
(but less than Flat bottom or
Catamaran designs)
• Slower than traditional “V”
hull designs
• Difficult to fabricate
• Medium Center of Gravity
• Must be loaded properly
(equally distributed)
Tri-Hull
Front/Back – Top View
Square Design
“V” Shaped Design
Tapered Design
Curved Design
Front/Back – Side View
Square Design
Tapered Design
“V” Shaped Design
Curved Design
Key Terms
Hydrodynamics - the natural science of fluids (liquids and gases) in
motion. “Hydro” (of or pertaining to water), dynamics (a force that is
constantly changing). A sub-discipline of fluid mechanics that deals
with fluid flow or how fluids react when they come in contact with
other objects.
Displacement - In fluid mechanics, displacement occurs when an object
is immersed in a fluid, pushing it out of the way and taking its place.
An object that sinks displaces an amount of fluid equal to the object's
volume.
Buoyancy - is an upward acting force exerted by a fluid, that opposes
an object's weight. If the object is either less dense than the liquid or
is shaped appropriately (as in a boat), the force can keep the object
afloat.
Key Terms
Draft - is the vertical distance between the
waterline and the bottom of the hull (keel).
The depth of water that a boat hull draws.
The draft can also be used to determine the
weight of the cargo on board by calculating
the total displacement of water and then
using Archimedes' principle.
Key Terms
Center of Gravity - is a geometric property of any object. The center of
gravity is the average location of the weight of an object. The higher
the Center of Gravity the greatest the chance of tipping over, the lower
the Center of Gravity the lower the chance to tipping.