Adventist Youth Honors Answer Book/Arts and Crafts/Model Boats

Model Boats
Arts and Crafts General Conference	Skill Level 2
	Year of Introduction: 1991

Contents

1. Do two of the following

2. Identify and define these words

a. Displacement

Displacement is the volume of water a boat's hull moves out of the way when it floats. The displaced water is the same weight as the boat as long as the boat is floating. If the boat sinks then the amount of water being displaced is equal to the volume of the boat instead of the weight.

c. Propeller pitch

Propeller pitch is the distance a propeller would move in one revolution if it were moving through a soft solid, like a screw through wood. For example, a 21-pitch propeller would move forward 21 inches in one revolution.

d. Thrust and lift

Thrust is the force exerted by a propeller to move a boat through the water. As the boat moves forward, it may experience lift, which is a force that will raise the boat slightly.

e. Mono hull

The body of the boat.

f. Hydro

something similar to a speed boat. (hydroboat)

g. Bow

The front of the boat.

h. Keel

has two distinct meanings related to two different types of boats: one a riverine cargo-capable working boat, and the other a classification for small- to mid-sized recreational sailing yachts.

i. Transom

The wide, usually flat area at the very back of a boat. This is where an outboard motor is typically mounted. This is also where you usually find the name of the boat on larger vessels.

j. Cavitation

Inefficient low-pressure pockets on propellers form bubbles that collapse against the blades resulting in premature wear. Cavitation causes vibration, noise and serious damage to a propeller.

k. Heeling

Heeling is normal, sideways tipping. Heeling is a result of the force of wind on the sails. Some heeling is inherent in sailing; as the force of the wind is transferred into forward motion, any excess is transferred into sideways motion, some of which is slippage and some of which is heeling. A boat that has too much sail set so that it heels over beyond a certain angle will sail less efficiently.

When a boat is heeled, the center of effort changes. The center of effort is the pivot point of the sails and is related to the center of lateral resistance, which is below the waterline. One way to reduce heeling is to move the center of lateral resistance upwards by raising the centerboard or daggerboard. The boat will have less resistance below the waterline and consequently less heel.

l. Planing

is the mode of operation for a waterborne craft in which its weight is predominantly supported by hydrodynamic lift, rather than hydrostatic lift (buoyancy).