Definitions

# Springboard

[spring-bawrd, -bohrd]

A springboard or diving board is used for diving and is a board that is itself a spring, i.e. a linear flex-spring, of the cantilever type.

Springboards are commonly fixed by a hinge at one end (so they can be flipped up when not in use), and the other end usually hangs over a swimming pool, with a point midway between the hinge and the end resting on an adjustable fulcrum.

## Springboard materials

Because of the need to be light and flexible, springboards are usually made of fiberglass. Most springboards are painted, usually blue, and texture is often added to the surface by mixing crushed glass or sand with the paint to provide additional grip.

## Adjustment of the spring constant

The spring constant of a springboard is usually adjusted by way of a fulcrum that is located approximately mid way along the springboard. Springboards are usually operated in a linear regime where they approximately obey Hooke's law. When loaded with a bather, the combination of the bather's approximately constant mass, and the constant stiffness of the spring(board) result in a resonance frequency that is adjustable by way of the spring constant (set by the fulcrum position). Since the resulting system is in an approximately linear regime, it may be modeled fairly accurately by a second order differential equation. Typically the resonance frequency can be adjusted over a range of a 2:1 or 3:1 ratio.

## Counter-intuitive user-interface

The fulcrum usually travels over a range of approximately 0.75 metre (30 inches), and is set by way of a knob that is approximately 0.35 m (14 inches) in diameter. To stiffen the spring (as if tightening it), the knob is usually turned counter clockwise. This is counter intuitive, since usually things are tightened by turning clockwise. Additionally, if standing on the springboard, it is difficult to push the wheel with the foot, because the top of it needs to turn the other way from the way it moves. This is because the gearlike mechanism (usually a "soft gear" made of rubber) is on the board and not the base, so the wheel pivots against the board when rotated. Thus users often need to bend down and set the wheel, or come down from the board to set the wheel. Thus it would be much better if the gearing were on the base so that the wheel could be pushed with the foot, but tradition (consistency from board to board) dictactes maintaining a "backwards" convention.

• Note - Standing behind or in front of the knob, rather than directly above it, will give you better leverage to move the fulcrum. This is accomplished by holding on to the hand rails and leaning the body a few degrees, then placing your foot as low as possible on the knob. In this way, it is possible to move even the most difficult fulcrum.

## Heights of springboards

Springboards are usually located either 1.0 metre or 3.0 metres above the water surface. It is very seldom that one is mounted at a height other than these two standard heights. In olympic competition, only the springboards of height 3.0 metres are used.

### Historical heights of springboards

Some years ago, springboards, usually made of wood, were located at heights of either 10 feet (approximately 3m), or 20 feet (approx. 6m), above the water.

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