Hunter 28.5 Owner Modifications and Upgrades

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Performance Ratios

posted 09-12-2008 by Warren Milberg

Hunter 28.5 Performance Ratios:

Hull speed in knots: 6.5
Displacement to length ratio: 263
Sail area to displacement ratio: 17.3
Capsize screen: 2.19

*Hull Speed
This form allows you to calculate the theoretical maximum speed of a displacement hull. This is an approximation, and boats may occasionally exceed their theoretical hull speed for brief periods, as when surfing down large waves, or when temporarily planing in unusual conditions. Also, this limitation generally does not apply to multi-hulls, though they are technically displacement vessels.

**Displacement to length ratio
This is a useful rule of thumb for determining the relative heaviness of a given design; in other words, is the boat heavy for its length? A boat of a given length may fall into one of a number of categories, from extreme ultralight racer to armor-plated crab crusher.
Over 380: Very heavy; may be equipped with tank treads.
320 - 380: Heavy.
250 - 320: Medium.
120 - 250: Light.
50 - 120: Ultralight.
Under 50: Extreme ultralight; do not expose to air.

***Sail area to displacement ratio
The sail area/displacement ratio is a measure of power to weight. Though the speediness of a given boat is determined by a host of other factors in addition to this one, its still a useful comparison tool. Other factors being equal, the boat with the higher ratio will be the faster boat overall. Boats with sail area/displacement ratios below 16 will generally be fairly slow. Boats with ratios over 22 will be very fast, and some extreme multihulls will have ratios over 30.

*****Capsize screen
The Capsize Screening Formula was developed by the U.S. Sailing Association as a rough rule of thumb, helpful in comparing the initial resistance to capsize of various boats. Boats with a Capsize Screen factor of 2 or less will have a normal initial resistance to capsize and will in general be safer offshore boats than boats which exceed this value. The lower the value, the better, all other things being equal.