Technical » Database Maintenance

Release Date: 4/21/2006

Database Maintenance

 

To develop the database for the Multihull Dynamics Inc. website, boat specifications were collected over more than a decade from boating books, magazines, websites and communications directly with designers, builders and brokers of Multihulls.

 

Since the data offered by various websites and publications is not always consistent, particularly with regard to displacement, centerline beam and sail area, we established standards to make the comparisons apples to apples. We have attempted to obtain the design displacement, the weight of boat and payload that bring the boat to its design waterline. Often the figures presented are either empty boat or fully loaded boat (the max load a charter party may choose to put on board.)

 

Boat manufacturers offer and owners have a bewildering array of sail choices, especially in jibs and spinnakers and their derivatives. We have chosen to use the main sail plus working jib only in our formula calculations, or in the absence of that figure, an estimate of 100% fore-triangle for the standard sail area.

 

Few spec sheets include the centerline beam for catamarans and trimarans. If we are unable to obtain the figures from designers or manufacturers, we either scale them from available drawings or approximate them using formulas shown on the website.

 

Several other factors, however, make this a very frustrating endeavor. From one magazine to another, one website to another, one year to another the numbers change! A designer may make custom changes to a standard design for a particular customer and not rename the boat. He may even stretch the boat hulls two feet and still call it a Magic 40. Or the buyer may specify a larger or smaller sail area to adapt it to particular sailing conditions.   However, it is still called a Magic 40.

 

We have chosen to deal with this in two ways:

 

1. We will use the data we have unless we get new information that is highly credible, for example from the designer.

 

2. Most important, we have provided a way for the site users to evaluate the effects of specifications that are different from what we have listed on the website. By using the CUSTOM MULTIHULL EVALUATION feature on the site. For a modest fee, a user can see what another 50 gallons of water or fuel and 500 pounds of gear will do to performance. Or he can see what adding a 150 Genoa will do for performance and stability. Or stretching the hulls two feet. Or whatever. We feel this is a powerful capability.

Calvin H. Markwood
Engineering Analyst
Multihull Dynamics, Inc.

Contact Cal: multihull.analysis@comcast.net