Board Design:

The battle of balance

by: Marc Lefebvre

When designing a board there are design features that are in constant battle and must be balanced to make a good design. Balancing these contradictory features are what a board designer faces on a daily basis. It is important to note however that balance does not mean equal. The balance you achieve is based on what kind of design you are going for. For example a wave board has vastly different goals than a slalom race board. A wave boards design goals are looseness, turnability, and durability; a slalom race boards design goals are top end speed, control at high speeds, and upwind ability; a recreational slaloms design goals are early planing, easy turning, and control.

Some of the design parameters you fight with are "vee", "tuck", "outline curve", "wetted surface area", and "rocker", forget volume at the moment.

Vee

Vee causes the water to stick to the board more and when taken to the extreme can make a board hard to plane, but at the right amount will help with control in the top end. A flat bottom board although fast will be hard to control and will bounce a lot.

Tuck

Tuck on the rails controls how easily the board will release water when in a turn. Hard rails will be fast in the straight aways but when it comes time to jibe they will skip and bounce rather than bite. Hard rails also help with upwind ability of a board, hence they track better. Soft rails will not release water as easily as hard rails and thus will stick to the water better in tight jibes.

Outline

Rail outline decides the turning radius of your board. A real curvy outline will turn on a dime and accelerate quickly but not track as well upwind. A straight outline will track upwind like a yacht but won't turn as well or in such a small radius as a board with a curvy outline. Outline also has to do with where you put the wide point of your board. A wide point forward will help stabilize the board in the low end and top end of the boards speed but you loose early planing. If you move the wide point back you start to gain in early planing and jibing but may be hard to control at high speeds. If you notice most boards keep their wide points near the middle because this is usually a good happy medium.

Wetted Surface Area

Wetted surface area determines the speed characteristics of the board. Maximum surface area aids in early planing but at the sacrifice of top end speed. Minimum surface area gives you maximum top end speed. This is why speed boards are hard to get onto a plane but once you do they take off like a rocket. Finding that top end speed and early planing are tough factors to maximize.

Rocker

Rocker works with the outline curve to determine how turny your board may be but the final goal of rocker is to provide speed in rough conditions. Although a flat bottom board would be fast, it would only be fast on flat water. Introduce a few bumps and this board is no longer fast. Add some rocker in the tail and you'll get the speed back. Too much rocker will cause the board to be slow but for wave boards this is what you want. Wave boards use the waves power to propel itself while slalom boards rely on sail power and need less rocker. Nose rocker helps you when you are in steep chop and you don't want to spear any incoming waves. Extreme nose rocker is usually found on waves boards and moderate nose rocker on bump and jump boards but not usually on slalom or course boards. I have always felt that a little more nose scoop on Slalom board would help with their down wind ability and it the least give you more security of not going over the handle bars when you are submarining. Just my opinion of course.

With these often conflicting variables you have decide what the design goals of the board you want are. Once you have that down it is just a matter of finding that right balance. If you can't find what you are looking for you can always make your own. Many board makers today started that in the business because they were unhappy with what was available to them. Apparently many agreed and thats why they are in business. Good luck and may balance be with you.


For more information on board design check out the following web sites:
DAT Designer http://www.windsurfer.com/DATDesigner/
Shape3d   http://www.worldnet.net/~evilmin/

For more information on board building check out the following web sites:
IHD Boards http://www.vtt.fi/tte/staff/immo/Building.html
TopClass Boards http://titan.glo.be/erik.plouvier/

For more information on fin making check out the following web sites:
Dr. John Pilling http://callisto.my.mtu.edu/windsurfing/fin.html


Marc A. Lefebvre (lefebvre@iwavesolutions.com)

Copyright © 1995-2004 by Marc A. Lefebvre. All rights reserved.