Thursday, June 29, 2006
MODEL YACHT BUILDERS GUIDE "G.R.P. LOAD SPREADING"
Flat surfaces or slightly curved surfaces such as the bottom of the Sirius 45 model have only moderate fiberglass strength unless sandwich construction or several layers of glass are used. To avoid this added weight, load spreaders are used to distribute loads over a wide area of the flat surface. A sectional shape called a Tee or Top Hat will greatly strengthen a flat glass panel. This works on the same idea that an I beam works in steel construction. A piece of cardboard, plywood, spruce, or another fiberglass component is used to form a right angle to the flat surface. A piece of glass tape or matt is placed so as to form a right angle with the flat surface being the. top of the letter T. When molded in place with some activated resin the finished Tee section acts as a solid brace equal to the height of the Tee. The cardboard former or plywood may be removed if it was waxed before the resin was applied. For still additional strength, form what is called a Top-Hat that is a double Tee section with a cap between the tees. Cut in half it would look like a top hat. The former used a build the Top Hat can not be removed. Using Tees and Top Hats can strengthen a hull or component without using up significant hull space. You may use bulkheads of poly-urethane foam to make tee sections and leave the foam in for flotation. Do not use Styrofoam or any styrene-based foam; it will dissolve away in resin. Once again, remember that surfaces must be prepared for gluing or bonding to them.
Posted by Dave at Thursday, June 29, 2006