I am new to the site, I have found many good and questionable forums. I finished a 13 foot drift boat in April and was not real happy how it turned out. I have just started my 16 footer and will be glassing soon. There are sooo many fabrics and epoxys out there, i get frustrated. I see there is alot of experienced boat builders on this page, and would like some input on your past builds, and what worked best for you. Thanks again Matt
Matt, perhaps this will help. First of all if you are using the fiberglass to add resistance to damage from hitting rocks and such it must be installed on the inside of the boat. when the fiberglass fibers are in tension or being stretched they are the most resistant to damage. If you are interested in abrasion resistance or to keep fir plywood from checking or unevenly drying out causing mini cracks laminate it to the outside of your boat. Four or six ounce S-glass will suffice for basic check control. For greater abrasion resistance increase the weight of the fabric, maybe 10 to 12 ounce.
I mentioned S-glass, it is the most commonly available glass fabric, the least expensive for use with epoxy. There is also E-glass which is formed by a different process and has greater tensile strength and greater cost.
When you see "Tri-axial" fiberglass fabric you are seeing fabric made with three interwoven bundles of fibers. The first two bundles run at right angles to each other similar to standard fabric and a third fiber bundle is added running at a 45 degree angle to the other bundles. These are often stitched together loosely to keep it in one piece. These fabrics come in 12, 18 and other weights depending on the intended purpose. The heavier the triaxial fabric the stiffer the finished product and the greater the resistance to abrasion.
The heavier the fabric the more epoxy required to saturate it and fill in the weave. Also the greater the finished weight of your boat.
As an example when I chose fiberglass for my boat I laminated 6 ounce S-glass to the inside of the side panels prior to assembly. My boat is made with Meranti plywood I believe so I wasn't worried about controlling checking on the outside of my boat. The inner floor of my boat had 12 ounce triaxail E-glass laminated to it. More epoxy was added with micro balloons to "fair" or smooth out the surface between all the fiber bundles. It was difficult to bend the floor to meet the frame members, I had to use weights, straps and many stainless steel screws. Check out "Snap, Crackle and Pop" to see pictures here on the site.
After the floor was fastened to the frame and chine logs I added 18 ounce triaxial glass to the bottom with epoxy and additional coats of epoxy and graphite powder. I have three coats of epoxy and plan to add two more and then spray it with clear two part polyurethane finish.
Others have chosen other ways, weights and types of fiberglass fabric to achieve their goals. So the bottom line is, what do you want to achieve? Strength, abrasion resistance, reinforcement to maintain shape?
Good luck, hope this helps.
Fiberglass fabric is available in a variety of weaves, starting with the most basic with the bundles of fibers running at right angles to each other and interwoven one over the other, one north/south, one east/west and so on. The larger the "bundles" the greater the weight of the cloth. Weights are measured in weight per square yard. Four ounce cloth would be