As the size of the repair increases, especially when a large section of laminate is being replaced, the shrinkage causes the repair to be stressed before the structure sees any working loads. Discarding a reusable skin when replacing core Prepare the new core then bond the original skin back in place A common fiberglass repair is replacing damaged core, often because of water absorption. Applying thick layers of fairing compound can trap air bubbles and cause you to lose the shape of the surface that you have carefully mapped as mentioned earlier. For some reason the link seems to be down at this moment. Polyester resin is not recommended for repairing vinylester or epoxy laminates.
These epoxy instruction manuals allow us to go beyond providing our customers with a strong line of epoxy products by sharing detailed information for obtaining the best results with our marine-grade epoxies. Acetone was often applied to the sanded area and was thought to soften the polyester resin and improve the bond between the existing laminate and the repair resin. To cure reliably, general-purpose polyester resin needs to be applied in at least 15 to 25 mil. He says that polyester has a volumetric shrinkage of about 7% during cure. .
If the repair laminate is too thin from being compacted by a vacuum bag it may not be as stiff as the original laminate; if the repair is thicker than the original, it may be much stiffer which can concentrate stress around the perimeter, possibly resulting in cracks. It has great thin film cure characteristics, cures in cool temperatures and has a long shelf life. This can be difficult enough when using a mold so in the case of vacuum bagging to a laminate the risk of a leak is substantial. Plan on using a variety of sanding tools if you are dealing with a repair that bridges both a flat area and a detailed area such as a chine or gunwale. After a ten-year hiatus for school, Paul is now living in New Orleans, working to fix up a classic fiberglass boat on a budget so he can set off on a cruise of his own. Using the 15oz fabric from that guide as a ballpark I ordered a roll of quite heavy bi-axial fiberglass cloth and a yard of end grain balsa.
Their concern is related to the shrinkage that occurs in polyester resin. Laminates built with the new polyester are more difficult to repair because the resin cross-links more completely during cure. Adhesion failure in the repair laminate is the most common failure mode for fiberglass repairs. To repair these laminates, the technician would grind away damaged laminate and sand a gradual taper around the perimeter before laminating with new fiberglass and polyester resin. Along the way he hopes to acquire some the sailing and maintenance skills he never quite picked up as a kid.
In addition to the tests conducted to support in-house product development, our materials test lab also conducts testing to support our outside builders, designers, and government organizations in the engineering of epoxy composite structures. These mistakes are made by both professionals and amateurs. It has excellent adhesive qualities, wets out fiberglass fabrics and it is tough. Though Paul knows all about life aboard, he's still got a thing or two to learn about sailing. Qualified samples undergo additional tests for hardness, tensile strength, tensile elongation, tensile modulus, flexural strength, flexural modulus, heat deflection temperature, impact resistance and moisture exclusion effectiveness. The idea here is to fill all gaps with thickened epoxy.
Current product data is published in our , in , and on this website. The cracks can also point to a structural defect that must be corrected. I had trouble getting a consistency I liked with the fairing filler. G-10 fiberglass laminate tabs were added to both ends of the tensile specimens, providing a grip area for the test machine. We keep our dealers up to date on best practices for using epoxy, new products as they become available, and of course, safety considerations. In many cases, sanding tools designed for automotive bodywork will not work well because boats often have much larger areas to sand.
Wiping it with solvents increases the risk of introducing contamination either from the rag or a recycled solvent. A key to strong fiberglass work is consistency in structure so it is important to avoid filling large gaps with epoxy. The repairs were typically successful if done by an experienced repairer. Matching the original thickness ensures that the stiffness will be the same as the surrounding area, reducing the chance of a crack around the repair area. Before grinding the scarf onto the surface, take the time to create a nice rounded shape to the repair area. The sandpaper has exposed resin and fiberglass that has only been touched by the sandpaper so there are no contaminates on the surface. The information provided by a comprehensive test program, along with our own building experience, and customer feedback contributes to a data base on epoxies and epoxy composites that have been growing since 1969.
The scarf on the original laminate helps in many ways. Creating stress concentrations by not filleting corners and tapering laminates Taper your laminates Sharp corners can cause a problem in the laminate just like they can in the shape of the repair area. Also, in automotive work the original metal surfaces are much harder than the body filler. Smooth the transitions with thickened epoxy to make a fillet on inside corners. Bonding the original skin back onto the new core can save significant time and money. Our products are formulated to provide maximum physical properties while being easy to use.
All of our instructional boat repair manuals and the entire book, , are available here as free downloads. This requires identifying and removing all damaged material. It adheres to many different substrates including wood, metals, cured polyester laminates, vinylester laminates and epoxy laminates. A few boatbuilders using new polyester formulations are now glass tabbing in their bulkheads with epoxy instead of polyester resin. The thick mat gave me a very rough edge which required lots of sanding with a belt sander.