Top: Epoxy fillers are two-part products composed of resin and hardener that must be thoroughly mixed before use. We suggest you use WEST SYSTEM 105 resin and 205 fast or 206 slow hardeners as this system can be used to over coat the wood and laminate the reinforcements. For deep and irregular voids in wood that say has experienced dry rot or termite damage I will first get the area as clean as possible and then prime the area to be filled with a polyester resin such as a laminating resin. I also discussed this at length with one of the chemical technicians of the company which produces the commonly known automotive filler Bondo after receiving their MSDS and tech data sheets.
The back face of a C.397PA laminate will be prone to chemical attack if the surface was not protected with a coat of resin with wax addition or a flowcoat of gelcoat with wax addition. IMPORTANT: to prevent recurring rot, all wood in the surrounding area (even if it is not rotted) needs to be treated with CPES as well. The inhibited resin is then thinned by adding styrene to secure a solution composed of 70% resin/30% styrene. A gelcoat would normally have about 3 times more thixotrope than a typical laminating resin.
When considering where to place the resin / vacuum points, it must remembered that the resin will always flow along the path of least resistance and the whole laminate should be filled prior to resin reaching the vacuum point. Epoxies have been used since the 1940s to manufacture a wide variety of products and, in the last three decades, have become a primary tool for repairing building materials, especially wood and concrete. I discovered what people were saying about using Bondo automotive body filler and so I tried it out. If you’re a beginner resin caster, I cannot stress here enough that you need to start with an epoxy resin.
Isophthalic polyester resin is now becoming the preferred material in industries such as marine where its superior water resistance is desirable. Basically what you do is drill access holes in the top of the stringer 5 to 7 inches apart, allow the wood inside to dry (or blow dry it), treat with CPES injections, and then fill all voids with Layup & Laminating Resin. I’m working on a research project for school, and am trying to create an alternative filler for the polyester resin. The pastes are available mixed with fillers, such as talc, to be used for wood fillers or automotive body fillers.
My experience with the epoxy is that if the wood swells in the summer, the epoxy is pliable enough that it will be forced out leaving a little ridge. The polyester based resins/gelcoats do not offer great bonding strength to the epoxy. Instead of gelcoat or polyester we recommend using an epoxy or urethane based primer and paint to finish your epoxy made part. For bonding use our Layup & Laminating Resin, but wait until the CPES on the treated wood has cured. Then you prime the exposed surface of the sound wood with an epoxy primer, and fill the void with epoxy paste filler.
Also since it is such a large object I am worried about cracking and how stable the resin will be once it fills the handle. No, Rovicore contains a synthetic core to allow the resin to flow through which is used in closed mould applications, the core compresses depending on the mould cavity and comes in either 3mm or 5mm, various grade of glass are available to sandwich this core.