Preventing Rotten Balsa Wood Core
Balsa wood is a common construction material used in the manufacturing of fiberglass boats. Used as a core material, balsa wood is placed between two layers of fiberglass to add strength and rigidity to structures that require it, usually the deck, many times the hull, and sometimes the other areas that require strength.
Using this wood in a marine environment where the boats are constantly exposed to water is dangerous because of the ability for the balsa wood to rot. Once water enters the cored areas of boats using balsa wood, it is a complicated repair job. The balsa wood is between two layers of fiberglass, and to remove and replace it requires removing a layer of fiberglass. This usually involves grinding and sawing as seen here:
As you can see, there is a lot of dust created from removing the fiberglass to get to the rotten balsa. The balsa must then be replaced before the removed fiberglass layer is restored. Care must be taken to ensure that this is completed correctly in order to maintain structural integrity of the area that is being repaired.
To prevent balsa rot in the first place, care must be taken when doing activities that have the potential to expose it to water. Adding fittings and features to structures that contain balsa wood require careful craftsmanship to prevent water infiltration.
Installing fixtures and fittings through balsa wood is possible, but careful work upfront will be very valuable in the long run. There are several ways to do this, one of them is here:
This method of making holes through your balsa wood-cored structure will provide a wall of epoxy resin around the hole and keep the balsa wood back away from any water that may pass through the hole. Good marine-grade sealants applied to the hardware will add another layer of protection.
Carbon Fiber Repair Panel
I found a great video demonstrating the repair of a carbon fiber composite panel. The is is a carbon fiber reinforce epoxy structure that needs a localized repair to the core material. This repair uses a vacuum bagging process to help maintain a high-quality laminate.
The video is sped up to quickly demonstrate the overall process required. This process requires a high level of attention to details, as they are very important. Training and experience are necessary for good results.
Chemical adhesion between all of these layers will create a bond that is durable and suitable for restoring strength back to the structure.
Infusion-Test Panel and Fuselage
Ran across an interesting Youtube video demonstrating an epoxy resin infusion process on some test panels and fuselage. It is interesting how everybody has their own terminology and technique for resin infusion. There is definitely more than one way to get the job done.
They use an interesting layup, including lots of the Soric material. I have used this before, and it is a good material to infuse with. Made by a company called Lantor, it is a non-woven polyester material that acts as a core material. It appears that the folks in the video are using the SF grade Soric, which comes in several thicknesses.
An advantage of using Soric as a core is that it flows resin very well for infusion. It is easy to cut and handles well.
Disadvantages also abound. One of them is the possibility of print-thru on the surface of the laminate. Another is the negative effect on the structural properties of the laminate. This non-woven material does not have much crush resistance such as a balsa or foam material. A serious issue that I have found is the higher risk of delamination. Like any core, this material works by separating the two skin layers to create a sort of “I beam” effect. The problem is that this material is not inherently strong within itself. Though it does become saturated with resin during a proper infusion, it is not nearly as strong as glass or carbon fiber reinforcement.
As the video demonstrates, a proper resin infusion can look easy. With proper materials, practice, and knowledge it can be.
Environmentally Friendly Composites
Many experts argue that composites already are very environmentally friendly based upon their long life span and their good strength-to-weight ratio that saves energy. Many composites structures have long made use of end-grain balsa wood as a core material. This is a renewable resource that is favorable to the carbon footprint.
The strikes against fiberglass composites as being environmentally friendly point out that most of the resin systems are derived from oil and natural gas feedstocks. Most of these feedstocks come from the extra byproducts of making diesel and gasoline. Fiberglass reinforcements consume lots of energy in their manufacturing process.
Resin and reinforcement companies have been working to “green” composites materials. BioResins have been successfully made and used in products that see the real world. These resins use soybean and corn feedstocks to replace the oil and natural gas derivatives to make them from a renewable source. Much work has been accomplished with reinforcements to move towards natural materials. Hemp has proven very useful in this application. Recycled thermoplastics have also been applied to composites products as a reinforcement.
Further research and development, along with identifying appropriate real-world applications will allow composites to flourish as a true sustainable material. It has already proven to be a great material for lightweighting vehicles and structures to result in great energy and material savings. The long life and durability of composites keeps it from landfills to minimize environmental impact.
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