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.
Cutting Epoxy/Fiberglass with Ring Saw
Cutting and machining of cured composites parts can be challenging. Cured composites can wear cutting blades out very quickly. They are also very dusty when cut without using some sort of cutting fluid.
Many of these problems can be eliminated with the proper equipment. I found a very interesting video of a fiberglass-reinforced epoxy resin block being cut using a water-cooled ring saw. This saw is called the Revolution XT and it uses some neat technology to get a relatively quick and clean cut without making dust. It looks like it would also allow some good freehand movement to cut curves and angles in composites parts.
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.
NASA Composite Crew Module
NASA, the space agency for the U.S. government, has investigated the use of advanced composites for use in future vehicle programs. The Composite Crew Module (CCM) has been designed and built as a travel vehicle for astronauts in future space programs to travel. Drawing parallels to the Apollo program, this module will be launched on a rocket and break away as a module.
This technology and material are undergoing testing and evaluation before it is officially accepted for the Orion program. As a partnership between government agencies and public companies, this technology aims to reduce weight and improve performance of the manned vehicles.
From NASA’s website “Led by the NESC, the project team is a partnership between NASA and industry, including design, manufacturing, and tooling expertise. Partners are civil servants from nine NASA Centers – ARC, DFRC, GRC, GSFC, JSC, JPL, KSC, LaRC, and MSFC; the Air Force Research Laboratories; and contractors from Alcore, Alliant Techsystems, Bally Ribbon Mills, Collier Corporation, Genesis Engineering, Janicki Industries, Lockheed Martin, and Northrop Grumman. The CCM team operates in a virtual environment, electronically connecting participants across the country.”
This full-scale structure has strain gauges attached to monitor loads on the structure. It was announced on January 25 that it has passed a battery of stress tests to prove viability.
The structure appears to be made with carbon fiber materials, maybe with some graphite reinforcement and an epoxy resin system. Mention of aluminum honeycomb can be found in the online reading materials. The main pieces are autoclaved, while bonding of the large sections (upper and lower shells) is accomplished outside of the autoclave.
Composites technology is being developed for future space exploration structures and vehicles, and this is good news for the composites industry!
Moldless Car Body
Building a custom car body with fiberglass can be achieved without using a mold! This will be a truly custom, unique vehicle. It will take lots of planning and hands-on work, but is very possible as shown in these YouTube videos.
There of course are several ways to go about building a basic structure to use for the basic shape. This video gave lots of good ideas and examples of materials that are relatively inexpensive.
The second part of the video shows some of the actual fiberglass work. This video of less than eight minutes does not nearly do justice to the amount of work and effort that went into finishing this project! It was great that the author documented his work and shared with all. This was a major project that is not for the faint of heart.
He does a very good job explaining the process and materials used in this construction. Every project is unique, however. When discussing the thickness of the fiberglass skin, there are many variables that determine the finished strength. The number of layers to use is dependent on the amount of underlying support structures, part geometry, and required load bearing capacity of the structure. Some areas may need to be stronger for impact resistance and structural loads.
The video author discusses only using epoxy resin with Styrofoam as opposed to polyester resin which will react with the Styrofoam. Polyester resin can be used if separated from the Styrofoam with an additional layer. While I have only seen it advertised, there are new spray on primer materials available to cover the Styrofoam and allow polyester resins to be utilized afterward.
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