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Fibreglassing
By SARocketMan
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Fibreglassing should only be attempted by skilled rocket builders. Some prior knowledge of fibreglassing techniques is recommended. Warning: When sanding fibreglass wear a dust mask or better. Frequently Asked Questions When do I need to start fibreglassing my rockets? To begin, a rocket will not exceed 3,000 feet will never break the speed of sound - there are no exceptions to this rule - so unless the rocket is getting to the point of exceeding the speed of sound or flying over 5,000 feet, fibreglassing would be very unnecessary. Other things to consider… 1. Is it a minimum diameter rocket? If it is, you will need to fibreglass a rocket of this style before a rocket with a motor mount. This is because minimum diameter rocket fins are only attached at one point on the bodytube, so these rockets need more strength. This is unlike other types of rocket that are glued at the motor mount, inside wall and outside wall. 2. Does your rocket break off fins like clock work? This could be because of hard surface landings or just the sheer pressure
of flight. 3. How do I know what parts of my rocket need fibreglassing? Well where do you think you will need the strength? The first place that will need fibreglassing is the fin section because this takes most of the force during flight and landing. After the fins if necessary the bodytubes. 4. If it's a kit does it need fibreglassing? If it's a kit, it will say if it doesn't need fibreglassing. As for scratch built rockets, if you are skilled enough to be build a scratch rocket then you will know if it needs fibreglassing. The Fibreglassing Process If you are to fibreglass the bodytube, do this before progressing further in the building process but leave the fin section clean and clear of any fibreglass or epoxy. (This is because if there is any damage to the tube during fibreglassing, you can begin on a replacement tube without having to replace fins, motor mounts etc.) This section is about fibreglassing fins on your rocket. A bodytube fibreglassing guide will be put up at a later date. To begin attach the fins to the original mounting points on the bodytube. Allow the epoxy fillets to dry completely. Only then can you begin to fibreglass the fins. Use 220 grit sandpaper to sand the surface to take the gloss off the parts that are to be fibreglassed. Now it is time to put on the fibreglass cloth. To cut the cloth to size, place one piece of cloth across the fins and in between the fins on the bodytube. Cut it to a suitable size so it still overhangs on all sides. The top of the fibreglass cloth should stop where the top of the fins meet the body tube (see photo 1). Set the cloth aside for use later.
Working with one fin section at a time, mix up the epoxy and use a paint brush to coat the surface. A longer setting epoxy is the best to use (20 or 30 min or longer). Now take the fibreglass cloth and lay it over the epoxy. Cover the surface on one section of fins with the cloth and allow it to overhang all sides. **Be very careful to not distort the cloth. Press the fibreglass cloth on to the epoxy making sure not to get any air bubbles under the cloth. Now brush on more epoxy on top until the cloth becomes transparent and all areas are wet. Once the epoxy has set firm but not cured cut the over hanging cloth with some old scissors. Don't worry about making it perfect at this point. Wait until it is fully dried then repeat this process on all sides. (See photo 2)
When the epoxy has fully set on all sides, sand it smooth with 150 grit sand paper. Then wipe it clean and re-epoxy. Sand it smooth again, wipe it clean and re-epoxy. Continue this process until the surface is smooth. (It could take as many as 5 re-epoxies to get it completely smooth. Then sand with 320 grit sand paper and make the sides of the fins smooth during this time. It should also merge into the body tube smoothly. Now it is ready for painting. (See photo 3)
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