In 2017, we were required to make our own nosecone. To maintain consistency with the rest of the rocketBecause its high strength to weight ratio, we decided to use a fiberglass/epoxy composite. To manufacture this, we needed a mold to hold the shape of the part while it cured; we decided on a female mold because it would make it easier to remove the part after curing.
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The first attempt at a nosecone mold was to layup fiberglass on top of an existing nose cone. However, the mold tended to flex during the layup and cure because it was so thin.
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For small (~3") nose cones, the fiberglass nose cone mold is sufficient. A tutorial can be found here.
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The CAD model for the mold, with all the details. On the left is the nose cone section, and on the right is the coupler section. | The block of MDF being glued together before machining. | The mold being machined on a CNC router. | The mold after being coated with gelcoat, and sanding.On the right, an accessory tool for nosecone layups | Closeup of an alignment pin and pry slot. |
The second attempt at a nosecone mold was to cut it out of a large block of MDF.
- We glued together 4 sheets of 1" MDF from Boulter Plywood with Titebond II; we intentionally made the bottom sheet slightly wider than the rest to create a ledge for handling and for fixturing to the router.
- We cut the mold on a CNC router. We screwed the bottom ledge to the router table, and then started by drilling several holes for alignment pins. Then, we cut slots to allow the molds halves to be pried apart easily. Then, we did a rough pass of the shape with a 0.5" straight router bit. Finally, we did a finish pass of the shape with a 0.5" round endmill, using the constant scallop feature of MasterCAM.
- We coated the mold in polyester gelcoat, and sanded down that surface until relatively smooth.
- We accidentally cut the coupler section of the mold too large, so we glued on a sheet of thick mylar to make the part smaller. The mylar was just glued on with 3M super 77, and released the part cleanly later on. If possible, we might want to do this on purpose next time.
- We bolted the coupler section onto the nosecone section, and used wooden alignment pins to keep the mold parts correctly positioned.
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