| CPC F17C 1/06 (2013.01) [F17C 2201/0104 (2013.01); F17C 2203/067 (2013.01); F17C 2203/0673 (2013.01); F17C 2209/2163 (2013.01)] | 7 Claims |

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1. A mandrel around which fiber-reinforced resin is wound, the mandrel comprising:
a cylinder portion that has a plurality of first flat surfaces; and
a pair of dome portions that are formed at respective ends of the cylinder portion and each have a plurality of second flat surfaces,
wherein the first flat surfaces and the second flat surfaces are discontinuous with each other.
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