# Mast Moment of Inertia

Discussion in 'Boat Design' started by JCD, Sep 30, 2007.

1. Joined: Jul 2006
Posts: 359
Likes: 3, Points: 0, Legacy Rep: 36
Location: Coney

Hello all,

I have a "help me decide" question.

I solved for my required section modulus for the mast as denoted below.

RM = 91000 ft #’s
91,000 x 12 = 1,092,000 in #’s
Aluminum: yield stress 60,000psi, ultimate stress 68,000
1,092,000 / (60,000 / 3) = 54.6 in^3 = Required section modulus

That is to be the minimum for the traverse direction...correct?
In your opinion, which extrusion shape would best fit that modulus for a cruiserperformance catamaran of approximately 450^2 feet of sail with light displacement SDR's of 22 and heavy SDR's of 18? Why and how did you solve for that solution?

Thanks
J

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