Dumbbell

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Description

A single-spar column, with a cantilevered top deck, and (possibly) expanded buoyancy at the bottom of the spar.

Detail

http://farm3.static.flickr.com/2288/2533676529_a4015a7111_t.jpg (from http://flickr.com/photos/27160491@N06/2533676529/)

Requirements Analysis

• Safety
  • Structure may not be able to handle waves hitting top hull, as big shear stresses will be very hard to take. Spar needs to be long enough to ensure that this doesn't happen.
  • Should be safe in specced wave conditions.
  • It is not clear that it will be able to handle tilting well, due to the shear stresses on the central column, especially if the column is made from ferrocement. Steel will be safer but more expensive.
• Comfort
  • Low waterline area, bottom hull acts as a heave plate to EntrainedSeawater
  • Lots of solar area.
• Cost - ??
• Pretty - Moderately pretty.
• Modular
  • If top deck is a polygon, two platforms can be locked together along a side to form one unit. Since the whole side is locked, it should be strong enough to deal with the stresses of different instantaneous wave heights along the two platforms.
  • If the bottom buoyancy is smaller in size than the top deck, spacer bars can be used for the locking. We want to lock both, otherwise we put weird stresses on the central columns.
  • May also want tension lines cross-bracing connections.
  • It is possible that this does not work with a single spar design, due to bending/shearing stresses on the central columns.
  • Can exit by LowerAndSneak
• Cargo - Does not solve problem. Actually makes it worse - even if we get a load, we can't hoist large loads unless they are very close to the central column (ideally, in an elevator inside it), because it unbalances the top hull and puts shear stress on the central column.
• Free Floating - Yes
• Scalable - Can be built at many different sizes.
• Standards
• Mobile - Yes, although slow b/c large wetted area. May be able to shape spar and/or lower hull as teardrops to reduce drag.
• Draft - Requires a solution from LowDraftColumns