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most seasteads are semi-submersibles with poor space usage

Home Forums Archive Structure Designs most seasteads are semi-submersibles with poor space usage

This topic contains 5 replies, has 5 voices, and was last updated by Profile photo of  Anonymous 4 years, 11 months ago.

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  • #1091
    Profile photo of Josh
    Josh
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    a semi-submersible is a boat in which the majority of its mass is under the waterline. this results in a craft with exteremly good stability because most of the ship is under the surface of the water. Spar and muti-spar seastead designs are basically semi-submersibles with a poor use of space. about 90% of the mass is under water as a ballast and 10% is used above the surface for a seastead. with a semi-submersible you have the 90% underwater, but it is in the general shape of a sub, not a spar and is used as living space, resulting in a cheaper more mobile seastead.

    #8268
    Profile photo of Eelco
    Eelco
    Participant

    Agreed, to a certain extent. There is lots of overlap between different concepts; most have semi-sub characteristics.

    There is some fuzzy use of terms in the material written so far. Often, the term spar is used, where semi-sub would be more appropriate.

    Im editing the wiki at the moment, to try and clarify things.

    #8272
    Profile photo of
    Anonymous

    It seems like semi-submersible refers to a method of operation and not a particular shape. Semi-submersible oil platforms have large underwater horizontal pontoons. They also have vertical cylinders. Seadrome, ClubStead and Spar Buoys have only vertical cylinders. All generally have living spaces above the water.

    #8274
    Profile photo of Eelco
    Eelco
    Participant

    Semi-sub mostly refers to shape, although the historical origin of the word probably reflects a mode of operation (towing vs stationary deployment). Indeed, the classic semi-sub has horizontal submerged pontoons.

    If you try and break down the physical principles on which a semi-sub is based, its real-estate above water, air-gap with minimal structure, flotation below the water. This has the effect of staying clear of the waterline, where most wave-action is going on. Thats essentially the same thing as multi-spars are doing though, modulus the horizontal pontoons.

    Clubstead can be regarded as a multi-spar, but given its lack of slenderness, its more of a semi-sub id say. Same thing for seadrome.

    #8845
    Profile photo of thebastidge
    thebastidge
    Participant

    It seems nearly any design that floats, and has basically stable characteristics, will be semi-submerged. However, this description misses the point and could be misleading.

    Submersible seems to imply deliberately changing state between above water and below. If you’re not designing for dual-purpose operation, it would seem that semi-submerged is a better term.

    So for proposed definitions:

    Submerged: Fully underwater, all the time. Probably requires a submersible vessel to reach it.

    Semi-submerged: a design that has significant usable space underwater, all the time. Key point: The focus of the design is the underwater portion of the structure. Personally, I would not count simlpe displacement requirements as semi-submerged- for example in a conventional ship. Otherwise, everything that wasn’t a raft would be semi-submerged. That’s a change from the generally accepted usage that will be confusing to neophytes and possibly experts as well.

    Submersible: a vessel which is able to change state at will from surface operations to completely underwater operations.

    Semi-submersible: a vessel designed to change state from surface operations to mostly underwater, but maintains access/ a portion above the surface.

    #9233
    Profile photo of
    Anonymous

    Look-up “Flip ship” and “SeaOrbiter.” Both designs run counter to your description, although the purpose isn’t to be self-sufficient, they are efficiently designed, with rooms below the water-line, to efficiently provide for the specific missions they perform/will perform(SeaOrbiter is still in the works and design finalizaton stage).

    Later,

    J.L..F.

    If you can’t swim with the big fish, stick to the reef

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