We are working on a seastead design.
This is NOT a normal boat hull shape, but it is a bit like a trimaran in that their are 3 floats.


Above the water there will be a big triangle frame, 80 feet front to back and 40 feet wide.
The triangle frame will be a sort of truss structure that also doubles as a 4 foot high railing to keep humans from falling off.
We will call the 3 points on the triangle "front", "left", and "right".
And the edge between left and right we will call "back".

There will be a floor and roof/ceiling (7 foot inside) the full area of the triangle.
The enclosed living space will be 14 feet wide and 45 long on the centerline but one edge close to the back.
There covered area around the living space make an open porch.  
The living area will have lots of windows in the font and back and some along the side.    

There will be 3 floats/legs/wings that will be the buoyancy.
Each leg/wing will 19 feet long and have a NACA foil shape with 10 foot chord and 3 foot width.
This makes for a "small waterline area" similar like a small oil platform but one that can move through the water easier because of the foil shape.
Each of the 3 legs will be attached to the underside of the big triangle near one of the 3 points and going down into the water.
The 3 wings will all be parallel with the blunt or "leading edge of the wing" forward  so it is easy for the seastead to move forward.
Each leg will be 50% under the water (so 0.5 * 19 feet) and the top 50% out of the water.
On front of each leg on the top half that is out of the water will be a built in ladder.

There will be 6 RIM drive thrusters, one on each side of the legs/wings about 3 feet up from the bottom.
These will be aimed so they can push water past the wing and toward the back of the seastead.

On top of the roof there will be solar all over.

Behind the living area will be two supports going over the railing and 2 ropes going down to a dinghy that
is a 14 foot RIB boat with 1 outboard motor that is sideways against the other side of the railing.   
When the seastead is moving the dingy will not feel the wind as the living area will block it.

There are 3 stabilizers that look like a little airplanes, one attached near the back of each main seastead leg.  
The little airplane has a 10 foot wing-span, 1 foot chord, the body 6 feet long, and the elevator has a 2 foot wing-span and 6 inch chord. 
A small actuator makes the elevator angle up or down so it can adjust the angle of 
attack of the main wing of this stabilizer without needing a large actuator.
While the thick part of the leg is 4 feet wide the back where the airplane will attach is very thin.  And to get the airplane's
center of lift to balance on the pivot a notch into the front/center of the wing only has to go about 25% of the chord of the wing.











About my biggest concern with this tensegrity design is the risk of waves making cables go
slack and then suddenly snap tight and break, the "snatch load" issue.  For example, waves on two opposite corners
might suddenly lift up the legs on those corners so the other two legs cables went slack,
then if it suddenly drops back the other two legs could get a sudden load.
I am not certain how much of an issue this is for real waves.
Small waves just won't be able to put enough extra lift on some floats fast
enough to make the cables for another float go slack.  Normally the bigger the
wave the more all of the floats are feeling the same part of the wave, say a   
long-period swell.
Can you tell if there could be Caribbean waves (non-hurricane) that could actually make one of the cables go slack?
Like perhaps it requires a 20 foot breaking wave and we can't get those in the Caribbean
without a hurricane.
Each float has a lot of lifting force pulling on the float cables, so it is not 
easy to make it go slack in normal Caribbean waves.

For now I expect the main cables are duplex stainless steel.
But these do not have much sping to them so having something inline between the cable and
the frame to provide extra spring for each cable could reduce the chances that any cable
goes slack or lets a float provide enough pull to make another cable go slack.
Some inline-spring can also reduce the "load cycling" and "fatigue" of the main cable.
Please discuss these options to provide some "sping" and any others you think might be better:
  1) inline elastomeric mooring compensator
  2) section of nylon rope
  3) metal marine spring

What diameter should the duplex stainless steel cables be?
What specifications for the "spring" if any?

Please try to optimize the design so the seastead can handle waves larger than the Caribbean sees outside of hurricanes.
How high a wave do you think your design could handle?

It seems the dangerous case is if a wave is hitting diagonally.  If we were using a sea anchor
and the biggest waves were just coming from upwind, so the seastead was always pointed into the
waves, then we might be able to handle even larger waves?

There are a number of reasons we want the "spring" at the end of the cable up by the body:
  1) Easier to have cameras or sensors to monitor the stretch and so know how much the load on the cable is
  2) Easier inspection and replacement access
  3) Last longer if not in the sea water

Note that the seastead will heave up and down with large waves, it does not stay totally still as a wave passes, and it
has a very sizable gap between the water and the bottom of the living area so "pounding" on the bottom of the living
area or "Under-deck Slamming" is not a issue I am worried about here.  Just focus on the cable issues for now.

Please discuss if we need to adjust cable tension over time and how we should do this if needed.

Also discuss fatigue/inspection/cleaning/replacement  issues.

For each cable position we will want two attachment points at each end so we can
attach a new cable before we remove the old cable.   Please discuss the issues with moving
tension from the old cable to the new one.