The design goals are discussed at http://seastead.ai/ai/seastead.goals.html

DESIGN IDEA

We want some ability to move but maybe like
0.5 to 1 MPH.  We really plan to look at which way ocean gyres are and make a route to 
take advantage of all the currents and wind.  We will have very large propellers.
I think the 3,000 watt 2500 mm submersible mixers from China that are used
for sewage mixing produce and produces 2090 newton thrust could work.  
These are sometimes called "banana blade mixers".
I think there are salt water rated versions in the $5,000 to $8,000 price range.
For redundancy, we will have 2 on each back leg (so 4 total).  Also a spare in storage.  
If we have at least one working propeller on port and one working one on starboard we should have reasonable control.

The propellers will be far off to the sides so differential thrusting should work well.
No need for a rudder.


The 3 floats/legs will be the buoyancy.
I am looking at 2 choices for these:
    1)  Duplex Stainless Steel (e.g. 2205) 1/4 inch thick for sides and 1/2 inch for the dished ends
    2)  Marine aluminum 1/2 inch thick for the sides and 1 inch thick for the dished ends.
Please discuss the weight, cost, and life expectancy of these 2 choices.
Each leg will 30 feet long and 2/3rds of the way in the water, so the water displaced is
that of 3 cylinders of 3.9 foot diameter and about 20 feet each.  What is the total displacement?


There will be a big triangle frame, 60 feet on a side.
The 3 legs that go down and out like 45 degrees from the 3 corners of the big triangle.

This is a tensegrity structure, the joints between legs and body are flexible though we don't really expect movement. 
Each of the legs will have two cables going from the bottom of the leg to the other 2 corners on the triangle.
The leg will be heading away from the corner it is at and down into the water at 45 degrees.
The buoyancy force will want to lift the leg up and out but the two cables will hold it down and in.

There will be an extra backup cable making a loop around the bottom of all the legs.  This gives us some redudancy
where if one section of cable someplace breaks we are still ok.  This will be jacketed (covered) Dyneema.

The living area or "body" will be a 3 sided pyramid out of the water on top of the big triangle.  
The center will be 25 feet higher than the base.  There will be 3 floors, about 8 feet
high for the first and second floor, and rest for the top floor.
Please estimate how many square feet of usable living space will have 7 foot high headroom or more.
It will be designed so it is a bunch of parts that can be shipped in a container and bolted 
together.

About 80% of the pyramid will be covered with solar panels.  The other parts can be doors,
windows, and openings for dinghies.


The 3.9 foot diameter legs make for a small waterline area.  Waves will
have less impact so the motion will be gentle on the humans than typical boats of similar cost or size.   

The legs in the water will make a lot of drag (we are clearly optimizing for ride comfort 
and not speed).  


We are thinking of changing the legs the 30 foot column would be replaced with 20 feet of column 
and a ball on the lower end that had the same volume as the 10 feet of the column it was replacing.   
This should give us a bit less water resistance as the seastead moves foward through the water.  It would also reduce 
the draft and probably offer more heave resistance.   Please figure out
the diameter of the ball.  Then see if we had 3000 watts or 4000 watts how fast the first design
(with just the 3 simple 30 foot columns) would move and how fast new option of 20 foot column and
ball on the end would move.  Also try to estimate the cost of either approach with marine 
aluminum and also with duplex stainless steel.   Please give any other analysis of these two
options you think might be helpful.