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 24 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 16 feet each.  What is the total displacement?


There will be a big triangle frame, 50 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.

I am thinking of a modest air pressure inside the floats to make them structurally stronger, maybe 10 psi.
We can also monitor the air pressure so we would get early detection of any leak. 
There will also be say 8 air bags inside each leg.  These will about fill the leg 
before we add the 10 psi but be smaller after that.  If pressure is lost they will expand
back so that water can not fill too much of the leg.  There will be a bolt down hatch
at the top end of the leg with rubber seals that can be removed to inspect or change the air bags,
after pressure is equalized. 

There will be stairs with rails going down the top of each leg.  There will also be a 
couple seats on each leg so people can sit down and fish.
A saefty ring around the leg like a foot above average water level so someone could grab onto
that if they were in the water.


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.


If we use duplex stainless for the floats then duplex stainless for the cables makes sense.
If we use marine aluminum them perhaps jacketed Dyneema for the cables is good.
We want lots of extra strength margin on the cables.  
What do you recommend?
How often should they be inspected, cleaned, replaced?

The legs and triangle frame will sort of have a ball and socket connection with some rubber (like car tire rubber)
in between.  It is only a compression joint, no torque.  The rubber also helps keep electrical isolation.
The rubber probably helps isolate some wave sound as well.

The 3.9 foot diameter is so we can get them all into a 40 foot container. We do
not want to increase the diameter or length of the legs.  

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).  


Note that there will be different strings of solar panels going the length of the body at each angle,
so that all the panels in one string have the same angle to the sun.
Not all will be in the sun at once, but in the morning and evening we may have some solar aimed in
a very good direction.  Please estimate the total watt-hours we might get per day.
If we wanted to be able to store 2 days worth of energy in LiFePO4 batteries, how heavy 
would the batteries be?
If we used a days worth of stored energy evenly over a 24 hour period how many watts would we have?

We will spread the batteries and any tanks or heavy things toward the 3 corners of the triangle since 
putting the weight to the corners increases rotational inertia and so reduces motion from waves.
We will have 3 seperate solar/charge-controller/battery/inverter systems so a problem with one
does not leave seastead without power.  Can have connections between them with breakers to issolate in case of trouble.

Imagine we are in high winds and turn the seastead to point into the wind.  What sort of 
drag would we have for 30, 40, 50 MPH winds and how many watts would it take for our
propellers to hold the seastead stationary?

For a normal day in the Caribbean estimate the average watts power draw of all electrical components.
How much percent extra solar power do we have?

The seastead will be pushing the legs through the water and the water
and waves can push sideways on the leg.  If the two ends of the leg are held, what sort of 
sideways water speed would make pressure enough to buckle the leg?  

Also discuss if you think it is better to use one type of metal for the
legs and a different for the body or keep all the same. 



Imagine we get a company in China to make the body and legs, and probably get other parts from there as well.

Please estimate weight and cost for each of these:
 1) legs
 2) body
 3) tensegrity cables
 4) motors and motor controllers
 5) propellers
 6) solar panels 
 7) solar charge controllers 
 8) batteries
 9) inverters
 10) 2 water makers and water storage
 11) air conditioning (AC) - maybe 4 units for 4 rooms but only using 1 or 2 at a time 
 12) insulation
 13) flooring, cabinets, kitchen stuff, furniture, bathrooms, bedroom
 14) waste tanks
 15) glass and glass doors at ends
 16) refrigerator
 17) biofouling weight gain in first year
 18) safety equipment
 19) dingy
 20) 2 sea anchors 
 21) kite for propulsion.  Can use as backup, fun, or extra speed - perhaps stack 20 kites of 6 foot each 
 22) 8 air bags in each leg so 32 total for extra safety in case of leak in leg
 23) 2 Starlink  - need a backup
 24) trash compactor
 25) anything else to finish it out

We want enough foam insulation under the roof that even if we lost one of the legs the body would still
have part out off the water so the people have a good chance to survive either by staying with the
seastead or moving to a life raft.  Need to be able to exit from either end.

Also totals for weight and cost.  

Try to estimate how much the body would tip in terms of feet higher or lower between front 
and back of body section if a typical Caribbean wave of the following heights were to pass:
  1) 3 feet
  2) 5 feet
  3) 7 feet

If the Seastead was sideways to the wind at what windspeed would it capsize?

The anchors are a bit tricky because of all the cables.   The current plan is to have the
2 anchor chains/ropes suspened below the floats.
The anchor will stay at the bottom of the float when not in use.  This is a bit extra drag but at 1 MPH it won't matter much.
The corrosion on the anchor will be more but I am thinking we probably want duplex on the
anchor and chain too so corrosion should not be too much of an issue.

What length catamaran would have comparable inside square footage to this seastead?
About how many times the cost would that catamaran be compared to this seastead?
Would you agree that this seastead will pitch and roll less in 7 foot waves than a 100 foot catamaran?
If we rented at $1,000 per day how many weeks of rentals would it take to pay for the seastead?

If we are in a storm (not hurricane) in the Caribbean or Mediterranean and we put out the sea anchor tell
me what are the bad cases to worry about.  Like how fast will it drift down wind?  How high could the
waves get?  Would you expect this seastead to be ok in waves that high?  How long could the storm last?   
How far could we drift during the storm?  With current weather forecasting ability is it safe to assume
we would always have enough warning time to either get out of the way or at least we could position the 
seastead to have enough open ocean downwind for drifting before the storm got to the seastead?  
I would love to test on in a storm without anyone on-board.  Maybe even test in a hurricane to see
how bad things could really get before it was destroyed.  

In St Marten the big lagoon will have a lot of yachts during  a hurricane.  Some will come lose
and these will then bang into others destroying them as well.  I suspect that if a fiberglass
boat hits against this seastead the seastead may not get damaged much.  What do you think?

Probably we have a small crane on the back to lift up the dingy or submersible mixers.  So we could replace
a thruster if it breaks.

If the above the water triangle frame is 40 foot on a side and there are 24 foot legs going down at 45 degrees from
each corner how big a triangle is the cable going around the bottom of the 3 legs under water?

How does the estimated cost per square foot of this Seastead compare to beach houses in Nantucket (Massachusetts),
Malibu (California),  Palm Beach (Florida), Bermuda, or Anguilla?

FEEDBACK
Also feel free to give any general feedback on:
  1) viability of current concept as a profitable business product
  2) how concept might be improved
  3) how big a market niche this first product could become
  4) Conventional wisdom among many boaters is that a fast boat that can keep away from storms is the safest way.
     This seastead is not fast.  What limits or problems might this cause in practice?
  5) Are there single points of failure that you think need to be further addressed or is what we have good?

Summary section.
  For a summary at the end please list:
    1) estimated total cost for first unit and cost each if we ordered 20
    2) average solar produced, average solar used not counting propulsion, average power left for propulsion
    4) lbs extra buoyancy for customers and their personal stuff