We are working on a seastead design.

Above the water there will be a big triangle frame.  The
left and right sides will be 70 feet long and the back part of the triangle will be 35 feet wide.
The point opposite the 35 ft side is the front.
The triangle frame will be a truss structure that is 7 feet high (floor to ceiling).
It will be enclosed and the whole inside the living area.  Lots of glass to see out.

There are 3 legs/floats/foils/wings that provide the buoyancy, so it is a bit like a trimaran but with a very soft ride.
Each leg/wing will 19 feet long and have a NACA 0030 foil shape with 10 foot chord and 3 foot width.
Each of the 3 legs will be attached to the underside of the big triangle near one of the 3 points (but the total top of the
leg will be inside the triangle) and going down so that the lower half is in the water.
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.
The 3 legs will all be parallel with the blunt or "leading edge of the wing" side facing forward so it is low drag 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 the top half of the front of each leg, so the top half that is out of the water, will be a built in ladder.

There will be 6 RIM drive thrusters of 1.5 foot diameter, one on each side of the 3 legs/wings about 3 feet up from the bottom.
These RIM drives will have the flat sides toward the front and back of the seastead.

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

Behind the back near the center will be two supports going out and 2 ropes going down to a dinghy.
The dinghy is a 14 foot RIB boat with an electric Yamaha HARMO outboard.  It is sideways against the center of the backside of the living area.
When the seastead is moving forward the dingy is shielded from the wind by the living area.
Also behind the back on the left and right of the dinghy will be a deck that is 5 feet wide extending beyond the back of the triangle.

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 12 foot wing-span, 1.5 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.
This is really the "servo tab" idea.
While the thick part of the leg is 3 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.

When the seastead is going to be staying in one place for awhile, we can put down 3 helical mooring screws and give the seastead tension legs 
so it becomes nearly stationary when parked.

Two seasteads will be able to connect together with a walkway, one behind the other, so that while underway 
people can move between seasteads, enabling a real community.   





We are working on a design to quickly put in and out helical screws for a prototype 1/2 scale version of the above
seastead.  This is to experiment with the tension leg idea in shallow protected water.

We would like a proceedure that works for the 1/2 scale prototype but also should work for the full scale.

The design goal is a 1000 lbs load on each of 3 screws.

We assume the seastead has 400 lbs thrust.

The current idea is to use single 6 inch helix mooring screws with hex shaft that is 8 feet long
and has a 1 foot diameter capstan wheel that can slide up and down the hex shaft.
What would you recommend so that it slides up and down well?

There will be a float attached to the mooring screw eye to keep that end up, but still
let the other end go to the bottom.  It will be stored sideways on supports outside
the railing.   Before releasing into the water a long rope will be wound around 
the capstan the right number of times (mabye 4) and there will be some spring
loaded thing that keeps the ropes in place before there is tension on them.

When in in the water one person will use the dinghy to make sure it is in the right 
position and vertical.  There will be some extra rope, maybe 80 feet, that goes from
the capstan to the seastead and lots rope, maybe 200+ feet on the other side of the capstan.

The surface of the capstan where the rope is wound around will have a texture to it to make the rope
less able to slip.  The rope will be very long so just the resitance of pulling it along the ocean floor
seems enough to start the "capstan effect".  The seastead captain then drives away, which spins the capstan wheel,
which drives in the screw.  When the mooring eye gets down to the capstan wheel
the capstan wheel can not slide any further along the hex shaft and is forced 
into the sand if it tries to keep turning but that makes it have lots of resistance,
which makes the rope release from the seastead.

The capstan wheel slides down the shaft and rests on or near the seabed while the shaft sinks 
through it, the sideways pull happens at ground level.  
The wheel is heavier than 
water and the seastead will be far enough away that the upward part of its pull vector
is not enough to lift the wheel.  We rather have a longer rope to reduce the angle than a heavier than necessary
wheel.  Estimate the weight of the wheel and how far out the seastead has to be.
Now, on second though, I don't really think this is an issue when screwing in.  The torque on the shaft
will and the shaft going down will tend to pull the capstan down and it will take
the force against the sand to make it slide over the shaft.  I don't really think we
need to depend on the weight of the capstan for any reasonable friction along the shaft for insertion.
What I am really worried about is when we are extracting the screw that the capstan will move
up with the screw instead of staying down by the bottom.  I am not sure how to ensure it stays down.
One idea is to have the seastead go slack many times during extraction so the capstan can 
side down the shaft, then resume pulling.  This would take longer but maybe not too much.

For normal operation we want the capstan wheel to slide over the sand, so some
rolly/sliding thing should be on the bottom that just handles the normal weight
of the wheel and enough force that it will slide over the shaft as the shaft goes down.  
But when it starts to get into the sand this first thing should compress
and a second layer of pegs/feet on the bottom of the wheel come into play.
These will be at an angle so it stops the wheel when trying to spin into the sand 
but offers little resistance when turning to go up.  

Each of the 3 mooring screws will have its own capstan wheel which can't come off.

Given how far away the seastead has to be before we start turning the wheel,
and how many times the wheel needs to turn to screw in about 7 feet, and
how much rope is used per turn, how long a rope is needed?
Note that the same rope and seastead will be used for each of the 3 mooring screws in series.

Please flesh out the idea and check if everything can be made to work.

Assuming we are in typical Caribbean sand, will the mooring screw be strong enough for 1000 lbs load straight up? 

Normal mooring screws just have a coating but the way we plan to use the screws, putting them in
and taking them out many times, a coating could get sanded off.  So we want to have 
marine stainless steel mooring screws.  What do you estimate it would cost for 3 of these,
in marine stainless with capstan wheels, if we ordered just 3 and also if we ordered a 
batch of 30 from someplace in China?  How heavy will each helical screw with capstan wheel be?

There will be a 20 foot floating rope in the eye of the mooring so it is always easy to grab on the surface
of the water.

To remove the screw it seems a swimmer will have to go down and put a rope around the capstan 4 times
and put the spring loaded thing to hold the rope till tension starts.

After a crew has done this many times, in shallow water like 8 feet,
how fast do you think two people (one in dinghy and one in seastead) could 
put in 3 mooring screws or take them out?  

If we later want to scale this mooring screw proceedure up to the full scale scale seastead, with 8000 lbs
of pull rating on the screw.  I am thinking double the helix diamter to 12 inches.
Make the shaft go from 8 feet to 12 feet.  The capstan diameter from 12 inches to 24 inches.
The seastead thrust from 400 lbs to 2000 lbs.  Rope length probably around double.  
Do these numbers work?  What is your estimate for the weight of the screw mooring and capstain total?
I am thinking maybe triple the lbs.  Will probably store the device laying sideways just outside
the railing on a couple supports.  Can have a pulley system to lift it into place.
Does it seem like it will still
generally be a workable method for the full scale seastead?   We can probably develop device that will
be easier to use but they will cost more, so something like this will probably be the base offering
and another system an optional extra.  Customers that don't use tension leg anchoring, or don't move often,
will be ok with base system and someone who moves every day might be willing to pay for a more 
automated method.