We are working on a seastead design. The goal is to design our seastead such that all the parts can pack into a single a High Cube 45 foot container which has: width 7.7 ft height 8.9 ft length 44.6 ft max weight: 62,000 lbs (rated bouyancy at desired waterline is 27,500 lbs and we hope structure is enough under this that humans and their stuff can fit) Above the water there will be a big equilateral triangle frame, 44.0 feet on a side. The triangle frame is also the wall of the living area and will be 7 feet high (floor to ceiling). It will be enclosed and the whole inside the living area. Around the whole outside of the wall, except where the dinghy is in the back, will be a 3 foot wide walkway and railing that is bolted on and has some diagonal supports from below bracing to the wall (so walkway is 1 food higher than bottom of the wall). The walkway will have an aluminum grating that would let a wave pass through but you can walk on. Also two doors on the back side, one two feet in from left and one two feet in from the right side. There are 3 legs/floats/foils/wings/keels that provide the buoyancy, so it is a bit like a trimaran but with a very soft ride. Each leg/wing will 14.5 feet long and have a NACA 0040 foil shape with 8.5 foot chord except that the last 0.5 feet of the thinnest part will be cut short, so with foil does not come to a point at the trailing edge and fits within 8.9 feet hight of container. But the buoyancy is very close to that of an 8.5 foot chord foil. Each of the 3 legs will be attached to the underside of the big triangle near one of the 3 points. The center of the thickest part and going 1.5 feet in all directions from there will be within the area of the triangle, but within that constraint, each leg will be as close to the point of the triangle as possible. The legs will go down so that the lower half is in the water. This makes for a bit of "small waterline area" similar like a small oil platform but one that can move through the water easier because of the foil shape. It is not an extreme SWATH design as a 1 foot change in water level is about 1/7th of the total buoyancy, so still significant change. The 3 legs will all be parallel with the blunt or "leading edge of the wing" side facing forward so it is lower drag when moving forward than a typical cylinder on a semi-submersible platform. Each leg will be 50% under the water (so 0.5 * 14.5 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. The reason for these sizes for the triangle and legs is so they can pack into a container nicely and shipped to a shipyard anywhere for assembly. Imagine the 3 legs end-to-end with thin/trailing-edge of foil up and leading edge down on the right side of the container. So the right 3.4 feet of the container (width of legs) is used by the 3 legs. Then the 3 frame/wall sections will be upright (so 7 feet high) next to each other along the left side of the container. I am not sure the width of the walls but if they were 10 inches wide then 3 widths is 30 inches and some extra is 3 feet on the left side. There should still be lots of room in the center of the container for all the other parts. Connecting the mid points of the walls both at floor and ceiling level will be structural beams that make another triangle 22 feet on a side. Then all the remaining spans will be less than 22 feet. The rest of the floor and ceiling will be small pieces that are bolted in. On top of the roof there will be solar all over. With batteries and electric thrusters as the main propulsion system. There will be 6 RIM drive thrusters of 1.5 foot diameter, one on each side of the 3 legs/wings about 2 feet up from the bottom. These RIM drives will be all be fixed orientation to provide forward thrust. It will use differential thrust to turn. For slow movements in tight areas like harbors it can reverse thrust on one side and forward on the other to turn in place. There will be a conduit/pipe welded to the back of the trailing edge to take electrical wires down to the thrusters. There will not be any "through hulls" in the legs. The legs will also have multiple airtight compartments each for safety. 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 (deflated for shipping) 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. On the lower part of each leg will be several bolt on heave plates. These will help dampen the response to waves. About 25% of the displacement will be for LiPo4 batteries which will be put low in the 3 legs. Each leg will have its own charge controller and inverter so there is triple redundant power on the seastead. Also, the thrusters for a leg will get power from that leg's inverter or batteries. So the 3 pairs of thrusters will have independent failure modes as far as power. 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. Near each corner there will be a pair of helical mooring screws with a motor unit between them. We only plan to do this in the Caribbean where tides are very small and in protected places where the saves are small, so pulling down 3 feet will be sufficient to never go slack. 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. The two computers for the two seastead will both work thrusters to minimize the movement of the walkway, particularly when warned that someone will be on it. I want to analyze the active stabilizers designed for this seastead. What is the additional buoyancy force of an additional foot of water around one of these legs? If a stabilizer could reduce 6 inches from the crest of a wave and 6 inches off the trough then it could make a 4 foot wave feel about like a 3 foot wave, right? The current plan is for each leg to have a stabilizer, so we can look at what one stabilizer does to one leg. Please estimate how many inches this can remove from the crest or trough, and total inches, as well as electrical power lost to drag, at the following speeds: 4 knots 5 knots 6 knots 7 knots 8 knots If we make this out of marine aluminum about how much would you estimate it would cost for the airplane and the small actuator? If this was an optional extra for the seastead how popular do you think it would be with customers? When estimating costs assume a batch of 20 will be made in China. Sometime a series of waves can make something with a resonant frequency near the wave period move much more than one wave but an active stabilizer can really help get rid of this issue. Another interesting case is really large swells, say a 12 foot swell with 12 second period and the seastead is going directly into it (head sea). As we are climbing up the side of the wave, we could have the front stabilizer try to lower the front and the back two stabilizers try to lift some to keep the seastead more level even on this giant wave. What it the wavelength for a 12 second wave in the Caribbean? When the seastead is at the steepest part of this swell, given the length of the seastead, how much higher could the water at one end be than at the other? How much help could this mode of stabilizer operation do in this case to keep the seastead level? And in a beam sea could it do even better? When the airplane stabilizer is moving through the water it can control the angle it is at but when the seastead is at anchor and moving up and down there is may be a problem. The pivot at the "wing center of lift" for the stabilizer is 25% along the chord is in balance when moving. However, when the seastead is stationary and bobbing up and down in the waves the 75% of the wing on one side and 25% on the other will not balance. So the stabilizer will rotate one way when the leg is going down and the other when the leg is going up. So I think we need to have another actuator that can lock it in position when. Please describe a possible design for this locking mechanism and estimate the cost. When the stabilizer is off where the tail will stay straight, or it could be "locked off" where it can not move. When the stabilizer is off or locked off, it will act as a heave plate and still provide some motion damping. When the stabilizer is on the stabilizer wing can be angled which will cause more drag for the seastead. But if the stabilizers are on the 3 legs will not be bobbing up and down deep into the water as much, which could mean some reduction in drag. I am guessing that on net it will take more energy to move at a certain speed with the stabilizers on, but not as much as a simple "drag of stabilizer" calculation might imply. What do you think? Can you estimate how much extra power it would take to move with the stabilizers on at 4, 5, 6, 7, and 8 knots? Show both drag from stabilizer and any savings from the legs moving more level. We will have a separate power system in each leg, so the 3 stabilizers will have 3 independent power supplies. They will each have their own computer and can operate even without central control (they just feel their own motion and try to resist it) so there will be independent failure modes. If something goes wrong with one stabilizer the odds are we still have two others working and that should still do a good job of stopping resonant motion.