Building Barges Using Advanced Concrete Methods?


I agree. Just didn’t get into details…

Not necessary so.

Would you live the rest of your life bobbing up and down on a “ball seastead” OR on a “barge like seastead” designed with a bow, etc. that can cut water nicely and overall maintain constantly leveled seakeeping abilities?


As I currently live on a sail boat I have a little experience with this. It has 11,000 lbs of lead weight hanging below it and it is a semi circle width wise and long and slender fore and aft. Generally it is very resistant to sideways motion or heeling, as long as they aren’t breaking 10 to 15’ waves are no big deal. On the other hand going bow first into a 15’ wave can literally launch you into the air if you are at either end.

Swells are the same, I don’t even notice quite large swells if I am sideways to them, going through them is an entirely different matter. The very worst designs are Trawlers, Tugs and barges and the ocean going versions all have rounded bottoms as compared to the shallow water versions. There is a caveat, size matters, wave height a third or less of freeboard is generally not noticeable unless it sets off an oscillation.

One more possibly interesting observation, running the anchor rode to the keel as opposed to the bow provides a wonderful anchorage as long as the boat doesn’t hunt or go sideways to the wind and waves. My boat hunts which means in a blow it goes to port and heels way over putting a lot of strain on the ground tackle and then it tacks to starboard and again heels way over. The cure is to put the engine in reverse and straighten everything out, it even lessens the strain on the anchoring system.

The instinctive response to engage the engine in the forward position to lesson the strain invariably increases the tension on the system because the rudder simply doesn’t work well at slow speeds and the boat will hunt worse. . .

Heaving to out in the ocean is a lot better than being anchored and it generally puts the boat sideways to the wind and waves and is very calm and relaxing, it is what we do when we are tired of fighting the storm, or the wife just wants to make a hot meal, or we just want a good nights sleep.

Bobbing up and down is by far the best way to deal with waves and the heavier the boat the better but only if the weight is in the right location, amidships. Weight at either end magnifies the effects of wave action.

(Richard Sheak) #44

I’ve been on research ships in a three point moor in 70 mile an hour winds and the deck did not move. Waves broke on the sides, but we were able to work replacing an array on the bottom of the ocean. Unless you are moving, a three point moor is needed for any stable seastead.


“Everyone is entitled to his own opinion, but not to his own facts.”

Seasteads CAN be designed without ANY curved surfaces, ALL straight lines and planes and still retain excellent stability and seakeeping parameters.

Bellow waterline hull architecture based on modified bilge keels design.


Your little drawing basically has a trimaran hull, probably the worst possible design for stability at rest, Check out the Neel Trimarans, they are horrible for rocking and plunging. They follow the slope of a wave or swell exactly which means the occupant feels everything, magnified.

I think the problem here is between initial stability and secondary stability. Yes a flat bottom or Trimaran has great initial stability, floating docks are a great example. As soon as the waves become large enough to overcome the initial stability however, the waves affects are leveraged by the height above the water.

A hemisphere hull on the other hand, has zero initial stability and if you were to walk to the outside edge you will go for a swim as the hemisphere tips over. If it is ballasted in the center (bottom) though and the bottom is deep enough then the hemisphere has great initial stability, that is what ballast is for. As long as the wave or swell height doesn’t exceed the freeboard of the hemisphere it has extremely good secondary stability as well.

Thems the facts : ) I know exactly where you are coming from though, initial stability is great, until it gets exceeded. Also size matters, bigger is better and if the mass is big enough in comparison to the waves they will have no effect at all on it, regardless of the shape.


Yes for a large vessel, much bigger than the waves, a three point moor is very good. The problem is that the force acting on the ship is the velocity of the wind and waves squared. That means that while the mooring handled the category one easily, it may not handle a category three at all, and in a category five, let’s just say no sane person would want to be aboard.


The problem I see with a submerged spherical design is the same as that of a submarine, broadside to the waves, with a tendency to roll, but amplified, since there is no major axis, so it can also yaw, while heaving movement is also still a factor.

A sphere may have the least amount of surface area per volume, but it will have the least useful space, as well. Until you’ve been inside a round structure, such as a yurt, or dome home, you really don’t have a great perception of that.


No, it doesn’t. It’s a mono hull. I even mentioned: “Bellow waterline hull architecture based on modified bilge keels design.”

On the contrary. My design has an excellent stability “at rest” AND under power, if necessary.

Scale model was successfully tested in the water.



You misunderstand, the sphere is not submerged only the spherical cap is submerged and it can be the cap of a very large sphere.

A Submarine rolls when it is on the surface because it lacks the proper ballast. When it is submerged it is ballasted and the ‘wave’ action is not circular like it is on the surface, it is side to side if there is any wave action at all.


From an authors post on the subject:

“The extent to which a wave affects the ocean is roughly 1/2 x its wavelength. My sedimentology textbook (Principles of Sedimentology and Stratigraphy, Samuel Boggs, fourth edition) cites Komar et al (1972) which states storms can affect the ocean as deep as 200m. So to answer the question, yes, they can in theory, but only in depths of <200m. Beyond that as the other posters have said, waves do not significantly affect the water.”

Generally speaking, getting below the thermocline, or the penocline (salinity) will reduce mixing and felt turbulence. However, even extreme depths can experience seafloor scouring, in hurricanes, as is documented elsewhere in this forum.


With buoyant sides and ends, I agree your design has excellent static stability and if you match the load it carries to the displacement underwater it has the very nice feature of keeping the top decks level with an unequally distributed load.

You seem to be claiming that when the surface of the water is at lets say a 20˚ slope, under the entire structure, that the tops sides will stay level? That the Port Ama will submerge while the Starboard Ama rises out of the water?

A ballasted spherical caps topside will stay perfectly level in a greater than 30˚ slope.

Do yourself a favor and toss a board into the surf and see if it stays perfectly level and then toss a weighted beach ball into the surf, you will be shocked at how stable the beach ball is.

Or hold my beer, put some sand in a bottle so that it floats upright and toss it in the water and see how level the bottle tops rim stays, except for breaking waves I bet you could put a level on it and it wouldn’t budge.

It is the same principle at work in the beach ball and bottle.


No. I never claimed or said that: “when the surface of the water is at lets say a 20˚ slope, under the entire structure, that the tops sides will stay level”.

What I do claim is that the stability of the design I presented is a matter of size.

At 40’ LOA, YES, she will run up and down on a 25’ swell like a dinghy in 6’ waves. All over the place.

BUT, at 1000’ LOA she will cut 25’ swells like butter, maybe less than 10 degrees heel/roll.

Also, please note that it’s been designed as a scalable modular structure intended to be rafted up with similar modules in order to form a bigger structure.

Now, I totally understand the beer can allegory, The Sea Orbiter would be the perfect example. Excellent design for a perpetual lab at sea, moving with the currents.


Ahh, I didn’t realize each block was going to be huge thousand foot squares, and I would guess 100’ high? I didn’t understand the scale.

Yeah I can’t argue with that, in fact a 25’ swell over 1000’ is asin(25/1000) = 1.4˚ much less than 10˚.

You are looking at building boats the size of 9 city blocks, I really had no idea the scale you were talking about. Why are you dealing with any structure on the bottom at all, these are just huge floating docks.

You do know that smaller structures rafted up together do not equal one large structure right? Each smaller structure will follow the contour of the swells which can be 60˚. That is why boats put fenders between them when rafting up.

Also I am curious, what material are you going to use to build these 1000’ square structures? Concrete cracks without expansion joints, steel has a pretty high coefficient of expansion, fiberglass isn’t stiff enough, the structure has to be quite rigid. Is there anything like this in the world?

(Bob LLewellyn) #55

Railroad trestles…


There are lots of rigid structures 1000’ long like aircraft carriers, his structures are equivalent to 4 aircraft carriers welded together.

I was thinking of a sky scraper actually, made out of a steel framework and concrete floors. Might be kind of cool to have a skyscraper bobbing around in the ocean : )


Please don’t take that 1000’ LOA literally my friend. That will require at least few hundreds of $ millions. It was just an example since the structure is scalable.

In practice, it will depend on the initial budget. It could be anywhere from 40’ LOA to whatever. Also, please keep in mind that I thought of them as “seasteading modules”. They are working best when rafted up to form complex floating island configurations. From a few, to whatever.

Yes, true. I was planning on modified, heavy duty fenders.


Sure, but the stability isn’t scaleable, each 40’ section will exactly follow the contour of the ocean swells and 20˚ to 30˚ is close to the norm. That means for a 25˚ angled swell (max is 60˚) each end of the module will rise and fall 17 feet just like a teeter totter. Rafting makes the oscillation worse.

On the other hand a round ballasted hull will stay level and only rise and fall the height of the swell and very gradually at that without the teeter totter effect. The problem with rafting spherical caps together is the connection between them will have quite a bit of vertical motion. One has to be very careful moving between rafted boats. The smaller the spherical caps the better for mitigating the vertical distances.

This is a tough engineering challenge.


Maybe so. BUT it depends on location:

  1. For a location in protected shallow waters very close to shore where there are no 30’ high and 200 yards long swells, 40’+ LOA rafted up modules will do very good.

  2. For a location in open waters, 40’ LOA rafted modules will be “allover the place”, I agree. That will require building 150’-200’ LOA modules, to start with. That will do, in my opinion.

Now, I don’t really have a problem with “rounded hulls”, other than the fact that building them will take more time and cost more than “straight” ones, mostly in labor.

Assuming the same construction method (steel reinforced concrete) bending rebar, frames, beams, bulkheads, etc. to rounded design specs it’s a precision, time consuming labor. Also, the whole rounded structure will have to be a continuous concrete pour, no way around it.

On the other hand, the “straight” structure could be built completely prefab, at any LOA. Much cheaper.


Maybe you should rethink that assumption too. I used to help (watch actually) David South make concrete domes by inflating a fabric and then they would spray urethane and then concrete with fibers in it.

It occurs to me that making a hull would be even easier. just spread a precut fabric between supports and with pre-bent rebar placed on it just spray in the concrete and done. A curved structure has the additional benefit that it is stiffer than a flat surface.

I am not certain, but I bet the hanging form might be the cheapest way to go and it could most certainly be done on site which is a not an inconsiderable advantage. Also variations of the theme would be as easy as changing the fabric design.

My purpose in this thread and my other post is to bring out the importance of starting with a floating facility capable of building boats and all of this stuff. A big old cargo ship would probably work wonderfully and some of them are pretty cheap.

(.) #61

That is a good purpose, in my opinion.

I would like to add, if I may, that whatever is built will have to be kept somewhere.
The floating facility also has to be kept somewhere. It has to be maintained and serviced.
I think, all that is possible. Planning ahead might be necessary.

So, I am not sure if my input is welcome. I have a belly bottom too, and an opinion.