Construction at sea?
October 29, 2008 at 7:26 pm #725
I know seacrete has largely been discredited, and for good reasons I think. But I had an idea I wanted to put out there, along with a few other concerns.
As I understand the seacrete process, the amount of energy used in depositing the minerals increases dramatically as the deposited material thinkens due to increased electrical resistance. But what if you did not try to create entire structures with it? What I am suggesting is that it may be much more efficient if you just use the process to make small aggregate, say the size of gravel. Experiments would have to be done to see if the smaller aggregate would be cost effective to produce at sea. I’m sure it would still be a very energy hungry process, but the advantages of onsite production may yet outway the energy cost. Of coarse, this all assumes that you have the energy….
I know the argument is that gravel and concrete are cheap to transport on the sea, but I’m not buying it. First, delivery of materials will actually need a “port” to unload the delivery. If you are constructing this at sea, how will you off-load your gravel/sand and other materials? Where are you going to store everything? Who are you going to hire to make this delivery – they don’t usually make unscheduled stops at sea like that. I’m not saying you can’t get someone to do it, but I think it will cost you, esp due to the increased logistical costs of not having the equipment that would usually be available at a port. I know seacrete would not solve all of the above issues, but production of aggregate on site would be a huge plus – if it is possible.
My larger concern is that nothing I have read on this site deals with the logistical problems of deliveries at sea or construction at sea. This is going to cost a lot more than anyone is thinking.
Is construction at sea even feasible? Are there any examples of structures like the ‘spar’ being constructed at sea? Will it be done on a floating platform of some kind, or poured under water? Or is the plan to do the construction at a dry-dock?
It all sounds VERY expensive to me…October 29, 2008 at 9:45 pm #4085
One use i can see for seacrete is as a thin coating on another material that caries most of the load.
Say you have a concrete structure covered in a metal wire mesh: the wire mesh is used to create a few mm of seacrete. Unlike concrete, seacrete cannot be corroded by seawater, and mechanical damage, like cracks, which concrete has a habit of developing, would be healed automagically.October 30, 2008 at 9:55 am #4089
I have seen your other posts about this, and I tend to agree that this could be valuable. I think it was you that suggested a graphite mesh covering the structure. That is how I’m thinking you couild ‘grow’ the aggregate, extend small graphite filiment ‘fingers’ into the sea water with the current applied. Very quickly, since resistance would be very low, minerals should grow in the graphite finger. When it gets thick enough, it would be cut off with an auto-cutter and a new graphite finger extended from a spool. The process could be heavily automated with seawater flowed into the aggregate growing pipes/tanks. In this way aggregate could be mass produced. I have a number of ideas for generating the power needed, but I wil save those for another thread. And yes, lots of power will be needed, but I think that will be a requirement for seasteading anyway. The trick is to grow the minerals in small nodules so that the resistance never becomes a factor. This will have to be tested to see if it makes it economically viable.
Does anyone have an opinion on whether the construction would be on land or at sea? The only way I could see doing it at sea is if you purchased a few used barges to store materials, make the forms on and do the actual construct on. Any other ideas? Anyone know how much used barges go for? You would also need some support ships for the staff living quarters and mess halls, etc.
I also think barges could also be converted into ‘floating greenhouses’ by replacing the upper structure with glass/plexiglass. They would be very durable structures since they are made to survive at sea. Probably not very confortable to live on though, but it could serve as temporary housing during construction for the workers. I would recommend keeping them far from storms though
If constructing on land, I certainly think you would have to do it in the developing world where costs for materials, docks and labor is very much reduced. I’m in the Philippines, and I think this would be an excellent choice for doing the construction.
That said, I think construction on land is a long-term deadend. If you are going to build many ‘spars’, I think you must be able to make them yourself and on site. In my mind the focus should be on building the platform on which you will build the spars, with all of the needed logistics, materials and support equipment. By making a ‘spar factory’ at sea you can continue to grow your seastead over time and at a minimized cost. The goal here is not self-sufficiency, but efficiency and cost reduction.
I assume we would have members volunteering to work on the construction. But there are also many skilled laborers that could be hired in the developing world that have the skills for this kind of work, and at rates seasteaders can afford. But if you are to take advantage of these cost-saving labor opportunities, you must have a platform for construction with all of the necessary logistical support on site.November 1, 2008 at 12:09 pm #4125
If it were an artificial island you were after, is there a way of drastically encouraging coral growth (aside from simply providing a solid substrate)? Can coral growth on a mobile concrete spar-type structure be beneficial? Coral would have the advantage of not requiring extra energy to be diverted to the growth, but has the disadvantage of not being uniform in development.November 1, 2008 at 7:17 pm #4129
One way is to launch a “seed” platform and continue building it in the water. For example we could start with the bottom cylindrical section of a spar. Float it like a bucket in the water with a bit of ballast on the bottom. Then you weld (or pour, depending on material) the walls a bit higher, add one floor and dump in some more ballast, then repeat this process until you reach your design height.November 12, 2008 at 10:44 am #4236
Joints between sections to be be weaker than one-piece construction. Significantly so over the length of a spar platform, I should think.November 12, 2008 at 12:59 pm #4242
Some welding expert would have to answer whether it´s realistic to achieve weld joints with equal strength to the sheets you are joining, but in practice I don´t think this is strictly neccessary. If the welds are a bit weaker you just up the thickness of the steel or aluminium until the weakest link is strong enough. Or you add reinforcements in the joints. Some very long ships are built by welding sheet steel together on a regular basis, as far as I know.
Concrete slipforming is more or less a continous process, I think. So that should result in no weak points. This might be a problem if you need to shut down construction due to bad weather though.
Besides, what exactly “is one piece construction”, and is this actually realistic? Can you buy a seamless steel tube with the diameter of several meters? Are there steel mills that have this kind of capacity?February 3, 2009 at 1:08 am #4811
One way is to launch a “seed” platform and continue building it in the water…
At the OP. The floating “port” could be built on land then dragged out to the area you want to offload cargo/equiptment to. But I agree that how can any of this be done with a ship delivering materials if there is no place for the ship to dock?
Could have a floating platform with a crane or something similar. But the idea of the gravel type concrete makes sense.February 3, 2009 at 4:14 pm #4815
There are barges available to do this kind of work from (docking ships and seasteads under construction to, offloading building material on), I´m sure.June 10, 2009 at 5:23 pm #6420
Anyone know about expansion joint placement?
i do in land buildings… but not on ships…
Attempting to Leave Living Footprints
http://tribes.tribe.net/acceJune 10, 2009 at 7:53 pm #6428
that you should mention that. I don’t know either. On the aircraft carrier USS MIDWAY (CVA-41) there were two of them nearly dividing the ship into thirds and were deep down below decks. They were, I presumed, tongue&grove affairs that got bigger the deeper into the ship you went. Once at sea we went through some weather that halted air operations and I had a chance to see them in action: it was weird and not a little scary to see the ship move in that way…
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