Low Cost Seastead
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August 20, 2008 at 2:18 am #672
I just thought I would share my latest thoughts on low cost seasteads . As usual, the raw material is in the wiki so people can fix obvious problems. General discussion, seems to work better on a dedicated forum thread — hence this post.
It should be no surprise to anybody that I am thinking in terms of a smallish truss-spar design. Read the wiki page for more detail. If anybody who is skilled with 3D modelers wants to try drawing the thing, I would be deeply indebted to you.August 20, 2008 at 10:16 pm #3604
I’m guessing the main purpose of these low cost seasteads would be a more direct commercially operated platform for recreational activities, fishing, diving, boating ect. Rather than a long term seastead solution.
I’m no engineer but the theory looks solid. How many people could each one support? And at what length of endurance.August 20, 2008 at 11:13 pm #3605
The purpose of a low cost seastead is to expand the number of people who want to give it a try.August 20, 2008 at 11:28 pm #3606
I like it. This should make for a lighter structure overall – lighter ballast neccessary, less structure needed underwater – thus making it cheaper. It will probably be more prone to bobbing up and down than a full size (and overall denser) spar, but should be ok with respect to rotational movements. I´m not entirely clear how the wires will function though, and having the ballast function as a air chamber, although clever, and probably useful, could present some problems with complexity and/or rust inspections. I guess you could build a really simple version with the truss made of just welded L-profile steel (like a power pylon) and a stack of square (or whatever shapes are available on the market, this shouldn´t matter all that much) steel plates as the ballast though.
Another benefit of this design is that you get rid of (and don´t have to pay for) all that internal space far below the water surface (in a full length spar) where noone would like to live anyway.
This should also be easier to tow and move, with the hollow truss producing less drag than a spar.August 21, 2008 at 4:15 pm #3607
I like it, too. This will add an entirely new level of people willing to join this movement. A 1500 sq. ft. dwelling that can survive a hurricane is great all by itself. Apart from new governments, I can see something like this being implimented just off shore of major population centers. The benefits of everything. I am really digging this design.August 23, 2008 at 1:21 pm #3608
This seems indeed like the most affordable design imaginable, and it seems like it would work well also.
This design is the one most similar to a ship, so lit lends itself well to comparisons with it. The two things that sets it apart from a ship are extra stabilization and a hull aimed at low cost construction, both at a sacrifice of manoevrability and speed. An excellent tradeoff given the different design requirements compared to a ship.
I could do some solidworks modelling, to give a feel of the dimensions and some possible implementations of this concept, but as i explained eariler, no pretty pictures unfortunately. If you are interested, let me know.August 23, 2008 at 7:11 pm #3609
It is really hard to describe the cable truss…
Please do the following. Take two equilateral triangles. Position one triangle above the other, but rotate it by 60 degrees. Now connect 6 rigid struts between triangle vertices. Now place a few more of equilateral triangles above the ones you have, rotating each equilateral triangle by 60 degrees.
For the cable truss, the equilateral triangles are mounted on the vertical pipe. The rigid trusses above are replaced by 6 stainless steel cables.
I have tried to draw this on a piece of paper and it completely exceeds my ability to draw it.August 23, 2008 at 7:13 pm #3610
This structure will have a deep draft due to the truss and ballast/damper. It may not be possible to bring these all too close to shore.
I can imagine a structure where the truss can be raised an lowered, but the complexity of such a design gives me the creeps.August 23, 2008 at 8:38 pm #3611
I was able to coax some software into drawing a rough picture of the basic idea. The image is attached to the main wiki page.
If people have better drawing skills than me, I will not be upset if they draw a better picture.August 23, 2008 at 8:43 pm #3612
My attitude is that if we can not design something that is better than a boat for our application, then people will simply buy boats instead. (I know that is what I would do!) The goal is to lower cost with improved comfort and safety with respect to boats.)
Another key concept behind this design is that is meant to be mass produced. The concrete forms for the living structure could be used over and over again. A jig could for the truss/ballast/damper could be easily assembled to make truss/ballast/damper construction really easy. I can imagine a factory that grinds these babies out at a rate of 2 or 3 per week.August 23, 2008 at 10:45 pm #3613
I saw your sketchup drawing now. That is some pretty funky design. Why do you feel this is better than a regular “truss-like” truss (i.e. like a power line tower)? I am asking because this seems like the most obvious, simplest and cheapest choice to me.August 23, 2008 at 11:10 pm #3614
It needn´t be that deep. If the cylinder is half submerged and we assume equal density throughout it should stay upright with the lightest of ballasts, and only a small leverage arm. If the roof is 3m above the sea (the top floor in the air and the bottom floor submerged, total 6m/20feet cylinder height ) I´m sure you could get away with like three times that below the sea as leverage. So, 9m(27feet) draft.
edit: Now I´m somewhat unsure whether my buoyancy logic above holds true… about the average density of the cylinder. It must be less than water anyway, for a number of reasons (like not sinking…).
A buoyancy program that lets you design simple shapes and experiment with CG, density etc would be very useful for these excercises…August 24, 2008 at 6:30 am #3615
My cable truss may be too cute. It may be the case that a more normal truss structure is less expensive. Suffice to say, minimizing truss cost is paramount. By minimizing cost, I include both material and labor cost.August 24, 2008 at 6:43 am #3616
Just like a boat, the interior is mostly filled with air. Even though concrete is denser than water, the exterior shell is not heavy compared to the amount of water being displaced.
A spread sheet would really help out here.August 24, 2008 at 11:58 am #3617
Its not really a pivotal feature of the concept. The space between the hull and the ballast needs to be bridged in a rigid fashion. Hard to tell which way is best without narrowing down on the static and dynamic loads this thing is going to have to deal with.
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