Simple, stable, modular, spar type interlocking platforms

(Garrett Herschleb) #1

Why not simple, stable platforms that look like semi-submersible drilling rigs? A single platform can be made to be high enough to ride over all waves. The cylindrical buoyancy system can use pumps and valves for automatic buoyancy control.
Then you put anything you want on the platforms, and add to and connect them as you see fit to expand.

With most of the displacement below the wave range, a single platform is already extremely stable, and more so when interlocked in a matrix.

I like Kim’s ideas of station control which could be adapted to this concept.

I drew this out to have 30m platform squares, and 100m buoyancy cylinders. That’s just TLAR (That Looks About Right) engineering, so the scale may have to increase to ride above the 99 percentile rogue wave.

Breakaway Civilization | Seasteading | Ocean Colonization | Advanced Oceanic Cities | Atlantis | Enlightenment | Oceanic Business Alliance | next big thing in business
(Kim Cowdroy) #2

Garrett, I like the simplicity of the spar design. It has been raised a few times though not as straight real estate base I believe.

I think the main concern with the proposal is the connections between the platforms and the extreme forces on them.

I would have some form of flexible connectors between the platforms to reduce this force and then gangplanks between. Still need to provide vertical adjustments and I think pumps for the ballast need to be supplemented with vertical thrusters for dynamic control.

I believe as far as station control, what you are suggesting is that if these were installed near the equator, then the surface current could largely be counteracted by the counter undercurrent, which is possible for this design provided some extra surface walls were installed I think.

However these opposing currents will put the spar column on a slant and as it stands this would put even greater pressure on the platform connections.
The platforms may need to be tilted appropriately and aligned.

Worth further consideration.

(Wilfried Ellmer) #3

The cost per real estate squaremeter analysis probably gives the answer you seek… | cost per squaremeter | understand floating real estate | the need for floating real estate |


the ramform | business proposals | captain nemo | subdue to nobody |

(Garrett Herschleb) #4

Thanks for the feedback Cowboy Kim. Much appreciated. I was thinking of that issue (torsion around a sub-sea horizontal axis induced by cross flows) and wondering if someone would bring it up.

My thinking for a mitigation was kind of going in the opposite direction of flexible connectors. I was thinking of rigid connectors on both the platforms and at the bottoms in order to stop torsional strain where we have the most leverage.

Along those lines, I was also thinking of shear stress between platforms induced by some spars being in wave troughs while others are riding on wave peaks. In order to mitigate that shear stress, I was thinking of tension lines running between the spars from the bottom of one to the top of its neighbor, and vice versa. I was also thinking of doing something to try to align the top and under current forces along a center of drag fulcrum to minimize the torsional stress.

What do you think of that approach vs. flexible connectors? Which do you think might be better?
Flexible connections might be ok as long as stresses don’t exceed the plasticity limit, but the ocean can be so unpredictable sometimes. :stuck_out_tongue: and also that would make walking between platforms more of a challenge. The rigid connections suffer from the same unpredictable forces, but have the advantage of minimizing material stress by being far from the fulcrum of the torsion / moment.

(Garrett Herschleb) #5

Thanks Ellmer. I think you are referring to the increased material needs of this approach due to the larger structure?

Yes, I believe this would require more raw material. I was thinking this might be more than made up for by saving on the size and complexity of a breakwater. As we’ve found in other discussions, break waters are neither simple nor cheap as they may seem, although maybe that’s not true in the case of that pneumatic breakwater. Hard to know.

A break water can not only be expensive, but it also makes mobility go from difficult to impractical. I don’t know how important that is since any sizable Seastead probably wouldn’t outrun a big storm.


There are a number of sparbuoy type platforms already suggested, and the ferrocement version for the offshore wind system as well as various proposed ideas for in-situ construction, using geopolymer might hold effective answers for various aspects of the idea.

Regardless of ‘the cost per square meter’ Nay-Sayers, stability in deep water is already proven with FLIP and so many offshore structures. Even Ocean Explorer Robert Ballard proposed such a structure, in an interview.

Jeff Frusha

(Kim Cowdroy) #7

Garrett, Having the platforms rigidly held together would be a huge benefit if it can be done relatively easily.

Effectively having land at sea, with all the extra possibilities particularly recreational space like playing fields, large swimming pools, open parks etc. And also removing the issue of getting from one platform to another.

Connections at the bottom as you have said would go a large way towards it. I would consider having something similar to the platform square at the bottom so the interconnecting pins are held solidly, and it can also act as a heave plate. You may want something similar halfway along the spar as well for extra strength. All adds to the cost I know.

The diagonal struts between from top to bottom also would make a lot of difference, but though I am no engineer, I would think of the combination like a big box, so I would think of having struts not just between adjoining platforms but right across three or four platforms and at different angles.

Having moveable connections between the platforms, still requires consideration at the limits when that huge wave comes through. Limiting chains and buffers have to be sufficient, so you are right, this does not get away from the extreme forces altogether.

(Kim Cowdroy) #8

Another possibility is to have upper platforms that are rigidly connected together and a lower section that allows movement between the separate sections and between the upper platform and a lower platform.

Still need to consider extreme events, and have dynamic positioning between the sections so as to keep reasonably central so not too much near the limits normally.

To show what I mean, have put a laminated rubber support with a spring on top to highlight movement between the two platforms on the one section. Full rubber would probably be too squashed. The springs can be made extra heavy duty as required.

This reduces the need for connection at the bottom but similar loose connection is possible. No struts required. May be possible to consider for a very long connection such as for an airport runway.

And closer to show the different movements of the two lower sections both vertically and laterally.


How about converting the multi-axis hydraulic motion simulator, to create the connectors…? Or, just maybe something like they had for the Space shuttles?

(Yes, connectors have been discussed. I did this in MS Paint, using a pic from a former member, both posts from Jul '15)

(Jill ) #10

Why not just use what’s already out there? There are dozens of semisubmersible platforms out there, they’ve been proven safe and stable. Don’t have to worry about ‘attachment’ or keeping them where you want them. You can put them wherever you want, keep them within 5 meter watch circle and move them wherever you want to go if/when you want. They’re selling for pennies on the dollar. A DP semisubmersible would be just what you need. I’ve spent months living aboard, they’re comfortable, plenty of space and could be adapted for permanent livaboard fairly easily.
Biggest issue would probably be fuel. Could possibly figure out how to trade for that and other needs.
I’ll be happy to be one of your DPOs!!

(Garrett Herschleb) #11

Really?!! Wow, that’s interesting to know. I guess you can’t find them for sale on Craigslist though.
Are they traded in private circles, or is there a public market place?

Do they need fuel for station keeping? Or are you referring to fuel for the activity of the inhabitants?

(Garrett Herschleb) #12

Wow, Cowboy Kim. That’s some heavy engineering. A little intimidating to be honest, but it just might have to be.

(Stephan Brun) #13

I’m not that sure that semisubs are necessarily that safe, especially in the long run, if made in steel. We Norwegians remember an accident with one in 1980 known as the Alexander Kielland. A fatigue crack in one of the bracing spars ended up breaking off one of the support legs, toppling the platform.

(Matias Volco) #14

Yes, it might be better to see semi sub platforms as vessels that share the same fate as other steel boats.

Zoon in on Demtaş Gemi Söküm NW Aliaga, Turkey,
Yes folks, that’s the Aegean Sea, not far from Homer’s stomping grounds, some of the most beautiful coastlines in the Mediterranean.
Time to take heavy industry and shipbreaking off the coasts.

(Garrett Herschleb) #15

Yes, the sea doesn’t treat steel very well, does it? I’ll be curious to see how geopolymer holds up against the sea in the long term, given its theoretical longevity.

(Garrett Herschleb) #16

Having looked at the public sales of old platforms, it seems there’s a common theme that the platform is free as long as you can remove it. That doesn’t sound like anything on which I’d want to build a city. There might be private sales that are more lucrative, but it appears steel structures in the sea have a planned obsolescence that doesn’t match the time lines sought by Seasteaders.

(Matias Volco) #17

Theoretically I’m a billionaire in potence! I mention that because at this point all we need to solve is the financial bottleneck

When the Dutch (and English) needed to prevent another Catastrophe like Christmas Day they didn’t second guess concrete.

Concrete Basics

Garret I love your first illustrated post. I can imagine a “dry” sun drenched town like that in a plate. It would be simpler, more stable, but not interlocking. A sea train or a ram form could be interlocking. Both approaches could work together, i.e. a plate shape with a bow.

(Stephan Brun) #18

It might be useful to keep test pontoons mixed to the same specifications as the ones keeping the city afloat somewhere nearby, where people could study them. After all, if the test specimens show signs of deterioration, active pontoons can then be exchanged early, if needed.


My experimentation with a Cheap DIY Geopolymer formula has been on hold, locating, and gaining permission to obtain certain ingredients that can be called ‘hazardous waste’. Not regulated, no permits, but getting authorization to obtain it has been a PITA. By this time October, I expect to have some practical results, from obtaining experimental supplies on the 30th of September, but it is one set of experiments, intermixed with my Anaerobic Digester construction.

Geopolymer is very non-reactive. Chemical-resistant, heat resistant, impact resistant, etc.

As for steel, there are various ways to protect it. One is sacrificial anodes, another is an active electronic process.If protected, then the area of concern shift to the wave-zone and above, since the air has access, and that speeds oxidation.

(GP) #20

Can we make these a lot smaller? What if you did one that was 1/8th as large? What if each large unit was composed of 4 or 16 smaller units? Can they be made to have a secondary submerged super structure?