December 8, 2008 at 11:39 am #768
I tried out on a small scale a format which can switch between a mobile or stable-spar configurations. Broadly the idea is based on the flip ship : http://www.sio.ucsd.edu/voyager/flip/ except that the living quarters remain horizontal throughout.
The basic idea is that a barge (which is also the living quarters) pulls one or more spars behind it, and on reaching the right location, the spar(s) are flooded to become vertical, lifting the barge above the water, all the while keeping the barge horizontal. The parts of the spar that remain unflooded can be used throughout the voyage for storage or even living purposes. Here are some photos :
The spars are constructed by attaching tubes to form 4 sections. The first section from left is to be flooded to attain the vertical format, the second from left is ballasted with wet sand, the other two are to provide buoyancy.
I suspended the barge from the spars. Alternatively the barge can also placed atop the spars for added height above water.
Three or more spars could be connected in a large triangle to make a more stable arrangement, something like vince’s water walker, except using spar buoys.
Water is pumped out of the flooded section to reverse the process.December 8, 2008 at 3:37 pm #4432
Simple and quite doable with existing materials and technologies. I like it.December 8, 2008 at 7:27 pm #4435
That is a clever idea. It can easily be expanded to 4 spars by using an “H” geometry where the bar in the middle of the H is the barge and the rest of the “H” is the 4 spars.
This allows the barge and spars to be built inexpensively on land and easily attached while still in a safe harbor.
Great idea!December 9, 2008 at 4:49 am #4439
How difficult/expensive is it to construct ferrocement spars suitable for the above configuration? Are other materials like those huge steel/cement sewage pipes adaptable for this purpose? Instead of circular cross-section spars, is it a good idea to make the spars of a boat-like cross-section, for better mobility?
The attachment of the barge to the spar(s) needs to be designed to isolate or buffer the barge from movements of the spars. Any suggestions? A small community of such structures could move independently to a given location, and then be tied together to form a small, stable network of barges, connected by walkways maybe?
Is it feasible to attach heavy components like propellors and engines to the lower sections of the spars to become part of the ballast? This way the need for dead-weight ballast is reduced, and we can avoid placing excess weight at the top of the structure.December 9, 2008 at 6:44 am #4440
I think that the H shaped configuration will be more stable. I tried a one spar design before doing the two spar design in the photos, and in both cases I noticed that when upright, it was susceptible to torque from top-heaviness of the barge. It seems to me that 4 legged seasteads can better resist keeling over from excess top-weight or even wind pressure.December 9, 2008 at 10:57 am #4441
The joints between pillars and barge will become a complicated and thus expensive issue at higher scales… Maybe a simpler way is to make the pillars a bit wider, and have them support the barge directly from below instead of attaching to the sides ? At one point someone suggested that a simple spar stead could glide down its spar and float on its security base in order to reduce the draft, this could be an alternative method.December 9, 2008 at 4:17 pm #4448
Joints can probably be made completely flexible. It should stay upright anyway. Or the spars can be rigidly fixed to one another, together acting like a big hinge hanging from the platform.
It´s a great idea either way. Excellent prototype work, livefreeortry!December 10, 2008 at 1:14 am #4454
At higher scales the joint will have to be more elaborate..but I don’t think it’ll be out of reach or unbearably costly..maybe someone with engineering exerience can shed light on this issue? Maybe a flexible joint as Carl is suggesting?December 10, 2008 at 8:39 am #4458
Suspension on cables ? But then corrosion and fatigue are issues.December 10, 2008 at 10:49 am #4460
One negative aspect of a design that needs to reconfigure could be the impact this has on the day to day operations on the seastead, whether business or just life in general.
It might not be a showstopper but it probably needs to be considered and engineered around. For instance, how is docking with boats accomplished in both configurations?
Using continous, dynamic positioning also seems at least difficult or awkward. You either will have to have an added propulsion system for this, in the upright config, or you will need to reconfigure frequently.
Again, this might be perfectly doable with clever design and engineering. I´m just mentioning a possible problem area that needs to be addressed.December 10, 2008 at 11:32 am #4461
What I had in mind is we remain at a given location in the upright configuration for say 3-4 months while the weather is favorable, then shift to the mobile shape, move to a better location in a voyage lasting 2-3 weeks, then be upright again. If rough weather hits during the voyage, we can deploy the upright form in a couple of hours.
I’m just speculating, but boats could dock at the base of the spar, and passengers could climb up a ladder, heavy objects could be raised up with a pulley or crane.
Dynamic positioning in the upright mode sounds awkward. Why bother at all? It’s not like the scenery will change we can tether a community seasteads together so they don’t bump into each other..if we’re far enough from shore drifting shouldn’t really matter for a long time.
Both the above issues are likely to arise with any fixed geometry structure too.December 10, 2008 at 11:37 am #4462
With proper monitoring and regular replacement fatigue and corrosion should be manageable.. I guess there’s no 100 year solution, we’ll just have to make sure the design is within acceptable costs..December 10, 2008 at 6:03 pm #4466
Both the above issues are likely to arise with any fixed geometry structure too.
Well, no they won´t because the issues are directly related to the variable geometry. A fixed geometry structure will always have its propulsion system available. Same thing with loading and docking. Any docks or marinas will always be in the right place. Another way to look at it is that a fixed geometry structure will only need one dock while a variable structure will need two. Then there is the period while reconfiguring where none of them will be available.
Again, a variable structure such as this one might still be better over all, all things considered. But we must not ignore any drawbacks it might have. They must be taken into account.
Using a tether to maintain spacing… technically this is not possible as a tether only limits the maximum distance between individuals. I agree we can minimize the risk of collision with a long tether, but this will also increase the distance to neighbors. Seasteads with propulsion available will be able to stay closer to neighbors. Then there is the need/cost for the tether.
I agree some of these issues are not huge. But we must acknowledge them if we are to make honest evaluations of different designs.December 11, 2008 at 12:58 am #4467
I was thinking of rigid tethers/connectors made of wood or steel frames. These could double as walkways.
I guess we’ll just have to build something on a small scale and see first hand what issues arise and how difficult they are.
Agreed about keeping all factors in mind, but overall I think a good variable geometry structure (not necessarily this particular one) beats rigid ones..December 11, 2008 at 2:24 pm #4469
Tensegrity is best at this IMO. Basically, you connect seasteads with cables, then get those cables spaced with a few long rods. It allows the use of compression and tension to keep the seasteads at a distance while avoiding all bending and shear stresses. Then you can add steps between two rods and get a bridge.
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