Forum Replies Created
March 27, 2014 at 2:05 pm #23255
According to one report of stationary cement and concrete structures at the marine environment, the thickness of rebar cover wasn’t the problem with rust and subsequent spalling, it was the permeability of the material. It’s the same issue with paint. Apparently the porosity of cement mix is directly related to the portland content and type, and with paint it’s using a two-part epoxy type with zero outgassing (no outgassing = no bubbles and no pores). Since cement is a lot less flexable before the sand grains in it separate, it must be thicker over the rebar than paint, but the correct paint (and application) proves you need only fractions of a mm to protect the steel. For this reason, at least in the usa, coated rebar is required in some locations. To minimise movement in the concrete, rebar is often welded where it crosses over each other, and you cannot do that if it’s coated.
What i mentioned yesterday about the cost of the cement used in making that boat on vimeo, the mix was very rich in portland (and they applied it pretty wet too, extra water = pores and voids), and portland isn’t cheap. The more portland in the mix, the less porous it is, the less cover needed over the rebar (and the vimeo boat used plain rod, not textured rebar!). But again, if the structure is stressed, especially if the rebar cannot be post tensioned, the cracks happen because the rebar will stretch and the cement won’t, and the cracks let in the salt. Adding glass or plastic fiber won’t help (much) because the portland will lose connection to those fibers as easily (or more easily) as to the steel. Sometimes things just simply do not work: after paving a portion of the interstate here with glass mixed in the concrete, they found the glass cut tiny bits from the car tires and made rubber marbles of it, causing accidents, so they had to grind up the road and re-pave it only a month later. A proper incubator for road innovations would have discovered this, and likewise we need one for seasteading.
Another report was about the use of coated steel cables failing in a suspension bridge, the problem was two-fold: 1) the cables overlapping and cutting into the coating between them, and 2) the compression grippers used in post tensioning had teeth that cut thru the coating. Because of the #1 issue, the bridge was re-strung with the proper layup of tendons. For issue #2, the anchor block of steel with the grippers inside was flooded with 2-part as the tendons were tensioned, sealing each gripper and the puncture inside the added epoxy.March 26, 2014 at 9:40 pm #23253
Kool, http://www.kgrawood.com/bb.htm is impressive. One of those first urls you gave looked rather sparse on the ferro part of the boat, not much rebar, and only chicken wire in lots of it. Maybe it was the lighting, but it looked fragile.
Ellmer, i think that one boat had no fiber in it at all, i don’t have sound, but the print on the screen said sand and portland, didn’t say fiber, and the amount of portland it looks like they used, looks pricey. That boat needed better bracing under the seats, get two people to sit there next year after it’s rusted a bit, and the seat will collapse and pull the boat sides in. I’d have cast/plastered hollow cement seats, not those little tubes and a thin wood plank. Plus those tubes wriggling will let water into the chicken wire.
Ocean, for my floaties, i hope to try deeper depths as life goes on. I will balance the floatie’s inside air pressure with the water pressure outside tho, so their depth is no concern. I am thinking of 2.5ft diameter and 5ft tall ferrocement cylinders, and standing upright. I figure they will support ~250lbs per foot they are displacing, use as many as needed. It may be a cheap way to make for a lot of floatation, and if it never cracks where it’s attached, will last forever. Ideally, they’d be horizontal like any other pontoon, but i cannot expect they’ll survive a lot of boat flexing if mounted in saddles like my steel pontoon boat, and i have not really solved that design problem.March 26, 2014 at 6:45 pm #23249
Ocean, is chicken wire adequate to hold that size boat together if they beach it? It’s a nice looking lil boat in that video (steel prop tube!?), but shouldn’t there be heavier mesh, and some diagonal runs of real rebar too? That’s a work boat, it’s not a front porch for a houseboat, i expect much different stress levels there.
Did you see http://www.youtube.com/watch?v=p0Ym1IkLTKM ? I need to get sound on a computer again. :-/
I seem to remember an engineering paper on the ww2 cement boats, they used so much steel you couldn’t see thru it, before they put cement on it. Part of the reason for ocean-going cement boats at the time was to do with rebar being made of cheaper steel, rebar is easier to move around, wasn’t welded (welders were in short supply), and could be bent into the shape of a ship with no pricey tools. Remember, back then they were transitioning from rivetted boats to welding, it wasn’t real common. When ww2 opened, the usa was still using rivitted submarines even.March 26, 2014 at 5:35 pm #23245
The deck, and it floating, and each piece of hull you add in not bouncing independantly like a seasnake.
And i have my reasons for wanting a steel deck, at least on my first attempt at seasteading, and i already have the steel for a 16x30ft deck (and some of it is already welded together) and two 4x16ft all-steel freight barges, and i am not going to landfill the steel and it won’t sell for anything but scrap prices. The barges to haul building materials will look like people expect a boat to look, so less interference, but i want the seastead to be held up by cement floats. I have my design, my reasons, i am working on it, i plan to do it, and you can either keep telling me i am doing it all wrong, or you can be helpful.March 26, 2014 at 5:07 pm #23243
I swear you get so dense sometimes, Ellmer. No one here can afford the first two pics, there’s no marina to launch or tie up anything like that anywhere in 100′s of miles, and i am not going to live on the the little 8x8ft bouncy thing in the 3rd picture. And i keep talking about launching small and growing, and to me the best way i can get a boat/barge built, carried to the ocean, and launched at the average marina with inteferrence is to make it look conventional in size and shape, and be easily growable after i push it to whereever the interferrence cannot see it. Frankly, i think it’s a fantastical that i am considering growing a personal seastead to 16x48ft/5x15m, but there is no way i can put anything that big in at one time, i cannot carry it, and there’s no place to launch it, or to park it. You want me to launch another Statfjord C base honeycomb, and you cannot launch a little submarine, or much of anything else? Hell, it would cost $millions just to build a new concrete plant where you want to build a new Statfjord C base honeycomb. You may as well show pictures of a base on Mars!
And you changed the 2nd picture so it’s not a concrete honeycomb anymore. I’m not editing my reply about it.March 26, 2014 at 12:54 pm #23241
There’s three of the longest floating concrete bridges in the world in the usa, one is being rebuilt now: http://www.wsdot.wa.gov/Projects/SR520Bridge/Gallery.htm . It’s not a one-piece construction.March 26, 2014 at 12:49 pm #23240
Ellmer, by mentioning this link, i am not promoting it or advocating it, only saying it serves as illustration of a concept of a situation where i would be using cement instead of steel in the water:
In that company’s scheme, it’s all welded steel. A good way to attach the cement tubes to the steel platform is needed there, and i guess they have not discovered that way yet. This is also a situation it should be easy to add more beam or length to the steel deck, and “putting floaties like a barril under a deck”. Waiting until you can afford to build a single huge cast concrete honeycomb structure, or getting investors, will mean it never gets built. But someone can build a deck with a tube at each corner, and then grow the seastead as they build more floaties and more deck.
I repeat, i am not planning on doing that plan, but it is a good showing of the reason to attach cement floaties to a deck or platform that someone is already living on.March 26, 2014 at 1:04 am #23237
Ellmer, i am not debating if it is ok to build floaties with cement. Over and over again i ask about how to attach the cement floaties i will make.March 25, 2014 at 7:15 pm #23235
I did find where that photo was likely taken: http://phys.org/news3985.html or http://www.flexibleconcrete.co.nz/?page_id=127
People familiar with it say it’s all about allowing microcracking, and hoping the polymer fibers pull the cracks closed again. The cement does not stretch at all, so the outer radius of a bend is full of microscopic cracks between the fibers and the cement. The greater the thickness of the material bent, the greater the damage to the outer radius. Typical uses are under 2in/6cm thick and placed on top of regular cement to keep it from flexing(!!), this is useless for trying to take advantage of the bendyness for a taller or thicker casting. I remember laughing about this stuff years before U-M (re)invented it, and now i know why there’s no mention of how to make it online. There’s no structural use for it, and latex mixes of cement last longer as coating material. It’s maybe possible to pour it around steel rebar, so the cement seems to stretch as much as steel does, but since it’s microcracking it’s only going to let the ocean salt in to the steel.
Unless you have some contradictory information, Ellmer?March 25, 2014 at 2:39 pm #23234
Ok, i do not see anywhere online how to mix cement to get that amount of bending.March 25, 2014 at 12:50 pm #23230
I have asked several times about how to attach small cement bouyant structures (i call them “floaties”) to another structure. The floatie someone can bring to the water in their pickup truck, or lawnmower trailer, has a much higher chance of being used than a single piece 30ft anything. But even regardless of the vessel’s LOA, it’s going to flex in the water, and cement and concrete are known for being the least flexable material for building with, and having poor tensile strength. So if i wanted to replace a set of cylindrical steel pontoons with cement ones, to prove the cement is a better choice in that application, what is the best way to accomplish the replacement, such that the boat deck flexing (or not flexing) won’t stress the cement pontoons and crack them?
The only way i can see to do this with one long hull is many self-leveling hydraulics like house movers use, to keep an apparent non-flexing interface spread out over the pontoon, but with a much larger range of motion. That will become an maintenance issue very soon.
So has anyone actually done this?March 25, 2014 at 12:38 pm #23229
The Dubai palms are islands, and each residence has lawns around it. The other picture cannot possibly be out in the ocean, i know bays it would not survive in, heck a passing boat can leave a wake that ruins that carpet.
Someone a decade ago did a little pricing and found using conventional technology a mansion on a barge could be built for the same money per acre as ocean front property sells for in an area like Miami. But then ocean front property won’t sink, has no problems getting electricity, natural gas, and mail delivery. And you can bet if someone does park a floating acre with a mansion on it to block the land view of the ocean, there’s going to be lawsuits. Ergo, the floating mansion cannot be in sight of existing mansions, you better prove it cannot sink (or incur any more other damages) under any conditions, and the owners cannot give up anything to live in it vs living in a mansion on land. So there’s no floating mansion in Miami, despite the huge shallow bay there, and the Florida Keys right around the corner, and the Cay Sal islands to the south just 60miles offshore.
So far, all you have done is show pretty computer images and islands. You cannot convince me to invest imaginary money, what is your sales pitch to make anyone invest real money?March 25, 2014 at 11:29 am #23227
I cannot help but think this must grow the same way that Venice did: it needs the same basics of human habitation (drinking water, sewerage, food, and energy supply) that Venice started with, on-site (not all of it imported), plus it must float in a storm and not make people sick. I suspect the only reason TSI and BlueSeed are looking at cruise ships is because that’s the only half-way working model so far, and still neither one has actually done anything. The cruise ship model, as it’s done, is “run from storms, burn tons of fuel per hour, import all foods, dump sewage overboard at night while cruising, export nothing”, so it’s a poor example of a seastead. It’s a fine example of a boat being a hole in the water that you keep pouring money into. Sure the cruise industry makes money, but only by a never-ending supply of saps paying boatloads of money to be on it.
I say a city like Venice started because it became self-sufficient first, and then it reached out in ways to make money off it’s situation. I do not believe a group of rich folks decided to move into the swamp instead of going to other lands, they first had to see the poor fishers were living just fine there. Well, we still do not have that model of startup to show a startup Venice, except the Tanka and others. But they are baystead, and that offers nothing to rich people trying to get away from interference, it offers nothing to me either, unless there was an incubator there for testing ideas, and floating them out to live on, and test, and see what the real-world cost of things is. Seriously, can you tell me what the best design is for a cylinder cement pontoon and how to attach it to a deck? Someone needs to find out this information so people can decide to use them or not!
Really, the Tanka provide most of their own food, what of the raftsteads or yachts you look down on do that? The Tanka do not burn gallons of gasoline or diesel every day, and they don’t haul their houses out for scrubbing and bottom paint every year. And being baysteads, none has survived a major storm at sea. Even Ocean says every vessel must run for shelter for a hurricane, and for all but maybe 100 surface vessels in all the world, i agree with him 100 percent.
I say that until the rich see the poor farmer can live on the frontier and be comfortable, there will be no investors. And generally what happens when the rich move to someplace, the poor cannot afford to be there anymore. And then the rich make rules to be darned sure they don’t see those poor people from their mansion balconies. What we need is an incubator where someone says “i know all the stuff that has not worked, i want to fund what’s not been done, at least on a trial scale”. Chances are they will learn something useful about seasteading, and by the contracts they sign they get some rights to the designs, and then they will have something to invest in. And i am talking a couple of years to prove someones can live out on the water before an investor risks building a second one.
Only then will you get beyond the Tanka model of widely spread out and low return private businesses on the ocean.
And at the same time, few people with money will drop $millions on a place to live and not have their own private deck space, and lots of it. They don’t want to be locked into a space where Justin Bieber will blast music and race a speedboat in circles and be the disagreeable teenager that he is. This alone pretty much voids the floating apartment building concepts. The investors will be on their own raftsteads about a mile from each other, once someone finds a raftstead that will not go to the bottom.March 25, 2014 at 7:57 am #23223
Ellmer, are you saying that there is no number of individual “family rafts”, which anchor to the same seamount (or around the same island, or in the same atoll, or etc), and have a cooperative framework, share common concerns, is not seasteading? And are you saying that such a group, which could grow into an important offshore farm of fish, seaweeds, clams, etc, is beneath all investors and should not be discussed on this forum?March 24, 2014 at 5:49 pm #23220
Oh, i misunderstood when you said “The trick is to design something a thousand people could live on”.