Cost of building a floating construction facility


#42

Sure, but tensile strength starts very low and increases and the fibers elongate as strain is applied. The Cement bond fails when the elongation is .1% where the fiber is exerting very little strength.

The engineering solution is to place the fibers in strain (prestressed) while the concrete cures and bonds to the fibers that significantly increases the tensile strength. The problem is that it is almost impossible to pre stress the fibers except on a straight shot.

Now let’s take Fiberglass and Epoxy for example and lets say the elongation is 5% and 6% respectively. Both will elongate up to the full tensile strength of the Fiberglass before failure. No pre stress required, no cracking or shrinking or deflection issues to worry about.

Let me give an example. let’s stretch a one foot wide quarter inch thick section of each across a 50 foot span in tension. I would have no concern at all walking across the Fiberglass and Epoxy plank, it would sag a little in the middle but It wouldn’t be anywhere close to failure.

I would let you walk across the Concrete and Basalt beam because each step you take will cause the Concrete to crack and by the time you make it to the other side it will be Fibers with bits of Concrete hanging off of it.

If you didn’t prestress the fibers it is likely that the cracks if sudden would exert enough force to break the fibers . . .


#43

Basalt rebar is a fiberglass composite. Basalt is a naturally occurring glass.


(noboxes) #44

Many long concrete bridge beams on
https://duckduckgo.com/?q=bridge+beam&t=ffsb&iax=images&ia=images


#45

Yes, it is a very good material and expensive, a much better choice than fiberglass with concrete.

How are you going to pre stress it in complex shapes?


#46

Yes very thick I beams and the Steel inside is pre stressed to thousands of pounds and they are primarily holding compression loads.

If you changed the fulcrum from the ends to the middle of the beams they would snap like twigs under load.

Did you know that some torpedoes are designed to explode underneath a hull? It breaks the hull open when it falls into the hole. Boat hulls have to be able to handle having their ends repeatedly dropped 20 to 30 feet or slamming into 30 foot walls of water. Not to mention the occasional concrete pier they get slammed into occasionally.


#47

@Talador

Don’t like it, don’t use it. It really IS that simple. Your personal preferences and prejudices aren’t going to justify trying to change the opinions of those of us that have made our own informed decisions… If you will do the research, you will find that those of us that are proponents for Ferrocement, in its’ variations, have well and truly documented it, especially in the face of naysayers.

You’re more than welcome to stick to wood and fiberglass. Your choice.

My main goal is to create a space for folks to come build. I want to build what I want, you want to build what you want. Ragging on another person’s decision is pointless.


(noboxes) #48

You have not done enough studying on this one. If you’d even watched high rez video in slowmo you’d see seawater up the stacks before the hull moves, and then the center of the hull is lifted as it’s separated by air from the water, and the bow and stern are still deep in water (experiencing suction to hold them down), the hull sides rips at the top first, even tho it’s obviously been holed at the keel, and then the ship center falls and often breaks in two. Not always does it break in two, but in all cases it’s had water blown thru it’s bottom at least as high as main deck. Reports of of a modern sub launched torpedo detonating under an old ww2 cruiser say everyone center-ship died instantly, the whole ship was accelerated up like an IED under a humvee, breaking everyone’s ankles/shins, and impacting them against the ceilings. No one evacuated ship, because no one could move. The high pressure water up the center of the ship, before the hull moved, blew bulkheads laterally and shredded people. Like i said, the boiler rooms were gutted and seawater was blown 100ft up out of the smokestacks. And then the hull began to visably move upwards, ripping apart from the top down. It was horrific, complete, and informative.


#49

Apparently not, I didn’t even know that they used that technique in WWII I thought all the torpedoes hit the ships just below the water line.

All the videos I have seen show the ship falling into a bubble and disappearing. And the video from above shows a bubble much larger than the ship.

Did you know that Carriers all have a couple of hunter killer subs under them or near all the time? And that they are the only vessels capable of keeping up with the Carrier at full speed?


(noboxes) #50

Did you know in Fleet Exercises a years ago, China surfaced a diesel sub inside the group, inside shooting range of a usa carrier? If i understand correctly, this happened twice. The speed of nuclear powered vessels is impressive, but the guided cruise missiles of usa diesels in the 1960’s would have put a nuke bomb in any ship in short order. No doubt China has learned from us in many ways. Pakistan recently launched, and Iran has failed, to launch missiles from their subs.
https://readtiger.com/img/wkp/en/Graybackmissle.jpg


#51

I highly doubt that you will build all that for only $200K.


#52

To start with the 40’ shipping containers run around $1k each. So 18 containers is $20K. For the hulls Steel sheet is probably the cheapest and that material is going to run around $20k for both hulls. There is going to be a significant amount of labor in the hulls so lets add an additional $30k. The top structure is mostly I beams and tin sheeting and labor lets say another $30k. The structure is going to be very close to $100k.

Add $20k for a generator for power and another $10k for electrical, $20k for living quarters/office, and that leaves me $50k for any guesstimating errors.

I bet my Chinese friends could do it for $100k and make a profit. . .


#53

My personal preference is to use the best combination of materials and designs I can to build whatever it is I am building.

My expertise is aeronautical so I am probably biased that direction, but I have done a finite element analysis on concrete and its variations, and ceramics, and steel, etc. There is no one solution that is clearly superior, except for maybe steel and it is often a little too heavy.

And yes I do like wood, except it unfortunately likes to rot. Other than that it may be natures best material.


#54

LOL, you’re building in steel. A future rust bucket.

No engine(s)? Water tanks? Fuel tanks? Holding tanks?
Primer, Paint, bottom, topsides, decks, interior? Price to transport from China to anywhere?

Regrdless,…

If that’s the case, but I hardly doubt that ANYTHING floating @ 120’ LOA, new construction AND turn key can be built for $100k ANYWHERE, then just call it a seastead and start operating.

What’s the point of building a “floating construction facility” when you can built a turn key 120’ LOA seastead for $100k?


(.) #55

In my opinion ( humble ):
18 container, $1000 / container coasts $18000.

It is possible to get a container for $800. ( close to $1000 )

18 X 800 = 14400.

It would be an interesting side job to get lost containers back to surface.
Containers fall in water from container ships and sink, or float for a while
and then sink. So some ROV (remote controlled vehicle) and some diving,

Anyways, the numbers: storage and transportation of containers could
add to the purchase price to make it $20K for 18 containers.

There was a place where I needed a shipping container. The purchase price
of the container would had been $800. The shipping would had been $800.

Local government solved my dilemma with new regulations: no containers.


(Larry G) #56

The ferrocement/geopoly/basalt dicussion go go on based on theory for a long time. What we do know is that properly built concrete vessels have lasted a very long time, under exactly the tough conditions you worry about. As JL pointed out, it is a composite material, so it takes on characteristics of the base materials, but also exhibits unique characteristics specific to the composite’s construction technique.

I would not walk onto your theoretical flat .25" fiberglass span any more than the flat cement one. Or for that matter .25" steel. The sag in the middle would probably pull the ends loose before it would break, but either way… But I might very well walk onto one that had a shaped compression span that was that thickness.

As we speak, there’s a (poorly maintained) ferrocement sailboat parked three rows from my Carver 350 in the next moorage upriver. It was built in the 1980s and it doesn’t appear to have any problems staying afloat (which is more than I can say for many zombie sailboats in this area made of more popular materials). The lines are very nice, there is no rust or spalling apparent. It seems that the builder made sure that all armature was well-covered with cement. You have to look hard to know it’s ferro, but the weathering of the paint just looks different than fiberglass. I have thought about buying it as a fixer.

The biggest problems with ferro boats have been noted as:

  1. Builder doesn’t know much about boat design and makes a clumsy boat
  2. Builder doesn’t understand the amount of work involved in building a boat and never finishes (or takes shortcuts).
    -These two points above are not unique to ferro boats.
  3. Builder doesn’t understand the importance of fully covering the steel armature
    (Note a theme for the top 3 problems?)
    -Up until recently, there simply hasn’t been a better armature material than steel rebar and wire mesh. Rebar takes a great deal of effort to shape, it’s moderately expensive, and great care has to be taken that it’s faired properly so as not to near the surface once plastered. Chicken mesh is not a good material for various reasons, but certain types of specialized metal mesh cloth have worked well. All of them require a great deal of hand work to shape and tie together (and some kind of support structure that holds it all up while waiting or and applying the cement). On the plus side, most of this armature work is not super time-critical like plastering is. It can be done slowly as resources permit.
  4. The density/weight benefits of steel outperform ferrocement for anything under about 27’-30’ lengths.
    -Cement simply must be a bit thicker than steel for the same durability against load and impact. Given simple volume/surface area ratios the bigger boats benefit more from ferro than smaller. On the other hand, it is far more durable against chemical attack from the environment.
  5. The amount of labor to form the armature is intense.
  6. Plastering with OPC has to be done expeditiously and all in one go. The armature has to be complete, correct, and it takes a large number of people (unskilled is ok) to fill the armature and a small number of highly-skilled people to finish the plastering all in a short period of time before it starts to cure.
  7. OPC requires significant time to cure and must be managed (moisture/humidity) for some time.
  8. Steel can be welded into any shape and essentially becomes one piece of material (not entirely true)

So what variables can we change to make the calculation come out differently? With geopolymer and basalt:

Points 1 & 2 have nothing to do with materials, and everything to do with knowledge of boat design. So start with a decent design and make sure you have expert help with modifying it if necessary. Hartley’s in NZ has the most experience world-wide with ferrocement construction. They don’t have published guidance on Geopolymer, so keep that in mind and take their advice seriously, but with a grain of salt for the change in materials.

Point 3 is moot: basalt simply doesn’t corrode. You still need to fair the shape for reasons of performance and aesthetics, but the inner armature doesn’t need any minimum covering or distance from the surface to prevent corrosion.
Point 4: Basalt fiber (and even the rebar substitute) is lighter than steel, stronger than steel. You can put thinner armature elements in place for comparable performance. This may or may not translate into smaller boats under that 27-30’ trade-off sweet spot.
Point 5: The amount of work to form a basalt armature should be less. It is more flexible than rebar for larger structural elements. It is easier to shape. It is easier to cut. It can be epoxied together rather than tied. There is experimentation to be done on making sure that any tension elements point that tension in the right direction. In addition, basalt cloth can be used in ways that steel mesh never could. One of the biggest advantages of the basalt over steel as armature materials is that the basalt becomes part of the concrete. It chemically bonds with the cement in a way that steel simply does not. So the resistance to elongation of the cement past it’s ultimate tensile limit is applied at every molecule along the way, not at macro-scale mechanical protrusions. In combination with geopolymer’s long chain molecules (better flexural modulus better endurance under repetitive loading, better impact resistance) the geopoly and basalt have MUCH lower maintenance issues due to essentially zero corrosion vulnerability. If some basalt fiber gets too near, or even breaks the surface after plastering, simply grind it down smooth- you don’t even have to plaster over it.
Point 6: Unlike a cold joint formed when you put more OPC over previously-cured OPC, Geopolymer actually chemically adheres to base layers. So if your plastering is delayed or interrupted, it doesn’t necessarily ruin everything. It may be possible to add some efficiency to plastering with geopolymer and basalt by using power tools
Point 7: Geopolymer can cure very quickly with the right temperature conditions. Moisture levels are not as critical because water is incorporated into the molecule rather than acting as a catalyst that must be out-gassed.
Point 8: You don’t have to cut out enough to make a macro-sized mechanical joint for patching and filling cracks or holes with Geopolymer because it actually chemically bonds with stone or other Geopoly, not just a mechanical joint.

Other points to consider:

  • Even steel has limits on scantling spacing and reinforcement. You can’t just leave an unsupported span or panel.
  • Cement has better vibration-damping than steel
  • Decks and bulkheads are opportunities for post-tensioning
  • Keels typically need ballast. While cement isn’t as dense as steel or lead for this purpose, “pigs” of these materials are often cast in concrete in the bilge for weighting keels. Proper design of a keel/bilge ballast based on cement could add considerable structural strength to the hull by being a monolithic part of it.
  • Managing geopolymer slump and mixture formula is more important than for OPC. Too much water or not enough changes the chemical composition and final strength. Water mixtures can affect final strength of OPC as well, but it is more forgiving.

#57

Sure in 50 or 100 years.

No engines, but all the rest that you mentioned. FOB China, it might cost more to transport it than its purchase price.

A seastead is of no value to me, A floating construction facility is valuable to me. If you want to live in shipping containers be my guest : )


#58

Thanks for the confirmation. Pointing out real numbers and costs can be an eye opener for everyone.


(Larry G) #59

Cost of shipping containers varies greatly over location, time, and condition. Right now, a 40’ container would cost me in Portland Oregon closer to $2500-$3k to purchase individually. I could almost certainly negotiate it down for multiples. I have purchased them for as little as $1500 and as much as $3300 (for a high cube= 9.5’ high by 8’ w)


(noboxes) #60

I once figured a trio of semisub floating drydocks which could be joined together. If any two joined, they could raise the third one for maintenance. Of course when not being used as drydocks, they could be used like any other flat-deck floating surface.

Cue posts about floating resort houses, floating bubble houses, and other non-work non-flat monohull designs as design competition.


#61

At zero percent elongation the basalt’s fibers tension strength is less than concrete. It doesn’t provide any (much) tension until it is under some strain.
This is the problem many of the early fiberglass chopper gun builds had, what saved them was that the resin molecules could elongate enough to put the fiberglass fibers under load and their tensile strength provided the strength at that point.

Here is another way to visualize it, lets say you have a two equal length lines connected to a weight. One of the lines doesn’t stretch and the other line is stretchy like a rubber band but when it stretches a little it becomes very strong. If you put strain gauges on each line and drop the weight the line that doesn’t stretch will take all of the load while the stretchy stronger line doesn’t take any of the load.

That illustrates a complete lack of understanding of what it means to pre stress the fibers and the purpose of prestressing them, it is tension along the length of the fiber that needs to be applied.

At a certain point with your geopolymer and fiber, you will realize it is cheaper and better to go with Epoxy and Fiber. . .

Steel has zero corrosion vulnerability if properly protected with a sacrificial anode like zinc.

How come I am not finding detailed cost and benefit comparisons between Steel, Fiberglass and Geopolymer? Hmm?