Experimental small hexagonal platform


(Larry G) #43

Connection systems:

http://www.floatingstructures.com/gallery/wave-attenuator/imfs-defender/


"Floating Island" design in the news
(Larry G) #44

Some benefits of this type of platform:

Storm resistance due to no sharp corners and round-ish shape
Efficient use of materials in shell- round is the most efficient use of materials for enclosing maximum volume, closer to round is closer to max efficiency
Can use a radial truss system for adding decks: not difficult to engineer, not too expensive to produce, adds to shell strength equilaterally.

The first 3 pictures below are from International Marine Floating Systems, of a bridge caisson, constructed to float into place. The construction methodology would be similar to proposals in this thread, but obviously the finish would be different. The last two pictures are from Deltec Homes, a pre-fab construction company specializing polygonal pre-fabricated “stick-built” homes for hurricane prone areas, illustrating how a radial floor truss works with multi-sided (hexagon+) buildings.




(Oleksii Konashevych) #45

Looks awesome! :+1:
What is inside? is it empty?


(Larry G) #46

Underneath concrete deck would be EPS (expanded polystyrene) for flotation. Inside the shell would be machinery & systems (water, sewage, power generation), work space, and possibly some living space. Above the radial truss deck would be living space.

Two decks provides about 3000 square feet total.


(Oleksii Konashevych) #47

I think I know how to scale the production of this. cheap prices and good quality in Ukraine might be a good option for industrial production.


(Larry G) #48

Notes:

They cast it on top of a barge, so point 1 in favor of these (rough) dimensions is that it can be done without excavating and constructing a lock.

Point 2: Hatches, through-hull connections, and connector points can all be cast into the shell structure. So also can “spud wells” with legs for leveling in shallow-ish water (up to perhaps 50-60 ft / 20 m). Keep the hatches above the waterline and they can even be replaced and repaired in situ.

Point 3: using basalt fiber and basalt rebar in place of steel eliminates a great deal of concern about corrosion and simplifies the sealing of the points where that rebar was supported (see the white patches of epoxy over these support points in the third caisson picture).

Point 4: the radial trusses can be inspected, maintained, modified, & replaced, etc over the life of the structure. They keep the main ballast mass low with a lighter superstructure.

Point 5: Flotation- in my personal concept there would be a concrete skirt projecting below the water line to contain and protect EPS foam for flotation.



(Larry G) #49

I think it depends on where the target location is. I’m thinking S Florida or Cartagena construction is practical to tow to most places in the Caribbean.

I have a colleague with concrete construction contacts in Indonesia as well.


(Larry G) #50

Machinery spaces:


(Chad Elwartowski) split this topic #51

2 posts were split to a new topic: Buying vs Building


(Larry G) #52

An additional level or a side-by-side Hex could provide guest accommodations for dive trips… The same footprint here provides 7 separate sleeping quarters roughly half doubles and half singles (kind of tight but better than some group trips I have personally been on).


#53

Yes, but for dive trips you got to be on top of (or very close by) a diving site. And most of the diving sites ARE NOT in shallow waters. For such operation you better be floating, IMHO.

You could be studded on a shallow reef but getting the permit to touch that bottom might be difficult. For example, in Florida it’s impossible since all the Keys are marine sanctuary. May be easier or permitted in other countries, I don’t know,…

Sometimes spuds are in the way :grin:


(Larry G) #54

Cay Sal has a lot of areas characterized as “scoured hardgrounds” (Khaled bin Sultan Living Oceans Foundation 2011 Coral Reef Assessment Cay Sal Bank, Bahamas April 2011) that support almost nothing in the way of benthic life. Some of these areas are in close proximity to “blue holes” that support a lot of diversity.

[quote=" 2011 Coral Reef Assessment"] “There are many unique habitats, including proliferent coral communities surrounding the rim of blue holes, unusual coral and sponge bommies within the bank, and an extensive high coral cover (>25% cover) shallow (4-8 m depth) lagoonal sites in the southeastern end of the bank.”

“many of the shallow fore reef sites were low-relief hardground areas with limited colonization by corals”[/quote]

So there are areas with virtually zero possibility of detrimental enviro-impact, in close proximity (Which I will arbitrarily define as <30 minutes by boat) to outstanding dive sites.

Recreational SCUBA diving is limited to 140 ft. Basic SCUBA certification gets beginners to 60 ft. This is almost the definition of “shallow”. Most of the best relaxation diving is done 45-60 ft, and is where your air consumption rate vs bottom time is reasonable. With the exception of super adventurous divers and wrecks that happen to lie in deeper water, the vast majority of dives are pretty shallow.

Spuds and a semi-permanent placement would cause less damage than dragging anchors does, and potentially a lot more long-term benefit in terms of micro-scale current calming and providing habitat.

I don’t believe that the Florida Keys prohibit mooring/anchoring, do they? Spuds are NOT pilings. They don’t drive deep into the sea floor in the way that pilings do.


(Larry G) #55

http://floridakeys.noaa.gov/mbuoy/welcome.html

Mooring buoys, which are 18” in diameter with a blue stripe, have been used in the Keys since 1981 as an alternative to anchoring, which can break and damage the coral reef. There are over 490 mooring buoys available for use within the sanctuary on a first-come, first-served basis at no cost to the boater. Anchoring on living coral within the sanctuary in waters less than 40 feet and when the bottom is visible is prohibited. If no mooring buoy is available and you are outside a no-anchor zone you may anchor in sand.

http://floridakeys.noaa.gov/regs/welcome.html

With certain exceptions, the following activities are prohibited sanctuary-wide:

Moving, removing, taking, injuring, touching, breaking, cutting or possessing coral or live rock.
Removing, injuring, or possessing coral or live rock.
Discharging or depositing treated or untreated sewage from marine sanitation devices, trash, and other materials.
Dredging, drilling, prop dredging or otherwise altering the seabed, or placing or abandoning any structure on the seabed.
Operating a vessel in such a manner as to strike or otherwise injure coral, seagrass, or other immobile organisms attached to the seabed, or cause prop scarring.
Having a vessel anchored on living coral in water less than 40 feet deep when the bottom can be seen. Anchoring on hardbottom is allowed.
Except in officially marked channels, operating a vessel at more than 4 knots/no wake within 100 yards of residential shorelines, stationary vessels, or navigational aids marking reefs.
Operating a vessel at more than 4 knots/no wake within 100 yards of a “divers down” flag.
Diving or snorkeling without a dive flag.
Operating a vessel in such a manner which endangers life, limb, marine resources, or property.
Releasing exotic species.
Damaging or removing markers, mooring buoys, scientific equipment, boundary buoys, and trap buoys.
Moving, removing, injuring, or possessing historical resources.
Taking or possessing protected wildlife.
Using or possessing explosives or electrical charges.
Harvesting, possessing or landing any marine life species except as allowed by the Florida Fish and Wildlife Conservation Commission Rule (68B-42 F.A.C.).

The bold statements would seem to be the relevant ones. I’m explicitly in agreement with the requirements there. Don’t anchor on coral, don’t tear up the bottom. I think spuds in the right place are much less likely to cause damage than an anchor chain would. I don’t plan to place the structure on the seabed, rather to keep the structure up in the water, and only moor it to the hardground by means of extensible legs. It remains a floating “off-shore accommodations facility”.

Anyway, Cay Sal Bank has none of those restrictions.


#56

I personally don’t know anything about the Bahamian coral conservation (protection) laws and if or how they enforce such laws in Cay Sal. But it is logical to assume that in this day and age it cannot be “nothing”, therefore they do have “something” and in consequence, anybody operating there will have to respect the law.[quote=“thebastidge, post:55, topic:2377”]
I’m explicitly in agreement with the requirements there.
[/quote]

Me too. Now, I don’t think anybody operates a permanent dive “resort” close by the Keys reefs (I mean one like that Quicksilver on the Great Barrier Reef) but I am almost certain that if such operation will be planed for the Keys it will come under HUGE regulatory scrutiny (mostly environmental) from both the State and the Feds, no matter if anchored or studded. [quote=“thebastidge, post:55, topic:2377”]
I think spuds in the right place are much less likely to cause damage than an anchor chain would.
[/quote]
Well,… true, if you do a sloppy anchoring job or if you let your anchor drag.[quote=“thebastidge, post:55, topic:2377”]
I don’t plan to place the structure on the seabed, rather to keep the structure up in the water, and only moor it to the hardground by means of extensible legs. It remains a floating “off-shore accommodations facility”.
[/quote]

But you do place studs on the seabed with a structure attached to them… I have no clue how Florida State, Federal law or Bahamian law would “interpret” such arrangement. Got to look into it, because if it’s considered “building” on that seabed it will be a different ball game, I guess.[quote=“thebastidge, post:54, topic:2377”]
and potentially a lot more long-term benefit in terms of micro-scale current calming and providing habitat.
[/quote]

I agree. And not only that, but you can build an artificial reef between those studs and around/beneath your HEXS. In few years you will be on the reef! That location WILL be gold for the business.

By the way, these guys http://www.reefdesignlab.com/about/ are pretty good with artificial reefs.[quote=“thebastidge, post:54, topic:2377”]
the vast majority of dives are pretty shallow.
[/quote]

My comment was related to the idea of being RIGHT on top of ANY diving site (lets say in 45’+ water depth) which is easily achieved if floating but impossible ? if studded…Correct me if I’m wrong. My assumption here is that 45’ long studs are too long for your HEX?

If planned for Cay Sal, then I don’t know anything about how deep the diving sites are down there.


#57

BASS design

Among these new designs is the BASS unit from Bennett & Associates, dubbed BASS 350 and BASS 400. The rig classes are essentially identical save for the rated water depth. The BASS class is an independent-leg, rack-and-pinion jackup designed for moderate environments. The design supports the higher loads required for drilling operations today while maintaining the industry-preferred footprint of the LeTourneau 116 design.

The leg length of the 350-ft (107-m) version is 492 ft (150 m) while the 400-ft (122 m) water depth unit has 544 ft (166 m) of leg. Both units can accommodate 150 people.

http://www.offshore-mag.com/articles/print/volume-71/issue-7/drilling-rig-report/new-jackup-rigs-are-more-robust.html


#58

@Octavian Not being an SA… Just looked it up as it is relevant to your question.


#59

Yes I saw that. It is pretty deep, but it’s a big barge.

My comment regarding 45’ studs being too long was for Larry’s HEX size which I think is only 52’ in diameter. On second thoughts now, it can be with 45’ studs, I guess.


(Larry G) #60

From research on existing spud barges, I don’t think that’s correct. I’m seeing 27 meter and more depths quoted for purchasing or leasing existing spud barges. Those are a much lighter design, planned to have the body above the water surface rather than engaged in it, so it is possible that the engineering works out to allow for less length or require larger diameter spuds. But I am also planning 1) more spuds (seven instead of the typical four) and 2) not engaging in as much industrial activity like using cranes to lift heavy loads very high. I plan to lift a much heavier barge only partway out of the water- enough to give it a solid gravity base, but not so far as to eliminate all displacement and therefore maintaint some buoyant support.

So to sum up pros and cons of this hex vs a typical spud barge, my concept has higher lateral loading due to current, less lateral loading due to wind, more weight pressing on more spuds, less tipping moment due to height, but less width between spuds than some of the longer barges (it’s about typical width, but most barges are longer than wide).

Most of the bank is 50-90’ with lots of areas of less than 30’. Some of the blue holes are hundreds of feet deep. I have been looking at bathymetric maps and think there are several likely locations in ~30’ on scoured hardground, close enough to a blue hole or other interesting features to make a dive resort (of the small, intimate camp style I posted before) feasible from both an engineering and market standpoint.

There are lots of places in the Berry Islands that are close enough to the reef drop-off for the same, in the lee of various cays, but that is actually within territorial waters, not just claimed EEZ.


(Larry G) #61

https://wiki.seasteading.org/index.php?title=Permanent_Mooring


#62

I stand corrected.

I understand the process and the fact that you want to be at a certain waterline but I still have to look into the physics of it,… My first impression is that you cannot claim both, gravity based AND buoyant support.

If you jack up (lets say 2’) then you HEX will displace a smaller volume of water than when it was free floating. Therefore, the weight of the volume of water the HEX displaces NOW is LESS than the HEX’s own weight. In consequence, no buoyancy.

Not that it really matters,…

Wikipedia lists it at max 52’ depth: “The lagoonal surface has a depth of 9 to 16 metres (30 to 52 ft).” I guess the shallower the better.[quote=“thebastidge, post:60, topic:2377”]
and think there are several likely locations in ~30’ on scoured hardground, close enough to a blue hole or other interesting features to make a dive resort (of the small, intimate camp style I posted before) feasible from both an engineering and market standpoint.
[/quote]

No doubt about it. [quote=“thebastidge, post:60, topic:2377”]
So to sum up pros and cons of this hex vs a typical spud barge, my concept has higher lateral loading due to current, less lateral loading due to wind, more weight pressing on more spuds, less tipping moment due to height, but less width between spuds than some of the longer barges (it’s about typical width, but most barges are longer than wide).
[/quote]

The only BIG concern I have with you HEX under the actual proposed design is transport, if transport means crossing the Gulf Stream in tow from a construction site in the Florida Keys.

It seems to me that the HEX is TOO heavy on top, meaning much of it’s weight distributed way above its metacenter. 7 (heavy) 25’+ studs hanging vertically in their wells above the WL. 3 meters of light EPS foam on the bottom “pushing” ALL the HEX weight above the WL.

We are talking about a poor stability letter UNDER WAY here. And it won’t matter if you’ll move 500 yards offshore. But 100 miles crossing the Gulf Stream in tow? The moment you get caught in between few bigger waves there is a HIGH probability that you will experience heavy, uncontrollable rolling that COULD lead to capsizing.

One remedy could be dropping the studs all the way in the water while transporting so they would act as “stabilizers”? Anyhow, I would suggest a small scale model test in a wave tank in order to be on the safe side.