Dive support vessel

Discussion in 'Boat Design' started by Adhithya, Jun 27, 2014.

  1. rxcomposite
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    rxcomposite Senior Member

    That is too bad. Very expensive database.

    Most vessel of this type are workboats (tugboat ratios and coefficients), configured in several different ways to maximize utilization for maximum profit. So it can be a supply vessel, crewboat, or a tugboat that can be modified (usually chartered for a year's contract)

    But if you want to zero in on DSV, Try DSV IMAGE SEARCH https://www.google.com.ph/search?hl...s_l=img.1.3.0j0i24l7.1475.26999.0.42664.31.25 , click on the picture of your choice, then view. Most likely you will get the vessels specs like I did. Then you can build up your own database.

    You can try this link for a newbuild, specs, and the mechanics (how to) of a DSV. http://www.marineinsight.com/marine...c-the-biggest-saturation-dive-support-vessel/ Skandi Arctic
    https://www.google.com.ph/?gfe_rd=c...DIDg&gws_rd=ssl#q=dive assist vessel&start=20

    You can also try most Oil & Gas companies that own their DSV and furnishes specs of their vessel like mcdermott. http://www.marinetraffic.com/en/ais/details/ships/9219410/vessel:THEBAUDSEA

    Or a newbuild press release http://www.dwtship.com/ship-sale-pu...7m-deep-sea-diving-support-vessel-detail.html most of the time available from WorkBoat magazine.

    In time you will build up your database. Many ways to skin a cat.
     
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  2. rxcomposite
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    rxcomposite Senior Member

    I remember I posted something similar in this forum.

    Sorry I disabled the formulae and links as this is a very large spreadsheet. You should be able to see the ratios, proportion, and coefficient in the error trapping cell. This is a preliminary sizing technique to enable you to quickly narrow down your parameters for preliminary design.

    Trawlers and Tugs (and DSP) are special type of ships, hence their parameters is different from "standard design". Different authors (Lindbladd & Todd, Watson, MARIN) have different interpretations on the parameters as the tables show. It is up to you to choose the design parameters that will suit your SOR.
     

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  3. Yobarnacle
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    Yobarnacle Senior Member holding true course

    Thanks Mr RX.

    A DSV as a self propelled vessel has some unique and difficult design conflicts.
    Again, I believe a barge is FAR more suitable and compatible with the design parameters.
    Stability and load carrying. Can't beat a rectangular barge hull. A DSV doesn't spend much time underway. it's on station at the dive site, or stacked in port awaiting next contract. Or waiting on weather, in port or anchored up river.
    For short infrequent voyages from port to project and return, devoting all that space and equipment to self propulsion seems ridiculous.
    As vessels increase in size, their manning requirements for credentialed seamen and officers increases dramatically. Not so for barges. and what credentials ARE required, are much lower grade and easier to acquire. An ablebodied seaman with tankerman endorsement, can be a barge captain in the USA and frequently that's what barge captains are. No licensed engineers required, nor mates. Able seaman are not required, though a sufficient number of crew need lifeboat certificates. A two week course.
    Insurance is less, inspection criteria less draconian. Design and construction costs less.
    4 point anchor systems work better from 4 corners than 3. DP thrusters work better from 4 corners also.
    All those 360 degree panorama bridges get reduced. Just ONE, the observation room is needed. Control stations like the dive shack still necessary but dpesn't need to see everything everywhere. To have multiple bridges with all around view, you have to stack them. otherwise they occlude each other. Just a large Observation room penthouse, means it can be top part of a lower superstructure.
    I can go on and on.
    Why do companies build or convert self propelled DSVs rather than use barges?
    A mystery to me!
     
  4. rxcomposite
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    rxcomposite Senior Member

    I see your point Yobarn. We have been involved with the design of a Non propelled-crew barge designed so that it can house the labor/temps working with Mobile Offshore Drilling Unit.

    We have also been tapped into a 3,000 man capacity of a floating labor camp (a decomissioned ship) designed to house labor working (restin in between shifts) on an offshore site.

    In both design, the labors being housed are not seaman or merchant mariners so I guess somebody has seen the loophole.

    In most cases, there are crewboats to ferry working crews to the site. Some so small they are called water taxis. The crew calls them to get away from the workplace so that they can smoke, drink coffee, or cook a meal they like because the workplace is so restrictive. Kind of abusing it but that is how it goes.

    There is a demand for DSV. I was a little bit surprised that it has evolve to a special type of ship and specifically designed vessels are being built.
     
  5. Yobarnacle
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    Yobarnacle Senior Member holding true course

    When you work for a large company, the golden rule applies. He who has the gold, makes the rules. Employees become numbers in the head office.
    I always preferred mom and pop operations, small family owned boat companies.
     
  6. rxcomposite
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    rxcomposite Senior Member

    With the oil & gas business so vast, there is always room to make money. I have boarded a crewboat so small that the only extra supply it can carry is a thousand liter FW housed in a plastic tank secured to the deck. Always trying to maximize profit. Hehehe.:)
     
  7. Yobarnacle
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    Yobarnacle Senior Member holding true course

    Often my cargo is for an oil company, when I'm towing. But I'm not vulnerable to their infamous abusive attitudes. My owners provide the tug on charter. Someone else provides the barge. I sit at the tug dock and prep MY vessel until sailing day. We motor to the loading dock, and inspect the barge and cargo lashings. I get the insurance papers, usually from LLoyds rep, who assures me I'm to rely on MY judgement and dismiss the demands/pressures of the charterer, whenever safety of barge and cargo are concerned. I'm always invited to call the LLoyds man to back me up.
    We hook up and wait for clearance papers and a tail tug. Soon, documents in hand, we depart and a couple hours later, release assist tug. Clear of seabuoy, we stretch out the tow wire. put the chafing gear on, change clock to destination time, set watches, and begin the routine we'll follow for the next month or better.
    Upon arrival in port, land the barge, clear customs, immigration, ect, disconnect and move tug to a different remote lay berth for several days or maybe weeks while barge offloading. Liberty call. time for a cold brew or two or three. And I still get paid EVERY day until I go home.
    I LIKE deepsea towing. :D
     
  8. Adhithya
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    Adhithya Junior Member

    thank you Rx for your input, I'm going through them. While on it i noticed that a lot of DSVs(near my dimensions) have a dead weight of around 5500T, why is this required? What do they use this 5500T for? Even if we include the sat dive sys, it only weighs about 80T( though it would be considered as light weight/outfit weight. and the sat gases are not gonna weigh that much, nor the tools carried by the divers. So, what other "thing" is a DSV gonna carry that it requires such a dwt?

    ref: Harkand Atlantis, Harkand DaVinci, Toisa pegasus, Toisa Proteus, seven Atlantic and Seven Falcon.
     
  9. Yobarnacle
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    Yobarnacle Senior Member holding true course

    Deadweight tonnage (often abbreviated as DWT, for deadweight tonnes) is the displacement at any loaded condition minus the lightship weight. It includes the crew, passengers, cargo, fuel, water, and stores. So this changes all the time. They use up fuel and fresh water and get lighter draft. Or change cargo.
    But you are probably confusing it with Gross tons or NET tons referring to volume . Masters and Mates licenses are based on Gross tons. An unlimited Master Mariners license is for "Any Gross Tons". GRT is an obsolete term. Gross tons is determined by a formula. Engineers are licensed for horsepower, unlimited the highest rating.
    5500 NET tons is a class not a weight. The ton refers to tun, an ancient barrel for wine and refers to cargo carrying capacity. Each ton represents 100 cu ft of internal volume not including engine spaces, certified quarters (bedrooms) certified control spaces(bridge) ect certified galley ect. Ballast and fuel tanks ARE included in the measurement. You may have heard of tonnage openings. Any two compartments that are connected so a 3ftX3ftX3ft box can be carried from one to the other count as a single compartment. Otherwise a fraction of a 100cuft ton is rounded off to next highest ton. They want as few fractions as possible.
    They want the lowest net tons they can get!
    Because Net Tons determines taxes, port fees, pilot fees, agent fees, crew size, number of officers required, how much firefighting and lifesaving equipment must be carried. Insurance is based on it too. Not just collision insurance, but pollution insurance as well. It's all about expenses. Money.
    And the vessel displacement is MORE than 5500 tons, but doesn't matter. :)
     
  10. Adhithya
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    Adhithya Junior Member

    I thank you for the info you have shared but, I was wondering why does a DSV requires a 5500T DEADWEIGHT? yeah dwt includes crew, supplies, provisions, etc, but why 5500T:!: A 80m PSV, that is required to carry cargo has a dwt of 2500T, (sorry i could not remember where I saw it), so why does a DSV, which does not carry any "CARGO"(I suppose:confused:) require 5500T of deadweight. Again I have not confused deadweight, GRT and displacememt.

    ref: http://www.harkandgroup.com/media/filer_public/2013/04/26/atlantis_spec_sheet_website_april_25th.pdf
    Vessel: Harkand Atlantis
    disp: 12,565T
    dwt: 5,662T
    GRT: 8,691T
     
  11. Yobarnacle
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    Yobarnacle Senior Member holding true course

    Dwt

    Spec sheets like this are advertising brochures for prospective clients. At some time or another, a client asked for this data, is my guess.
    A Norwegian captain, a friend of mine, always complains "Too many farmers in the office", meaning he has to deal with people who don't know what they are talking about regards ships and the sea.
    This deadweight is meaningless. at 0 meter trim, means level. But what draft? What loadline? They did include a displacement @ 0m trim. Subtract DWT from THIS displacement probably gives weight of hull, superstructure, and machinery. You could then subtract this lite ship figure from current displacement and get current DWT load I suppose, but why would anyone want to?

    below is a typical loadline. LLOYDS REGISTER. ABS does it for US ships. American Bureau of Shipping.

    The various loadlines depicted, abbreviations mean:


    TF - Tropical Fresh Water loadline
    F - Fresh Water loadline
    T - Tropical loadline
    S - Summer (Plimsoll Mark) loadline
    W - Winter loadline
    WNA - Winter North Atlantic ( seasonal Loadline mark)

    L - Lumber (On timber carrying vessel only)

    Spec sheet was created by office people FOR office people.
    They did include gross and net tonnage. Useful meaningful numbers for comparing different ships.
    Explanation of DWT in specs? Too many farmers in too many shipping offices.

    If I totally misunderstood your question, and you were only asking where is all this weight exceeding weight of crew, stores, tools, ect? A couple hundreds of thousand Gallons of fuel and something similar in freshwater, and the rest in saltwater ballast for stability.
     

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  12. Adhithya
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    Adhithya Junior Member

    I agree that dwt is no means of comparing ships, but a 5500T dwt is about that of a 100m oil tanker http://www.marinetraffic.com/ais/details/ships/9514444/vessel:HARLINGTON

    The deadweight and disp of the vessel given in the spec would mean at the max draught already specified.
    but is not the 'carrying capacity' of a vessel pretty important in its design stage, is it not one of the parameters you check at every design iteration.
    So, again what I want is, why a deatweight of 5500T, what could it be carrying :?: or is it provided just that it may double as a supply vessel, or some other type during free time or to provide for future additions and modifications?
     
  13. Yobarnacle
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    Yobarnacle Senior Member holding true course



    A couple hundreds of thousand Gallons of fuel and something similar in freshwater, and the rest in saltwater ballast for stability.
     
  14. Yobarnacle
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    Yobarnacle Senior Member holding true course

    You'll have to ask an expert, another N/A. Seems a logical assumption.
    My design limitations and experiences are a couple of plywood dinghys with developed surfaces I designed and built as a kid. And modifying my two 25 ft plastic sailboats. On the 25ft boats, my skills are often stretched or exceeded and I seek help here on those occasions. :)
    Operational concerns in design, I can address with experience on several specialized types of ships during roughly half a century at sea.
     

  15. rxcomposite
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    rxcomposite Senior Member

    That is probably the clue. They may be carrying other supplies like water, mud, cement, even acids. Workboats like this carry special tanks in its hold. so that it may double as supply vessel when not in charter for dive support. Most workboats are designed with a variety of function to maximize its usefullness. It is a compromise in design as dive crews or people carrying are volume (lots of volume for a given weight) based while cargo (high density) is weight based.

    First check if it is in accordance with recommended ratio and proportions and coefficients I have posted that gives you a design displacement and if it agrees with your detailed weight estimate.

    I always use the SWBS list as it is more detailed. Check your duration, the days the vessel will be out at sea to compute your consumables like F.O./F.W./stores/provisions ect.
     
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