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VersBuoy Video

Home Forums Archive Structure Designs VersBuoy Video

This topic contains 30 replies, has 12 voices, and was last updated by Avatar of Jeff-Chan Jeff-Chan 4 years, 7 months ago.

Viewing 15 posts - 1 through 15 (of 31 total)
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  • #816
    Avatar of Wayne-Gramlich
    Wayne-Gramlich
    Participant

    All:

    Steve Khachturian of VersaBuoy sent me the following YouTube link:

    http://www.youtube.com/watch?v=J7xkdL0EdOA

    It is very much targeted towards oil production right now.

    #4927
    Avatar of Joep
    Joep
    Participant

    That wave tank simulation is amazing!

    #4930
    Avatar of vincecate
    vincecate
    Participant

    Joep wrote:

    That wave tank simulation is amazing!

    Yes, multiple spars seems to work well. When ClubStead was secret that is what I thought it would be. My model of this is called “multispar” (the one you funded!). I did not fix the heave, but other than that it was good.

    http://wiki.seasteading.org/index.php/User:Vincecate/Models/Multispar

    #4936
    Avatar of livefreeortry
    livefreeortry
    Participant

    vincecate wrote:

    Yes, multiple spars seems to work well.

    I think the real improvement is coming from the joint connecting the individual spars to the platform. In any case, multispars are surely better than a single spar.

    Wayne, are any numbers available as to how much this system would cost for various different size structures?

    #4937
    Avatar of vincecate
    vincecate
    Participant

    I think the real improvement is coming from the joint connecting the individual spars to the platform. In any case, multispars are surely better than a single spar.

    In a multispar/versabuoy each leg is a ballasted spar that could float on its own. This means each leg can lean with the wave action and still provide the lift it is supposed to at the point it is supposed to. This means it does not need to be so strong and in fact can have a flexible joint (I used elastic cord). It also means the platform does not tip.

    In a semisubmersible this is not the case. Not having ballast means it can carry more cargo for the same displacement. But the legs are rigidly attached so have to be stronger. If the legs are at an angle the center of lift from them moves over, so the platform will not be getting the lift it is supposed to at the point it is supposed to and can tip more.

    Either of these probably need some water ballast tanks that can be adjusted for different payloads. Probably true for any small-waterline-area type seastead. These active ballast tanks add a risk that something might go wrong and either sink the structure outright or make it so low in the water that waves could hit and destroy it. With backups and a trained crew this risk can be kept reasonably small (but non-zero, see Ocean Ranger below). However, for safety and simplicity on a single family seastead I think it is best to avoid any kind of active ballast that could do something that put the structure at risk. This is another reason I like the WaterWalker and TensionCircle approach better than the spar or semisubmersible approach.

    http://wiki.seasteading.org/index.php/User:Vincecate/Models/Multispar

    http://wiki.seasteading.org/index.php/User:Vincecate/Tension_circle_house

    http://wiki.seasteading.org/index.php/User:Vincecate/WaterWalker

    http://en.wikipedia.org/wiki/Ocean_Ranger

    – Vince

    #4938
    Avatar of Wayne-Gramlich
    Wayne-Gramlich
    Participant

    Alas, I could never get Steve K. to give me any solid numbers. As the video suggests, Versabuoy is pretty focused on the oil/gas extraction industry right now.

    I still do not understand why the flexible joints make a difference.

    When the clubstead design is done, we can send the design to Steve K. at Versabuoy and have him comment on it.

    #4939
    Avatar of vincecate
    vincecate
    Participant

    Wayne wrote:

    I still do not understand why the flexible joints make a difference.

    The key thing is that each of the legs in a multispar is a ballasted spar that wants to be vertical, even if it was off on its own. This is why you can do a flexible joint. The legs in Clubstead do not have this property.

    In clubstead the further you pull it over the more the center of mass is shifted off the center of buoyancy and the easier it is to pull it further. As the legs tip the platform tips. At some point it will tip all the way over. This is why you can not just make the airgap arbitrarily large, it would tip too easy.

    In a multi-spar where each leg is ballasted, the further you tip it over the bigger the lever the ballast/buoyancy has to restore the legs to vertical, so the harder it gets to pull it further. And while the legs are tipping, the platform stays level (at least if all legs are tipping the same amount).

    VersaBuoy is the name of a company, so I called the idea “multispar” when I made a model as it really is just putting a bunch of spar-buoys together. But I think this is a very different idea than a semisubmersible, which is always rigid as far as I know.

    – Vince

    #4948
    Avatar of Carl-Pålsson
    Carl-Pålsson
    Participant

    I think an efficient truss design will be very valuable for ballasted spar designs, whether single or multi spar. Increasing the length of the truss on which the counterweight sits reduces the amount of ballast you will need.

    I´ve been thinking mostly about steel for this as this seems to be the popular choice. But I wonder whether this is really optimal. Steel is not very resistant to buckling, it needs to be reinforced a lot (see the drawings of the clubstead spars for example). Perhaps you can make this cheaper with concrete? Think an upside-down tripod consisting of three beams of pre-stressed ferrocement.

    Anyway, Versabuoy/multispar seems perfectly viable to me. I agree it has both advantages and drawback versus a semisub. I guess you need simulations or scale modeling to find out what is more efficient in real life and at real scale.

    One things about Versabuoy is the joints though. This is obviously a complex and potentially sensitive design compared to having no joints. Could be a problem. These are universal joints, right?

    #4949
    Avatar of Steffen
    Steffen
    Participant

    Carl wrote:

    One things about Versabuoy is the joints though. This is obviously a complex and potentially sensitive design compared to having no joints. Could be a problem. These are universal joints, right?

    There are some pictures of the joint at http://www.vbuoy.com/thesystem-joint.html

    #4951
    Avatar of Carl-Pålsson
    Carl-Pålsson
    Participant

    Looks like a U-joint to me. Replacing one of these seems like it could be awkward or expensive. But maybe they can be made durable enough to last the life of the platform.

    Can you use this thing without moorings, by the way? And when moored, do you need several lines or can you make do with a simple single line?

    #4953
    Avatar of Wayne-Gramlich
    Wayne-Gramlich
    Participant

    Carl wrote:

    Looks like a U-joint to me. Replacing one of these seems like it could be awkward or expensive. But maybe they can be made durable enough to last the life of the platform.

    Yes. They are basically massive U-joints. They do have a finite lifetime. They can be inspected on a regular basis. Lastly, they can be replaced in the field, if there are enough other spars to hold the rest of the structure up. It is a very nice technology. The costs (including royalties) are not understood at this time. (We’ve repeatably asked.)

    Carl wrote:

    Can you use this thing without moorings, by the way? And when moored, do you need several lines or can you make do with a simple single line?

    Yes. Versabuoy structures can be used without mooring. (Steve answered that question.)

    #4954
    Avatar of Joep
    Joep
    Participant

    May be this would suffice? (green is the Stead with a hole in it, blue the column, and black are three ropes connecting the columns to the edge of the hole). Basically the Stead is hanging from poles on top of the columns.

    #4955
    Avatar of Wayne-Gramlich
    Wayne-Gramlich
    Participant

    Looks like a U-joint to me. Replacing one of these seems like it could be awkward or expensive. But maybe they can be made durable enough to last the life of the platform.

    Yes. They are basically massive U-joints. They do have a finite lifetime. They can be inspected on a regular basis. Lastly, they can be replaced in the field, if there are enough other spars to hold the rest of the structure up. It is a very nice technology. The costs (including royalties) are not understood at this time. (We’ve repeatably asked.)

    Can you use this thing without moorings, by the way? And when moored, do you need several lines or can you make do with a simple single line?

    Yes. Versabuoy structures can be used without mooring. (Steve answered that question.)

    #5051
    Avatar of Thorizan
    Thorizan
    Participant

    I’m really digging the idea of Versbuoys… and I was wondering if it were possible to take this in a slightly different direction.

    Instead of a realtively complex and ultimately expensive Versabouy system, I would like to propose an ultra low-tech solution:

    Plastic barrels… with Knotted Ropes!

    Each barrel (and I’m tihnking a typical structure would have over 1000) is a ballasted spar, with a flexible joint, namely, a length of rope protruding from a hole in the center of its lid with several knots in key places. The first knot is immediately on the interior of the lid, followed by one immediately on the exterior. The length of rope travels up through (or around) the support structure and ends with a knot on the other side, securing the barrel to the structure. The knot in the middle would act as the joint, allowing the barrel to move with the waves while still having the structures weight resting upon it. Now, during large waves, I understand the pressures on the rope near the knots could be great, and “normal” rope or even standard knots may not be sufficient for the stresses over long periods of time, but with the maintenance costs being so low (get more rope… tie more knots), this could prove to be a possible solution.

    Basically what I’m trying to get at is, I think this multi-ballasted-spar-flexible-joint system has a lot of promise. We’ve seen Vince’s videos where four PVC spars being secured by elastic cords did a fine job, and we’ve seen the wave tanks from VersaBuoy that show how there system fares as well.

    This could be the answer to truly taming “normal” size waves, and provide a stable (enough) environment to build upon… literally, while doing it all at relatively inexpensive costs: that of a plastic barrel, a solid object, and a rope to tie them together.

    #5055
    Avatar of Carl-Pålsson
    Carl-Pålsson
    Participant

    Thorizan, a picture is worth a thousand words…

    Joep, are the ropes going to be attached rigidly to the top of the spar? I guess so, because if you used a hinge there the ropes would be redundant. Anyway, it seems to me the ropes would be subjected to bending while highly loaded in tension. So, they might fail from fatigue. Also, you lose a bit of height above the water that way, do you not?

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