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Sea anchors.

Home Forums Archive TSI Engineering Sea anchors.

This topic contains 6 replies, has 4 voices, and was last updated by Profile photo of wesley_Bruce wesley_Bruce 4 years, 7 months ago.

Viewing 7 posts - 1 through 7 (of 7 total)
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  • #1206
    Profile photo of wesley_Bruce
    wesley_Bruce
    Participant




    We don’t need to anchor to the sea bed to stay in one place against wind and wave drift. We could use sea anchors. For those that don’t know. A sea anchor is a canvas parachute trailed by a vessel below the water to slow the craft. The sea anchor hangs deep enough to be unaffected by surface forces and like a parachute it slows a vessel. Most sea anchors are designed to slow a vessel running down wind in a large storm.

    http://www.answers.com/topic/sea-anchors

    Most sea anchors are small because they need to be stowed on board. However in a sea steading context they can be much bigger matching the surface area subject to wind and wave effects. Up to 100 square meters since they can be permanently deployed. This will also mean that they may need to be made a little more robust to cope with constant duties and loads.

    The sea anchor has not advanced much over the past few decades. In the same period parachutes have largely been replaced with parafoils and sails have advanced hugely. Designing a much more sophisticated deep water sea anchor that is both cheaper and steerable like a parafoil may be the key to station holding. Computer controlled parafoil sea anchors would cost of a few thousand dollars. Anchoring to the sea bed would cost tens of thousands of dollars. http://en.wikipedia.org/wiki/Parafoil

    It also should be noted that there is an amplified drag effect at some depths where water of differing densities lie one upon the other here the drag is enough to stop a submarine under power dead in the water. They avoid these layers. We might target them. They are only a few hundred meters below the surface.

    Also note that at different depths the currents run in different directions. With sea anchors targeting the right depths we could use these forces to sail against the wind/ wave drift or even sail about. Such deep water sails and parafoil current rigs would be slow but faster than the wave drift. In most cases these deep water sails would be less than a kilometre deep. The lines holding them would be standard trawler lines and trawler winched. A few thousand dollars more than anchor winches.

    We will also need to consider adding sonar beacons to these sea anchors so they don’t fowl submarines; both ours and other nations. We don’t want to create an excuse for an argument with a passing navy.

    #9682
    Profile photo of hembergb
    hembergb
    Participant

    I was only today studying the major currents and the dynamics of them. Is there someway we could also use them as a power generation tool, maybe attach small generators to the sails.

    #9690
    Profile photo of wesley_Bruce
    wesley_Bruce
    Participant

    hembergb wrote:

    I was only today studying the major currents and the dynamics of them. Is there someway we could also use them as a power generation tool, maybe attach small generators to the sails.

    Yes if we have currenct running at the right speed but it would not be very economical. We will have an abundance of energy options including solar, some wind in the mid after noon. Assuming we are on the western pacific equator. We will have biofuels options, Have you seen my musings on farming the seas surface with floating ponds and bouyant algae bladders? http://vacoyecology.com/Bubble_ponds_fluke_boats.html

    I would favour the available high density energy technologies first over such a low energy density technology. Wave power is also available. Even in the Gulf Stream the energy density is very low and the current mills that are proposed have sail areas or blade areas measured in acres per kilowatt. The best we could expect form these currents is a few watts. If were running with the wind on a sailing seastead/ship then a sea anchor could charge batteries. There is one available commercially but I can’t find the site. But thats not station holding.

    Sea anchors are good for staying put not much else. Lets solve one problem at a time, mate.

    For everyone’s information I was involved with the original Oceania Project in a small way. I’m also in several space organisations. And I have a Degree in sustainable Development, sustainable agriculture and renewable energy, water and sewerage.

    #9691
    Profile photo of xns
    xns
    Participant

    So how would one use a sea anchor to keep a 2km2 island from drifting? I’m honestly looking for an alternative to deep water anchoring since the location I’ve chosen is 4.3km above the bottom. Because if it works, I’d be quite happy to sponsor a test platform in about 10 months.

    King Shannon of the Constitutional Monarchy of Logos.

    #9710
    Profile photo of wesley_Bruce
    wesley_Bruce
    Participant




    Your ambitious with a 2 km Squared unit but it should be doable. Even Oceania was smaller.

    We would need more than one sea anchor set at different depths to avoid tangling. About one per unit or one per 50 to 150 metres. That’s a forest of sea anchors. A set of weighted lines would hang below each component. One or more large sea anchors would be placed on that line at different depths.

    Any sail making company or tent maker could craft the anchor. We could do it our selves but the stitching requires special equipment and skills. Professionals are better but you must shop around and find the best price. A deal to make a set of prototypes at a discount may be possible.

    Each structure can also be moored together by lines with alternating buoys and sinkers and plate like sea anchors these resist vertical forces and the buoy sinkers system converts that into horizontal drag. Thus the whole system (city) acts as one with a huge sea anchor area. If your going for a very big structure I don’t know of that’s not a problem.

    See my latest blog post on how I think we will end up doing sea stead systems.

    http://appliedimpossibilies.blogspot.com/2010/03/sea-steading-as-fleet-of-vessel-classes.html

    Ten months it a good sign, your not in a rash rush.

    Note: We also have wave powered boats that could be added to counter any remaining drift.

    For everyone’s information I was involved with the original Oceania Project in a small way. I’m also in several space organisations. And I have a Degree in sustainable Development, sustainable agriculture and renewable energy,water and sewerage.

    #9738
    Profile photo of J.L.-Frusha
    J.L.-Frusha
    Participant

    Sea-Anchors don’t help you hold position. Sea anchors are good for being towed into the wind, or using to face the prow into the wind, versus the current flow.

    I remember a power-generation system that was proposed, using a loop with parachute-like attachments that filled with the current and collased when moving against the current. I don’t think it proved feasible.

    In India, there is a flapping, wind-powered pump that may have some adaptability. As it reaches the end of its’ travel, a simple rope causes the vane to pivot and move in the opposite direction…

    Anchoring to a sea-mount, or even in deep-seas is do-able. Use a buoy to ‘mark’ and keep the chain up, attach to that and use the currents to drive impellors, like a wind-generator. Set-up right, you could get your day-to-day electricity and use them to move away from approaching storms, as needed, then return to the anchorage…

    Later,

    J.L..F.

    If you can’t swim with the big fish, stick to the reef

    #9753
    Profile photo of wesley_Bruce
    wesley_Bruce
    Participant

    J.L.Frusha wrote:

    Sea-Anchors don’t help you hold position. Sea anchors are good for being towed into the wind, or using to face the prow into the wind, versus the current flow.

    That’s true for todays sea anchors but I’m talking about something that’s 20 times the area and is targeted at currents going the other way. No one to my knowlage has tried such a sea anchor system. I’m talking trawler net sized things. If the sea acnhor exceeds the surface area subject to wind and wave drift then, given basic physics, we should see the mass of the water countering these forces.

    I agree with you mooring to the sea bed is a possiblility in 5 kilometer deep seas and active sea keeping is possible if we have a cheap energy source. Always helps to have a plan A, B and C up your sleeve.

    One consideration is Patri’s idea of moving if you disagree with the local government. If we have big deep anchors these will be owned by someone. Anyone wanting to be moored to it gets ‘moored’ to the owner. My sea anchors may only reduce drift by half or so but they liberate us from the anchor king. There are also environmental considerations to any large anchoring system.


    For everyone’s information I was involved with the original Oceania Project in a small way. I’m also in several space organisations and I have a Degree in sustainable Development, sustainable agriculture and renewable energy, water and sewerage.

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