Deepest Anchoring

Discussion in 'Boat Design' started by mydauphin, Mar 30, 2009.

  1. mydauphin
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    mydauphin Senior Member

    What is the deepest anyone has anchored before and what problems did you find when you did ?
     
  2. Landlubber
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    Landlubber Senior Member

    Actually deep anchoring is something to be avoided, unless necessary.

    In a cruising yacht, the anchor chain and the anchor itself are the limiting factors, plus the total weight of these components.

    No good dropping the lot over the side in dfeep water is the winch cannot retrieve it all back up for you.

    My recommendation on ground tackle is go as heavy as you can, say 10mm for a 40 foot boat, with a 45 lbs CQR attached. Run about 120 metres of chain.

    The pull weight of the winch should be 3 to 4 times the total weight of the ground tackle.

    Anchoring in very deep water, such as in fishing offshore reefs, is another matter. This is done with rope and anchors that can be bent back to shape, such as steel grappling hooks and a few metres of chain. These can be hundreds of feet long if need be, but again a line hauler is required to get it all back on deck unless you have a teenager that is happy to haul in the mess.

    What exactly are your wishes for deep anchoring?
     
  3. Ad Hoc
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    Ad Hoc Naval Architect

    Anchored...as in temporary or fixed?
     
  4. FAST FRED
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    FAST FRED Senior Member

    The only place I have seen this analized is Oceanography ans Seamanship , Van Dorn , used at the US Naval Canoe U.

    His rec is 1/2 chain with 1/2 nylon yp to the capacity of hauling the weight aboard.

    400ft water would be 200 chain and 200nylon , not too large in diameter to keep the stretchability.

    FF
     
  5. Submarine Tom

    Submarine Tom Previous Member

    mydauphin,

    This is a strange question, but I'll answer: 40 feet and I had no problems.

    If you want to anchor deep you're going to need a really strong windlass!

    That's because you're going to need a LOT of heavy chain, a good

    cantenary, and a whole lot of nylon rope. A scope of 7:1 is a good

    objective. That means in 400 feet of water you're going to need close to

    3000 feet of rode!!! That's half a nautical mile!!! Where are you going to

    store that on board???

    Fast Fred: 400 feet of rode in 400 feet of water isn't going to work.

    That's zero scope...

    Tom
     
  6. apex1

    apex1 Guest

    80 meter, but that was to deep. I had 150 meter of chain (I do´nt use rope) but the anchor slipped several times. Insufficient scope as Tom mentioned. On 50 meter and below I never had a problem. My windlass and anchor are allways of the heaviest size, as you know. The problem is to add much weight where you do´nt need it, at the bow. If possible place the windlass and chain locker abaft the usual position. It may cost you some 80cm of accommodation, but the bow will not plough in.

    Regards
    Richard
     
  7. mydauphin
    Joined: Apr 2007
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    mydauphin Senior Member

    Wihile fishing a friend found a wreck at 400' in a drop off. We want to rig up a ROV and see if we can take a look but without any fancy equipment to stabilizing on spot we have rig up some kind of anchor to wreck so we can stay over site. That is why deep anchoring comes up
     
  8. Landlubber
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    Landlubber Senior Member

    Oh great mate, have fun, that will be a good project to play with.
     
  9. Submarine Tom

    Submarine Tom Previous Member

    mydauphin,

    Okay, now I get it.

    You'll need a lot of ground tackle, times three!!

    You'd have to triangulate your anchorage to keep from swinging off

    station in current and wind. I would think it much easier to use a GPS and

    stay on location under power, no anchor. I wish you all the best in this

    adventure. It's no small undertaking.

    Tom
     
  10. FAST FRED
    Joined: Oct 2002
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    Location: Conn in summers , Ortona FL in winter , with big d

    FAST FRED Senior Member

    A scope of 7:1 is a good objective.

    It is in shallow water with nylon rode , but not needed in really deep water.

    Anchoring in 100ft (half chain ,half nylon)will only require 3-1 or 4-1 (in Very Heavy weather) as the entire chain must be lifted clear of the bottom to effect the angle of pull to the anchor.

    Stretchy nylon helps a lot and 150 ft of chain is hard to lift in a straight line .

    FF
     
  11. mark775

    mark775 Guest

    I anchor sometimes six or seven times a day. I anchor in 200 or 230 meters In rock - No problem. 1.5 to 1 ratio is fine if you have a little rock ledge to grab onto and the weather is calm and the current is < 2kts. If using an ROV, current will need to be far less than that. Are you meaning a remote camara on a cable? .3 knots will be a max there. 400 ft is pretty fancy equipment. Had a hard time holding with bent rebar grapnels and such without holding too well. Try a used Danforth and just rip that thing outta there when done. Never plan on losing anchors but, like fishing line, you want your weakest point to be at the bottom.
    Not going by the book here; I use four hundred feet of 3/8 Amsteel Blue for this kind of thing because the drag on heavier rode is tremendous. But Amsteel doesn't stretch so you still need some nylon and chain. I use seven hundred feet of 3/4" doublebraid usually, with a weak link of older 5/8 doublebraid near the terminal gear or if the 3/4 gets frayed near the bottom, just use it anyway. I can pop this with my boat if it gets badly stuck. Size a chinese copy of a Bruce anchor and consider it disposable but it can almost always be tweaked out by pulling at an upcurrent angle. Herein lies the real beauty - the Chinese crap breaks and you take the remaining chunk back to where you got it for an exchange for new! If trying to hold in sand, you'll need scope like advised above or be prepared to slide - and you don't want to plow up your fishing hole, do you? Specific questions about this, feel free to ask. I know what works.
     
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  12. mydauphin
    Joined: Apr 2007
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    mydauphin Senior Member

    Thanks all for your great answers. I am looking forward to doing this. The weather lately is not helping. I dont know when we are going to try this. The ROV is homemade. Right know it is camera on a rope with propulsion made from bilge pumps and PVC pipes. But we are working on upgrades.
    thanks again
     
  13. kistinie
    Joined: Aug 2007
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    Location: france

    kistinie Hybrid corsair

    Unlimited relativ anchoring

    Parachute is a solution too
    The one i have on WINGOVER is an army modified air model with 3 Kg at the end
    works in heavy weather, motion become very slow

    Jordan serial drogue is also a good system, safer and much easier to use

    This could help active stability motoring slowly, drogue doing a almost fix point, if stream is low, can work
     
  14. Hägar

    Hägar Previous Member

    ANCHORING was the question! Not a good recipe to fight cockroaches.
    The ability to read is very helpful! You have been referred to that in another thread.

    Hä, hä Hägar
     

  15. Submarine Tom

    Submarine Tom Previous Member

    Drag

    mydauphin,

    I may know the ROV design you mean, I've built one.

    I don't know how much experience you have with it in deep water or how

    much current you have in the area, but don't underestimate the effect of

    current on your ROV tether in 400 feet of water. Your ROV may not have

    the power to overcome it.

    Hagar: as you can see, this thread is not so much about anchoring. See

    mydauphins second post.

    Tom
     
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