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Old 03 February 2008, 10:41   #1
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Anchoring

Hi

On a course today (the students are in the other class room now), we got in to a long discussion over Anchoring. For an average size RIB I have allways been a fan of a decent anchor, 3 - 5m of chain and 3 - 4 times the max depth depending on conditions and carrying 30 - 40m of Anchor Warp and allways being able to join with the other warps on the boat.

What do you use?

I see the "Start Powerboating" book (you know the one without a section on tides) reccomends 6 x the depth.

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Jono (very much a 4 x fan) Garton
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Old 03 February 2008, 10:54   #2
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Pretty much the same as you. My anchor is a bit smaller than it should be (small anchor locker) but I've only ever had trouble with getting it to hold in short chop. Once it's in, it holds ok.
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Old 03 February 2008, 11:42   #3
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I've got a Bruce and a CQR, both above minimum size for the boat, both with chain (8m on each) then warp. I tend to put down about 5x depth as either all chain or chain + warp.

I just don't think anchors are something to be stinted on. It's not so bad if you're stopping for a picnic or a swim, but if I lost power on a lee shore with breaking waves I want to be pretty certain I'm going to hold.
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Old 03 February 2008, 11:59   #4
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Hi

So if you anchor in 15m of water, you put down 75m of chain what boat have you got?

I agree its better to be safe, but if you got your life jacket caught in 20m of chain and an anchor, im not convinced you would float???

Jono
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Old 03 February 2008, 12:33   #5
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i'm with you on this Jono, 1kg anchor weight for each metre of boat length ( I like Bruce types best). Anchor chain equal to boat length, and 50m of rope (10mm is strong enough for most RIBs under 7m long)
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Old 03 February 2008, 12:35   #6
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I have a 4m boat, and IIRC it carries a 4.5 kg Danforth with 5 m of 6mm chain and 30m of 8mm rope. Never had it slip - but never been tested in really bad weather (>F4) either. I don't have a depth sounder (but do carry a home made "lead line") and try to put out 5x depth as scope.
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Old 03 February 2008, 12:48   #7
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I have a 4m boat, and IIRC it carries a 4.5 kg Danforth
Is it anchor wieght or surface area and design that counts? I use a Fortress, Danforth style which is made from Ally. lighter but large surface area.
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Old 03 February 2008, 12:55   #8
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Is it anchor wieght or surface area and design that counts? I use a Fortress, Danforth style which is made from Ally. lighter but large surface area.
both - but you are right you need less weight if you are comparing ali to steel. mine is steel.
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Old 03 February 2008, 13:56   #9
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So if you anchor in 15m of water, you put down 75m of chain what boat have you got?
Jono
One with the prop out of the water
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Old 03 February 2008, 13:59   #10
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Anchor weight is mainly to aid penetration. Surface area is definitely what counts unless you are anchoring on rock where a grapnel or fishermans is great.

I carry 2x 60m of 16mm octoplait - mainly because the bigger diameter is easier on the hands. My working anchor is a 5kg Bruce just attached direct to the rope. it works fine in most conditions. For emergency use I have a 6kg Delta copy with 8m of very heavy chain(can't remember size). Obviously if I need to I can join the 2 lengths of rope together so I have 128m in total which is 420' in real money.

A 3x scope is fine in most conditions with chain. In storm conditions even 5 or 7x may not be enough.

Remember chain is only there to keep the pull horizontal so a short length of heavy chain will be better than a long length of lighter stuff. Of course chain is pretty wear resistant!!!

I suppose this is why an angel is a good idea.

In South Wales especially the waters are very shallow. 100' is about the most we get. Imagine people living in places like Tenerife - 1/2 a mile out you get 14,000'.........
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Old 03 February 2008, 14:11   #11
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The answer is.....

The answer is of course.........'it all depends'!

3-5x depth, given a good length and weight of chain should do the trick in most condidtions. Obviously, the chain element of the rode is probably responsible for 50% of the anchor effectiveness. I tend to carry 20m if 'lighter' chain if going offshore, to keep weight in the boat down without sacrificing too much anchoring power.

Will also sometimes carry 2 anchors. General allrounder like bruce or danforth and a grapnel for any rocky bottoms or as a spare.

The safety element of anchoring is not to be under estimated of course. I will always encourage students to consider anchoring as a primary means of keeping themselves out of trouble in the event of engine failure, particularly in large busy harbours. As such, I would recomend keeping you anchor and rode to hand at all times in a bucket or similar, as near to helming position a s possible. If your bow line, attached to your D ring on the stem, is also lead back to the helm area, then you should be able to connect and deploy the anchor in a matter of seconds. Carbines or caribiners can also be used for a quick method of attachment, but shouldn't be relied on long term.
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Old 03 February 2008, 14:14   #12
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weight v length

Codds

The length of chain shouldn't be underestimated due to the catenary effect.
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Old 03 February 2008, 14:14   #13
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I also carry a sea anchor - anyone else carry them? I purchased on designed for 15m yachts but it's so small when rolled up it's not a problem. Have yet to use it though!!! Can also be used as a drogue.
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Old 03 February 2008, 14:15   #14
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Codds

The length of chain shouldn't be underestimated due to the catenary effect.
Yes but surely an angel at the right position will have almost the same effect?
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Old 03 February 2008, 14:24   #15
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Yes but surely an angel at the right position will have almost the same effect?
Bugger all if it's blowing a hoolie.
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Old 03 February 2008, 14:51   #16
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Catenary

Codds
I'm no architect but have a look at 'catenary' on wikipedia, particularly "anchoring of marine vessels"

BB
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Old 03 February 2008, 15:04   #17
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Returning to Jono's original observation both Start Powerboating & The RYA Powerboat Handbook advocate 6x as a recommendation to deploy in respect of mixed chain/warp.

By advocating 6x then this is an amount likley to deal with most scenarios, as a skipper if you assess all of the relevant factors and choose to deploy less then that's fine - indeed that's what I do when appropriate. To have advocated less as the default amount would have been wrong.

Regards

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Old 03 February 2008, 15:08   #18
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Codds
I'm no architect but have a look at 'catenary' on wikipedia, particularly "anchoring of marine vessels"

BB
Yes I do understand the principles.............

"the catenary curve given by the weight of the rode presents a lower angle of pull on the anchor or mooring device."

Which can also be replicated by hanging a heavy weight on the line which has the same effect of keeping the pull as horizontal as possible.
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Old 03 February 2008, 15:26   #19
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Codds,
Yup.
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Old 03 February 2008, 18:11   #20
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from the original Jono conversation, I'd be thinking of the following;

what is if you are really going to use a anchor for in the vast majority of boats folk think of when looking at level 2 etc. ; and then consider what you need maybe? :-)
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