Anchoring

Jono Garton · 03 February 2008, 15:41

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.

Cheers

Jono (very much a 4 x fan) Garton

Nos4r2 · 03 February 2008, 15:54

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.

SeaSkills · 03 February 2008, 16:42

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.

Jono Garton · 03 February 2008, 16:59

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

Cypman · 03 February 2008, 17:33

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)

Poly · 03 February 2008, 17:35

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.

yoyo · 03 February 2008, 17:48

Quote:

Originally Posted by Polwart

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.

Poly · 03 February 2008, 17:55

Quote:

Originally Posted by yoyo

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.

BogMonster · 03 February 2008, 18:56

Quote:

Originally Posted by Jono Garton

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

codprawn · 03 February 2008, 18:59

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'.........

BassBoy · 03 February 2008, 19:11

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.

BassBoy · 03 February 2008, 19:14

Codds

The length of chain shouldn't be underestimated due to the catenary effect.

codprawn · 03 February 2008, 19:14

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.

codprawn · 03 February 2008, 19:15

Quote:

Originally Posted by BassBoy

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?

jwalker · 03 February 2008, 19:24

Quote:

Originally Posted by codprawn

Yes but surely an angel at the right position will have almost the same effect?

Bugger all if it's blowing a hoolie.

BassBoy · 03 February 2008, 19:51

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

BB

Paul Glatzel · 03 February 2008, 20:04

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

Paul

codprawn · 03 February 2008, 20:08

Quote:

Originally Posted by BassBoy

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.

BassBoy · 03 February 2008, 20:26

Codds,
Yup.
BB

eilean mor · 03 February 2008, 23:11

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? :-)