Bent Anchor

[Chris_Robb]

I managed to bend the shank of a 35lb Danforth anchor (my kedge) last week end. It was stuck, so we motored gently ahead on tickover, The anchor freed - but came up with the shank bent at 45degrees.

I was slighltly shocked that it had bent so easily. Would you have it straightened or would you buy a different type - Bruce spade etc

PBO are running a thing on anchors - I'm not sure that the tests they are doing are representative of real life.

Any suggestions on type - remebering it is my kedge anchor on chain and nylon and has needs to be stowed below?

 

[incognito]

Danforth DO bend relatively easily - thickness is the thing. If you want to avoid any bending at all, it has to be a thick anchor, plough types like Bruce, CQR, SPADE. Bent anchors are better than broken anchors, I might add!
The PBO articles are interesting, and the results fly in the face of the rather authoritative book which I bought last year, it is a modern book, June 2001, and uses real anchoring with tugs to pull/drag/roll the anchors.

I think that Prof Knox's conclusion that SPADE is the best of the plough anchors is probably correct, but he hasn't shaken my faith in my 45lb CQR. I have a 15kg Bruce as kedge or extra storm anchor. (My boat is 7.5tonnes).

The Complete Book of Anchoring and Mooring
~Earl R. Hinz
Cornell Maritime Press

 

[Chris_Robb]

Thanks for that - I was leaning towards getting a Bruce, - what weight would you go for on a 40 ft 13 ton boat?

 

[incognito]

I couldn't answer that off the top of my head - the book is on my boat, so I can't refer. The PBO article gives a number of (for me confusing) formulae for calculating, but Hinz' book uses length, beam and, I think, underwater configuration, if I remember rightly. My boat is a long-keeler, and her underwater shape means she 'sails' on ANY current, in a way that deepfin boats don't. Often, anchored, she will ride UPSTREAM of the anchor, tho she has never gone so far upstream as to trip the CQR or the Bruce. Of course, she doesn't sail upstream if there is a real hooley blowing.

If I were you, and cost didn't come into it, I would buy a SPADE, then a Bruce if money did matter.

The Bruce was designed for oil rigs and doesn't itself need a chain scope, as the oilrig rodes come off more directly. I use a 5m starter of chain with the Bruce, and then rope.

 

[Twister_Ken]

Plea to PBO

As Incognito says, the worthy Prof with his anchors in six inches of water on the shores of the Firth of Wotsit seems to have got results which fly in the face of quite a lot of empirical evidence and received wisdom about anchor types. Howsabout either a right of reply from anchor manufacturers who presumably do their own research on these matters, or an opposing p-o-v from some other authority?

 

[Chris_Robb]

we are very much like you with a long keel. as spades are I believe French in origin, I'll probably try and get one when we are there in August - with the crowds!

 

[Chris_Robb]

Re: Plea to PBO

Having seen how they were testing the anchors, I am afraid I didn't bother to read the rest of the article. Strikes me that the tests have been done in the cheapest possible way and have absolutely no relation to realtity.

 

[incognito]

Re: Plea to PBO

Actually, although I have my doubts about the conclusions drawn from the results, I can see what he is trying to acheive.

Tests at sea, in 'real' environments, are very difficult to reproduce in a like-for-like way. By taking the anchors to a sandy beach, with pulley systems and load-cell measurements, he hopes to give us info which is repeatable and fair in like for like way.

I can therefore take his results on board, and add them to my store of accumulated wisdom (who said cobwebs!!) to use as a pinch of salt perhaps.

The Hinz book uses real tests in the sea, but I even have some doubts about those tests, simply on repeatability. Under the real circumstances, where anchor A and B give such and such result, it is possible that the same results might have been obtained with anchor A and A.

In other words, Prof Knox has done a lot of work and you should read it and decide what conclusions YOU would draw, rather than accept his conclusions.

 

[Twister_Ken]

Re: Plea to PBO

It does strike me that 'repeatability' would be the spanner in the ointment of real life tests.

As a lad I used to dig for bait on the foreshore at Eastbourne, and the difference in consistency of the sand almost from one pace to the next was considerable. To try and ensure that the anchor was placed in a bottom of exactly the same consistency each time would probably require it to be placed by a diver with some form of resistance measuring apparatus.

I also wonder with the Prof's tests what effect the shallowness of the sea had. The weight of pressure of 5 or 10 metres of water might make a difference (or it might not matter because the sea bed is also subject to the same pressure.) Having kedged in mid channel (no wind during a RORC race) at depths that required every spare bit of string to be added to the anchor warp I do remember that a lightish kedge (danforth-type) on a shortish scope held a heavy boat very well despite a considerable tide (but no wind). Could that have been because 60 metres of water were pressing the anchor into the bottom?

 

[Chris_Robb]

Re: Plea to PBO

I think the main missing ingrediant is the upwards pull. Some anchors may be more resistant than other to this. I know that the weight of chain etc should acheive a straight pull, but in extremes this will be a straight 30 degree pull.

Interesting to see which ones dig in the quickest, as I find the CQR sometimes can be difficult in hard sand.

 

[incognito]

Re: Plea to PBO

This is difficult to explain, but because the bottom is on the bottom and the anchor is on the bottom, there is no weight of water pressing the anchor into the bottom. On the contrary, the anchor 'weighs' more OUT of the water sitting on the sand, than in the water sitting on the sand - air being of lower specific gravity than water.

These are fairly marginal points however. The sort of problem I have with the tests Prof Knox has done is that he has eliminated too many unknowns. For example, when I am setting my anchor, the rode is surging, putting cycles of tension into the rode, making the angle the stock makes to the bottom vary - this will have a LARGE effect on the setting of the anchor - sort of like someone having hold of the stock and waggling it. Similarly, the anti-roll property would be muchly affected by these dynamic effects missing from his tests.

That is why I take his tests in mind, but reject his conclusions.

 

[NigelW]

I have a 45lb Danforth, which we bent in the cloying Suffolk mud whilst raising sail, rather than motor off the anchor. I was alos surprised when it came up and the sgaft was at 30 degrees.

As you will have found, it is then useless. I had it straightened and painted it with Hammerite. It is still fine, but I take more care now.

The anchor is on 60m of chain and a further 60m of rode, which may be a bit excessive. I also carry a Bruce as a kedge, which has dragged in sand with wind and tide against!

Nigel

 

[incognito]

Re: Plea to PBO

Just as a follow through, for a nicely biassed offering on the SPADE anchor...
http://www.spade-anchor.com/US/KnowMore.html

I have never dragged on my Bruce, once set in sand or mud. Getting him out is another story!! That can be a REAL joy, since it is designed to let the rode come off at quite a high angle of incidence.

 

[incognito]

Another anchor, which came out the best all rounder, in Hinz' book, is the Fortress. This is a pricey anchor, of the Danforth type, but the thing is amazingly constructed. They are both light and fiendish strong. For your boat, you would use a bigger anchor than they recommend - FX37, I guess. They are pricey, but the reputation is very high.

See http://www.pyacht.net/cgi-local/Sof...ide.htm?L+scstore+njwf5410ff37c537+1027499132 for a starter.

 

[Chris_Robb]

Nigel - getting it starightened - does that mean the Galvanising will be ruined?

 

[Guest]

The anchor is less important than the chain!! The job of the anchor is to hold the end of the chain, the job of the chain is to hold the boat. Chain serves no purpose in the chain locker so I like to get it down on the bottom where it will do some good, and forget the rules about 4 times the depth of water. Generally I do not sleep well with less than 30 meters of chain out in depths up to 6 meters, 40 for depths above that and 50 if the wind gets up. I always buoy the anchor and find that the boat lies close to the buoy with the chain in a loop , which rather proves that it is the chain which is holding the boat.
There have been several reports of bent Danforth type anchors, especially those lightweight Aluminium ones that are supposed to be so strong. Also reports of their getting jammed with stones. Anchors with no moving parts and short shanks seem imune to these problems, I have great faith in my Bruce , having just spent over six months anchoring in various locations, including fast flowing rivers.

 

[philmarks]

Re: Plea to PBO

I think I'll go for a spade when I refit. As it happens, last night I was thumbing through Heavy Weather Sailing and the Channel Storm of 1956 when all that saved Lutine from going ashore at Selsey was a broken anchor (she had already been abandoned). Sobering stuff.

 

[Guest]

Re: Plea to PBO

Ah, A fellow past bait digger that has also noticed that sand even a few feet away can be different in texture!

 

[Twister_Ken]

Re: Plea to PBO

>This is difficult to explain, but because the bottom is on the bottom and the anchor is on the bottom, there is no weight of water pressing the anchor into the bottom. On the contrary, the anchor 'weighs' more OUT of the water sitting on the sand, than in the water sitting on the sand - air being of lower specific gravity than water.<

Incog - I know you're probably right. I just have this vision of a 60 metre high pile of sea-water filled buckets helping press my anchor into the ground.

 

[johnsomerhausen]

In January 2001, "Practical Sailor" (an American "Which"-like magazine for sailboat owneers) published the results of an "Anchor reset test" in which they compared the holding power of 18 different types of anchors (some of them only only known in the USA, like the Bulwaga, the Barnacle or the SuperMax) in sand and mud. The tests were done in shallow water (to better observe the anchors) and a pull was first applied by one cable and than by another at an angle of 140 to 150 degrees from the original pull. The test was made in the two bottoms and the loads combined for the average holding power. The 16 lbs Spade came first with 830 lbs, The 35 lbs CQR was third with 760 lbs. The 22 lbs Delta came fifth with 553 Lbs. The 20 lbs Danforth Deepset came in sixth at 502 lbs. The 10 lbs Fortress FX16 came eighth at 446 lbs and finally the Bruce and Claw (the SL version) of 22 lbs each werre tenth and twelfth at 429 and 401 lbs respectively.
Don't ask me about the different weights of anchors tested; PS didn't say how they were chosen. The just say they were surprised by the poor results of the Bruce which had performed near the top in simple pull testsin sand and mud
john