Anchoring and Wind Strength?

I think all boats yaw around in a breeze with a single anchor. My boat has relatively low freeboard, but she yaws truly. I tried a dinghy sail up the back-stay, and it reduces yawing, but not completely. Worse than yawing though is when you are anchored in a tidal situation, and the boat insists on sailing over the anchor and, of course, causing the anchor chain to graunch into the bow sections. Anyone got a solution to that? /forums/images/graemlins/mad.gif
 
Regarding yawing, there are some boats that sit happy at anchor without yawing, I know 'cos I've watched them in anchorages when we've been dancing all over the place. Certainly most AWBs are more prone to dancing than old girls like a R38 and we probably dance less than some but not as quietly as say some of long keeled jobbies.

Regarding wide over tide have you tried using a snubber, about 5m of rope from the stem, attach to chain via a chain hook, then release about another 1/2 metre of chain. The boat is then holding on the rope, we use 18mm multplait, and whilst this doesn't stop the boat riding over the rode it does stop the noise and the graunching.
 
[quoteI think you've answered your own question, other than the obvious imperative that the anchor should be set regardless.

As you have found, the forces do not have to be high for the anchor to be given all the work.

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Yes ..... as I said above, I shouldnt have posed it as a question, it was actually an observation.

BTW - I enjoyed the articles you referred to on the mobo thread "Havent Got a Clue"
 
Two anchors on two separate rodes, set between 45 and 90 degrees apart. I set the first in the normal way and usually take the second out in the dinghy.
I've never used tandem anchors (the crown of one connected to the other by a length of chain) in anger - it has never appealed to me. It doesn't provide redundancy, my anchors have sufficient holding power anyway and it is a potential complication when retrieving. Others may be comfortable with it and, if it provides confidence and pacific slumber, that's a good thing.
I find two anchors, set as I've described on all chain, virtually un-draggable - provided the anchors are properly set.
Regarding yawing: On a single anchor using nylon rode you get a condition in heavy winds which I call 'bungy-jumping'; the boat appears to be leaping from one side to the other almost as though the elasticity of the rode is letting the boat stretch off in one direction and then yanking it back to the centre before letting it leap off in the other direction. It can get quite dramatic and the motion on the boat must be awful!
 
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Anyone got a solution to that?

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Yes! Rig a pole so that it sticks out over the bow a few feet. Arrange an extra line from the buoy via a block at the pole end and lead it back on board and belay it to a cleat [I think this is called a "bull rope"] . Adjust things so that if the boat is driven towards the buoy the bull rope becomes taut and stops the boat reaching the buoy but, when the tide or wind changes and the boat is tending away from the buoy, the main mooring rope takes the strain.

There's a photo in "Cruising Under Sail" by Eric Hiscock.
 
Mmm, I would have thought my boat and yours would behave pretty similarly (I have always admired the Rival 38). And, yes, I do exactly as you say, as sailing over the anchor chain or buoy seems a characteristic of long-keelers in the tide.

/forums/images/graemlins/ooo.gif
 
I found the reference in Hiscock p183, but couldn't find the photo you referred to, what page was that on?

<span style="color:red">I was referring to the worst-case which is an anchor, this solution relates specifically to buoys</span>

I think this is a duff idea. The forces involved when a long-keeler sails over her mooring are pretty considerable (you should know with a Twister), especially if there is any chop as well - and I cant think of how I would 'rig a pole' as you describe in a secure fashion. Hiscock is describing a situation where one has a proper bowsprit, designed to take the force. /forums/images/graemlins/smile.gif
 
Thr photo I referred to is on page 189 of my edition and you are right in pointing out that it refers to mooring to a buoy and not an anchor. I aplogise for mis-reading your question.

However, having tried the method several times I find it works very well. The worst case being during an Easterly gale in L'Abervrac'h when the wind was against the tide and driving the boat over flood tide and onto the buoy. Not having a bowsprit I simply used a spinnaker pole lashed to the stemhead and the sampson post. Nothing was under any great stress at all, in fact the main concern was keeping the rain from driving in around the companionway doors! It certainly saves being woken up by the buoy knocking on the hull! /forums/images/graemlins/grin.gif

The forces inolved when a boat is in a wind against tide situation are not as great as in a wind with tide situation; one force is counteracting the other. If the wind becomes stronger than the tide then the boat will turn round and become wind-rode, as happens when the tide slacks. The boat responds to the strongest force acting upon it. When ships had rope cables, they had permanent servings at different points on the cable for weather or lee tides. With a weather tide they would shorten in the cable and pay it out to the lee service when the wind was with the tide.
 
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I tend to use 4:1 quite successfully, increasing to 5:1 or 6:1 if I get a bit nervous. maximum wind to date, (at anchor), has been about 17kts with 1.5m wave/swell, so not really a big deal, but big enough to cause other boats to drag - I'm not certain it was a problem with their anchors, more the inclination of many skippers to drop the hook and chain and think that's all you have to do.


[/ QUOTE ] A suggestion here. Do a test to find your anchor's critical scope (they're all a bit different from each other)

Method: anchor, and let out 8 times the depth (enough for all anchors I've ever used). Lock the rode (to take the stress off the winch drum) and gently increase your astern revs until (say) full astern. Your anchor should hold: this is like the hard jerks at each end of a yaw in a 35kt wind. You'll note that there is no discernable bend in the rode, even if it's all chain.

Next, shorten your rode to (say) scope 6. Try again. Then 5, try again. Then 4, try again. Then 3 . . . at some scope the the thing's going to jump out.

Now re-anchor completely, using one more scope than the one at which it dragged. Set the anchor, lock the rode, and gently increase to full reverse . . . if it jumps out (which it shouldn't, but first time round you may have dug the thing in so deep that you got a better result than you should have) . . .

re- anchor again with yet another one on the scope . . .and test again.

This way you'll establish, for certain, the critical scope for that anchor. Never again will you have to allow for the vagaries of other people's opinions and their unstated assumptions. You'll know. Guesses are no longer needed.

Do the same thing with lower revs if you wish for a fuller picture. And try it with different bottoms too. With ploughs I found no discernable difference between bottoms. With Britanys I found that once set in hard sand, they stuck hard til 4:1, while in mud they pulled at 6:1.

Learn to test - then test to learn.
 
Ooh. Not sure I've ever used 6:1 even in quite windy anchorages.

I did find that if you are too quick to reverse, then the anchor doesn't bite so well. My procedure was to let the boat settle back under tide/wind first, then engage reverse at tickover leaving it for a bit and then half throttle to make sure it had dug in. Th 25kg delta is supposedly rated for boats up to 56ft, so should be up to the job.

Glad to hear she it getting well used already /forums/images/graemlins/smirk.gif
 
You'll have to ask SPGE, as he bought my M44 from me /forums/images/graemlins/smile.gif

New boat is likely to have a Rocna.
 
It would be good to have some real life experiences and opinions of Rocna anchors in particular, but also Spades and other new generation kit.

e.g.

when you drop a Rocna, does it bite immediately, to the extent that care needs to be taken that the crew dont fall over with the jerk, or that damage isnt done to the stem head and windlass, and to the extent that you dont have to allow a few hards for dragging whilst it gets a grip.

or

does it grip quickly in weed, where a previous anchor would have no chance

is it solid as a rock in 20, 30, 40, 50 knot winds

and so on.

I get the feeling that some Rocna users here may be afraid of telling their story for fear of being flamed by those that give Craig a hard time
 
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and to the extent that you dont have to allow a few hards for dragging whilst it gets a grip.

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That should, of course, read "yards", not "hards"
 
Richard you'll find more opinions on other forums - in my experience people here are particularly conservative and tradition-minded.

For example (SailNet in the US).
Perhaps not your same cruising ground but I admit we have little penetration in the Med.

One can find comparable bottoms though.

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when you drop a Rocna, does it bite immediately, to the extent that care needs to be taken that the crew dont fall over with the jerk, or that damage isnt done to the stem head and windlass

[/ QUOTE ]Don't set it hard while on your windlass or you could damage something.

From a local Marauder association member: "I of course like every first time user, read the anchoring instructions on the manufacturers' website, www.rocna.co.nz, and noted that they recommend to slowly reverse to bed the anchor and that the anchor grips faster than other types. Yeah right! First anchorage was Izzy Bay, Rangitoto Island – Pauline did her usual reverse circle at modest speed and I nearly shot over the pulpit as the anchor set so quickly in the mud. Wow! I'm sure my arms are a little longer. Over the course of that weekend we anchored in several bays with the same first-drop setting, in the end virtually nil reverse – just let the wind blow you back."

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does it grip quickly in weed, where a previous anchor would have no chance

is it solid as a rock in 20, 30, 40, 50 knot winds

and so on.

[/ QUOTE ]Sand bottoms, grass and weed:
Scottish west coast / Hebrides
... and this

Or a recent customer's entry on his blog yesterday. Did someone mention 50 knots? (Location: Mexico - very comparable to the Med).

Craig,
FYI - Excerpt from our log

Aug 13, 2007 - Santa Rosalia - Last night we had our first Chubasco. It was quite a little storm. The winds were around 35 knots with gust as high as 50 knots. Also, had a bit of rain with it at times. Obviously, we made it through OK. I am happy to report that the new Rocna anchor held with a seriously tenacious grip on the bottom. We were on a very short scope of only about 50 feet of chain in approx. 15-18 feet of water. This not a good recipe for anchor scope in these conditions. Unfortunately, we could not let out more scope due to the fact that as the wind changed directions, we had Momo, right on our stern. Anyway, we didn't move an inch, even with all the boat weight on the anchor.

All that led to some serious pulling to get the anchor off the bottom a couple days later...;-)

Jamie Eileen Adrian
Flying Cloud
www.flying-cloud.org

(More down the bottom):
We had a huge weather system come through today with 3' swells in the harbor and gusts to 50kts. We are getting used to taking down covers in a hurry and then relaxing because the AWESOME ROCNA ANCHOR holds in all weather and bottom conditions!

Sorry I know that seems a bit over-the-top to us non-Americans but hey I didn't write it.

And so on.
 
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It would be good to have some real life experiences and opinions

[/ QUOTE ] Opinions, we get a lot of. I'm proposing tests to establish one fact, relevant to any anchor, any boat. That is, find out how much scope is needed for that anchor, rather than relying on opinions.

I take your point about quick setting - but I cannot think of an objective test to establish that! Apart from noting a torsional fracture of the winch spindle!

Distance to set can be noted if you dive . . . but that may vary according to scope so you'd have to be careful there . . .

Solid as a rock? Well, that's determined by the full astern test, as long as you've taken steps to minimise the jerks (long snubber, forked moor, steadying sail)

And if the tide is going to turn, by making a fore and aft moor (bahamian)
 
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I get the feeling that some Rocna users here may be afraid of telling their story for fear of being flamed by those that give Craig a hard time

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I have changed to a Rocna from a CQR and so far it has well lived up to expectations. I have not tested its ultimate holding ability, but when comparing its digging in ability then it is streets ahead.
 
Jim - I'm not fully persuaded by the concept that an anchor has an ideal scope. In my experience (and we anchor whenever we can in preference to using marinas) the scope needed is far more related to wind strength and the windage of the boat.

3:1 in a flat calm will do nicely for lunch

4:1 will do the night in a F3-4

5:1 or 6:1 needed in a F5 or where there's variable direction wind

I understand your point about being able to break it out under power but you'll break any anchor out given enough power. All you do is surely to establish points on a graph which show the more scope you have out, the more horsepower you need to shift it.

Simon
 
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