How About a Running Start?

[thinwater]

Originally Posted by Jim Cate

OK, fair enough. I can see the possibility of soil characteristics changing after an initial set has brought the anchor into its correct orientation and perhaps buried it a bit... but that is a different proposition than just leaving it as dropped, which I think has been recommended by some.

And obviously, one can not photograph that which occurs below the surface of the sea bed!

I apologize for dragging (?) the subject away from sand!

Jim

I like thread drift!

Actually, in very soft mud, when a person just "leaves it to soak," that probably is not what actually happens. The anchor does settle in some, they did set it some when they drifted back inicially, and over the next few hours, the wind was moving the boat around. So they probably did not actually "just leave it soak." This is why the myth of "soaking" persist; they are not actually just soaking.

[thinwater]

Originally Posted by Panope

Thin,

Thanks for clarifying your intention, ie low power/no power vessels. In my original responce (post #6) I was focusing on your words "storm tension" from your opening post.

That said, I'm all for using momentum to set the anchor. The abruptness of of the set can give some good feedback about what is happening in the absence of cameras or clear water.

In sub-straits like the ones I have been testing, there really is no reason to put up with an anchor that requires ANY special technique to set. Numerous anchors exist that are simply impossible to move more than an anchor length or two NO MATTER WHAT the skipper does with the controls of the boat (excepting a high power boat).

Regarding the snatch force during my SNUBBERLESS 3.5 knot reversal tests, yes the momentary loads are immense. I'm quite surprised that the only damage incurred (so far) is one bent shank on an arguably undersized anchor (Fortress FX-16).

Steve

I didn't know there was no snubber. I'll bet there were some thumps!

I understand what you are saying. Many anchors just slam into sand. I've recorded up to 600 pounds with 2-pound anchors in good sand, and even those didn't move far (and were surprisingly difficult to recover for 2 pounds!). That really is the answer, I think, and the bumping is just for very low or no-power boats.

Forums are for discussion, after all.

[Alan Mighty]

Originally Posted by thinwater

Actually, in very soft mud, when a person just "leaves it to soak," that probably is not what actually happens. The anchor does settle in some, they did set it some when they drifted back inicially, and over the next few hours, the wind was moving the boat around. So they probably did not actually "just leave it soak." This is why the myth of "soaking" persist; they are not actually just soaking.

"Soak time" is not a myth. IIRC the notion started with expert mechanical engineers doing anchor research for the US Navy.


The notion is specific to bottoms that consolidate, meaning silt and mud bottoms. Time does not consolidate a sand bottom or a rock bottom. But mud and silt bottoms, and sandy mud, do consolidate or recover from the disturbance caused by the penetration of the anchor. What happens, as described by that research done for the US Navy, is that the column of water (i.e. water pressure) compresses the soil and squeezes out some water that has entered the soil because of disturbance by the anchor penetration.


Thinwater is likely correct that the small cyclical forces applied to the rode by wave and wind may accelerate that consolidation. But only if those forces all in the same line.


Power setting the anchor does a few things, two of which are (1) test the strength of the bottom soil; and (2) consolidate the bottom soil.


Again, power setting consolidates mud, silt, and sandy mud soils by squeezing the soil particles together and squeezing water (caused by the disturbance of the penetrating anchor) out of the soil. With a clean sand, power setting is testing the soil and maybe a tiny tiny bit of consolidating by forcing a tighter pack of the sand grains.


And of course, if you have something much bigger than a typical auxiliary engine on a sail boat, you can plough from here to wherever. Even with only an underpowered auxiliary engine, you can plough soft mud unless you allow soaking time. And some mud and silt soils need one or two days to consolidate over time.


All of that is in published research, declassified years ago, done in the 1960s and 1970s by the US Navy and confirmed by the UK royal Navy. Your search engine should be able to find it.

[valhalla360]

I believe you are overthinking this.

Setting the anchor is just about making sure it has a decent grip. If the anchor is just lying on the surface, the weight may be enough in calm conditions to keep the boat in place but as soon as the wind pipes up it may or may not set.

If you did set the anchor and if a storm comes in, it will do a deeper set for you as the wind loads apply the heavier loads. Typically the wind gradually builds over minutes or hours. Plenty of time to get a really deep set before the peak winds arrive.

[jkleins]

Originally Posted by valhalla360

I believe you are overthinking this.

Setting the anchor is just about making sure it has a decent grip. If the anchor is just lying on the surface, the weight may be enough in calm conditions to keep the boat in place but as soon as the wind pipes up it may or may not set.

If you did set the anchor and if a storm comes in, it will do a deeper set for you as the wind loads apply the heavier loads. Typically the wind gradually builds over minutes or hours. Plenty of time to get a really deep set before the peak winds arrive.

I was thinking the same thing. Setting the anchor under power is really just providing peace of mind to the boater that the boat will not drag on a bigger blow. If the anchor is going to set anyway a bigger blow will be the perfect force to do just that so that setting under power is not necessary.
It seems that if you cannot generate the force necessary to simulate a big wind that you really have no other option then to just trust the other parts of your technique (dropping the anchor correctly, proper scope, anchor selection, etc) and then allow the wind to do it's thing.
The question I would have in this scenario is what would you do if the anchor did move a bit as you "jerked" up but then stopped. Would you pull up and try again in another place?

Jim

[darylat8750]

Originally Posted by valhalla360

I believe you are overthinking this.

Setting the anchor is just about making sure it has a decent grip. If the anchor is just lying on the surface, the weight may be enough in calm conditions to keep the boat in place but as soon as the wind pipes up it may or may not set.

If you did set the anchor and if a storm comes in, it will do a deeper set for you as the wind loads apply the heavier loads. Typically the wind gradually builds over minutes or hours. Plenty of time to get a really deep set before the peak winds arrive.

I prefer to make sure I have a solid set because of the possibility that the wind direction may change before it increases. I prefer to increase the odds that it will "shuffle" to the new direction of pull rather than break out and reset. I have a trawler that has enough power to set with the engines.

[barnakiel]

On our boat this only works fine for a lunch.

The challenge here is the boat will back fast while head on to the wind but the wind will push the bow away and at this point our drift rate is maybe half a know at best. Not enough to set the hook.

So it would be to drop it running downwind under a small jib perhaps.

b.

[thinwater]

Originally Posted by Alan Mighty

"Soak time" is not a myth. IIRC the notion started with expert mechanical engineers doing anchor research for the US Navy.


The notion is specific to bottoms that consolidate, meaning silt and mud bottoms. Time does not consolidate a sand bottom or a rock bottom. But mud and silt bottoms, and sandy mud, do consolidate or recover from the disturbance caused by the penetration of the anchor. What happens, as described by that research done for the US Navy, is that the column of water (i.e. water pressure) compresses the soil and squeezes out some water that has entered the soil because of disturbance by the anchor penetration.


Thinwater is likely correct that the small cyclical forces applied to the rode by wave and wind may accelerate that consolidation. But only if those forces all in the same line.


Power setting the anchor does a few things, two of which are (1) test the strength of the bottom soil; and (2) consolidate the bottom soil.


Again, power setting consolidates mud, silt, and sandy mud soils by squeezing the soil particles together and squeezing water (caused by the disturbance of the penetrating anchor) out of the soil. With a clean sand, power setting is testing the soil and maybe a tiny tiny bit of consolidating by forcing a tighter pack of the sand grains.


And of course, if you have something much bigger than a typical auxiliary engine on a sail boat, you can plough from here to wherever. Even with only an underpowered auxiliary engine, you can plough soft mud unless you allow soaking time. And some mud and silt soils need one or two days to consolidate over time.


All of that is in published research, declassified years ago, done in the 1960s and 1970s by the US Navy and confirmed by the UK royal Navy. Your search engine should be able to find it.

You miss read what I posted. Pure soak time, with NO INITIAL SET is a myth. However, all of the my testing and the Navy testing are after an initial set. The anchor must be dug in a little bit or there is nothing to consolidate (it is sitting on top of the mud). Perhaps this is so obvious you glanced past it.

[thinwater]

Originally Posted by valhalla360

I believe you are overthinking this.

Setting the anchor is just about making sure it has a decent grip. If the anchor is just lying on the surface, the weight may be enough in calm conditions to keep the boat in place but as soon as the wind pipes up it may or may not set.

If you did set the anchor and if a storm comes in, it will do a deeper set for you as the wind loads apply the heavier loads. Typically the wind gradually builds over minutes or hours. Plenty of time to get a really deep set before the peak winds arrive.

I'm guessing you are not in a thunderstorm area. From zero to gust front here is typically about 1 minute.

In soft mud, we have (and the Navy and oil platform people have) established that consolidation in soft mud takes many hours. A few minutes is not effective, as much testing is soft mud has shown. You may drag, even with a large anchor, since it will not dig in pudding. Strange to your thinking, but true and provable.

[thinwater]

Originally Posted by barnakiel

On our boat this only works fine for a lunch.

The challenge here is the boat will back fast while head on to the wind but the wind will push the bow away and at this point our drift rate is maybe half a know at best. Not enough to set the hook.

So it would be to drop it running downwind under a small jib perhaps.

b.

With an engineless boat, downwind sets have been the norm for centuries. The sail was typically luffing, but you needed it in case the anchor did not grab.

----

Using the engine to power-set is probably one of the best reasons to have an engine. I just thought this would make an interesting discussion. My books suggest a bump-set, but they never offer enough explanation or detail to make sense of the merits. To me it is obvious you need to regulate the impact force to keep it within the setting range (vs. the tear-out-and-start-over range).

[groundtackle]

https://www.youtube.com/watch?v=asLkFlDxvVM

This high speed snatch testing video of various anchors is interesting and relevant to this discussion.
Nick

[Hydra]

Originally Posted by groundtackle

This high speed snatch testing video of various anchors is interesting and relevant to this discussion.
Nick

I'm not so sure that a test in unsaturated, almost dry, sand is relevant to the setting ability of anchors in mud.

Alain