Anchors Aweigh

[Cheechako]

I would always have two anchors avail at the bow. #2 doesnt need to necessarily be in the bow roller, but a Fortress or something on the bulwark or pulpit ready to deploy can save your boat. It did mine in a 70mph+ blow at 6am one morning. An anchor that had been down 10 days pulled right out of the bottom with the bottom clay/sand mix still attached to the anchor! The motor wide open would not quite stop the boat from moving. With the stern in the surf nearing shore I literally threw the pre ready Fortress over the pulpit, snugged it up and it held! It was a 20 minute micro cell, but pretty deadly.

[Ancora Latina]

[quote=skipmac;255476]Well I don't think it is quite that simple. It is really a combination of many factors including weight.....quote]

I believe Anchor and anchoring is perhaps the nautical area where « perceived wisdom » is the most common...

Let’s talk again about HOLDING:

As long as the anchor is deeply buried, holding is related to:
- The cohesion of the sea bottom
- The angle of pull
- The shape of the anchor blade ("scoop" the best)
- The surface area of the anchor blade

Parameters which have no or minor influence on the HOLDING:

- Weight of the anchor (but tip weight has a close relation with the anchor penetration)
- Weight of the rode (at least with strong winds< 25 knots)
- Catenary (nearly inexistent with strong winds< 25 knots)
- type of rode (as long as you have the same pulling angle)


With some « new gen » anchor, you can have a much bigger anchor (+ 25% than the « best » one) for less weight!

João

[Cheechako]

It is amazing how much catenary stays in the chain in fairly strong winds though, really surprising. I had about 125 ft of chain out in a 35knot blow in the Tobago Cays once. I was anchored in shallow, maybe 12 ft of water. The water was pretty flat, very little chop due to no scope in front of me. I snorkeled forward to check the anchor. It was buried so well I had trouble finding it and 15-20 ft of chain in front of it never came up out of the sand either...... This makes me believe the 10 pound ball on the rode might work, especially for keeping the angle of the rode low.....

[Ancora Latina]

Originally Posted by Cheechako

I would always have two anchors avail at the bow.

Sorry, but again a different opinion,

Although I have a very large (long) experience of anchoring, I NEVER had two anchors on the bow... it’s the worse location to have weight...

On the bow roller, you should always (except for long passage) have a VERY GOOD anchor always ready to be launched...

Yes, I also had a second anchor ready to be launched, and Noelex 77 would agree (?), in place like the MED, an anchor stored on the stern of the boat is very useful. In case of emergency, it’s very easy to move the rode to the front of the boat (or to anchor from the stern) and the weight is much better located.

I had also a “misericord” anchor dismounted into the bilge...

João

[Ancora Latina]

[quote=Cheechako;255502]It is amazing how much catenary stays in the chain in fairly strong winds though, really surprising. I had about 125 ft of chain out in a 35knot blow I was anchored in shallow, maybe 12 ft of water.[/quote]

This means a scope of more than 10/1.. for 35 knots of wind (at least with a good anchor) a 5/1 scope is far enough!..

Yes, you can use 250 ft of chain to prove that catenary works well! or use a 18 mm chain (for a 25' boat) - then I have to agree with you, catenary works!..

João

[boatpoker]

I disagree with a lot of what has been said here and with over 1500 nights at anchor and over 25,000 underway hrs. logged I think I speak with some experience.

I have several pages with diagrams and photographs on this topic in my article "Primer For First Timers Heading South". I am fairly new on this list and don't know if a link is kosher so it may be stripped out but here it is.
http://www.pcmarinesurveys.com/Prime...t%20Timers.pdf

[noelex 77]

Originally Posted by Ancora Latina

Yes, I also had a second anchor ready to be launched, and Noelex 77 would agree (?), in place like the MED, an anchor stored on the stern of the boat is very useful. In case of emergency, it’s very easy to move the rode to the front of the boat (or to anchor from the stern) and the weight is much better located.

Yes a stern anchor is very desirable especially in the Med. I keep an aluminium Fortress at the stern ready to go. It can be used as a stern anchor, or put easily into the tender. The rode can also be used without the anchor as a stern line to secure to rocks or a tree.
Its other use has been to loan to other boats that have been dragging or to kedge them off when they have run aground.

[bene505]

Originally Posted by Cheechako

It is amazing how much catenary stays in the chain in fairly strong winds though, really surprising. I had about 125 ft of chain out in a 35knot blow in the Tobago Cays once. I was anchored in shallow, maybe 12 ft of water. The water was pretty flat, very little chop due to no scope in front of me. I snorkeled forward to check the anchor. It was buried so well I had trouble finding it and 15-20 ft of chain in front of it never came up out of the sand either...... This makes me believe the 10 pound ball on the rode might work, especially for keeping the angle of the rode low.....

I think you just proved the case for putting the 10 pounds into a longer chain instead of using a sentinel. That's exactly what others are saying, that the 10 pounds of chain will give you better scope, which means better holding.

I don't see anyone talking about shock loads. IMHO, if you've already exhausted all your chain and rode, putting a sentinel down the line a ways will help with shock loads. I seem to remember the sentinel being placed half way down the line, if possible. Near the bottom only helps a little with shock loading. That said, I'll defer to other who have more real-world experience with sentinels.

Something else: I seem to remember reading somewhere that the greatest pull on an anchor is when the boat is at the peak of a wave (shock loading). Being at the top of the wave means your scope ratio is decreased (distance to the bottom just increased). Something to think about, you rarely hear about adding wave height (or at least amplitude, or half the height of the face) to the height above the bottom. Again, an opinion.

[Ancora Latina]

[quote=bene505;255527]I don't see anyone talking about shock loads. IMHO, if you've already exhausted all your chain and rode, putting a sentinel down the line a ways will help with shock loads..[/quote]


Well, this is another different question!

Shock loads are the worse, as they can break your anchor free... or even break your cleats or Samson post or also the chain...

No, in this case, again with strong winds, a kellet is not efficient – you have two possibilities:
1° to use a mixed chain/rope rode
2° If you have an all chain rode, to use a looonnngg snubber.

I will suggest you to have a look at the following web page:
Tuning an Anchor Rode

João

[mangomuffins]

Someone on the forum posted a study he had conducted about catenary effect and anchoring scope. I can't remember the poster, but I believe that his conclusion was that to truly take advantage of the effect, one should deploy 100' of rode + the water depth... and that was for chain!!! Perhaps someone knows about this posting???

cheers,

mm

[bene505]

Ancora,

Love it. I got a little lot in this. (And I'm an EE!) Granted, I'm not in a quite place right now.

Is there a specific graph that we should be looking at?

Regards


[quote=Ancora Latina;255534]

Originally Posted by bene505

I don't see anyone talking about shock loads. IMHO, if you've already exhausted all your chain and rode, putting a sentinel down the line a ways will help with shock loads..[/quote]


Well, this is another different question!

Shock loads are the worse, as they can break your anchor free... or even break your cleats or Samson post or also the chain...

No, in this case, again with strong winds, a kellet is not efficient – you have two possibilities:
1° to use a mixed chain/rope rode
2° If you have an all chain rode, to use a looonnngg snubber.

I will suggest you to have a look at the following web page:
Tuning an Anchor Rode

João

[Bash]

...I feel comfortable with two anchors with the Rocna/Fortress combination I currently carry, but I felt the need to carry three anchors back in my Bruce/Delta/Danforth days because I didn't have full confidence in any of those anchors in certain conditions.

I should add that even though I only carry two anchors these days I still carry three rodes.

[roverhi]

A 45# CQR would be a good primary anchor for a 20,000# boat and a secondary/lunch hook for a 30,000# boat. So yes, your anchor is too small for serious anchoring. If you are just wandering up and down the coast with no intention of hanging on the hook in bad weather, it's adequate. If you want insurance just in case you get caught in less than ideal conditions,

[roverhi]

Get the the next size up, at least. We had a 45# CQR, 220' of 3/8" chain, (20,000 pound boat) and used that anchor exclusively including a tropical depression that just didn't quite make official hurricane strength.

We also carried a 35# CQR, a 50# yachtsman, and a 20H danforth. Used the Danforth very occasionally for a stern anchor but the rest just sat in the bilge. Not to say that I regretted having them but that I just didn't get around to using them. Should have used the 35# CQR in tandem with the 45 pounder for the tropical depression but it didn't occur to me till it was too late to deploy it. Fortunately, the 45pounder held in the relatively shallow soft mud without a problem.

If all the hype is correct, I'd get one of the newer inverted plow anchors the next size up from 45#s. I haven't had any personal experience, other than playing with a model, but people that have used them claim they work well. Played with models of most of the current types of anchors in sand. The Spade look a like set quicker and held better than all the other types. This was not a scientific test. The mesurement of resistance was simply how it felt to me and the bottom was beach sand, way more coarse to these small scale models than a typical bottom to a real anchor. Still the Spade look alike dug in way more quickly.

Aloha
Peter O.
Pearson 35

[bene505]

Originally Posted by bene505

Ancora,

Love it. I got a little lot in this. (And I'm an EE!) Granted, I'm not in a quite place right now.

Is there a specific graph that we should be looking at?

Regards

Edit: I got a little lost in this. (Not "lot")