Private moorings in public places

[Maine Sail]

Maine Sail;

1. That is a very nice woodworking bench!
2. The entire point of lengthening chain rode scope is to induce catenary so as the "wind pipes up" the actual angle of the anchor shank remains zero. What is that 100:1?

If you believe you still have adequate caternary to keep your shank flat to the bottom in storm conditions then I certainly would not want to be anchor down wind of you in a storm. We have had our all chain rode drawn near bar tight on 4 occasions, all with minimal fetch.

Here's a photo taken by Peter Smith the designer of the Rocna anchor which beautifully illustrates how caternary is lost when the wind pipes up.

Peter has written some great stuff on caternary: Caternary Article (LINK)

1. Chain rodes achieve zero angle because of weight. Putting more/bigger chain out assures that consistent outcome.

Yes in benign to moderate conditions the shank of even mixed rodes lies flat. Sadly this only happens until you really need it and then your effective caternary can all but vanish.

I took this photo of a mooring in 38-42 knots. This was approx a 3:1 mooring, at that tide, with very heavy 3/4" bottom chain and 5/8" top chain. The chain was being drawn near bar tight. I watched it do this for over a half hour and the snatching loads were tremendous.

1. Never-the-less it's about the anchor and the bottom. Down our way, a good plow anchor doesn't care if it is has a 3:1 or 7:1 in a mud bottom. They hold all the same.

1. 
   
   So go anchor in 50-60 knots on 3:1 and let us know how that works..
   

I was looking at your evaluation of the claim made by the guy who said he held on his chain alone. That is some good, totally scientific stuff! Here's the thing - I think he actually had a 140 lb chain anchor by your calcs (52' of 1/2" BBB @2.7 lbs/ft) plus 190 lbs of chain on the bottom (70'@2.7lbs/ft) he was hanging on 330 lbs - enough to keep him anchored in 15kts. [/quote]

The simplest math still tells you that a 330 pound dead weight is not enough to hold a boat of his description, size and tonnage in 15 knots...

And for my test I too dropped all the chain into a big pile. The loads never approached anywhere near what would be needed to hold even our 36 footer in 15 knots.

This conforms with a similar (frightful) experiences where I dove on an anchor after a night in the Trades only to find the anchor flukes up and chain rode akimbo across the bottom, right where the daywatch had dropped it...and the boat had not moved. I think you are missing some component of coefficient'o'friction and the angle'o'dangle.

Not missing much accept that he perhaps wrapped a coral head. I specifically purchased that load cell to study anchoring loads and have done so quite extensively. Having been dragged into numerous times I wanted to get a better idea of just what it is folks are doing wrong. We get many wind and tide shifts up here and even when using our all chain rode the boat is always setting to the anchor with straight chain, if the winds are in the 15 knot range.

Feel free to read this post from 2008 where an "all chain/CQR" user dragged into us in under 15 knots of wind...

Dragged Into (LINK)

 

[Deadhead]

MS - the Peter Smith article was excellent. I have not come across that one before. Interesting to learn that there is no additional benefit to increasing scope beyond 8:1.

As far as a 3:1 anchor scope goes - please do that in the next cove over.

 

[Gunni]

Me, and Steve Dashew routinely anchor at 3:1 scope (or less). You do what works for you!

 

[Maine Sail]

Me, and Steve Dashew routinely anchor at 3:1 scope (or less). You do what works for you!

Steve is specifically talking about deep water anchoring in Alaska and BC in that blog post. There's a difference between 140 feet of water and 3:1 scope and 20 feet depths at 3:1. In deep water short scopes work but in shallow waters longer scopes are warranted if there is risk of higher winds.

Are you using a grossly over-sized Rocna in 100+ foot depths like Steve is?


Steve over sizes his hooks and is currently using a Rocna that is 242 pounds vs. the already conservative recommendation of 154 pounds that Rocna recommends. I would feel perfectly comfortable in 100+ foot depths with his set up. Most do not have a set up like Steve and the average cruiser is normally in considerably shallower depths..

While the Rocna, Manson Supreme, Spade's and some others can perform admirably with less scope many of the older anchors do not.

Steve and Linda lie to longer scopes when it is warranted.

Weve been anchored in a lovely channel amongst the Marquesas Keys west of Key West (off the NW corner of Boca Grande). There is good holding, a reversing current running at two to three knots, and 15 to 20 knots of breeze to keep us cool. The direction of the wind, out of the east, holds us off a steep to shoreline (there is sufficient depth for us within spitting distance of the beach). We’d normally lie on three to one scope, but in this case, with the direction of pull reversing with the current, we are at six to one – 175 feet/56m in the 20 foot/6m deep channel.

That is still with a grossly over sized new generation anchor..

 

[Gunni]

I think you missed the part about anchor size in your obsession with scope.

 

[FourPoints]

There's a difference between 140 feet of water and 3:1 scope and 20 feet depths at 3:1. In deep water short scopes work but in shallow waters longer scopes are warranted...

can you explain this more? I can't seem to come up with any technical reason for being able to use a shorter scope in deeper water (the part about the oversized anchor is clear though)

 

[Maine Sail]

I think you missed the part about anchor size in your obsession with scope.

Actually I did not forget about it I wrote based on what most boaters use for hooks. I don't want folks to read these forums and assume a 3:1 scope is safe or prudent as the vast majority here do not have over-sized hooks and are not and will not likely be considering them the the extent that Steve Dashew does in terms of over-sizing. I also wrote based on your location and shallow waters of the Chess. If you had sailed in BC or Alaska 3:1 is not an issues and is more the norm, even without over sized anchors.

Most boats we see out there have just the opposite of Steve, undersized hooks. That and 3:1 or less can be a recipe for disaster in a summer microburst. Anchor manufacturers all rate their hooks differently and most not as conservatively as Rocna does. For us to do what Steve Dashew does would require a HUGE Bruce, CQR or Rocna and most production boats are simply not set up to use this size ground tackle.

I also can't forget that we were dragged into by a short scoped Rival 40, with all chain and a CQR in VERY benign conditions after a wind shift and the anchor failed to re-set..

How big is your anchor and what type?

 

[Gunni]

How big is your anchor and what type?

Anchors

1. 60 lb CQR
2. Fortress 37
3. 50lb Bruce (sold)
4. Rocna33 (delivering to Annapolis boat show!)

Different bottoms, different anchors. Two always ready to go!

 

[Maine Sail]

Anchors

1. 60 lb CQR
2. Fortress 37
3. 50lb Bruce (sold)
4. Rocna33 (delivering to Annapolis boat show!)

Different bottoms, different anchors. Two always ready to go!

So your primary will become the Rocna 33kg? That design is well suited to shorter scopes the CQR is not. I still don't feel comfortable on our Rocna at less that 3:5.1 even though I've loaded it up at 2:1, 2.5:1 and 3:1 and had her hold. It is the swings in the night that worry me as the anchor sets far more reliably at 4:1 + than that it does at lesser scopes. This does not mean they don't still set better than just about anything except the Manson Supreme at short scopes but they do set less reliably than themselves, when set longer. In the middle of the night with no-one there to make sure it reset I certainly want the best odds I can get.

During some of my testing I set a genuine CQR on 7:1 until the boat could not move it (not an easy task in mud). I then began shortening scope and by the time I got to 4:1 it was literally plowing the bottom at mid RPM in reverse. I repeated this three times to be sure it wasn't a fluke. I can normally shorten the Rocna, Manson Supreme and on occasion the Spade steel to as low as 2:1 and still get it to not budge. The original Bruce was / is a decent short scope performer as are the Fortresses, unless of course you have a wind shift then they can un-set.


Have you been made aware of the lower spec shank steel currently being used in the Rocna's than what the designer, Peter Smith, insisted was necessary? It's probably not to late to go to a Manson Supreme instead as they are still made with 800 Mpa shank steel. I own both of these anchors and the Manson Supreme is everything the Rocna is, only today, it is made with stronger steel than the Chinese made Rocna's. You're about to spend some good money on a product that has been "cheapened" from the designers very stringent specs, likely in the name of profit over quality, and I just wanted you to be aware of it.

I love my Rocna but it was an original 800Mpa model and if doing it today I would go Manson Supreme in a heart beat.

 

[Gunni]

I did not know that the Rocna material had been changed, thanks! And I like that the Manson Supreme is offered at a better price by my favorite supplier.

 

[Maine Sail]

I did not know that the Rocna material had been changed, thanks! And I like that the Manson Supreme is offered at a better price by my favorite supplier.

Good article in this months Practical Sailor. The company has become quite dishonest and West Marine offered a voluntary recall on them...

 

[Ross]

My CQR has always set when I needed it but often with a very long scope. For my 30 foot 4 1/2 ton boat i carry a 35 pound cqr with 30 feet of 3/8 chain. I think that sometimes I needed a 10:1 scope for an emergency stop.