SailNet Community - View Single Post - Anchor Setting Woes
View Single Post
  #44  
Old 06-28-2013
Brent Swain Brent Swain is offline
Senior Member
 
Join Date: Jan 2012
Location: British Columbia
Posts: 2,297
Thanks: 19
Thanked 30 Times in 29 Posts
Rep Power: 3
Brent Swain is on a distinguished road
Re: Anchor Setting Woes

Quote:
Originally Posted by MedSailor View Post
I get the impression that the Chesapeake is soft mud in many places. I'm surprised that nobody here has yet mentioned the folly of using too much chain with a danforth style anchor in soft mud.

You heard right, there can be such thing as too much chain (in special circumstances).

If the mud is soft, and the chain heavy, the shank of the anchor can pivot BELOW the flukes. You drag with the shank buried and the flukes stay on the surface. This is especially problematic if you set your danforth style anchor with a lot of scope. I know this is counter-intuative to setting every other type of anchor, but I think it's your problem.

Quote from an email I got directly from Fortress anchors in 2008 on this very subject:
..."One downside of using more chain is that with any “pivoting fluke” type of anchor, such as the Fortress, Dan forth, etc. the extra weight of the chain can sink the flukes below the shank [he actually means sink the shank below the flukes--Med] if you are using a long scope in a very soft bottom, like soft mud. I have attached an image which may help you to visualize this.

To prevent this from happening, you simply need to permanently install the Mud Palms on the anchor, which are included with all Fortress anchors. The Mud Palms will lift the rear of the anchor up and force the flukes to take a more aggressive angle into the bottom. You should also use a shorter scope in a soft bottom when initially setting the anchor, which will keep the shank up so that the flukes will dig in first."...


From Fortress's website (see point #8):Fortress Safe Anchoring Guide


If you have a bunch of scope out, 30ft of chain and you're setting it slowly, odds are it won't work in soft mud. I've had this happen and confirmed what was happening with scuba gear. You are better off setting your danforth with short scope (fortress recommends 2:1), to ensure you are pulling up on the stock enough that it is not below the horizontal and only after it's set you can add your scope to 5-7:1 and back up on it hard.

There is nothing wrong with a danforth style anchor area for your bottom types. I have over a hundred nights at anchor on a Fortress and it worked, but setting it was tricky and required skill. Sometimes I had to try 4 times (but usually got it first time).

While I say there is nothing wrong with the fortress/danforth (I have 3 fortresses aboard) I STRONGY prefer the Mantus anchor or the genuine Bruce for their setting ability. If you get an Mantus, Rocna, or Mansun you'll never go back. Actually... now that I mention it, has anyone ever heard of anyone going back from a next-gen anchor?

Happy anchoring and thanks for the good question!

MedSailor
A wide angle may work in mud, but on anything harder, it causes a danforth to flip up on it side and drag forever. Every degree over 32 degrees on a danforth reduces its holding power in hard sand by 50% Try dragging a danforth with a wider than 32 degree fluke to shank angle, on sand, and you will see exactly what I mean.
I remember sailing fron Vanuatu into Lautoka , The depth sounder said ten feet so I put out a stern danforth , slowly. With 100 fet of rode out it hadn't hit bottom. When I pulled it in, the flukes were pointed up, and it was flying along, just below the surface.
__________________
Brent Swain, Boat designer, Builder, and author of "Origami Metal Boatbuilding"
Reply With Quote Share with Facebook