Anchoring with a bridle [Updated Apr-2017]

Everyone and every boat has their recipe for anchoring, setting a snubber or bridle [or not...] all with the goal of sleeping well... 

This is just a description of our ways of doing things that work for us, and why; not the right way of doing things- only you can determine what's best for you... 


–––– Latest revision 9-Apr-2017 [by Bill] ––––
These kinds of posts are also a discussion about our SOPs [Standard Operating Procedures], so we update them as needed and include lots of external references, and append relevant forum discussions where appropriate.

So... on to our bridle story... [Yes, my spelling is correct... My apologies to you romantics...]


Because we have all chain anchor rodes. Our chain stoppers don't buffer shock loads to the boat or ground tackle, but do prevent the load(s) from transferring to the windlass. 

Therefore we use a bridle [double snubber] made of rope with some elasticity on the anchor rode.


Our normal use bridle is a single length of 5/8" 3-strand nylon line: I attach the middle of an ~80ft length  [our boat displaces 22 tons loaded] to the anchor chain with a Prusik knot.
This method evolved over 30 years from first using hardware, then a pair of rolling-hitches, a cow-hitch [which has been determined in testing to slip and also doesn't hold as well if one line fails...] and ultimately a Prusik knot. [Which will not slip under extreme loads, and holds if one side of the bridle goes slack; a cow hitch does not...]
Future knotting experiments will include a Klemheist hitch- if I can determine whether it will hold if one side goes slack. 
In the future I will switch over to using a soft shackle for the chain attachment point. 
All of these hitches are easily untied after being loaded. [The hitches; not the crew untying them... Hmmm, more potential experiments...]

When we switch to a soft shackle for the chain attachment point for improved chafe prevention, I will start with a figure-eight loop in the center of the bridle [a figure-8 loop is stronger than an overhand loop, and more easily untied after being loaded) and graduate to an eye splice with a closed thimble in the middle of the bridle should this become the SOP... This allows the soft shackle attachment point to be easily changed, and it still readily rides over the bow roller assembly...

I don't always use the entire bridle length, and that allows for adjusting the chafe points in rough conditions. It is also long enough to lead to the primary winches if desired for safer handling of adjustments in inclement conditions- and maximizing bridle length and stretch...

In the current bridle iteration [sans soft shackle] the
Prusik knot is easy to deploy if you flake your bridle line while it is 'folded' in half. I start flaking at the 2 bitter ends so the middle [hitch portion of the loop of line] is on the outside of the coil of flaked line. 

I may experiment with an Icicle Hitch in the future as well... I need to determine if it still holds if one side goes slack...

For context, following is an overview of our overnight anchoring procedures: [Every time; regardless of anticipated (and welcome) benign conditions...]
  • Drop the hook and deploy most of the chain scope needed
  • "Soft set" the anchor [vessel momentum only... no engine power...]
  • Let out more chain while slowly backing until desired initial scope is reached 
  • Unwrap enough flaked bridle line to expose a couple of feet of the loop
  • Slide the loop end under the deployed chain, open the loop, and tuck the remaining coil of line through it twice and cinch it up [Prusik knot...]
  • Flake the rest of the bridle line on deck, lead fair and cleat the 2 bitter ends
    • Why not soft eyes on the two bridle ends? You cannot get an eye off a cleat when it is loaded...
  • Let out enough chain to put the load on the bridle with an appropriate amount of slack chain [typically 6 to 12 ft]
  • Back down hard to fully set and test the anchor
If I need to let out more chain it is quick to retrieve enough chain to bring the hitch back on deck (it goes over the bow roller easily.) I open the Prusik knot so it is about 2ft in diameter and then adjust the chain length. When I get close to the new length of chain desired, I again cinch the hitch and let out enough chain to re-engage the bridle.

I suspect it takes less time to do it than read about...

I should mention for years I used a Devil's claw to attach to the chain As they keep the load uniform on the link it is attached to... [and that would likely still be my preferred hardware if I went back to a hard chain attachment...]
But I, too, got tired of having to lean over the bow to attach/detach the Devil's claw and associated safety line to keep it attached to the chain. Once I changed to using a Prusik knot, I haven't gone back to hardware for the bridle-chain attachment.

Switching to a soft shackle as the chain attachment method will likely be even faster and better- especially for post deployment chain length adjustments.

We also have a couple different bridle approaches for storm conditions:

One adds a second, single snubber [which can be the primary or secondary snubber as needed] which connects to the bob-stay attachment point at the waterline. I built a simple, heavy-duty snatch block that allows for bridle adjustment on deck. 

Homemade anchor snubber snatch block for attaching to bow eye near waterline.
The longer bolts will be trimmed leaving room for double-nutting- like the bolt in the bottom of the photo.

This also allows us to use the warp drum on the windlass for adjustment if needed- leaving the longer loop of chain in the water during adjustments in rough conditions- or lead it back to the cockpit winches...

Another is our current storm anchoring SOP: if we need a longer bridle than our standard 80ft of 5/8in 3-strand nylon [e.g., storm bridle is twice that] or if we anchor in shallow locations [very rare in our current sailing grounds] we run the bridle and/or snubber through the bow chocks [or alternatively over the port & starboard anchor rollers on the bow sprit] through the jib sheet return blocks on the stern, then to the primary winches on each side. 

This allows either keeping the bridle off the bottom in shallow anchorages or for a longer storm bridle [80ft/side or more] that can be adjusted/managed from the safety of the cockpit in inclement conditions. 

We use ChafePro [Yacht Series] to mitigate chafe at the bow chocks and anywhere else it is needed [and on our 1in 3-strand nylon dock lines...] with great success.

We are lucky that our deck configuration lends itself well to this approach.



We all have different needs and situations, and I enjoy learning about everyone's approach for dealing with this common need.



And here are some related forum discussions:

Link to original forum post [19-Dec-2015]

Re: Line size for anchor bridle

Quote:
Originally Posted by cabo_sailor View Post
I'm about to make up a new anchor chain bridle and could use some input on the size of the 3-strand.

My dock lines, secondary anchor line are all 5/8 three strand. The chain rode is 5/16 with a 45 lb CQR.


In the past I've made up the bridle with 1/2 in 3-strand to encourage stretch. It's about 20 ft long.


Question: Should I be using 1/2 or 5/8? Does it really make any difference?


Thanks,

Rich


Sent from my iPhone using Cruisers Sailing Forum
Hi Rich,

I've come to the conclusion that the 'right' formula for an anchor bridle is one that will hold up in the worse conditions you expect. [It is no fun- even dangerous- setting or replacing a bridle when conditions have the chain bar tight...]


On our present boat I attach the middle of a ~80ft length of 5/8" 3-strand nylon [our boat displaces 22 tons loaded] to the anchor chain with a cow-hitch Prusik knot [edited 8/13/2016] for our bridle. [The above is an excerpt from a recent related post- which contains more details including deployment variations and storm rig...] This on an all chain rode. [5/16" Grade 43]


[Edit] It may be worth mentioning we rarely if ever anchor in less than 30ft depth [at low water- with a 15-20ft tidal variation in current cruising grounds...] We typically anchor in 60-90ft...


We deploy our bridle every time we anchor overnight. Why every time? Because I'm lazy; I don't want to get up in the middle of the night because the conditions changed... [Deployment only takes 2-3 minutes total including take-down/flake/stow.]



____________________________________

Re: Line size for anchor bridle

Quote:
Originally Posted by cabo_sailor View Post
5/8 fits the cleats easily. My concern is attaching two such lines to the Mantus hook without it being too cramped. Our boat is around 24 K lbs but our waters are shallow. Typical anchorage is only about 10-20 ft.

Hi Rich,

Safe, shallow anchorages [something rare up here...] would require us to rig our bridle as we do for inclement conditions: fair lead from bow to primary winches [with anti-chafe covering at bow fairleads. (Or maybe hi-mod line in the future.) ] This way the bridle legs are long enough to do some good, and the attachment point doesn't have to contact the bottom...


In case this might work for you...

____________________________________

Re: Line size for anchor bridle

Quote:
Originally Posted by Quote:
Originally Posted by wrwakefield View Post
...............................
................... Safe, shallow anchorages [something rare up here...
would require us to rig our bridle as we do for inclement conditions ............
...........

Hudson Force;1992151] I was confused by this. I was thinking just the opposite and considering a safe anchorage as being one with little fetch and no waves or swell. This would mean no surge or changing tension on the bridle and therefore, no need for a long length or stretch.


My practices are influenced by spending most of my anchored times at 10 to 20 feet with no more than a half mile fetch, often far less, so I'm usually using a bridle with a pair of 5/8" lines no more than 20' and often just 10' deployed.
I'm sorry to cause any confusion, Hudson.

What I was trying to describe is how we would keep our longer anchor snubber/bridle length without letting the chain attachment point hit the bottom in a shallow anchorage: Instead of attaching at the bow and only have 15ft or so of bridle/snubber length, we would lead through bow fairleads back through return blocks near the stern, then to the primary winch(es) so the line is much longer, and chain attachment point just below the water surface. [This is also what we do if expecting inclement conditions so we can adjust the bridle from the cockpit...]


One possible difference with us is we always set the [overnight] anchor and bridle as though we are expecting storm force conditions. [And this has occurred several times over the years- once being blown off my anchor in unanticipated williwaws. (Think zero to Force 11 in under 15 seconds... then back to zero again...) Hence my conservative approach in higher latitudes...] It doesn't take any longer to do so and- being inherently lazy myself- I don't feel compelled to get up in the middle of the night to check things if the predicted conditions deteriorate. [And, in the case of williwaws, there is no time to take additional preventative measures...]


RE: Protected anchorages- your point is well taken, and I agree with seeking them out wholeheartedly. Though our average anchorage may be deeper than we usually read about, we only select those that are well protected from anticipated winds, with little fetch or wave/swell potential.


RE: Snubber/Bridle length: We choose to use a longer bridle because of our tidal variations of 15-20+ft; our scope ratio changes several times over the course of 24 hours. We keep the longer snubber to help ameliorate the smaller scope ratio [i.e., at higher tides in deeper anchorages we approach a 4:1 ratio- sometimes slightly less- with our 360ft of chain (+ 100ft of nylon rode for Hail Mary scenarios)...] The idea with the longer snubber/bridle is to reduce sudden forces on the anchor [and vessel attachment points...] in high-wind and/or gusty [e.g., williwaw] conditions- especially when at reduced scope due to high tide in a deep anchorage.


So far, so good... knock on wood...


I hope this helps clear up any confusion I may have caused.

____________________________________

No comments:

Post a Comment

Please play nice...