Category Archives: Anchoring

Tripline Use and Cautions

Sanctuary and crew cruise mostly on the US East Coast, where water depths for anchoring in-the-main range from 12 to 25 feet.  Sometimes more, sometimes less, but a working average of 15 feet.  The deepest water in which we have anchored was outside Boothbay Harbor, Maine.  I think our “record” was in water depths of 56 feet at low tide with a 12 foot local tidal range.  These are not big numbers compared to the Pacific NW.

When we anchor, I put out a minimum of 4:1 scope, and my preference is to put out more.   Our rode is all-chain.  That scope is my precautionary approach against something changing in the overnight hours when I may be less alert and too slow to appreciate and respond to rapidly changing/deteriorating conditions.

When we first began full-time cruising, we depended on Skipper Bob Cruising Guides for the Atlantic Intracoastal Waterway (A-ICW).  Skipper Bob suggested using triplines in areas of the Carolinas and Georgia, where underwater hazards included numerous deadfalls and stumps.   The first couple of years we cruised, I avoided anchoring in those areas.  I was afraid of the hassle and unsure of my skill in freeing myself from a snag.  But, we really liked the quiet and beauty of that area, so I decided to build and experiment with a tripline, and learn to use it, so we could feel confident anchoring in that region.

Our “proof-of-concept” assumptions for the tripline were twofold.  First, we knew the tripline would be useful in freeing an anchor snagged on some invisible underwater hazard.  Second, we thought it would signal the location of our anchor to other boaters looking to place their own anchors; “mark our swing circle,” as it were.

I designed our trip line to be self-adjusting to accommodate average East Coast tidal ranges.  One end of the tripline was permanently attached to the anchor, and the fly end of the tripline ran through the loop on a red float ball.  The fly end was permanently secured to a 1# lead fishing weight.  The size of the weight prevented the line from running back out of the float’s attachment loop.  As the tide fell, the weight fell by gravity to hold the ball floating centered over the anchor.  As the tide rose, the weight rose by the buoyancy of the float ball.  That held the ball floating on the surface of the water, centered over the anchor.  The line itself was 3/8″ nylon, 30′ long.  The system worked fine in water depths ranging from 12′ to 25′.  In waters less than 15′ deep, the weight would come to rest laying on the sea bed, but the ball would stay very close to the anchor’s position.

My design worked to keep our tripline float located immediately above our anchor.   Deployment was easy; we just threw the ball over the side after the anchor settled onto the seabed.  Retrieval was also easy; we’d just allow the anchor to come up and then catch the tripline.  Both tasks were easily managed from our foredeck.

I made it a point to use the tripline virtually every time we anchored for about one full cruising season.  That season included a 1400 mile southbound migration from Baltimore to SW Florida, and the 1400 mile return to Baltimore the following spring.  I never did actually need the trip line to free the anchor from a snag.  OK, I grant that’s not valid in evaluating the usefulness of the tripline for freeing a snagged anchor.  The idea of the trip line is for it to be there IF AND WHEN it’s needed.  We can certainly agree, it isn’t going to be needed very often.  However, our “proof-of-concept” trial didn’t work out as well in practice as I had hoped.  While we were using the trip line, we also encountered some significant disadvantages (risks) to having it deployed.

One realization was that the only time a tripline float helps other boaters understand our true swing circle is if wind and currents are up a bit.  In gentle to moderate breeze conditions (Beaufort 3-4), the rode becomes stretched out to the point that the bulk of the rode is lifted off the sea bed in resisting the drag forces on the boat; not taut, but stretched out along its entire length.  But in calm conditions, anchor chain lays on the sea bed.  With the rode laying on the sea bed, the swing circle appears rather smaller than it really is.  That is particularly true in deeper water where the length of the scope triangle’s hypotenuse becomes increasingly significant.

beaufort3    beaufort4

In calm conditions, the boat is typically held to the sea bed by the weight of the chain, not by the anchor itself.  The natural chain-fall location is the point at which the rode comes to rest on the sea bed after relaxing from the mechanical load of setting the anchor.  In my experience retrieving our anchor after a calm overnight, the chain usually comes up in an “S” pattern, formed by the movement of the boat in reversing tidal currents.  The result is that the boat never moves through it’s true swing circle.


In calm conditions, when tidal current reverses after slack, our boat will simply “pivot”  around the chain-fall location.  At that time, the tripline float will be positioned aft of our boat.  In that location, it’s hard for others to even be sure the tripline float is our’s.


As the strength of the flow of the reversed tidal current increases, there will be a time when the chain’s weight alone can’t hold the boat, and the chain gets partially pulled back on itself; that is, pulled away from the natural chain-fall location and towards the position of the anchor.  Thereafter when the tidal current reverses again, the boat will pivot back and be pulled slightly back away from the anchor’s position.  While this is happening, the tripline float often winds up aft of, or alongside, the orientation of the boat on the surface of the water.  Occasionally, we found our float would wind up under our own swim platform, snagged on one of the support brackets.  That never actually caused us to unset ourselves, but it certainly could have.  We have friends on a Monk 36 who unset their own anchor that way, in a t’storm, in the dark, at 03h00.

Furthermore, we discovered the hard way that the presence of the float ball does not stop it from being “run over” by other boats moving through an anchorage.  We had that happen twice in the year of our “proof-of-concept” trial.  Once in Georgetown, SC, a sail boat came through the anchorage looking for a spot; 15h00 on a sunny afternoon.  The person on the bow was fully occupied sorting out his ground tackle, not at all focused on keeping a lookout.  The helms-woman probably could not see our red float ball from her cockpit helm station.  Poof, they ran over our float.  On another occasion in South Florida, we were preparing to depart our anchorage, just before dawn, in pre-dawn low light.  A neighboring boat was a few minutes ahead of us with their departure preparations.  When they motored out of the anchorage, they ran over our float.  Fortunately for us, neither of those incidents snagged our float or unset our anchor.  But no matter our good fortune, had they snagged our float, we would have been the worse for their inattention.

So, it’s only some of the time – probably a relatively small percentage of time – that having a tripline float is actually helpful to others in understanding our true swing circle.

I do not like lying over another boat’s rode and I work very hard to avoid that.  I think most boaters feel that we’d be way too close to them if we were lying over their rode.  I would not want another boat to swing over our tripline ball, because of course, that risks unsetting our anchor.

So it is true that a tripline float can reliably mark the position of the anchor in the sea bed.  Whether that is helpful to me or others is less clear to me.  There are times when it may help, other times when it does not.  The real key to seamanship in anchoring is to honor the location of boats that are already settled in the anchorage.  Stay an appropriate and suitable distance away from others in anticipation of the possibility of fast changing wind and weather conditions.  That decision requires seamanship skills, forethought and high value of personal courtesy to strangers.  Sometimes, it means moving on, which we do if we can’t be certain we have safe swing room.  After all, a t’storm in the middle of an otherwise calm overnight changes all appearances and risk assumptions.  If a t’storm were to move through when the tripline float is snagged under the swim platform, that could easily become a perfect storm of undesirable coincidence and unwelcome outcome.

Conclusion: I gave up on using the the trip line.  Ultimately, I decided the benefits weren’t worthy of the risks.


Anchor Rode – Calculating Capacity

In the United States, the American Boat and Yacht Council1 (ABYC) publishes a table of rode sizing2 that is suitable for use in coastal and intracoastal waters. This table makes rode selection safe and fairly easy for the vast majority of boaters. It also provides a criteria against which to evaluate installed ground tackle systems. I suggest the ABYC table be thought of as a “minimum standard.” For persons anticipating more demanding anchoring conditions, an understanding of rode forces is not just an interesting scientific curiosity; it can be a matter of life-and-death safety. Some cruisers will encounter – by the nature of their travels – more severe conditions than others. Coastal and intracoastal cruisers will not experience conditions that “blue water long-range cruisers” will encounter. Coastal and intracoastal cruisers will be able to seek and find protection that may not be available to blue water long-range cruisers.

In studying this subject, I have found it difficult to understand and integrate the huge volume of material written about it. After some years of trying to get my arms around it, I have arrived at this summary. For those wishing to verify the size of the ground tackle fit on their own boat, or those engaged in re-fit or equipment upgrade, I see the effort to manually size anchor rodes and snubbers as a multi-step process.

  1. Understand the sources of energy that will have to be absorbed by the boat’s snubber, rode and anchor.
  2. Determine the design capacity for the total load that the rode or snubber will be asked to withstand without damage.
  3. Determine rope size required based on Average Breaking Strength.
  4. Settle on a Safe Working Load (SWL), or a Working Load Limit (WLL), for the chosen rope size.
  5. Determine the working length required to accommodate shock absorbing stretch.

Step 1: Understand the sources of energy that will have to be absorbed by the boat’s snubber, rode and anchor.

Anchor rode and/or rode snubbers experience loads that originate from three different sources:

  1. wind-induced load consisting of nominal wind speed which is present more or less continuously, and gusts occurring in bursts;
  2. surge-induced load which comes and goes with the rise and fall of passing waves; and,
  3. loads cause by currents present in the water in which the boat is anchored.

These sources of load are independent of each other. Each source adds to the others within the rode. Wind loading tends to be predominantly static, with long-period variations caused by gusting. Heave/surge loads tends to be dynamic and variable with each passing wave. Current loading is a static, and a relatively minor contributor to total loading in more severe situations. Sizing anchor rode and/or snubber involves making many assumptions about the maximum potential load that the rope will experience from these three sources in combination.

The total load on the anchor rode must fall at or below the Safe Working Load (SWL), or Working Load Limit (WLL), of all of the manufactured and man-made components that make up the ground tackle and anchor rode “system.” This includes chain, rope, splices, pad eyes, shackles, swivels, toggles, thimbles, seizings, and whippings; i.e., all of the individual components that make up the mechanical connection between the anchor and the structural frame of the boat. In the ground tackle system, the weakest link is indeed the most likely cause of failure.

Step 2: Determine the design capacity for the total load that the rode or snubber will be asked to withstand without damage.

Wind-induced load is a major contributor to rode loading. Wind-induced loads increase as the square of wind speed. Refer to our article at to see the analysis. For Sanctuary, I calculated the wind loads that would be experienced under a range of wind conditions by a Monk 36 while at anchor. This analysis probably also applies to other classic trawlers with similar LOA and physical profiles; i.e., Albin, Grand Banks, CHB, Marine Trader, other Taiwanese, etc.

Once wind-induced load is applied to the rode, a portion of the total available SWL of the rope is “used up.” Additional load that is imposed by both seastate heave and surge forces, and water currents, must fall withing the limits of the remainder of rode capacity.

Some facts about our Sanctuary:

  1. Sanctuary’s bow elevation presents a surface area, at zero degrees of yaw to the direction of the wind, of 165 ft2 with the Flybridge enclosure in place, and 143 ft2 without the flybridge enclosure. The Monk 36 (and other boats) tends to “sail,” or “horse,” or “veer” back-and-forth at anchor, and routinely reaches a yaw angle of +/- 30° to the wind, often more. The surface area elevation for Sanctuary, at a 30° yaw angle to the wind, is 214 ft2 with the enclosure and 180 ft2 without.
  2. Whether referred to as “sail,” or “horse,” or “veer,” loads on the rode increase significantly when the angular travel reaches it limit, and the motion is slowed, stopped and direction-of-travel reversed.
  3. With a yaw angle of 30° and a surface area of 214 ft2, a wind of 50 knots will exert 1812.1 lbs of load.
  4. In an open seaway, Earl Hinz3 suggests that heave/surge loads presented to the rode can equal wind loads. Most near coastal and coastal cruisers would seek the cover of a safe anchorage to ride out a blow, so the percentage of wind load would most probably be larger than the percentage of heave/surge load.
  5. If we assume a moderately protected anchorage and allow 1160 lbs of wind force at a 30° yaw angle and 640 lbs for heave and surge, we reach our wind force limit at 40 knots.
  6. In a highly protected anchorage with little heave/surge component, winds could range above 40 knots, but not higher than 50 knots.
  7. This design assumption is marginal for summer thunderstorms, where wind forces at 70 knots could, all by themselves, drive periodic peak rode loads to 3500 lbs or more.

Step 3: Determine rope size required based on Average Breaking Strength.

Different manufacturers of 3-strand nylon rope have different specifications for the “tensile strength,” or Maximum Breaking Strength, of their products. Using 5/8”, 3-strand nylon rope as an example, there is a considerable range of manufacturer-published tensile strengths (Average Breaking Strength). Some examples:

New England Rope, brand 1 5/8″ 12200
Erin Rope 5/8” 9350
New England Rope, brand 2 5/8″ 11650
Buccaneer Rope Co. 5/8″ 10400
Samson Rope Technologies 5/8″ 11300
Phoenix Rope & Cordage 5/8″ 9000
Consolidated Cordage 5/8″ 10000
CNDRope and Industrial Supply 5/8″ 10400
AVERAGE Breaking Strength: 5/8” 10,500 pounds

Step 4: Settle on a Safe Working Load (SWL), or a Working Load Limit (WLL), for the chosen rope size.

The industry standards group for rope manufacturers, The Cordage Institute, specifies that the Safe Working Load (SWL), or Working Load Limit (WLL), of a rope “shall be” determined by dividing the Tensile Strength by a Safety Factor. Safety factors increase from about 5 for

  • non-critical applications,
  • used under normal service conditions,
  • where rope is in good condition,
  • with appropriate splices,

to 20 or more for lifting applications and to 25 for life-line applications. The Cordage Institute guidance is, SWLs should be reduced where life, limb, or valuable property are involved, or in exceptional service conditions, such as shock loads, sustained loads, etc.

In the example of our 5/8″ average Breaking Strength rode/snubber rope, here are three data points for safety factor:

10500 / 5 = 2100 lbs
10500 / 6 = 1750 lbs
10500 / 8 = 1320 lbs

Note: There is also a further useful data point for consideration in this discussion. The ABYC Standard, H-40, shows an SWL for 5/8”, 3-strand, nylon line of 1114 lbs. This specification appears to have been de-rated by a further 200 lbs. A table note states: Working loads for nylon rope are based on factors of safety, line strength loss due to knots and splices and additional factors including abrasion and aging. The point is, consistent with the criteria of the Cordage Institute, aging and condition of materials does affect SWL.

It is clear that SWL is exceeded in operation earlier, and more often, than most boaters think.

Step 5: Determine the working length required to accommodate shock absorbing stretch.

The first 4 steps, above, deal with slow, steady loading of the rode, and slow, steady energy release; that is, winds and seas at largely steady-state velocity. But that is not natural! Under more variable conditions, instantaneous loads within the rode can rise very dramatically. I highlighted the Cordage Institute suggestion, above, that SWLs should be reduced where life, limb, or valuable property are involved, or in exceptional service conditions, such as shock loads, sustained loads, etc. Note that reduction is reflected in the ABYC recommended number of 1114 lbs for 5/8” rope.

Very high instantaneous loads can cause deck hardware to fail and can cause the inelastic and relatively brittle metal components of rode to break. That is why all-chain is not a good choice of material for anchor rodes that will see severe or extreme conditions. To decrease very high instantaneous loads, elasticity in the rode is absolutely essential. The elastic component of the road absorbs high instantaneous shock loads and disperses the energy that would otherwise be transmitted to deck hardware and anchors.

Elasticity and shock-absorption capability is found in the ability of Nylon fibers to stretch and return to their original length, without damage up to a point. In the process of stretching, energy is absorbed and released. The following figures are from New England Rope. The numbers vary somewhat among different rope manufacturers, and they vary among the various types of rope made by the same manufacturer, but they remain proportionally similar. For three-strand nylon rope:

at 7.5% loading, three-strand nylon rope stretches 3%;
at 10% loading, three-strand nylon rope stretches 5%;
at 15% loading, three-strand nylon rope stretches 8%;
at 20% loading, three-strand nylon rope stretches 10.4%; and,
at 30% loading, three-strand nylon rope stretches 13%.

Rope manufactures and most experts recommend using 3-strand nylon rope at an SWL of 15% of maximum loading. This is to minimize potential damage to the internal fibers and microfibers of the rope and maximize the useful life of the asset.

Example 1:

Using the generic Average Breaking Strength of 10500 lbs, as derived in Step 3, above, the choice of a maximum of 15% loading for a Safe Working Load limit would allow 1575 lbs, or a safety factor of about 7. A snubber that is sized so that the total load on it will be 15% of its tensile strength will stretch 8%. Assuming worst case conditions, one half the 15% total load (787.5 lbs) is wind-induced, and the other half (787.5 lbs) is seastate-induced. The 787.5 lb wind component will pre-load the rope, stretching it 3% of the total available stretch of 8%. The stretch that remains available to cushion the 787.5 lb seastate heave and surge load is the the difference of the wind induced stretch (3%) from the total available stretch (8%). Thus, 5% stretch capability is available to absorb the heave/surge energy. Five percent is sufficient for the stretch that the surge can produce within a 15% SWL criteria.

Example 2:

A smaller snubber, one sized so that the total load on it will be 30% of its tensile strength (3150 lbs assuming 10,500 lb ABS, 5/8”, 3-strand nylon), will stretch the rope 13%. Half the load (now 1575 lbs) is wind-induced, the other half, also 1575 lbs, is seastate-induced. The 1575 lb wind component will pre-load the rope, stretching it 8% of the total available stretch of 13%. So taking away the wind induced stretch (8%) from the total stretch that is available (13%), the difference is 5%. So we can see that when the surge develops its full strength (1575 lbs), the stretch that remains in the rope (5%) is not sufficient for the load caused by the surge. In all likelihood, overloading the rope will cause failure of internal rope fibers.

Another way to look at the case of Example 2 is that “the line was too short.” When checking shock load, the rope will fetch up hard as the rope runs out of stretch. It will run out of stretch before the surge runs out of energy.

So if the rope is sized to allow load greater then 15% of the rope’s tensile strength, the result will be increased probability for chafing, melting and tearing of the rope’s internal fibers. This progressively decreases the safety factor chosen for the design point of the the system, and permanently damages the strength of the rope.


This article is offered solely as an example. It contains averaged numbers and assumed design points. For any individual boat, all of this would need to be validated using manufacturer-published specifications and specific boat characteristics for wind loading. This is only a methodology for owner/operators to consider in analyzing their own ground tackle systems.

Related Posts:





1   American Boat and Yacht Council, 613 Third Street, Suite 10, Annapolis, MD, 21403 – Phone: (410) 990-4460

2   ABYC Standard, H-40, Anchoring, Mooring and Strong Points, 2008, Table 1, page 6.

3  The Complete Book of Anchoring and Mooring, Second Edition, Earl Hinz, Cornell Maritime Press, 2001.

Wind Loads on the Anchor Rode

The “rode” is that line or chain, that is permanently secured to a vessel, usually at the bow, and reaches from a structural part of the vessel to the shank of the vessel’s anchor; the term includes all in-line connecting devices (splices, shackles, swivels, toggles, thimbles, seizings, whippings, etc).  All forces experienced by a vessel at anchor will be transferred from the vessel to the seabed through the deck hardware, rode and anchor.  A failure of any component of this system can result in a fatal loss of the vessel.

For Sanctuary, I calculated the wind loads that would be experienced under a range of wind conditions by a Monk 36 while at anchor.  This analysis probably also applies to other classic trawlers with similar LOA and physical profiles; i.e., Albin, Grand Banks, CHB, Marine Trader, other Taiwanese, etc.  The numbers are based on well understood and long accepted science.  These calculations are consistent with the numbers in Earl Hinz’ book and with the tables presented in American Boat and yacht Council (ABYC) Standard H-40, “Anchoring, Mooring and Strong Points,” 2008 (the current edition of that standard; it’s probably up for review in 2013).

Sanctuary’s bow elevation presents a surface area, at zero degrees of yaw to the direction of the wind, of 165 ft2 with the Flybridge enclosure in place, and 143 ft2 without the flybridge enclosure.  The Monk 36 (and other boats) tends to “sail,” or “horse,” back-and-forth at anchor, and routinely reachs a yaw angle of +/- 30° to the wind, often more.  The surface area elevation for Sanctuary, at a 30° yaw angle to the wind, is 214 ft2 with the enclosure and 180 ft2 without.  The table below shows the results of the calculations:

Monk 36′ Values
Wind Speed: 10 Knots 20 Knots 30 Knots 40 Knots 50 Knots 60 Knots 70 Knots 80 Knots 90 Knots 100 Knots
drag force:
(0º Angle of Yaw)
(Includes area of FB Enclosure)
55.9 223.5 503.0 894.2 1397.2 2012.0 2738.5 3576.8 4526.9 5588.7
drag force:
(0º Angle of Yaw)
(w/o area of FB Enclosure)
48.4 193.7 435.9 775.0 1210.9 1743.7 2373.4 3099.9 3923.3 4843.6
drag force:
(30º ~ Angle of Yaw)
(Includes area of FB Enclosure)
72.5 289.9 652.4 1159.7 1812.1 2609.4 3551.7 4639.0 5871.2 7248.4
drag force:
(30º ~ Angle of Yaw)
(w/o area of FB Enclosure)
61.0 243.9 548.7 975.5 1524.2 2194.9 2987.4 3902.0 4938.4 6096.8

Note that this table describes only wind speed loading.  There is no component in the above numbers for the additional contribution of heave/surge due to sea state.  Hinz (Ref. 1) and others suggest that heave/surge can as much as double these numbers.  Hinz suggests that the displacement-to-length ratio (D/L ratio) of the specific vessel is the key contributing factor to rode loads for sea state induced heave and surge.  Live-aboards and long range cruisers have emergency gear, spares, tools, stores, big battery banks, genset, fuel, water, ballast, etc., so their D/L ration is higher than nominal; i.e., the boat is heavy.

At 20 knots, rode is only loaded to 300 (289.9) pounds of stretching force.  Doubling the wind speed to 40 knots would increase the rode loading by 4 times, to 1160 pounds.  And increasing the wind speed up to 60 knots result in rode loading of 2610 pounds.  At that point, rode loading exceeds the rated Working Load Limit (WLL) for 5/16″ BBB chain.  At a wind speed of 80 knots, rode loading increases to 4600 pounds, and exceeds the WLL for 5/16″ HT chain.

In consideration of the foregoing, analysis, I suggest some questions:

  1. In order to protect your family and your boat, what scope would you want deployed in 30 knot winds?
  2. At 40 knots, do you really believe you’d still have useful elasticity in the rode from the remaining catenary in an all-chain rode?
  3. Do summer thunderstorms contain 60 ~ 80 knot down-bursts?  Is considering that possibility really so unrealistic?
  4. At what point would you prepare for the possibility of higher winds?
  5. If you’re in a crowded a fair weather anchorage where a winter cold front is going to pass through in – say – 48 hours, what action(s) would be appropriate?

As for me, aboard Sanctuary, I would try to move to a more protected spot and I would put out all the rode I have, regardless of scope.  It would certainly be at least 10:1.


1)  The Complete Book of Anchoring and Mooring, Second Edition, Earl Hinz, Cornell Maritime Press, 2001.

Related Posts:



Anchoring: Reference Materials

I strongly recommend two books on anchoring and ground tackle:  They are

  1. The Complete Book of Anchoring and Mooring, Second Edition, Earl Hinz, Cornell Maritime Press, 2001, and
  2. The Complete Anchoring Handbook, Alain Poiraud, Achim and Erica Ginsberg-Klemmt, International Marine/McGraw Hill, 2008.

Both of these books are primarily experiential, backed up with theory and math.  Hinz’ presents more conclusions and relatively little math.  Poiraud et. al. include a very thorough Appendix of the mathematical analysis of both static and dynamic anchor and rode behavior authored by Alain Fraysse.  This analysis is heavily mathematical, for those interested, and can be skipped by those dis-inclined toward the math.  Hinz writes in US units of measure, Poiraud et. al., in metric units.  Conversion of the units back-and-forth is possible and fairly easy with today’s Internet conversion tools.  Poiraud is a Hylas designer and inventor of the spade anchor.  Fraysse maintains a very useful, if technical, web site, here:

Both books cover the same general material, but each presents “pearls” of their own.  Both books cover the subject primarily from the point of view of blue-water sailors cruising remote parts of the world and occasionally encountering severe to extreme conditions.  That profile of prolonged offshore cruising greatly exceeds the lifestyle and preference criteria of Sanctuary’s crew.  Sanctuary and crew are US near-coastal, coastal and river cruisers.  We do occasional offshore passages of less than 200 miles, such as crossing from Florida to the Bahamas, or crossing the Gulf of Mexico from Carrabelle, FL, to Tarpon Springs, FL.  We sometimes run off the Georgia and South Carolina coast, offshore around New Jersey, and the New England coast.  We select these trips as carefully as possible for “acceptable” sea-state conditions.  If the weather forecast looks at all questionable, we stay in-shore or seek marinas, for cover and the possibility of extended weather delays.  That said, I nevertheless wanted a ground tackle system that would handle the “what if” times when we just got caught out.  We have several times found ourselves in short term storm-force conditions in summer thunderstorms.  That is never pleasant.

Key points I took from the above-mentioned books are:
1.  All anchors perform better in some bottom materials than in others; no anchor is a “universal fit” for all bottom grounds.
2.  To ensure secure holding and prevent/avoid dragging, adequate scope is by far the single most critical routine and controllable variable every captain must consider.
3.  All-chain rode is not the best rode for conditions above 35 kts; at that point, chain sizes found aboard pleasure craft loose all catenary.  Once catenary is lost, chain rode cannot absorb or cushion heave and surge motions.  The addition of kellets or additional lengths of chain makes surprisingly little difference.  When catenary is gone, heave and surge loads can unset an anchor and/or damage deck fittings/gear.  Furthermore, the instantaneous forces in the chain will far exceed the Working Load Limits (WLLs) of BBB and G4 Chain, which can result in parting the chain.
4.  In light of item 3, above, experts generally recommend use of a hybrid rode consisting of a chain leader attached at one end to the anchor’s shank and spliced at the other to a length of 3-strand nylon line.  The chain leader at the anchor shank resists abrasion as the anchor buries itself and works into and against the bottom.  The 3-strand nylon section provides elasticity, so absorbs, cushions and disperses the energy of both working load and shock forces.  Poiraud, et. al., suggest that the length of the chain leader should be equal to the “average depth of the water” in which one typically anchors.  Other experts advise a length of chain leader equal to the weight of the anchor.  Others recommend a length of chain leader equal to the length of the boat.  Whatever your choice, in calm conditions, the chain will lay on the bottom, and the nylon 3-strand component of the hybrid will hang vertically from the bow roller to the bottom.  As wind forces increase, up to the point where the rode is fully taught, the weight of the chain will help reduce vertical loads on the anchor shank that might tend to lift the shank and unset the anchor.  When winds and seas reach the point at which the rode is fully taught, the only game in town is the shank-to-seabed angle.  Shank-to-seabed angle is a controllable variable which is directly related to the amount of scope deployed.  As scope is increased, elasticity (shock absorbency) is consequently also added to the system.  Increased elasticity accommodates worsening wind and sea state conditions by absorbing increasing instantaneous heave and surge loads.  For the US Mid-Atlantic and Southern coastal regions, Ontario and the Inland Great Rivers, all of these mixed (hybrid rode) chain formula seem fine.
5.  With chain rodes, both authors discuss and recommend the use of bridles to buffer the attachment point of the chain-to-deck hardware in light-to-moderate conditions and snubbers in moderate-to-severe conditions.  These accessories relocate anchoring loads from the windlass to hard points on the hull, accommodate chafe reduction in more severe conditions, and increase crew comfort by reducing mechanical noise in the forepeak in calm conditions.
6.  Chafe can be an enormous problem in conditions as little as 15 – 20 knots.
7.  Neither author recommends swivels in the anchor rode.  If used, they offer several suggestions to increase safety.  Sanctuary does have a swivel installed.  Ours is not attached directly to the anchor itself.  We installed a 6 inch length of chain from the anchor shank to the swivel, then placed the swivel in-line, then attached the rest of our chain.  This approach reduces the chance of side loading and failure at the swivel’s pivot pin.  But, it does add to the total number of connection points in the rode, and each connection point is its own potential point-of-failure.
8.  Both authors strongly caution the use only high tensile-strength shackles, such as thse made in the USA by Crosby (  These shackles have their safe WLLs cast into them.  Both authors strongly caution against the use of the Chinese-made utility hardware found at big-box and hardware stores across the US.  In the Annapolis metro area, the only place we know of that stocks high tensile shackles is Fawcett’s Boating Supplies (  Otherwise, source these items from the Internet.



Our main anchor is attached to its rode with a toggle, not a shackle.  The design of the toggle allows it to slip over the end of the anchor shank, where it fits well very little excess clearance for undesirable movement.  The inherent design of a toggle is stronger and passes more smoothly through our bow roller assembly than does the largest possible shackle the chain can accept.

Our rode is fit with a 5500# WLL swivel.  The design of the attaching ends of the swivel allows it to slip the ears directly over the end of the anchor shank.  The swivel is made of up two attaching ends connected together by a large diameter swivel pin.  The swivel pin is essentially a large diameter bolt.  The nut is welded to the bolt so it can not turn off.  The pin is oriented axially along the pull of the rode.  The bolt is very strong in tension, but substantially weaker in shear caused by side-loading pulls.   To avoid shear forces caused by side-loading, we have added a 5-link length of 3/8″ chain.  That short piece of 3/8″ chain is located between the toggle and the swivel.  The swivel and connecting chain is visible in the above pictures.  Our configuration eliminates any possibility of side loading and allows for larger connecting hardware than would be possible with a conventional shackle.

Related detail:


Sanctuary’s Anchor & Ground Tackle

When we acquired Sanctuary in 2004, she had no windlass.  At that time, she was fit with an OEM-provided 35# Danforth-style anchor, fabricated of SS for appearance.  The anchor was fit with about 6′ of 3/8″ chain attached with a solidly rusted 7/16″ shackle.  There was no swivel.  Attached to the other end of the chain, also with a rusted shackle, was a length of about 200′ of somewhat worn, 3-strand, 5/8″ nylon line.   Sanctuary also carried a 30# CQR-style knockoff anchor aboard, stored in the bilge.  The previous owner/seller told us that he essentially never anchored; “maybe once,” he said, “in 6 years of ownership.”

Ground tackle immediately became an issue in our pre-purchase survey.  We knew we wanted, and expected, to anchor out.  We agreed with the surveyor that the then-existing ground tackle was inadequate for the boat.

Immediately upon purchase, we fit up a new Simpson-Lawrence H900 windlass (600 watt) and 250′ of 5/16″ BBB chain.  At the time, the windlass was available on-the-shelf at what was at the time a favorable price.  The chain was selected because it fit the 8mm wildcat of that available windlass.  We would make different choices today.

As part of the windlass install, we also replaced the pretty SS Danforth-style OEM anchor with a 35# “genuine” CQR and added a 5500# WLL swivel, obtained from Fisheries Supply in Seattle.   Although this selection of equipment falls within the guidelines of ABYC H-30 for Working Load Limits (WLLs) for Sanctuary’s windage profile, in hindsight, I would prefer a greater margin of WLL capacity for the chain.

The 5/16″ BBB chain weighed just over 1 pound per foot, so 250′ of chain added about 300# to our forepeak.  To adjust the boat’s trim for that weight, the weight of a genset that we added at that same time, and the natural bow heavy trim of Monks, we added 1000# of lead ballast in the aft mechanical space, behind and below the master berth.

Then one summer day at St. Michael’s, MD, we had the pleasure of meeting an experienced cruising couple aboard their Monk 36′.  They invited us for a tour of their boat, and we liberally adopted (read: stole) several ideas.  One was that we mounted a 1/4″ SS plate on the port flybridge rail.  On it, we hung our SS Danforth fit with a hybrid rode of the 6′ of chain and 250′ of 3-strand nylon line.  That was a definite improvement in accessibility of that “backup” anchor.  Stored in that location, it was fairly well out of the way yet also quite reasonably accessible.  It could be deployed quickly either fore or aft.  It was cumbersome to handle, deploy and retrieve, so although a workable solution, it was still not yet as optimum a rig as we wanted.

Manson Supreme, showing swivel attachment that reduces side-loading of the swivel pin.

Manson Supreme, showing swivel attachment that reduces side-loading of the swivel pin.

Over time, we had our share of difficulty getting our 35# “genuine” CQR to set.  Once set, though, that anchor never failed to hold us.  We did worry about it, though, and there were certainly nights that we didn’t get much sleep.  In 2009, we upgraded the 35# CQR to a 45# Manson Supreme.  The Manson Supreme is, indeed, “supreme.”  It sets immediately and positively.  I would never consider going back.  With our Manson on duty, we sleep very well.

There are two things I suggest any prospective Manson or Rocna buyer check before dragging one home.  First, these anchors have a shank that is made from plate steel vs. a forging.  The steel plate is thinner in its width dimension and taller in its height dimension than comparable CQR, Danforth and Bruce fluke or plow-style forged shank anchors.  That high rise shank will not fit in some bow roller assemblies originally made to accept lower profile forged shanks.

Boom Bail allows clearance for Manson Supreme anchor shank

Boom Bail allows clearance for Manson Supreme anchor shank

So the first thing to do is verify that the bow-roller will accept whatever anchor you decide to install.  This caution is especially important for fully enclosed fiberglas bow pulpit designs; those fabricated of fiberglass and molded as a continuous extension of the foredeck.  I was easily able to adapt Sanctuary’s bow roller using a SS bail from a sail boat’s boom.  Second, the angle that the spade makes to the shank where they are welded, and the length of the spade tip itself, is such that the anchor roller may need to be re-positioned slightly farther forward to avoid interference between the spade’s tip and the forepeak of the vessel.


45# Manson Supreme main anchor with 35# CQR backup anchor


Toggle attaches anchor shank to chain to minimize mechanical side-loading.

Aboard Sanctuary today, we have fit a second bow roller, very similar in design to the OEM unit.  It is manufactured by Vetus/Maxwell, model OBELIX, at an Internet cost of around $275.  Our primary anchor now is the 45# Manson Supreme; probably around $450 today.  On the second bow roller, we’ve permanently mounted our old 35# CQR.  Our Manson Supreme is on an all-chain rode attached to the anchor shank by a SS toggle, not a shackle.  The CQR has 8′ of 3/8″ chain leader, then 200′ or so of 3-strand nylon.  Until it’s necessary to re-galvanize the chain, we plan to leave the existing BBB in place.  At that time, we expect to change the wildcat and upgrade to high-tensile chain.  The primary (chain) rode is stored in the boat’s chain locker.  The 3-strand nylon is stored on deck in a basket.  Not elegant, but I’m thinking out better ways.  The Danforth is on the flybridge rail, still accessible and available, as a tertiary backup.