Rode & Line

Definition:

WLL: Working Limit Load /Safe Working Load (SWL)/Normal Working Load (NWL) is the load that the rode can safely support without fear of breaking. Usually marked on the equipment by the manufacturer and is often 1/3 to 1/4 of the Minimum Breaking Strength (MBS) for chain and 1/10 to 1/12 the Minimum Breaking Strength (MBS) for rope 

 

***When sizing your gear you should make sure that the SWL/WLL of you rode is higher than the loads expected in a Storm. Sizing your working rode for a hurricane might not be practical but sustained winds > 40 knots are commonly enough encountered by cruising vessels on anchor and sizing for such conditions is a reasonable way to approach the problem and is the basis for our  recommendations. ***

 

Chain:

Common Marine Chain Types:

 

Note:  the WLL (working load) is ¼ the MBS (minimal breaking strength)

1/4 (7mm) 5/16 (8.7mm) 3/8 (10mm) 1/2(13mm) 5/8(16mm)
Proof Coil Grade 30 1,300 WLL5,200  UTS

 

1,900 WLL7,600 UTS 2,650 WLL10,600 UTS 4,500 WLL18,000 UTS 6,900 WLL27,000 UTS
BBBGrade 30 1,300 WLL5,200 UTS

 

1,900 WLL7,600 UTS 2,650 WLL10,600 UTS 4,500 WLL18,000 UTS 6,900 WLL27000 UTS
Grade 40 2,600 WLL7,800 UTS 3,900 WLL5,850 UTS 5,400 WLL8,100 UTS 9,200 WLL27,600 UTS 13,000 WLL39,000 UTS

 

Stainless Steel 316 2,000 WLL8,000 UTS 2,400 WLL9,600 UTS 3,750 WLL14,200 UTS 6,500 WLL26,000 UTS 11,000 WLL33,000 UTS

 

 

PROOF COIL Grade 30:

Proof coil chain is a general purpose chain for all ordinary applications not requiring high strength characteristics. Frequently used for light duty tow chains, tie down chains and logging chains. Identified with “”L3″” or similar grade marking

BBB Grade 30:

A low carbon steel, general purpose anchor (windlass) chain, with a short, compact link.

The short link makes it more flexible and ideally suited as a windlass chain. Compatible

with all major brands of windlasses.

 

G40:

High tensile strength carbon steel anchor (windlass) chain with an ISO short link.

The short link makes it more flexible and ideally suited for use as an windlass chain.

Check fit or contact windlass manufacturer before purchase.  Marked : “G4” or “A4” every link

 

Stainless Steel Chain:

Imported stainless steel chain made to NACM specifications

US made stainless steel chain that also conforms to NACM (5/32, 3/16, 5/16 and 3/8) dimensions.

US and French made stainless steel chain that conforms to Gr 40 (G4) and triple B (BBB) windlass chain (also called “ISO short link”) specifications in 1/4, 5/16, 3/8 and 1/2″ sizes.

 

 

Boat Size

0- 14 feet
< 1,000  lbs

14-20 feet
< 5000   lbs

20-30 feet
< 11,000 lbs

30-35 feet
< 15,000 lbs

35-40 feet
< 20,000 lbs

40-45 feet
< 40,000 lbs

45-50 feet
< 50,000 lbs

50-60 feet
< 60,000 lbs

60-70 feet
< 70,000 lbs

70-90 feet
< 110,000 lbs

Chain

BBB, Proofcoil

1/4

1/4

5/16

5/16

3/8

3/8

7/16

7/16

1/2

5/8

Chain

HT

1/4

1/4

1/4

5/16

5/16

3/8

3/8

7/16

7/16

1/2

Chain Sizing Recommendations:

 

How Much Chain:

An average cruising boat carries 300 feet of chain, which will give one 1:10 scope in 25 feet of water (5 feet allotted for freeboard height).  This set up will ensure that most of the time you are anchored on chain and reduce the likely hood of rode failure.

 

LINE RODE:

The SWL is a guideline for the use of a rope in good condition for non-critical applications and should be reduced where life, limb, or valuable property is involved, or in cases of exceptional service such as shock loading, sustained loading, severe vibration, etc. The Cordage Institute specifies that the SWL of a rope shall be determined by dividing the Ultimate Tensile Strength of the rope by a safety factor. The safety factor ranges from 5 to 12 for non-critical uses and is typically set at 15 for life lines.

 

Assuming 1-8 safety factor we generated this table:

Line Diameter (inches) 1/4 5/16 3/8 7/16 1/2 9/16 5/8 3/4 7/8 1
Nylon Three Strand  250WLL

2,000 UTS

375WLL

3,000

UTS

550WLL

4,400 UTS

737WLL

5,900 UTS

937WLL

7,500 UTS

1,175 WLL9,400 UTS 1,525 WLL12,200 UTS 2,087 WLL16,700 UTS 2,937 WLL23,500 UTS 3,675 WLL29,400 UTS
Nylon Double Braid 250WLL

2,000 UTS

375WLL

3,000

UTS

550WLL

4,400 UTS

737WLL

5,900 UTS

937WLL

7,500 UTS

1,175 WLL9,400 UTS 1,525 WLL12,200 UTS 2,087 WLL16,700 UTS 2,937 WLL23,500 UTS 3,675 WLL29,400 UTS

 

Nylon is subject to degradation with time from chafe and UV exposure, further this damage is not easily identified nor can be easily quantified. Trying to envelop such uncertainty would require you to use very large line (For example: 7/8 line to substitute 3/8 BBB chain) and even then frequent inspection would be necessary to insure line integrity. Thus is it is our recommendation to use chain as the primary rode when possible as it is more forgiving and durable. Nylon could be used as shock absorber in the form of a bridle or a snubber system.  It is reasonable to extend the length of chain rode with nylon line to accommodate deeper anchorages and/or increase in scope. A typical cruising boat carries 300 feet of chain, which will give one 1:10 scope in 25 feet of water (5 feet allotted for freeboard height).  This set up will ensure that most of the time you are anchored on chain and reduce the likely hood of rode failure. However anchorages deeper than 30 feet are plenty and it is often impractical to carry more than 300 feet of chain, in such situations it is important to use line that is appropriately sized and well inspected.

 

Boat Size

0- 14 feet
< 1,000  lbs

14-20 feet
< 5000   lbs

20-30 feet
< 11,000 lbs

30-35 feet
< 15,000 lbs

35-40 feet
< 20,000 lbs

40-45 feet
< 40,000 lbs

45-50 feet
< 50,000 lbs

50-60 feet
< 60,000 lbs

60-70 feet
< 70,000 lbs

70-90 feet
< 110,000 lbs

Line Dimeter

(inches)

3/8

1/2

9/16

5/8

5/8

3/4

3/4

3/4

1

1

Sizing Line for your Rode:

 

Shackles:

Sizing a Shackle:  Click here to learn more about shackles

Generally Shackles Come two grades:

  • Industrial Grade (Type IV A)
  • Specialty Alloy Shackles (Type IV B)

If you are trying to match the strength of your chain you can use these two rules:

  • If sizing for BBB or Proof coil chain use Industrial Grade (Type IV A) shackle, one size bigger than your chain
  • If sizing for HT (G4) chain use Specialty Alloy Shackles (Type IV B), one size bigger than your chain
  • If sizing for stainless steel chain use a forged SS shackle that is one size bigger than your chain.

***Shackles are sized by their body dimension, the pin is usually one size bigger than the size of the shackle***

 

Boat Size

0- 14 feet
< 1,000  lbs

14-20 feet
< 5000   lbs

20-30 feet
< 11,000 lbs

30-35 feet
< 15,000 lbs

35-40 feet
< 20,000 lbs

40-45 feet
< 40,000 lbs

45-50 feet
< 50,000 lbs

50-60 feet
< 60,000 lbs

60-70 feet
< 70,000 lbs

70-90 feet
< 110,000 lbs

Shackle

Specialty Alloy Grade

5/16

5/16

5/16

3/8

3/8

7/16

7/16

1/2

1/2

5/8

Chain

BBB, Proofcoil

1/4

1/4

5/16

5/16

3/8

3/8

7/16

7/16

1/2

5/8

Chain

HT

1/4

1/4

1/4

5/16

5/16

3/8

3/8

7/16

7/16

1/2

 

***Chain and shackle sizes are presented as a fraction of an inch***

 

 

 

Swivels:

Swivels are used to attach an anchor to the chain with the purpose of preventing chain twisting as the boat moves around in the anchorage.  Swivels also help the anchor come up in the correct orientation into the bow roller on retrieval.

  • In the practical sense swivels are often unnecessary unless you intend to anchor for a long time in one spot, further twist usually gets undone as the chain is retrieved with the windlass. If anchored in one spot for an extended period or if designing a mooring system swivels do solve a problem.
  • Swivels are generally considered to be the weakest link between your anchor and the boat.

One issue is swivels often fit directly into the shank and if so can be side loaded (when the anchor is stuck in rocks for example) and fail at much lower loads than the SWL they are rated for. To solve this attach a shackle or a shackle with some chain to the anchor first and then the swivel this will prevent the above mentioned problem with side loading. Further it is often hard to size a swivel for to match the strength of the HI TEST chain, though some well-designed products are available on the market.

One should pay attention to the SWL (safe working load) rating on the swivel as compared to the chain.