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BOAT LINE DEFINITIONS & MARINE APPLICATIONS
Mooring Line is a general term to
include both Anchor and Dock Lines

• Dock Lines are used to Moor (connect / fasten) or Make Fast a boat to a dock (dock lines) or a permanent mooring (mooring lines) like a pile, pier, wharf, or buoy field. Most often the connecting points are cleats, but not always. Fenders are employed to cushion the movement of the boat against the mooring.

• Loop (Soft Eye) — Dock Lines are provided with a spliced loop on one end (eye splice), which provides for an easy method for making fast around a cleat, pile, bolted eye ring, etc. While the bitter end (free end) of the dock line is made fast to another cleat and the slack adjusted for tension (slack removed) using a cleat hitch.

• Chafe Protection (Covered Eye) — Use Leather, Nylon Cordura Tubing, or Dipping to increase the life span of your lines as they rub against cleats, chocks, and your moorings. Chafe protection is most often used on dock line eyes, but can be used to protect other sections of the bitter end too (chock areas).

• Bow, Stern, and Spring Lines — Most average sized boats can be moored using two groups of dock lines (4 dock lines). For the first group there is one each of a Bow Line and a Stern Line, which are +/- 2/3 the length of the boat, and are used to make fast the bow and stern to the mooring. For the second group there is an After Bow Spring Line and a Forward Quarter Spring Line, which are +/- the same length of the boat. The spring lines cross each other forming an x-pattern to the mooring. (Please refer to sketch.)

• Breast Lines — Larger and heavier boats use the same lines mentioned above, but can use relatively short lines that connect direct from a boat cleat to the nearest cleat directly across on the dock. Breast Lines are often employed on houseboats in a slip.

• Buoy Field Mooring — When a boat is moored to a buoy field, custom mooring lines can be utilized, which have characteristics of both dock lines and anchor lines. A typical line will have a dock line eye for connecting to the boat’s cleat and a thimble eye with a stainless steel swivel hook or shackle for making fast to the buoy cable. The mooring line might be fitted with a buoy or rope float.

• Lake Shore Mooring (Shore Lines) — For many inland applications, a power boat is moored from the lake shore where the bow faces outward to the lake and the stern faces the shore. The bow is moored using an anchor line secured to the lake bottom, while the stern is moored to an anchor line secured to the shoreline. The bow mooring line may have a chain rode attached. Both mooring lines might well be fitted with buoys or rope floats; especially, the bow connection. The bow and stern lines will have some type of hardware required to make the connections to the boat like swivel eye hooks or spring clips.

• Augers — As an alternate to using anchors, a boat owner may use augers. Set one auger to the lake bottom to secure the bow and set another auger on shore to secure the stern. Here a variety of mooring lines can be utilized like anchor lines, dock lines, plain straight lines, and or custom mooring lines. The bow line may have a chain rode attached. Both mooring lines might well be fitted with buoys or rope floats; especially, the bow connection. The bow and stern lines will have some type of hardware required to make the connections to the boat like swivel eye hooks or spring clips.

• Houseboats — typically use a minimum of four 5/8" to 3/4" diameter dock lines for each side of the boat and secured in locations to prevent the boat from moving side-to-side, forward and backward, during bad weather conditions using the classical dock line techniques mentioned above. The bitter end (free end) of the dock lines are made fast to cleats located on the dock and the slack adjusted for tension (slack removed) using a cleat hitch.

• Large Boat in a Slip — When any boat is moored for long periods of time in a slip, use the classical dock lines techniques already mentioned, but often dock lines are utilized on both the port and starboard sides of the boat. Therefore, a large boat may need two bow lines, four spring lines, and two stern lines. Add breast lines as required. Slip Dock Lines are often short due to the close proximity of the cleats on the boat and the dock. Chafe Protection for slip dock lines is highly recommended.

Anchor Lines

• Anchor Lines are used to temporarily Moor (connect / fasten) or Make Fast a boat to a lake or sea bottom.

• Thimble (Hard Eye) — Anchor Lines are provided with a thimble eye splice on one end, which provides for chafe protection for an anchor shackle. An anchor shackle connects the thimble eye of the anchor line directly to the anchor or in most applications a chain rode. Three strand nylon anchor lines can be spliced directly to the chain rode. The bitter end (free end) of the anchor line is made fast to the boat’s cleat or bow eye ring and the slack adjusted for tension (slack removed) using a cleat hitch.

• Proof Coil and Windlass Anchor Chain — For most applications, a long nylon anchor line connected to a chain rode is adequate. Vessels without a windlass can use standard Proof Coil Anchor Chain. Larger boats; especially, ocean going are provided with a chain windlass. Windlasses require either BBB Chain or G4 High Test Chain.

• Rode Chain has two purposes. First, the chain portion of the rode will resist chafe that would otherwise occur if a nylon line was lying along the bottom. Secondly, the weight of the chain portion has the effect of keeping the angle of pull on the anchor low, which keeps the anchor flukes dug in.

• Anchor Rode Package — An example of a windlass rode package is 200-600 feet of windlass grade 3-strand or 8-plait nylon line spliced directly to 6 to 25 feet of 1/4” – 1/2” windlass specified chain (G4 HT or BBB). The chain is connected via a shackle or anchor swivel to an adequately sized anchor. Seize the shackle pin with a nylon cable tie or wire. If the boat does not have a windlass, one can use double braid nylon or 3-strand nylon with proof coil anchor chain.

• Scope is defined as the ratio of the depth (draft plus freeboard) divided into the length of anchor line paid out. The typical minimum scope is from 3-5 with 7 being the best practical. The larger the scope ratio, the better the holding power of the anchor because the angle of pull on the flukes remains low. However, during a bad storm an even larger scope should be used i.e. (10:1).
(Please refer to sketch.)

• Scope Ratio Example — For a 40ft depth (including draft and freeboard) and a scope ratio of 5 desired, then the length of anchor line to be paid out is 200ft (5 x 40).

• Small Scope Ratio increases the angle of pull and in turn reduces the holding power of the anchor flukes. Heavy rode chain and can be used to mitigate this from occurring. The heavier chain will help keep the angle of pull low when the scope ratio is also low.

• Scope Holding Power — Consider the following scope ratios and % anchor holding power: 2:1=10%, 3:1=40%, 5:1=70%, 10:1=100%.

• Wind Speed — As the wind speed doubles the holding power of the anchor quadruples. Consider having a spare emergency anchor / anchor line available in case an anchor line gets cut, gets stuck, and or for bad storm conditions (storm anchor).

• Equipment — The anchoring system includes any of the following: windlass, deck cleat, anchor chain, shackles, splices, thimbles, and the anchor. All of these should be checked regularly for wear and all be sized properly.

• Anchor Setting and Retrieval — With the line paid out at the proper scope, back down on the anchor line very slowly and confirm the anchor is set. To retrieve move over the anchor pulling the slack up. Snub the line on a cleat and back down to pull the anchor out.

Tow Lines & Misc Info

• Tow Lines are used to tow a recreational power boat behind a larger boat like a houseboat or yacht.

• Thimble Eye Splice — Tow Lines like anchor lines are provided with a thimble eye splice on one end, which provides for chafe protection for connection to a shackle, swivel eye hook, or spring clip. The hook or clip connects the thimble eye of the tow line directly to the bow eye of the power boat. The bitter end (free end) of the tow line is made fast to the towing vessel’s stern cleat and the slack adjusted for tension (slack removed) using a cleat hitch. The tow line might be fitted with a rope float.

• Permanent or Shackle Connections — The connection between the tow line and the swivel eye hook (or shackle) can be a permanent connection (the hook is connected directly to the thimble) or temporary (the hook is connected to the thimble via a shackle).

• Thimble Eye Both Ends — The tow line can also be provided with a thimble eye on each end of the tow line. Connections are made as already stated, but are required on each end of the tow line. For boaters who tow often this may be the most convenient method.

• Custom Towing Bridle — The ultimate tow line solution; especially, for ocean going applications, is a Y-shaped custom towing bridle made to the customer’s specifications.

• Houseboat Anchoring (Shore Lines) — Many captains will moor their houseboat to the shoreline using a set of 3/4” x 150 foot double braid nylon shore lines where the bow is run aground with the stern sticking out into the lake. Shore lines might well include any combination of the following types of mooring lines; long dock lines, anchor lines, windlass anchor rode, and or hand winch anchor lines. Considering this typical scenario, use the last two aft cleats on each side of the houseboat as connection points for the shore lines. Therefore, there are a total of four shore lines, two on each side of the houseboat. The shore line connected on the most aft cleat might form an acute angle not to exceed 60 degrees between the houseboat and shore, while the inside shore line might form an acute angle not to exceed 45 degrees. Larger houseboats might increase the rope diameter of the shore lines and smaller ones might have one shore line per side. All houseboats should have emergency shore lines available in case a shore line gets cut, breaks, and or for stormy conditions (storm lines).

General Note on Anchoring: The anchors may get secured / wrapped around large rocks, buried in a sand hole, and even secured with steel pins, and driven rebar. Slack can be removed on shore at the anchor or on the house boat at a cleat, by a windlass, or hand winch. Use the houseboat's engines as required to help adjust tension on the lines. It is highly recommended to utilize a thimble and chain rode as means of chafe protection for each anchor line. Similarly, dock line eye splices can be covered with chafe guard.

Adjusting Tension on Houseboat: Using the bitter end of the shore line, adjust tension at the cleat and secure using a cleat hitch. Otherwise use the windlass or hand winch to take the tension out. In this scenario, the other end of the shore line is typically a stainless steel thimble splice with an anchor shackle connecting to either an anchor; an anchor rode chain, an auger, a driven rebar stake, or other. The shore line can also be wrapped around a large log or boulder.

Adjusting Tension on Shore: Using the bitter end of the shore line, adjust tension at the anchor or anchor rode chain’s an anchor shackle and secure using a single turn two half hitches knot or similar. Otherwise use the same knot and either wrap the shore line around a large log or boulder, secure to an auger, driven rebar stake, or other. In this scenario, the other end of the shore line is typically a covered dock line eye splice secured to an aft cleat on the houseboat.

• ANIMATED KNOT TYINGanimated knots
Go to Animated Knots by Grog and select "Boating" knots.

 
custom recovery ropeClick here to Download Catalog PDF, View Chapter 6 Boat Definitions & Knots and View Appendix
 
Tow Bridle / Tow Line Design Considerations
Generally pay out enough tow line length to place the towed vessel behind the second wake of the towing vessel based on speed and weather conditions. This specification is more often applied to ocean towing, but less often when towing a recreational boat behind a houseboat on a calm lake. Select the working load of the tow line to be as much as the full weight of towed vessel. This specification is very important when towing during bad weather conditions and or where the wave action will create probable shock loads on the tow line to be equal to the towed vessel’s full weight. Again, this specification is more often applied to ocean towing.Select a Y-Shaped Towing Bridle for high performance towing applications (USGC recomended) as opposed to a single leg tow line, which is typical for lake towing applications.

Example No.1
• A 55 ft Sportfish towing a 25 ft 5,000 lb center console boat to / from FL to Bahamas. In this case we would recommend a fully specified Y-shaped towing bridle with a safe W.L. of approximately equally to the 100% full weight of the center console. In this example we would specify 2 Y-legs at 7/8” x 50 ft double braid nylon for connecting to the sportfish’s stern cleats. Here the connection to the cleats can be via bitter ends using a figure eight knot or covered dock line eye splices. Then we have a 1/2” x 150 ft 12-strand dyneema tow leg with a thimble and bearing shackle connection to the center console’s bow. Very often the captain will choose to include an optional snubber line so the towed vessel can be quickly disconnected from the tow leg and put underway even with the snubber line still attached to the bow. Comment: reducing the W.L. to 75% will reduce the stern leg rope diameter to 3/4” double braid nylon & the tow leg can be changed from 12-strand dyneema to 3/4” double braid. Consider adding rope floats.

Example No.2
• A 75 ft Houseboat towing a 22 ft 3,800 lb wakeboard boat on Lake Powell. In this case we would recommend a single leg tow line with a safe W.L. of approximately 50% of the full weight of the wakeboard boat (2,000 lbs). In this example we would specify a 5/8” x 75 ft double braid nylon tow line. Here the connection to the houseboat’s stern cleats can be via a bitter end using a cleat hitch or a covered dock line eye splice. On the opposite end of the tow line we would specify a swivel eye hook for connection to the wakeboard boat’s bow. Very often the captain will choose to place a rope float near the houseboat’s stern and even another rope float near the wakeboard boat’s bow. Comment: reducing the W.L. to a 33% will reduce the rope diameter to 1/2”.
 
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Apply these definitions and techniques as required to fit your circumstances. An excellent literary resource is the latest edition of "Chapman Piloting Seamanship & Small Boat Handling". At Denver Rope we strive to offer the best custom boat lines made to your specifications. We also offer stainless steel and galvanized marine hardware and special assemblies of custom colored rope, hardware, chain, and buoys all made in the USA to your specifications using the best nautical techniques.