The LaHave River mooring experience
A fixed mooring relies on three design criteria to hold your vessel in place during storm force winds and high waves; a massive block, suction to hold the block in the river bottom mud and shock strain relief. Unlike temporary anchors, the scope for a permanent mooring should be close to three times the depth at high tide to avoid large vessel swing. The size of the components are chosen to account for wear and shock strain, more than raw strength. The bottom chain weight provides shock relief when the vessel is pounding in high surf during storm wave action and the boat weather vaning. Some skippers may also use a shock relief system in the pendant.
The most common mooring practice at LRYC is to place one or two concrete mooring blocks, with an embedded steel loop or through hole for the ground chain. Larger vessels should consult with the Dock Master or Rear Commodore regarding block size. Good quality galvanized hardware and chain is recommended. Stainless steel corrodes quickly in low oxygen bottom mud. The ground chain is shackled to the mooring block and to the downline at the other end. A swivel is inserted at the intersection of the downline and the ground chain. The goal is to keep the hardware in the oxygen deprived bottom mud most of the time, which greatly reduces corrosion. Corrosion is most often discovered at the end of the ground chain, at the shackle/swivel, and is caused by the buoy lifting the ground chain off the bottom. The downline should be a bit longer than high tide depth to avoid lifting the ground chain when the boat is not on the mooring. A smaller second concrete block may also be chained 10 ft or less from the large block. The ground chain then continues from the smaller block. This system provides even more shock relief when the smaller block is lifted during storm force winds and waves.
To aid divers in recovery of missing moorings, consider attaching a buoy to the block that would float about three feet off the bottom, or even some lengths of floating line at intervals on the chain to assist in finding the tackle when it's covered in mud. It's quite deep in places in our field and some blocks and chain sink well out of sight even when you are right above them
If the existing tackle is too long, the best method is to shorten the ground chain. Simply move the downline shackle from the end along the ground chain towards the mooring block. The extra chain can be shackled back along the ground chain to add additional shock lifting weight. When maintenance is required the other components can be adjusted and the overall length and scope maintained.
Expect a large amount of marine growth on the first few feet of your mooring tackle. Some skippers find a coat of leftover bottom paint on these surfaces greatly reduces the mass of growth.
It is common practice to leave the pendant attached to the mooring ball.
Nylon pendants will sink, whereas polysteel line will float. A double pendant is called a bridle. It is recommended that the second pendant be spliced in a foot or so from the buoy. This method avoids twisting and chafing of the line near the thimble, a common failure point. Pendants should be sized to fit through the bow chocks. Pendants must be marked with a small buoy, or a few in-line net buoys, to mark the bitter end for passing boaters.
Mooring balls in Canadian waters should be white, however, white was difficult to source locally and less expensive orange was chosen. The mooring ball must be marked with the vessel name and LRYC grid location. The size of the ball is determined by the weight of the downline, a much larger ball is required for the extra weight of a chain downline.
White or red winter sticks, or other small buoys, are strongly recommended. During the winter freeze-up, the local practice is to remove the tackle from the end of the ground chain and replace it with a ½” or larger polysteel line attached to a white or red winter stick. The winter stick downline is sized so that the stick is submerged above low tide. The winter stick should not be so large as to cause lifting of the ground chain. Add weight near the the end of the winterstick downline to avoid ground chain lifting. Winter sticks are often constructed from treated 4x4, no more than 16” in length, tapered at the end where the downline through-hole is made to avoid snagging in the ice flows. Carve your LRYC grid location into the side of your wooden buoy to avoid confusion.
George Matthews, LRYC Rear Commodore 2015
LRYC mooring field has a range of depth of 6ft:
inner to outer mooring field depths:
5 to 17 ft low tide
11 to 23 ft high tide (6 ft average tide range)
Ground chain should be, high tide times 1 ½ (g).
Downline, high tide + 1ft (d)
Pendant (bridle) for the boat, 1 ¾ times the freeboard + length to cleat (p) ft.
Total length, g+d+p = x ft
The vessel swing will be close to the boat length + x at low tide.
Downline length is sized longer than the highest tide to avoid lifting of the ground chain, shackle and swivel, unless we have a strong wind. Also reduces the down force on the buoy and shackles causing wear when wind is light. A few moorings use chain for the downline which means a much larger buoy is required. The benefit is that down chain has more shock relief during high wave conditions.
Depth at your assigned mooring grid location is 8ft (low tide)
High tide: 8 + 6 (tide range) = 14ft high tide.
Ground chain: 14 * 1 ½ = 21 ft. (1 ½ to 2 times recommended)
Down line: 14 + 1 = 15ft. Add line for splices and loops
Pendant: Freeboard for the boat 4ft * 1¾ = 7ft pendant. (Add line for distance from where the pendant or bridle crosses the bow to the cleat (1ft for this example), splices and loops)
Total length: 21 + 15 + 7 + 1 = 44ft
Scope: 44 / 14 = 3.1 (Should be between 3 to 4. Shorten existing ground chain to reduce scope and swing)
Link to our online mooring tackle calculator:
Recommended chain, shackles and downline size
(Only vessels to 30ft listed)
Ground Chain ⅝” (16mm) or larger. Boats less that 20ft, ½” (12mm)
Shackles to fit ground chain and thimbles
Downline ¾” (19mm) to 1” (25mm) polysteel or nylon 1” with galvanized thimbles
Down chain ⅜” inch galvanized schedule-40 or better
Pendant or Bridle ½” to ¾ polysteel, or ⅜” to ⅝” Nylon with white net buoys and thimbles
Recommended concrete mooring block dry weight:
10 - 17 500 lbs.
18 - 26 800 lbs.
27 - 35 2500 lbs.
36 - 45 2500 lbs.
45 - 55 3000 lbs.
Diagrams next page...
Three alternatives shown for buoy attachment.
- Mooring field and Tackle Guide