Anchor Mooring South Lake Tahoe Boat Salvage
A permanent mooring must remain secure for long periods while unattended, occasionally under adverse conditions. For peace of mind, it should be properly sized for the job, and determining the minimum size has a lot to do with the conditions under which the boat is moored, the amount of fetch for waves to build up, and whether your mooring is a temporary one, designed for overnight use in fair weather, or a mooring capable of riding out a hurricane. Below are the basic components.
Anchors
Several types are in common use, and we’ll review them in order of their holding power, from the wimpiest to the most tenacious:
- Concrete Blocks: Many boats use 50-gallon drums filled with cement, concrete blocks, auto engine blocks and other types of dead weight. This type provides the least holding power, working on the principle of sheer weight, but is reliable if pulled out of the bottom. If they drag, they will resist motion with a constant amount of force. Note that concrete loses over half of its weight when submerged in water, so a mooring designed to withstand a 500lb. the pull will need 1,000lb. of concrete.
- Mushroom Anchor: the most common type of mooring anchor is the mushroom, which, under ideal conditions, with the right kind of bottom, can dig in, create suction and develop good holding power. Mushroom anchors work best in a silt or mud bottom and are not as effective in rocks or coarse sand. If a mushroom gets pulled out of the bottom, it is less likely to reset itself completely, and will merely skip along across the bottom. A weight of 5-10 times boat length is a good rule of thumb, as a bare minimum. The heavier the better, as long as you don’t have to move it.
- Pyramid Anchor: The cast-iron Dor-Mor pyramid anchor is a superior alternative to the mushroom. Its smaller size, concentrated weight and pyramid shape allows it to embed itself more rapidly, and its holding power (at a scope of 3:1) is up to about ten times its weight. Recommended by Practical Sailor/Powerboat Reports in 2009.
- Helical Screw: while the above types rely for holding power on sheer weight or a combination of weight and embedding themselves in the bottom, the helical anchor is screwed into the seabed, usually by a barge-mounted hydraulic device. Helical screws have long, high-tensile steel shafts (8′ length is common) with large screw threads (10″ to 14″ diameter) on the bottom and an attachment eye at the top. These professionally-installed anchors, originating in the offshore oil industry, have gained popularity with recreational boaters since the 1990s and have the most extreme holding power in relation to their weight.
How to Install a Permanent Mooring
Unlike ordinary anchoring, a permanent mooring system is designed for leaving your boat unattended for long intervals. A mooring, in many cases, is the safest and most cost effective way to leave a boat in the water, whether riding out a storm or leaving it til next weekend.
The following is a guide to building your own mooring; it provides an outline of common practices, including recommendations from maritime authorities such as Chapmans and various harbormasters. Whenever installing a mooring, it is absolutely necessary to first check with local harbormaster. Before purchasing gear, find out the ground tackle requirements in your harbor.
The anchor weight and type are crucial to holding strength on any mooring. The more exposed a mooring site, the rougher it will be during storms. For exposed moorings go supersize. Exposure to open sea or fetch allows wave and wind strength to build enough force to drag gear around.
On the other hand, protected inlets require less hefty ground tackle. In general, permanent moorings are designed with less scope than traditional anchors, thus forming a tighter swing radius. The compromise, shortened scope means a more effective anchor is required.
Therefore, a permanent mooring anchor must be significantly heavier than your everyday use anchor. Mooring scope from anchor to the end of pennant should be at minimum 3 times the depth of water at highest tides. Your local harbormasters will specify type and weight of approved mooring anchors in the harbor.
In general, a mushroom anchor is the most common, great for softer seabeds. As the mushroom anchor digs in it buries and creates suction. For effective holding power the mushroom must remain embedded in mud or sand, otherwise storms with wind direction opposite the prevailing will cause the anchor to “spin out” and drag.
For estimating the mushroom weight, multiply the boat length by 5-10 times as a good rule of thumb. On hard or rocky bottoms, heavy deadweight anchors such as massive concrete blocks are the norm. Since a blocks holding power relies on shear weight, deadweight anchors must be significantly heavier than mushroom style.
Density is also a consideration, more concrete is needed than comparably denser cast iron for equivalent weight in water. Block style moorings are set with a barge and crane. A third option is the Pyramid anchor, for sand or hard bottoms.
An approved professional mooring installer can set the whole rig for you for a fee. Most towns have a list of approved installers in the area. Professionals installers can also offer more than just the traditional anchors.
Helical screws driven into sand bottom seabed with a hydraulic tool have superior holding power. Pioneered by oil rigs decades ago, sand screws leave only an exposed eye to connect tackle. Along with better holding power, sand screws are less likely to foul, but they’re also easy to lose should the gear part.
Best chain for moorings
Aside from unavoidable corrosion, chains biggest wear comes from continually brushing the bottom. The sand abrades the metal over time, making those unseen links near the bottom precariously thin. Be sure to have a certified mooring inspector that periodically inspect the integrity of chain. (Annual inspection is the standard.)
It is commonplace to replace the chain every 3 seasons or so in salt water. Wider diameter chain has thicker metal per link to wear away, thus it should last longer. Chain diameter is measured by the thickness of the wire forming each link, not the opening of the link (link opening measurement is coil size).
When selecting chain, there are 3 basic considerations: grade (metal tensile strength), diameter (thickness of chain) and coil (opening size). A secondary concern is a finish for corrosion resistance. For moorings, Proof coil, preferably with hot dip galvanized finish, is the most common and economical.
Buoy
The mooring buoy serves a dual function. It floats all that heavy chain to the surface and also increases holding power by absorbing the shock of heavy weather waves and wind. USCG regulations require standard white with blue stripe mooring buoys. The chain should thread through the center of the buoy before connecting to the pennant.
Stopper rings cut like washers from old tires are a good provision to prevent the shackle from pulling through and crushing buoy core. Quality mooring buoys are made with a hard plastic shell filled with closed-cell flotation foam. This ensures sufficient buoyancy, even if shell integrity is compromised.
A lighter pickup buoy at the end of the pennant makes hooking up to the mooring easy. A small float does the trick. For boats with higher freeboard, a mast buoy is a huge help, making pickup easy without a boat hook.
Pennant
The pennant-ties the boat to the mooring. Choose the largest diameter that reasonably fits through the bow chocks and around the mooring bit or cleat for best bet. Easy splicing 3 strand line is most common, made from nylon for shock absorbing stretch. Equivalent diameter double braid polyester offers more strength than 3 strand.
Either should include some kind of chafe gear sleeving to prevent abrasion. To connect the pennant to the chain, use an eye splice around a galvanized thimble and a heavy-duty galvanized shackle. Some larger, heavy-tonnage vessels opt for stainless steel wire pennants for maximum strength and chafe resistance.
The Tahoe Area
South Lake Tahoe is an alpine lake, 6,200 feet in elevation, approximately 22 miles long, 12 miles wide and 1,645 feet deep at its deepest point. It furnishes excellent boating opportunities under generally safe conditions. There are, however, unique restrictions and hazards that boaters should be aware of.
There are numerous mooring buoys and mooring buoy fields around Lake Tahoe. Use caution and slow speeds when transiting around these mooring areas. DO NOT USE MOORING BUOYS FOR NAVIGATION.
There’s also a place located in the city of Homewood where it’s possible the best supplies for mooring your boat, it could an anchor or a buoy.