Ground Tackle: Anchor, Chain, Rode and Scope
Guidelines from a power boat cruiser.
Your vessel needs adequate ground tackle to hold it in place at a safe depth in any weather you may encounter while off the dock.
Anchors: The type of anchor varies greatly so personal preference is where I will leave that.
Scope: The ratio of the length of the anchor line / rode to the depth of the water.
Rode: All the chain and or chain and line, here again personal preference.
All anchors require some chain to work correctly; rule of thumb is, the chains length is equal to or greater than length of the vessel.
Chain: Perhaps the most important part of the ground tackle it helps maximize the holding power of the anchor. The heaver and longer the chain the better your anchor can hold.
Things I look at when arriving at an anchoring area:
- Other anchored vessels; where are they anchored, are they scattered all over the bay, or are they mostly in one area, if only in one area WHY? What do they know that I don’t?
- Check your charts for underwater obstacles you may not be able to see at this time.
- Current and wind direction, easy to tell current and/or wind by looking at the other boats.
- Tide when is high/low tide, how much more or less water will be under you then.
- Adequate swing room for my vessel once I have laid out ground tackle and what I feel will be a safe scope for the forecasted conditions.
- Pay attention to the boats that will be anchored around you and what does their rode look like, is the rode pulled tight in a minimal wind or current, if so they could present a potential problem later on. I will stay clear of them when setting the hook.
- When in an unfamiliar anchorage I will run the boat around encircling what would be my swing area watching the depth finder to see if there is anything under me I may not beware of.
Once I have picked a spot that I feel will be safe to anchor:
Things I do when preparing to set the anchor:
- Know my depths.
Let’s say its 30’ deep and its 1 hour before low tide with a light wind for this example.
- With my bow in the same direction as everyone else (bow to the wind in this case)
I will run 100’ – 150’ past the area I want to end up.
- Drop the hook 35’-40’ then gently back down while letting out rode( you don’t want to let the chain pile up on top of the anchor) once I have 70’- 90’ feet out. . .turn the boat sideways to the anchor. . . and give it just a little reverse power then go to natural and drift back, when the hook grabs it will turn the boat back to straight at that time you need to drop another 50’- 60’ feet again while gently backing down and do the turn sideways one more time when the boat straightens out the 2nd time. . . . . you are set. I have never had my anchor slip using this method.
Now that your anchor is set:
- Time to deal with how much scope you need, the 120’-150’ out is good for a short stay on-board and light conditions.
- If you plan on leaving the vessel, spending several hours, maybe the night, or having other boats raft-up you need to do more.
- 150’ of scope at 30’ of depth is only 5 to 1 – – – 120’ is 4 to 1 remember you will have an incoming tide soon so you could easily be in 35’- 45’ depth you’re scope will soon change to 4 to 1@ 150’ out or 3 to 1@ 120’ out, or less . . . . Not very good holding power, add some wind or a strong current and before you know it your slipping anchor.
- 7 to 1 is the suggested scope (30’ depth = 210’ scope)
- Keep in mind as conditions change you may need to increase the scope to hold.
- Every additional boat added to a raft is more weight and mass to hold
- add wind or current in the equation and you are asking a lot from 1 anchor
- Adding help for that anchor do its job is prudent
- add more scope,
- a better solution is to have every 3rd boat drop hooks.
- Place the largest boat and anchor in the center of the raft-up.
Thanks to Gary Bradley. Gary lives aboard his power boat M/V Lucky Dog, and has cruised extensively from South Puget Sound to Canada, Desolation Sound and points north.