Anchor in Shallow water

[thinwater]

Originally Posted by Shaneesprit

I am the OP with wind it’s easy.
I think I said in less than 2m which is why I said it’s a multihull question. But still listening to mono replies I am not a CAT diehard.
If there was the possibility of a squall then yes deeper water required.
I was interested in what everyone else does because in calm you can be anywhere facing in any direction inside your anchor circle.
I had scope hence why my boat moved across the anchor West to East I had about 10m of scope 7m of chain, possibly more but moved about 20m in the direction of another boat.
Boat at no point circled the anchor. Just a 20kt breeze arrived.
The comment/reply wasn’t directed at you personally.

A few things.

• You only need deeper water in a squall if there is fetch more than a 1/2 mile or so. Waves cannot build in smaller harbors or if you are near the windward shore, or even with enough tall trees. Exposure and fetch are key.
• The importance of short scope is regional. Many of the places I frequent I am the only boat. Other places are crowded. I adjust practices to the location. I leave if it does not add up.
• The bottom matters. Good holding? Mud that is more like soup than soil, or patches of weed and shale and it's hard to tell? No anchor is better than the bottom.

[valhalla360]

Originally Posted by Shaneesprit

I have less chain than you! Maybe I need another 5ft of chain 😂
Less likely to be fighting for space! Not in the UK, it’ can be a struggle to find space. Literally looking for someone leaving to take their space. .

Yeah, not many harbors where people are drying out in the mud at low tide on this side of the pond (it's possible but not common).

Anchoring in 3ft at low tide, almost never have to fight for space.

[s/v Jedi]

Originally Posted by Shaneesprit

I am the OP with wind it’s easy.
I think I said in less than 2m which is why I said it’s a multihull question. But still listening to mono replies I am not a CAT diehard.
If there was the possibility of a squall then yes deeper water required.
I was interested in what everyone else does because in calm you can be anywhere facing in any direction inside your anchor circle.
I had scope hence why my boat moved across the anchor West to East I had about 10m of scope 7m of chain, possibly more but moved about 20m in the direction of another boat.
Boat at no point circled the anchor. Just a 20kt breeze arrived.
The comment/reply wasn’t directed at you personally.

I meant “original post” with OP. It said under 2 meters plus 1-2 meters of tide.

I get stuck in 6’ but occasionally choose to anchor there anyway. With my 5’ freeboard, this puts me at 11’ so 60’ of chain is just over 5:1. I am also 64’ long so my circle is well over 100’ immediately.

When it is calm, we always end up right over our anchor. I believe this is typical and all boats anchored move back and forth with the tide.

The reason for a minimum length of rode isn’t the scope but the dampening effect. Without it, it’s hard to not drag anchor even in 30kts wind gusts in squalls.

Unfortunately where we sail there’s always squalls.

In your case, when there isn’t much fetch, you can even anchor so that you stand on the seabed at low tide

[Anders]

Originally Posted by Shaneesprit

I am the OP with wind it’s easy.
I think I said in less than 2m which is why I said it’s a multihull question. But still listening to mono replies I am not a CAT diehard.
If there was the possibility of a squall then yes deeper water required.
I was interested in what everyone else does because in calm you can be anywhere facing in any direction inside your anchor circle.
I had scope hence why my boat moved across the anchor West to East I had about 10m of scope 7m of chain, possibly more but moved about 20m in the direction of another boat.
Boat at no point circled the anchor. Just a 20kt breeze arrived.
The comment/reply wasn’t directed at you personally.

Not sure why less than 2m would be a multihull question?

With 1.2m draft I sometimes anchor in less than 2m but not much tide to worry about usually using the standard 5:1 with 8mm chain and a 15kg Rocna.

[Nicholson58]

Originally Posted by Mike OReilly

Not sure if I'm allowed to comment since I'm once of those monohull folks, but I prefer anchoring in shallow waters. I like it because it means I'm close to shore.

I'm happy to swing in waters with just a few cms between my keel and the bottom. I just came out of an anchorage where my six-foot keel was scraping the bottom at low tide.

We are with Mike on this. We have lived aboard in the Caribbean for six years, entering #7. We are quite familiar with many anchorages in the windwards and Leewards. We prefer to find shallow anchorage too. We draw 2 meters. We routinely choose to leave about a foot under the keel. In settled weather, 4:1 on the 121# Rocna is about half a boat length. You don’t get much swing. I prefer to drop 60-80 feet if space permits. Winds are nearly always East +/- 5 degrees, every day. Tide is one foot.

Know the bottom. Are you OK with a bump? Rocks and pointy things or soft stuff? Will the bottom swallow your anchor? You need to be very comfortable there will be no dragging.

We have had two surprises, both in Jolly Harbor. A very strong, non storm blow, about 40 knots for several hours pushed the water out of Jolly. The effective low tide was minus three feet. We settled in the soft bottom and stopped rocking, eerie. The second instance was an earthquake in the BVI caused a mini tsunami in Jolly. Middle of the night I woke to rushing water. About 3-4 knots outgoing. We lost 2-1/2 feet in fifteen minutes. The reversal was as dramatic. Boats were spinning all around. The next day The water was muddy and full of debris including thousands of bottom dwelling jellies. We started a bit deeper so ended up with inches clear through the swings.

[Goodxcharly]

I would think the scope would be the same. Shallow or deep.
While taking in your comfort level and experience with setting a anchor.

[skipperguy]

Old rule of five to one always worked for me. 30 years of practice. The object is to create the proper angle between the pull of the rode and the fluke Angle

[Lodesman]

Originally Posted by Nicholson58

We draw 2 meters. We routinely choose to leave about a foot under the keel. In settled weather, 4:1 on the 121# Rocna is about half a boat length.

You don't factor in the height of your bow-roller in your calculations?

[David Mathis]

A scope of between four and six to one, a little more in a nasty blow, has worked well for us in all depths and conditions. The 2:1 scope you mentioned, even in shallow areas, is acceptable for only short daytime stops during calm conditions but not for overnight and never in even moderate weather. A short scope compromises the ability of the anchor to adequately penetrate. One of our favorite anchorages has a depth of three to four meters so all chain, with no catenary to speak of, would result in significant shock as the sea conditions become more severe. We have 30' of chain then 9/16" three strand nylon. With 60-90' of rode in the shallow anchorage, we have good holding, adequate shock absorbing, and don't swing within the radius of other boats. After one strong storm lasting most of the night, I snorkeled down to the anchor the next day and found it to be completely buried with the top of the 20k Bruce about 6" below the sea bed which was a mixture of coarse gravel and clay. The scope was about 5:1. Anchor line and chain is cheap compared to the price of a boat. Use enough to hold.

[billve]

I have seen first-hand how important it is to lay out more scope in shallow water. When anchoring in less than 10 ft, 5:1 scope may not be sufficient. Go to 7:1, 8:1 or 10:1, even if there is no storm coming. In my case, I was anchored off Jost Van Dyke in BVI. There was wind, but nothing particularly crazy -- just the usual 15 kts. I laid out 5:1 scope in about 8 ft of water, and within a few hours, I had dragged back almost to the point of running aground in the shallows. The bottom was sandy -- no issues with the anchor. As has been the case with most of my "sailing lessons," someone told me about this right AFTER I had nearly run aground. That's how I learn most things! ;-) -BVE

[thinwater]

When I read of 2-5:1 scope in very shallow water I think of this:


Would you rather the boat to windward anchor 2:1 and leave you more room, or anchor 7:1 and not drag down on you? The difference is probably about 40-50 feet. Big deal.



I really don't want you to shorten up too much. Take what you need and I will work with it. Just make sure you won't drag if a squall comes up. Spacing and swing is on me.

[pressuredrop]

As long as the Anchorage isn't tight I put out 100' min regardless of water depth... 5' water in the Bahamas... 100' of chain... I like to sleep

[lestersails]

Originally Posted by Pete7

Us anchored in about 1.7m at low water just outside Dartmouth at Woodhuish . Think we had about 10m of chain out and .5m of depth under the keels We were laying to the chain, not the anchor.

Pete

Wow, I looked up the moody 31 (really pretty boat, BTW) and it says the draft is 1.52 M. I would never have the courage to anchor with 7 inches under my keel. I would think uncharted bottom variation could easily be greater than that. And I assume that is rocky bottom, not like the forgiving mud of the Chesapeake or sand of the Caribbean. No criticism - I am genuinely impressed!

[daydreamer]

Our general rule is in up to 20ft of water we put out 100ft of all chain rode. Up to 30 ft deep, 150ft of rode. Up to 45ft deep, 200ft of rode. We've never had to anchor deeper than that. We draw 4ft and have anchored in 5ft.

Of course, wind, waves, neighbors, etc., can influence our decision.

[Lightwave99]

We have a small (37') professionally but self-built Gypsy 28 catamaran, extended now to 37 feet. Our draft is only 2.5 feet so we anchor in shallow water all then time and in the summer time we actually anchor where it dries out 6 hours a day so we can clean the bottom (no scraping, just brushing off algae and barnacles, the latter of which are few if any because we keep it on a river, fresh water).

Anyway, our rule of thumb is 3 to 5 X the depth, once we have added the 2.5 feet to what the depth sounder on our GPS reads, as the transponder is not located on the bottom of the keels but on the bottom of the sole.

So if it reads 10 feet, we would multiply 12.5 x 3 or 5, depending on the predicted wind. If strong wind, we go for more. And you have to add the length of rode from the anchor roller to the water to get measurement right. Of course, when we add on our bridle, which keeps the boat centred into the wind, that adds a bit more.

Cheers!
Light Wave, Garett & Carllie