Maybe you bought a racing boat, the previous owner was one of those smart guys who make their anchors in thin plywood and spray it with grey metal coloured paint and keep it at a distance from the Racing Committee equipment controllers.
This is straight from Rocna. Whenever they submitted anchors for test, years ago, they selected anchors that were perfectly aligned. Their own tests proved that a 2 degree misalignment compromised setting and holding significantly.
. There is a difference - the worm digs itself to safety, anchor remain inanimate
If you dive on your anchor and the chain is off the seabed then you can feel the anchor twitching. Movement of the yacht is transmitted straight down the rode which acts like a long steel rod. You can test this yourself. Take a long length of chain and suspend it between two points and have someone gently hit the end of the chain. You at the other end can immediately feel the effects of the hit. This is happening repetitively for your freely suspended rode - as your yacht moves with a slight chop. In seabeds the twitching could be sufficient in many seabeds, most except very hard sand, to encourage the anchor to settle (specially so in muds).
The seabed in immediate proximity to the anchor has had its cohesion destroyed as a result of the anchor being pulled, slightly or aggressively, the seabed shear strength is not that of the 'untouched' seabed and will take time to regain that shear strength.
The anchor acts just like a worm in a flower bed.
You can do something similar your self. Stand on a beach in the shallows and simply twiddle your toes and your feet will slowly settle in the sand.
The changes in shear strength has been a major research topic for the US Navy.
This one reason to have a scope such that the rode is on the seabed and for the use of snubbers. The chain on the seabed and a snubber reduces or removes completely the ability of the rode to cause twitching and the seabed will have a higher shear strength in the presence of a non-twitching anchor.
Jonathan
I'm not arguing with you, nor with those whom you mention - as long at the OP is bright (and he must be, he has enquired on YBW.
) he can sift through the comments and try the various options offered to him. ) can feel vindicated. I'm just waiting for a gap in the discussion to complicate life much more seriously and talk about snubbers.....I jest - I thought I'd raise the ire of those who think I talk anchors too much......
They didn't anchor at that speed. Veered out loadsa chain, and as I said, stopped engine, slowed down and snubbed.
Yes but you neglected to make yourself a cup of tea, if you had done that the anchor would of dug itself in
The key is to start the digging in process very slowly. You do not want to move the anchor more than an inch every 5 seconds or so.Yes but you neglected to make yourself a cup of tea, if you had done that the anchor would of dug itself in
Please don't be offended but, in terms of advice, to an inexperienced boater, this is a just a waste of time. How in the name of God does he control this. Most of the time you can't even see the anchor and, even if you could, you certainly can't control the momentum of a 10/15/20 tonne boat so precisely. Anchoring is not a science. It's a matter of developing a technique, through experience, that suits you, your boat, and your anchor, and being able to tweak or vary it to suit the type of seabed you're encountering. The OP has lost confidence in himself but he'll overcome that and develop a method that suits him.
That is left as an exercise for the reader.One in inch in 5 seconds
What's that in knots?
I just re-read your post. I thought it was OK, but it isn't. You need to not go into reverse with only the depth of chain out. You will go too fast backwards and it won't dig in. The chain needs to be at a shallow angle to the seabed to dig it in, so let out enough to be sure that happens before backing up, then go very slowly backwards that you maintain a shallow angle from the chain to the anchor. If there is wind, let the wind do the job instead of the engine until you have full scope out. Only then use the engine to dig in. Do it with pulses to avoid pulling out. The anchor needs to dig in slowly in hard substrates. Mud not so much. Remember also in case it's not obvious to measure the scope of chain correctly. It is chain out divided by to the vertical height from the anchor roller to the seabed.
I think .01 knot (but I'm probably wrong) which in the grand scheme of things is too small to measure and certainly too small to control.That is left as an exercise for the reader.
You calculation to get 0.01 knots is about right.
A 15kg anchor is more than adequate for a modern 36' sailboat. Smack bang in the middle of most of the manufacturers' sizing charts. The setting problem experienced in Platarias where the OP is (and most of the Ionian) is nothing to do with the size (or probably design) of the anchor but the nature of the seabed. There is a technique for overcoming it that has been well described already by many. The Delta is probably the most common anchor used in the area as just about all the charter boats use it, and before that became standard used mostly CQR copies or Britany anchors as that is what came with the boats.