You can have the ultimate anchor but if you don't give it enough chain length- It will be USELESS.
The scope is the ratio of the length of the rode vs the distance between the seabed and bow roller. When you calculate scope you need to add the depth of water to that distance between the waterline and bow roller.
When it comes to anchoring your yacht, many factors come into play. One of the most critical aspects of anchoring is setting your anchor properly. While much has been written about the scope and related issues, deploying our anchor at a 3:1 scope and using a power set to engage and set the anchor is the minimum scope you should use.
Modern anchors are much more forgiving than their older counterparts, and most can perform adequately at ratios of 3:1 - 5:1. We take advantage of this forgiving nature and deploy our anchor while the yacht is moving slowly astern. This ensures that the chain is deployed in a straight line and ready for the tension to be increased to align the anchor fluke point ready to engage. If the anchor does not engage almost immediately, we apply tension. If there is something unusual about the seabed or the anchor has been fouled by a foreign object, we immediately retrieve the anchor, check and start again or move the location slightly.
When we decide where to anchor, we set the location on the chart plotter at the point of deployment, which we later use to set our anchor alarm. Our anchor alarm is then centered on the anchor, not some indeterminate offset.
Once we have ensured that the anchor is engaged and started to set, we deploy more rode. Normally, we deploy to a 5:1 scope, but if the weather is questionable, we might deploy more. However, deploying more rode might not be possible in tight or busy anchorages. We always power set to ensure the anchor is set and not moving.
To ensure that we know how much rode we have deployed, we mark the chain with a simple code. We write the code into the underside of the chain locker hatch, so anyone who deploys the chain knows exactly what the marks are. We mark every 10m with cotton ribbons or hemp/sisal cord. The ribbon or cord passes through the gypsy and, unlike cable ties, paint, and plastic inserts, does not contaminate the seabed.
Once the anchor is set and the snubber attached, we attach another snubber or secure a chain lock. This practice ensures that we are not relying on the windlass as the ultimate fallback. The additional snubber can be a short length of Dyneema with a chain hook or soft shackle and attached to a strong point independent of the windlass.
The penultimate task is to set the anchor alarm, incorporating the length of rode and snubber deployed, plus a few more meters (2-4). Finally, with all the formal tasks complete, it's time to break out the chardonnay or a decent malt whisky and enjoy the atmosphere and scenery.
Setting an anchor should be an easy task and should involve no anguish. It can be completed by one person, leaving the rest of the crew to prepare those welcoming drinks and set to prepare that gourmet dinner!
Try to use a long chain if possible. No need for more than an 8:1 scope. A long chain with a good anchor will do the job.