At a 5:1 ratio we are now down to approximately a 10 degree anchor shank angle pull. Many boaters rely on 4:1 or 5:1 in tight anchorages in benign conditions but some have ridden out severe weather on nothing more than 5:1 with the right anchor.
Here's the 6:1 scope visual..
6:1 Scope = 8 Degree Angle
Going from 5:1 to 6:1 you lose roughly another 2 degrees of shank angle.
Here's the 7:1 scope visual..
7:1 Scope = 7 Degree Angle
As you can see as the scope gets longer the law of diminishing returns applies to the angle of attack. Going from 5:1 to 6:1 we lost two degrees but from 6:1 to 7:1 only 1 degree. At this point the rode is pulling fairly close to the ocean floor and the angle is what most any well designed anchor can and should be able to handle.
Here's the visual for 8:1 scope..
8:1 Scope Angle = 6 Degrees
We lost roughly another degree going from 7:1 to 8:1. Keep in mind this is a lot of rode for very little return in shank angle and you are increasing your swing radius dramatically.
There is nothing wrong with more scope but just be sure you have the swing room to do it. As you continue on out in rode length the changes in angle become smaller and smaller and this is why 7:1 is the generally advised scope for anchoring when you need good holding power. In tighter places a 5:1 or 4:1 can work but the angle on the anchor shank clearly becomes more upright the shorter you go with scope.
Help Support This Site
Like what you saw or read in this article? Was it helpful? Could the information save you some money? Would you like to see more articles like this?
If so feel free to donate, support the site, and keep it growing. Please DO NOT feel obligated at all. If you like it and want to make a donation, please do. Your donations help keep the content coming and also help keep it FREE.
Click the DONATE button below if you would like to make a donation via PayPal.