What type of anchor rope depends on the boat size.
For starters, you will want an anchor rope that does NOT float. For that reason, nylon rope is the best choice. The last thing you want is being in a position where you have to cut your anchor line if stuck or to get out of harm’s way and have your anchor rope floating for some other boater to run over it and have it wrap up in their prop or get caught in their pump.
When determining what type of anchor rope you need and we have figured that nylon anchor rope is the right choice, you now have to choose between braided and twisted.
Both twisted and braided are light weight and have good elasticity, which means they will stretch when tension is on them, reducing pull and shock on your deployed anchor. This makes nylon a very good choice when determining what type of anchor rope you need.
Twisted nylon is generally less expensive and easier to splice, where braided is stronger, generally suppler and therefore easier when handling, which is the reason, more boaters prefer braided, especially solid braid nylon rope.
To reduce the abrasion on your rope that is sitting on the bottom near your anchor, you will want to add a length of chain between your anchor and your anchor rope. The standard rule is the length of chain should be equal to the length of your boat, but that, in my opinion is not necessary. For me, 6’ – 10’ of 5/16” chain is appropriate. If you wanted to go by the standard rule, you would probably want to go with a 3/16” chain or at most, a ¼” chain to reduce the amount of weight of your rode.
My standard setup on my 19’ fiberglass boat is, 3/8” solid braid nylon rope with 6’ of 5/16” galvanized chain.
Now the last factor in determining what type of anchor rope you need for your boat is the rope thickness or diameter.
You can follow this general guideline. Boats up to about 24’ will do just fine with a 3/8” thickness. Boats from about 25’ to 40’, you can go with a 7/16” or 1/2".
I’ll stop there, as you can get the idea of anchor rope size increasing with the boat size.
Keep in mind that these rope and chain sizes are guidelines only and may vary depending on water and current conditions, but will cover most common conditions.