Re: spare anchor
What anchors to carry? The issue is that different anchors have different strengths. From what I've seen there are three overall types with variations.
Plow/delta/bruce etc. These anchors work in a variety of bottoms and reset more quickly than other types.
Danforth/Fortress etc. These have, by far, the greatest holding power for their weight but need to be in sand or mud bottoms.
Fishermans/Northhill These anchors can set in a rocky bottom and punch into kelp. They tend to be heavy and run the risk of the anchor line wrapping the anchor stock when the boat swings.
You can find anchors cheaply at consignment places.
I carry one of each type. My regular hook is a Bruce which I use in anchorages at shorter scopes. My Fortress is also on the bow as a ready stand-by and for sandy bottoms. Stowed away is a folding Northill if I have to anchor in a rocky bottom. I also carry an old Danforth which I can hook in series with the fortress if I ever get stuck in reeeeely high winds. I think it's important to look at the rode and the cleating so that they are all up to what load the anchor can carry. I did the numbers and found the deck cleat wasn't up to what it would take in a blow.