The single davy knot does not hold very good on larger lines. Try going through the loop again with the tag end. This is a double davy knot and will hold much better. One other thing is pull the knot tight from the tag end not the hook. For some reason the knot will come loose the other way. I tied the davy knot at a bass expo at one of those knot strength tester places. I used the double davy and the knot did not break. You might give it a try that way. I think you can go on utube and search for a double davy knot.