Hi Pat,
There are several ways to add "ball ends" to nylon strings (tying knots, gluing beads on the end, or by melting the ends of the strings to form a "blob"). you can also buy nylon strings with ball ends:
https://www.stringsbymail.com/classical ... amond-949/ A few more pictures showing some of the mods to make the guitar neck removable and transportable:
The first picture shows the "studs" that hold the neck in position that allows it to pivot slightly to raise and lower the action.
The second picture shows the readily available (and easily replaceable) low cost hardware needed to make it a "travel guitar"
The third picture shows the "hollow" in the neck block that the peghead fits into to secure it in the body and the T nut used to bolt the lower part of the heel to the body when assembled. The forth picture hopefully shows this idea more clearly.
If you don't want to store the neck inside the body a greatly simplified design can be made. No Tail port and neck cradle, no hollow neck block, and for a classical, no truss rod need be used.
One thing not pictured is the "cap" for the nut which holds the strings in place when the neck is off the guitar. It can be either screwed on with small screws or glued on with water (vinegar) soluble glue so it can be removed when nut repair is needed.