Two types of this mine are known to exist, both designated by the Japanese as "Mark 2 Explosive Hook". Only the "Mark 2 Explosive Hook, Modification 1" has been recovered. The "Mark 2 Explosive Hook" has been reported from intelligence sources.

The intended use of the JD is an explosive grapnel for minesweeping. It has been used, however, as a controlled beach mine. When used as a grapnel it is towed behind a ship, and when it snags a mine mooring cable, the Explosive Hook is fired electrically from the ship. When used as a controlled mine it is planted on beaches and approaches to beaches and is fired electrically from an observation post.

General characteristics of the mine are as follows:

Case

Shape – Cylindrical, 8" in diameter, with rounded ends. Fitted with 4 projecting prap-nel arms with a maximum span of 11".5, and a towing bracket on each end.

Length – Body 10"; Overall 25".

Color – Black.

Mateial - Steel.

Charge – 8 to 19 lbs. cast Shimose, or granular Type 88 explosive.

Total Weight – 28 to 39 lbs.

External Fittings

Detonator Carrier – 1".5 in diameter in the middle of the body

Filling Holes – One on each end, 2".5 in diameter.

Pad Eye – One, on the top center line next to the detonator-carrier keep ring.

Towing Swivels – Two, one attached to each towing bracket.

Operation

This mine is armed during assembly. When used as a grapnel, a sweep wire serves as a towing cable and proper depth is maintained by suspending the mine from a mine-sweeping float on a float pendant. The mine is electrically connected to the towing ship by a rubber covered cable stopped off on the towing cable. When an object is snared, an observer on the towing boat fires the charge electrically. The only differences bet-ween the Mark 2, Modification 1 and Mark 2 is that the latter fires both electrically and automatically when an additional tension of 55 lbs. is put on the mine.

Safety Precautions

Neither type has any disarming features.

Figure 10 – Mine type JD.

Figure 11 – View of Type JD "the explosive hook".