French ebonite as supplementary torpedo protection

How effective was the French use of ebonite as a torpedo defence?

It was an inflammable hard-rubber compound that could be applied to structures as supplementary torpedo protection; no quantified performance is given.

Ebonite is described as an inflammable hard rubber prepared in a mixture that could be sprayed or painted onto structures. Its intended role was to supplement a ship's existing torpedo protection. The brief explanation provides no test results or numerical assessment of its effectiveness.