Did the Whitehead torpedo make spar submarines obsolete?

Did spar-armed submarines become a dead end once the Whitehead torpedo made attack more practical?

Yes. The Whitehead torpedo greatly increased practicality and displaced the spar-torpedo approach.

Spar-armed submarines do not appear in large numbers after this experimental period. The Whitehead torpedo greatly increased the practical possibilities of submarine attack. Hunley therefore belongs to a transitional technology rather than a durable weapons model.