Rotating funnels appear in the recalled French warship proposals. Moving the outlet would direct exhaust according to the ship's orientation in battle. Smoke could then be kept clear of optical rangefinding equipment. No specific completed ship is identified with this arrangement.
Notable Point · 7:15:43-7:16:00
Why a warship design might use a rotating funnel
A rotating funnel could redirect smoke during battle to keep optical rangefinders clear.