Tunnels

Sizing a thruster tunnel correctly

A thruster tunnel has to be matched to the thruster fitted, not chosen independently, since tunnel diameter, wall thickness and material all affect how much thrust actually reaches the water rather than being lost to turbulence inside an oversized or undersized bore. Quick specifies tunnel diameter against each thruster model, and departing from that figure, even by a small margin, changes the thrust and noise characteristics of the finished installation.

Tunnel length matters almost as much as diameter: a tunnel that is short relative to its diameter increases turbulence and can reduce effective thrust, which is why the ratio between length and diameter is part of Quick's specification rather than left to the installer's judgement. Material choice, usually GRP or aluminium, generally follows the hull construction it is being bonded or glassed into, so match the tunnel material to the surrounding hull rather than picking on cost alone.