Harbour launch
The harbour launch, commonly termed 52 1/2ft harbour launch (based on the waterline length) was a type of small launch used by the Royal Navy for general duties around Royal Naval dockyards and sea ports. They were of a double diagonal oak plank over lightweight teak frames hull construction (the diagonals of the inner and outer skins running in opposite directions & separated by a skin of oiled calico cloth), as were RNLI lifeboats of the era, making for an extremely light but strong construction.