Which splice is known as the strongest when placed in a line, even though it doubles the size of the line?

The strongest splice when placed in a line, despite doubling the size of the line, is indeed the short splice. This type of splice is particularly effective because it allows two ends of rope to be joined together while maintaining much of the rope's original strength. By interweaving the strands of the two ropes, the short splice creates a very strong connection without introducing significant weaknesses, except for where the splice is itself.

The doubling of the line's thickness can be a drawback in certain situations, but the overall integrity of the line remains exceptionally high with this method of splicing. This makes it preferable for applications where maximum strength is critical, such as in towing or hauling operations.

In contrast, the long splice, while also effective, is designed to taper the thickness of the rope, making it less bulky but not as strong when compared to the short splice. Other choices, like the square knot and sheet bend, are indeed practical for joining two ropes but do not provide the same level of strength and reliability in a load-bearing context.