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> Using the simplified formula for distance to horizon, 1.169(sqrt height of
> eye) the observer's horizon would be 9.8 nm away.  If the observed vessel is
> 5 nm away, as stated above, the observer should be able to see the hull and
> waterline, in which case Table 16 would apply.  (Note that the geographical
> range would be 21.5 nm from 70 ft aloft.)

Getting down to short strokes, I am assuming 100 ft of mast visible above
the deck (as opposed to a 100 ft mast keel stepped, showing maybe 92 ft
above deck).

In reality, a sailboat large enough to sport a 100 ft stick above deck would
probably have a deck at least 6 ft above the waterline at the mast.
Therefore, geographical range (at 10 ft observer height of eye) of the
mast's base would be approx. 6.6 nm, more than enough to see the entire mast
at 5 nm.

Is the devil indeed in the details? ;-)

Bill

   

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