. That is, the taffrail, the upper part of a ship's stern, sometimes a railing there.
The spelling in the text is a corruption of the 18th-century usage, “tafferel” which
is derived from the Dutch taferell,
a panel. OED
, in a later account, referred to this as “some thing, the technical term for which,
in naval architecture, I have forgotten.” JA
to David Sewall, 29 Jan. 1811, 9 JA, Works