Thanks. I missed the part about the Royal Bounty for rating's widows.
The Kew guides are better at providing information on what records the Kew has rather than background information. The situation as far as officer's pensions is much clearer.
The best source of information I am aware of on pensions is "Naval Records for Genealogists" by Rogers.
Here is what I know:
* there are ratings who are receiving pensions during this time period, but the Kew guides do not seem to provide qualification details. At one point it says "deserving" candidates may receive a pension, but do not define the word "deserving":
"Until well into the nineteenth century no officers or ratings were entitled to superannuation, and the limited number of pensions available were regarded as a privilege to be granted to deserving candidates."
* at this time an amount was withheld from pay for "Chatham Chest", but I don't know who was entitled to receive payments from this source.
* the Kew guide lists records for the Chatham Chest from 1695-1779, but the Chatham Chest continued long after 1779.