"Ghost" wrote:
LOA (Length Over All) is a measurement from the tip of the bow, around the
edge of the deck - as in toerail - , to the edge of the stern). LOD (Length
Over Deck) is the straight line measurement you describe.

Therefore, two 30' yachts, one with a 12' beam and the other with a 10' beam
will have different LOD's!

I hate to say this but deep breath Neal is right and you are wrong.

LOA is a straigh-line measurement, including things like bowsprits and
sugarscoop sterns. It is what it calls itself: overall length. That's
what can make it differ from LOD, which is also a straight-line
measurement but of the deck only, not including things like bowsprits.

LWL (load waterline) is also a straight-line measurement.

So, in your example, two 30' boats with different beams will have
identical measurements for LOD *and* for LOA, assuming neither has a
bowsprit or other appendage which would add to the LOA. For example,
if both were 30' LOD but one had a sugarscoop transom, that one would
have a longer LOA than the one without the sugarscoop.

Frank