NE Sailboat wrote:
"I got involved in 40 foot waves with a 27 feet sailboat. ..."

I don't believe this for one moment. 40' waves? And you were in a
27' boat?

The waves were 20 feet. How do I know this? During the time that I was
researching sailing vessel casualties and working on the project to help
write the stability regulations for sailing school vessels, the accuracy of
wind and sea state reports were a significant issue so I looked into these
questions quite a bit.

There are solid physical reasons why even the most experience sailors
overestimate wave heights by about 100%. These have to do with the motion
on the wave face that makes the local "down", or direction a pendulum would
point, be perpendicular to the face of the wave instead of towards the
center of the earth. This is one of the illusions that promotes
seasickness.

There is a fairly precise method of measuring wave height. Even knowing all
these things, I look at waves I've just measured as six feet and I could
still swear that they are 12. In fact, a very reliable way to measure wave
height is to simply take your best guess and cut it in half.

--
Roger Long