The navigator© wrote:

Yes, repeatability is the whole issue.

Why?

Repeatability is always an issue when measuring things, but is there some
specific reason why a boats rigidity should be uniform & consistent? To what
standard should it be?



.... Once again you reveal your lack of experience with big
boats by suggesting otherwise.

Really? Is it you that's been following me around all my life? Maybe you can
really tell me how many big boats I've sailed, I never did keep a written tally
myself.


....This typifies your inability to grasp
even simple ideas.

You mean like how to measure things?


As for measurent of a boat to 5 thou, look at the coefficent of
expansion of say GRP or even Al (which expands muchg less) and then tell
me how much a boat moves during a typical day/night temperature cycle.

Why is that an issue? BTW did you miss the thread about how much an aluminum mast
expands or contracts due to temp variation?


Now you want to tell me it's easy to measure a 5 thou deflection over a
40' boat?

Sure is. All you need is a yardstick slightly longer than the boat.

Even if the boat builder had access to interferometric
equipment (which I'm sure they did not use

Now you're claiming you were there? How do you know what they used?


.... -as there would be no point
in such an accurate measurement) it would still be hard.

Not really, if you know how.



My point is that Ella is not a large racing boat and yet still has more
than 1 ton rig tension.

Umm, Navvie©..... did you think that the terms '1-Ton' and the like refer to the
rig tension carried by the boats of this particular class?

BTW the specific boats I had in mind, which had aluminum struts forming a big
truss inside, were 'IMP' (designed by Ron Holland IIRC) and 'Ydra' (which was a
German entry in the Admirals Cup IIRC) and the Canada's Cuppers which I already
mentioned. Ben Lexcen (Bob Miller) designed at least one boat with the same type
structural elements. There were a bunch of less successful copies. A few years
later the advent of practical carbon fiber laminations made truss frames seem too
heavy.

There was also an early 1900s America's Cup contender with one.

Do you still think it's all BS? Will you never learn?

Fresh Breezes- Doug King