But the boat is not solid steel is it?

Cheers MC

Peter Wiley wrote:

Actually quite a few sailboats *are* much more rigid than you seem to
know. You're taking your experience on plastic boats and assuming it is
generally applicable. The flex in a steel or ferrocement hull is
certainly there (everything flexes to some degree), but it's a fraction
of what is common in lightweight toy racing boats which are built to
minimal standards of seaworthiness and do, indeed, flex. In fact, the
toy boats often break when coming off a fairly moderate wave, as recent
Sydney-Hobart races have shown so well.

The remark about water being much less compressible than the boat is
pure & utter bull****. Even frozen water is a lot more compressible
than steel. Also has lower shear strength, tensile strength etc.

As to measurement of a boat to 0.005", I can easily believe that this
is possible. It's not even all that difficult. Whether there's any
point and whether the measurement is repeatable are different issues.

Peter Wiley

In article ,
The_navigator© wrote:


That boats are built differently has nothing to do with it. Sail boats
are not rigid nor even near it. To be as rigid as you suggest would
probably mean they would not float. If you had ever been in a real boat
beating to windward your would know they are *not* rigid. Put your hand
on the forstay and look at it unloading when she buries her bow and look
at it going tight on the crest (that's revealed by the luff bending).
It's loading up/unloading because the boat is flexing. If you ever get
the chance (assuming that any boat owner could put up with your big
mouth and BS) have a good hard look at the hull of a boat pounding hard
to windward and look and feel hull panels flexing. The boat needs has to
flex to reduce impact loadings because water is much less compressable
than the boat. Once again you reveal your lack of experience with big
boats by suggesting otherwise. This typifies your inability to grasp
even simple ideas.

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.
Now you want to tell me it's easy to measure a 5 thou deflection over a
40' boat? Even if the boat builder had access to interferometric
equipment (which I'm sure they did not use -as there would be no point
in such an accurate measurement) it would still be hard. If you think
it's so easy how come you need a 'crew'. Lets face it this is yet more
Doug Kig (I'm a ****ing hero) BS. Have'nt you ever wonder why you don't
make more money -after all, you are such an expert...

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

Cheers MC

DSK wrote:

The navigator© wrote:



I'd say It's BS because boats are simply not that rigid


Oh yeah, and all boats are built to the same structural standard, aren't
they.



and it's hard to
measure to an accuracy of 4 thou on big objects.


Now that is total BS. It costs, but if you're willing to pay, I'll bring a
crew and and gear, and show you how to measure movement in any axis on
objects of any size & orientation down to 5 ten thousands +/- 1

It's part of what I do for a living, thanks very much. The NIST has
occasionally asked me for advice on this type of thing.




.... Even Ella has a backstay
tension of 2,500 lbs when beating.


Gee, and there's no difference between "2500#" and 15,000# is there?

Why do I bother answering your posts?

DSK