Yes, repeatability is the whole issue. Since you agree that steel and
ferro hulls flex, how much do they typically flex (sag/hog)?

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

Completely & utterly impossible to say without knowing design &
construction details and doing some sort of finite element analysis
which is way beyond my technical competence. That'd only give you a
theoretical measurement anyway.

Think about it for 5 seconds, Nav. How thick is the plating? How many
longitudinals and frames and what spacing? How many welds and at what
spacing? What sort of keel? Is the deck a different material or not? Is
the shell monococque or not? Etc etc. Steel (I know little about ferro)
boats are typically a monococque construction with steel decks attached
to the hull by welding. Plastic boats may have their decks 'glassed to
the hull but usually it's a handful of self-tappers and a tube of
sikaflex. No rigidity there.

I do know that some steel boats can be easily lifted by a couple of
eyebolts welded internally without any worries about deformation, and
others are built with their stiff, heavy keels only supported in 2
places and the plate tolerances are typically 1.5 to 2mm before
welding, to minimise possible weld distortion. They don't sag or hog as
you're using the term. Maybe a few millimeters at most.

The issue isn't repeatability at all. You're merely trying to shift
goalposts. Your Ella is a racing boat and built like one - minimum
weight and what you see WRT flexing is what you'd expect. As a class
they break in really bad weather because they're outside their design
envelope.

PDW

In article ,
The_navigator© wrote:

Yes, repeatability is the whole issue. Since you agree that steel and
ferro hulls flex, how much do they typically flex (sag/hog)?

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

Peter Wiley wrote:

Completely & utterly impossible to say without knowing design &
construction details and doing some sort of finite element analysis
which is way beyond my technical competence. That'd only give you a
theoretical measurement anyway.

But it is possible (not that difficult) to measure the hull's deflection along any
axis in the real world. Not everybody has a dial indicator handy, though.



Think about it for 5 seconds, Nav. How thick is the plating? How many
longitudinals and frames and what spacing? How many welds and at what
spacing? What sort of keel? Is the deck a different material or not? Is
the shell monococque or not? Etc etc. Steel (I know little about ferro)
boats are typically a monococque construction with steel decks attached
to the hull by welding. Plastic boats may have their decks 'glassed to
the hull but usually it's a handful of self-tappers and a tube of
sikaflex. No rigidity there.

I disagree. Most structures are essentially the same, a box girder. Steel is
surprisingly limp all by itself. That's why they make I-beams instead of just steel
planks.

You're right that the details of the hull-deck joint are important to the boats
structure. A lot of mass-produced boats do not have a very good hull deck joint,
but others do. It is not inherent in the material.



I do know that some steel boats can be easily lifted by a couple of
eyebolts welded internally without any worries about deformation

So can many fiberglass boats. But this wasn't really an argument about the relative
merits of steel vs fiberglass, was it?


The issue isn't repeatability at all.

It is to Navvie© since his knowledge of engineering (among other things) is
limited. Besides, when you 'discuss' things with him, you have to accept his
tendency to bring up irrelevant oddities as though he were playing some kind of
trump. It's one of his more amusing character traits.

Fresh Breezes- Doug King

Good lord

Cheers MC

DSK wrote:

Steel is
surprisingly limp all by itself.

In article , DSK
wrote:

Peter Wiley wrote:

Completely & utterly impossible to say without knowing design &
construction details and doing some sort of finite element analysis
which is way beyond my technical competence. That'd only give you a
theoretical measurement anyway.

But it is possible (not that difficult) to measure the hull's deflection
along any
axis in the real world. Not everybody has a dial indicator handy, though.

I agree completely. What I meant by saying you'd only get a theoretical
measurement. As a machinist I keep DTI's that measure to tenth's about,
of course. Hell, I've just been using a cheap laser level to level
formwork for a concrete slab I'm about to pour. When I finished, the
formwork was level to plus/minus 3mm all round, or 0.120". Today it'll
be something else, no doubt. We've used surveying gear to locate 3D GPS
antennae on ships to better accuracies. Isn't rocket science.


Think about it for 5 seconds, Nav. How thick is the plating? How many
longitudinals and frames and what spacing? How many welds and at what
spacing? What sort of keel? Is the deck a different material or not? Is
the shell monococque or not? Etc etc. Steel (I know little about ferro)
boats are typically a monococque construction with steel decks attached
to the hull by welding. Plastic boats may have their decks 'glassed to
the hull but usually it's a handful of self-tappers and a tube of
sikaflex. No rigidity there.

I disagree. Most structures are essentially the same, a box girder. Steel is
surprisingly limp all by itself. That's why they make I-beams instead of just
steel
planks.

True.


You're right that the details of the hull-deck joint are important to the
boats
structure. A lot of mass-produced boats do not have a very good hull deck
joint,
but others do. It is not inherent in the material.

Also true but I thought that's what I said - some plastic boats have
decks glassed to hull and this is damn strong, minimises possible
movement & flex (not to mention leaks.....) Those put together with pop
rivets or self-tappers have a lot more potential to flex.

I do know that some steel boats can be easily lifted by a couple of
eyebolts welded internally without any worries about deformation

So can many fiberglass boats. But this wasn't really an argument about the
relative
merits of steel vs fiberglass, was it?

Nope. Different materials, different strengths/weaknesses. Ditto ferro.
Friend just bought a 38' ferro sloop in really good shape for $30K AUD.
He knows the resale value is going to be the same - crap - but it's a
lot of boat for the money and for him it's a good choice. As he says,
if he gets 10 years out of it that works out to $3K pa even if he can't
sell it at all after that. Still worth it.

Peter Wiley

Peter Wiley wrote:

snip

The issue isn't repeatability at all. You're merely trying to shift
goalposts. Your Ella is a racing boat and built like one - minimum
weight and what you see WRT flexing is what you'd expect. As a class
they break in really bad weather because they're outside their design
envelope.


Was it so bad a voyage/tour of duty, Peter, that even on your
return you insist on clubbing insensible elephant seals?

--
Flying Tadpole

-------------------------
Learn what lies below the waves of cyberspace!
http://www.internetopera.netfirms.com

What a pathetic post.

Cheers MC


Flying Tadpole wrote:


Peter Wiley wrote:

snip

The issue isn't repeatability at all. You're merely trying to shift
goalposts. Your Ella is a racing boat and built like one - minimum
weight and what you see WRT flexing is what you'd expect. As a class
they break in really bad weather because they're outside their design
envelope.



Was it so bad a voyage/tour of duty, Peter, that even on your
return you insist on clubbing insensible elephant seals?

Well, it's in harmony with its subject matter, what did you
expect?

The navigator© wrote:

What a pathetic post.

Cheers MC

Flying Tadpole wrote:


Peter Wiley wrote:

snip

The issue isn't repeatability at all. You're merely trying to shift
goalposts. Your Ella is a racing boat and built like one - minimum
weight and what you see WRT flexing is what you'd expect. As a class
they break in really bad weather because they're outside their design
envelope.



Was it so bad a voyage/tour of duty, Peter, that even on your
return you insist on clubbing insensible elephant seals?


--
Flying Tadpole

-------------------------
Learn what lies below the waves of cyberspace!
http://www.internetopera.netfirms.com

More!

Cheers MC

Flying Tadpole wrote:

Well, it's in harmony with its subject matter, what did you
expect?

The navigator© wrote:

What a pathetic post.

Cheers MC

Flying Tadpole wrote:


Peter Wiley wrote:


snip

The issue isn't repeatability at all. You're merely trying to shift
goalposts. Your Ella is a racing boat and built like one - minimum
weight and what you see WRT flexing is what you'd expect. As a class
they break in really bad weather because they're outside their design
envelope.



Was it so bad a voyage/tour of duty, Peter, that even on your
return you insist on clubbing insensible elephant seals?

You mean, you want a heroic ode, based on the poor elephant seal,
cumbersome and easily attacked by vicious sealers on land, speedy
and graceful on/in the water, but nevertheless doomed by its
liberal outlook and engineering limitations?

FT

The navigator© wrote:

More!

Cheers MC

Flying Tadpole wrote:

Well, it's in harmony with its subject matter, what did you
expect?

The navigator© wrote:

What a pathetic post.

Cheers MC

Flying Tadpole wrote:


Peter Wiley wrote:


snip

The issue isn't repeatability at all. You're merely trying to shift
goalposts. Your Ella is a racing boat and built like one - minimum
weight and what you see WRT flexing is what you'd expect. As a class
they break in really bad weather because they're outside their design
envelope.



Was it so bad a voyage/tour of duty, Peter, that even on your
return you insist on clubbing insensible elephant seals?




--
Flying Tadpole

-------------------------
Learn what lies below the waves of cyberspace!
http://www.internetopera.netfirms.com