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