Stiffness vs Tensile Strength in Foam Sandwich Construction?

An optimized structure, ie a "very light" hull, could weigh, for example, 60 tons. Would that be kind to the human frame?.

 

I think he gets it. He also makes a valid point about ultralight hulls bobbing about. As expected, with a wide open thread, at some point, the stitching starts to unravel and the selvage is lost.

 

The foam is crushed and the skin delaminates.

And then in order to hold the boat together we sing the "ode to snot instead of confidence" that ad hoc alluded to.

 

I would expect being too light wouldn't affect a catamaran or trimaran as much, assuming the hulls were shaped correctly for the reduced weight.

 

Actually, making it too light makes it worse....This is why they have the Ancient Interface talks, a 40 hour week of how physics works for these things... Light is not better for wave followers, heavy is not better for non-wave followers... see?, it's simple!

 

There is no such thing as "too light" just poor design.

When we did offset oscillation trials in tech school, if a member didn't break by one million cycles, it never did.

 

Again...cluelessness. It has nothing to do with strength, but everything to do with "ugly bags of mostly water". If I never put a person on a vessel, I could build a much better vessel...I have built a much better vehicle...but that is not what ships are for.
Tansl had it right...

 

Exactly.

 

Optimized for what ? I know for many years there was a strong prejudice against lightweight alloy trailerboats, that were very light by comparison to GRP and ply boats, by virtue of pressings in the thin hull panels that gave sufficient strength and stiffness at very light weight. They "murdered" occupants in even slightly ruffled water, because of lack of inertia, and relatively flat bottoms that had to be that way, to not be tippy at rest. It was and still is, a double whammy, the boat being light was only an advantage in terms of easy trailability, low power needs, less material cost etc, but for the comfort of occupants, a sell-out. There definitely is such a thing as too light, and for the type of boat mentioned above, it is also a safety issue, as high winds are a real threat to them, moreso than wave action. I could go further and mention planing power cats that have a fair degree of dynamic lift, at light weight they too are a menace. I don't buy the "lighter is better" mantra, and neither does the boating public, largely.

 

That is the point. There are real limits to the human body. No matter how "good" the vessel performs, but if it damages the occupants?

 

This is going to be a long thread.
You guys are made for eachother.
"Clueless" look in the mirror.

 

I despise the word - optimised.

Optimised for what...for bigger windows.. for less motions...for cheaper build, for... for...etc etc ad nauseam.

A word thrown around by those that do not understand its implications and yet claim it solves all....

 

Lightweight works better for boats that don't go directly into waves, or at speed, or rely on dynamic lift for that speed.

 

Yup

Bulk oil carriers are built like a tin can but is designed to hold several hundred thousands tons of cargo.

 

I think that the only way "optimization" is a valid parameter is when it is clearly defined. It should be kept in mind that optimization is applicable to a narrow application or range of applications. Optimized for everything is a fallacy. Traditional boats were optimized for a particular use and geographical area. Modern boats try to fit many uses and geographical areas, which makes them not optimal for any. However, they are adequate.