if boats have twist and flex is that a good thing or a bad thing ??

I do have a clue what you are talking about. But your arguments seem to ignore one fundamental request for a boat hull - to be strong enough to survive an impact with occasional floating objects (bottles, logs, ice etc.) and also to survive an occasional grounding or beaching at a moderate speed. I can't see how a membrane-thin hull can perform better than a more rigid (hence thicker) one against hull punctures, for example.

Another problem with elastic structures is vibrations. Vibrations are really nasty thing to get rid of and very often require reinforcing several apparently unrelated areas of the structure. Which means more closely spaced reinforcements and added thickness to the plating. At the end of the process, bye-bye to the dreams of thin hull.

You seem to have have concentrated all your attention to the aspect of shock absorption for very-high-speed powerboats. But for many other types of boats that aspect is not at all fundamental when designing a hull. For what concerns human occupants, a comfortable seating is more than enough for a majority of cases.

The communication problems here (and in some other threads of yours), imo, come from the fact that you tend to address a single issue which comes from your personal experience with high-speed powerboats. While doing it, you seem to forget other considerations which have to be made before deciding whats good and what is not for other types of boats or for other speed regimes. Then there is a problem of not clearly defining what the words thin, thick, flexible and rigid mean. So everyone is entitled to say anything and the contrary to anything. Not a good example of decision-making process, don't you think?

Cheers

 

Nobody has you included.. To answer your question, yes, and yes or maybe no and no, all answers equally right..

 

I seem to remember a time tunnels, when you were fixatedly arguing that gun applied chop strand was the most wonderful thing around and that all this new fangled stuff was just so much useless NA/Engineer BS, but now you're here berating everyone because no one has hopped on the alleged state of the art wobbly composites bandwagon.

Chop strand and flexibility seems like the yin-yang of composites.

So tell us tunnels, in the number of years you've been in your Chinese boat factory with those terribly lazy, stupid, unambitious Chinese workers and numerous chop guns, in what innovative and substantial ways have you introduced flexible composites?

 

Most small boat hulls are curved in 2 directions so that when a force is applied to the hull rather than bending it behaves like an arch or domed roof and is much stronger and stiffer than you would expect from thin materials. It is also similar to how an eggshell works.

With flat areas or slightly curved ones that are not sufficient to produce this effect, the panel needs to be designed for bending. It is usually cheaper and lighter to build with a panel and frame.

It is similar to a timber floor or flat roof. The floorboards and roof decking are designed to span between the joists and the joists designed to span between the walls.

As an example if you have a floor that needed 200mm x 50mm joists @ 400mm centres. If you wanted to do away with the joists and rely on the boarding to span between the walls, to get the same strength it would need to be 71mm thick and for the same stiffness, 100mm thick.

In canoeing there is an expression "oil canning" where the hull moves up and down as a wave passes. The ones with curved bottoms are usually OK but some flat bottomed ones do flex.

In the case of the boat I am building there is an area of the floor about 2.4m by .9m which is effectively flat and was easy to move up and down by hand, it felt like a trampoline. For reasons of strength and stiffness I am beefing it up, it did not inspire confidence as it was. However the sides where it is curved and there are chines are very stiff.

When these threads started the thought crossed my mind that you had built a boat with a wobbly bottom and were looking for benefits from it to convince the customer.

 

Time for change like it or not is coming , so what are you going to do about it ??

the concept of flexible structure has been round and will always be around for ever and a day .
the thing of trying to make boats ridged and stiff has draw backs because of the amounts of materials that have to be used to achieve this .
Thick cores and thick heavy lay ups alone with stiff heavy thick framing and stringers that run from end to end , internal grid and top hat systems that stiffen and tie the bottom panels so they cant move even though they would and could .
I am all for using better materials in better ways and reducing internal structures to a minimum and making lighter so they can move in conjunction with the hull skin as the boat rides over rough waves . impact resistance of panels that move is much higher than ridged panels so skins don't have to be as thick but hey do have to be better made , framing doesn't have to be heavy stiff structures, in general don't have to be built like a brick out house , end result is its lighter and stronger .
In my mind I am convinced along with lots other people lighter more flexibility is and will be the way in time to come like it or not .there lots of money being poured into research and development by big well known companies and I am sure its not going to be wasted . boat designs and thinking has stagnated for ever almost and if you dared to step outside the box of ordinary thinking and be seen to be different you get ridiculed by the die hards and non progressive thinkers and get told "THAT WONT WORK !!" or "YOU CANT DO THAT !! " well it does work but it works differently .
sorry you can argue as much as you like I am all for change and the development of new ( NOT REALLY)and exciting ideas and ways of making boats !

 

How much do we really know and understand about the boats we make ??

Unfortunately not a lot !!
a good place to learn about the way boats are built is to go work and do repair work ! there you see first hand the wrecks and destroyed dreams ! its there you see and get to study first hand what works and what doesn't and how things break or simply come apart , what materials shear and literally peel off in great long sheets while others don't and only receive minor damage .
Parts that shatter and get ripped to bits while same parts on other boats only receive gel coat scratch's !
why so much difference ??
does simply using different materials make that much difference ?
workmanship and materials used to stick and hold things together plays a big part in the amount of destruction and the way it simply come comes apart .
you get to see how the different materials behave when subjected to extreme situations !!
DOING REPAIRS IS A PLACE WE SHOULD ALL SPEND TIME AND TAKE NOTE OF WHAT WE SEE !!.

 

Why did I bother to read this?

 

If there are no structural problems that arise, and the boat performs it's task better than it would if less flexible, it is a good thing. If the flex causes premature structural failure, and/or detracts from its performance, it is bad. I don't know if any design programs cater to variability in shape due to flexing.

 

I love ORACLE! And they have had the answer for YEARS!

It depends.

 

Does any one know when there boat is planning ??

No life here !!so on sense hanging about any more !! .
soft ride , flexible hull bottoms ,panels that are able to bend and not break no one is the slightest bit interested in anything !.
Most all the books and reference information came from Noah's library
Guess I'll just pack up and move on !! what a boring , uninspiring lot !! dead from the feet up !!

 

Sorry that it didn't work out and hopefully you will find another place that is more in tune with your interests. Good luck and best wishes in your future travels.