flexable bottomed boats ??

TANSL,

I think you need to be more clear in your reply. Since for me, this is not true. All the professional commercial yards I have worked in and deal with, build to Class and fully comply with Class QA/QC rules i.e. an MPQA and have their own in-house QA depts. And I always inspect the work and insist upon proper QA standards being applied and check regularly myself for compliance. Design and construction go hand in hand, they are not and should never be treated as “isolated” processes or functions. If you don’t know how something is built and more importantly, consistently (QA Standards to satisfy that fulfils the design intent), how do you know how to design it?!

Yards that do not produce work for the commercial sector, have no requirements to comply with any of the above. Where a vessel is built by such a yard they simply let the surveyor, if the vessel is built to any particular standard, perform the yards QA for them. In other words any sloppy workmanship is picked up, or not, by the surveyor of the vessel since there is no in-house independent QA dept nor is the work force familiar or conversant with QA standards. Where conflicts exist, owing to lack of expertise and technical ability, these yards “overkill” the work to placate the surveyor. To the point they often make matters worse. Where there is no surveyor....well, you can often guess at the outcome!!

These yards are just as poor in composite construction as they are in steel as they are in ally. It is not a composite related issue only; it is across the board with sloppy garden shed type small yards and one man band that has “sweated blood and tears for 40 years, you can’t tell me” types. This is especially true with yards where they always questions the need for standards with the familiar reply of “..why bother..” because as always “...they think they know better...”. They always see the reason for having someone checking and independently verifying their work and workmanship and hence the quality as not necessary to the point of being abusive for someone (they see as inferior) questioning their work and being inspected to begin with; “I know what I am doing….” blah blah blah rhetoric.

 

Ad Hoc, dear friend, I fully understand that you feel upset with my words because, though true, are very hard.
I have worked many years in shipyards building ships of steel and I'm very proud of the rigor and professionalism in them breathe. I learned a lot of their work systems, quality control and efforts to increase productivity. And all this, as well, having to meet very stringent regulations, inspection of Classification Societies, etc.. I feel, I repeat, very proud to have belonged to that world.
The last years of my career were spent doing projects, and project managers for small shipyards that build GRP. I worked for 6 yards and over 150 different boats are sailing designed for me. I have to say, and it is true, that in them there is no way to control the quality. The reality is that it builds bad enough to ensure that owners take the boat. It is also true that shipowners, in ship building, do not know much.
And this, my friend Ad Hoc, is my experience and, regrettably, no one can say that I have no reason as I have lived it.
I think that, like you were asking me, I have been clear enough in my answer. If your experience is better than mine, it's better for you, but I usually talk about what I know and, although sometimes I'm wrong, I try to be honest and truthful.
With all due respect.

Final comment: the boat usually looks quite similar to the project, but nothing more.

 

It is indeed your experience, I am not questioning that per se.

I have come across equally poor boatyards, some truly shocking examples of “professionalism”. My point is, those that comply with proper QA do not have such issues, or rarely. Those that do not and generally those in the non-commercial sector are often where the issues are found.

I make a conscious decision not to work with yards that have no appreciation or understanding of what QA means or an openness to quality and all it entails. As their poor workmanship reflects back to me too, mud sticks, no matter where it is thrown. However, when my client selects a yard, not of my preference/choosing, then of course I have no choice but the deal with them.

 

Unfortunately I rarely have been able to select my clients.
In my country there are many small shipyard who think they have the obligation to pay a naval architect, because the Administration so requires, but THAT is only a kind of tax that must be paid. They pay, there is no choice, but follow the instructions of NA ...... ?, that's too much.
With my last client ended my relationship with him because I refused to sign the project he "forced" me to do. That was last February.

 

Need to read !!

http://www.compositesworld.com/articles/re-inventing-the-rhib-shock-mitigation

 

Tunnels, do not be too harsh on Tansil. He knows FRP otherwise he will not be able to write the scantling software. He works with standards and is guided by standards.

Whilst while you are saying is true that loading up the fiber with resin will make it more flexible (the opposite of reducing resin to make it stronger and stiffer), it will also make it thicker.

Thickness is the enemy of flex. The thicker it is, the stiffer the panel. So, the designer has another option. Make the panel relatively thin (single layer or multiple layer) to make it flex.

This can be graphed to show where the the two shall meet but naah, you don't like graphs and formula.

 

graphs are ok but formulas ,! to much thinking involved and by the time you have the answer you forgotten the question and left wondering why your tea is cold !
I like hands on and just get out there and do it can most times tell if its going to work or not and how good simply by looking at what you have done and ended up with !! .

 

Flexible bottom boat, easy, apply about 100mm of polyethylene foam to the existing bottom surfaces, then glue on to that, in two pieces, one for each side of the bottom so they can flex independently, a thin but resilient, even stretchy, material. You'll soon find out if it's a goer.

 

Suppose I do not know anything and I try to see, according to the scantling rules, how to get the right thickness for my hull panels. Immediately I will realize that all the standards require a minimum amount of fiber but no talk of amount of resin. Accordingly, I should put the resin required, but not an ounce more, to lock either the "mix". And since I do not understand anything, ask what advantages apart from weight gain, I get to put more resin?. (What I need is to make a boat whose hull, among other things, allows me to anchor the main engine and other elements that often go inside the hull.)
Now I understand that in the case of flexible RHIB my questions do not make sense but for other vessels that were built in the world, are very relevant.
Now I understand that tunnels exposed an idea, not his, for a very specific type of boat while I talked about boats in general. So probably everyone has partly right.

 

No, it won't soften the ride but well studied flexible structures are able to absorb higher "peak loads" like the slamming by the waves in the bottom of a high speed boat and thus it can be lighter than the "rigid" structure. Any NA and NE having worked on military and ferries fast boats knows well the problem (with the corollary of natural frequencies, absorption and dissipation, resilience, fatigue, etc...brief the ordinary job of a structural engineer on boats, planes, trains, cars and so on, it's not an amateur job)

The idea of controlled flexing for dissipating stresses is pretty old (the Eiffel Tower made in 1880 uses this feature), so it's nothing new under the sun.

Happily these structural calculations on small "slow yachts" are rather primitive and a "recipe book" is largely enough...On a 30 meters trimaran weighting only 13 metric tons ans running at 40 knots is another thing (yes the maxi tris use controlled flexing to keep the structure light and safe).

 

Hmm, using air pressure to pressurize a fiberglass hull and distribute the force. Sounds like a good idea.


http://www.boatdesign.net/forums/fi...building/glassing-over-stryofoam-30867-2.html

 

For those interested; "Naval Architecture of Planing Hulls" by Lindsay Lord covers flexible bottoms, flexible hulls and structures, clearly, using techniques unliked by Tunnels (solid engineering), with examples over 100' in length in high speed service. We managed to get a man on the moon with aluminum foil (literally) and bubblegum, but it did require the 12 grade high school math, that Tunnels seems to think isn't necessary.

As to human tolerances and addressing these issues, Professional BoatBuilder Magazine recently did a reasonably comprehensive series on the subject. Of course it requires some more of the distasteful to Tunnels methodology (reading and possibly further studying).

I'm not sure why you seem to think, difficult engineering principles or problems should have a simple, easy for the laymen to understand, let alone execute, explanation, but for the most part, if well versed in the applicable disciplines, the concepts, engineering approach options and usual solutions aren't difficult to comprehend. There's no short cut to understanding and the resulting comfort level associated with it. Though in your case Tunnels, I can see why you have a discomfort level about certain things, as there's no easy, simple answer to concepts you clearly don't fully understand. There's only two logical choices here, improve your level of understanding, with some personal study of the related subjects or learn to live with the frustration you've displayed on this and other threads.

An example would be my personal take on Lindsay Lord's strip planking method. After reading about it I was very skeptical, but after some study and running some models, I not only began to like it, but have adapted it to suit more modern build methods and materials.

 

ooooh arnt we the smart one !! why is it your nature to belittle and put people down all the time?? is it the wrong time of the month again , is the moon troubling and you fell off the fence again ?? Or your are just the usual pompous *** you try and pretend not to be .
Why don't use your hard gotten talents and skills that some can find simple and do some good and stop being an really ignorant silly person !!
Remember you started this not me !!
Enough said
Read !! why is it people keep referring to information written 100 years ago all the time .they can quote long passages of other peoples work but have they written anything worthwhile and can they put there finger on things they done themselves ??
Would be a very short story !!
Proves my point there are not many true thinkers any more!!, just push button "nerdish fruit cakes" !!

 

Let's please try and keep the forums polite to other members and stay away from insulting others. Thanks.
<Thread closed since it appears to be moving in the direction of insults/annoyance rather than productive discussion.>

 

let shake hands and get on with the job !!

if you push I wont back off !!
if you start!! you will get what you deserve like it or not .
I totally agree ! lets get on and do what is necessary and help people any way possible !!