Is bulkhead tabbing now redundant?

because boats are guess work
aircraft get tested, rules made then built to that rule

Perfect example was ABS rules on canting keels, they had no idea of the forces that actually happen after you leave the marina so they learnt by other peoples guesses

 

What DIDNT evolve, was their manufacturing techniques - they were in blissful ignorance, happy with a system that worked for them, most people are reluctant to change from what they know best - Tunnels is a perfect example of this

WOW would it be right to say that I come to a company to teach and show there workers a little more up to date method of building new styles of boats ?? a company buys a set of clapped out moulds that have seen hundreds of products taken out and then they look at the specs given by a previous company and told this is how they should be made , but these guys never done anything like this , so that's where I get called in to help them sort and teach and show techniques and methods I leaned long time ago but its all new to this bunch of cookies . . So you think I am reluctant to change ?? its not what I am here for . I could show them infusion and all kinds of wondrous things with all kinds of materials but its way beyond there scope of learning,and really when push comes to shove are all these things you trying to make look and sound good are they really that great anyway ?.infusion is not the be all to end all and has problems of its own just like carbon and Kevlar they all amazing materials but need to be used where they should be used to get the best from there properties each one has . Building for lightness is a catch phrase on everyone's lips but its usually only taken so far and not carried on all the way through a whole project right to the last nut and bolt used . no good saving 10 kgs here and then fitting some useless piece of equipment that's 30 kgs and may only get used once a year . you are a little confused I think !!
Survey will come one day to the whole of the marine industry because of the slap happy she''ll be right attitude of a few , Tell me why have some companies reverted back to hand laminating and doing all there boats like what we did 30 years ago .and people are lining up to buy them and don't want anything else !! explain that if you can .

Question !! if I had a block of German steel and I cut in half and sent one half to Sweden and one half to china to have each country make a BMW car which one would be the best and why should it be ??

 

Ha ha ha, very romantic indeed... And now i think you are confused.

First you said this;

Then you say, from above;

Different loads should not matter, the math is the same for an engineer.

Neither should the environment, so what if a structure operates in water or in air, if the loads are understood, they should be able to be calculated very accurately, and thus not need such large fudge factors, ahem safety factors...

The fact such large safety factors are used in marine design, can only in part, be explained by quality control issues.

The rest, can only be put down to a lack of understanding, of the complex stresses at work inside a composite boat structure. If it were better understood, such as in industries which have invested far more money in the research, then much lower safety factors would need be applied.

 

what rock you been hiding under ??

YES plywood is still used for bulk heads and under floor framing and is still tabbed same as was done in the 1950s , woven roving is still by far the most popular glass used in conjunction with chopped strand matt to build all those fancy high class shiny gin palaces you pay mega bucks for . if you get you head out of the clouds and see the real world not a lot has changed in the last 30 years .!! think what every you want it all works like it always did and some folks don't like change !

 

Hmmm......tunnels, how does one hide under a rock, whilst having one's head in the clouds ?

 

its not easy!!

 

In your zeal for a Voila moment, you’re getting yourself mixed up in knots. It is not surprising since you’re not a professional engineer, thus only looking at the periphery, without understanding the core of it is you’re observing.

With a structure, one has a material and then one has the response of said material, from an applied load. The loads, are just that, loads.

Then a material is selected based upon the loads. If the loads on a boat are say 10kN force and those on an aircraft are 1000kN, it is still a force which the structural material must resist.

So is the material used for a boat with 10kN going to satisfy that of an aircraft with 1000kN?...if not, does that mean the material is now different, if so, how so and is more testing required to ascertain what, where and why?

As for environment, simple issues like corrosion, stress corrosion, fatigue etc etc, all are major inputs into structural design. Each one is influenced by the selection of material(s) and vice versa. To suggest otherwise is showing your lack of knowledge in structural design.

In this I would agree in part. The other, but important issue is the loads(ing) that which a vessel is designed for. For example, say a boat is designed for a sea state 5, the structure is designed and built using the expected loads for a SS5. However, will the helmsman go home if the sea blows up to sea state 6 or 7? No, of course not. So a design requires margins and with boats the unpredictable can never be taken for granted, especially with non licensed vessels by overzealous sailors, ergo belt and braces for safety. The safety of people that won’t stay within the design limitations.

Unless of course you're suggesting that an aircraft half across the Atlantic is thinking, bugger, I’m only designed for clear weather flying not turbulence, it’s getting bumpy, perhaps I should return to base to stay within my design limits…or is the aircraft designed for all scenarios and thus the loads are more consistent, unlike most boats.

 

Some important differences between air & water.... I remember some quote I read in pro boat some years back... roughly misquoted as "the panel pressures on a boat doing 20Kts is the same as an aircraft doing Mach?"

The point of overzealous sailing is even more pertinent in regards to power vessels, having had customers in the sail & powerboat fields, often the powerboat guys in particular game boats had a "king of the ocean" mentality & would drive the same regardless of conditions. Of course the powerboat guys were better customers for other reasons
Jeff.

 

I thought we were discussing composites here? But thanks for the detour on corrosion...

Stress corrosion and fatigue are equally relevant, if not more so, in aircraft design as the structures are generally more flexible. Yet the safety factors are still far more modest... You keep avoiding the unavoidable, can you say the words "A naval architect cannot predict loads and stresses with as much accuracy, as say, an aeronautical engineer"? At some point you need to admit, that engineers do not know everything...

Take this, from the NR546 rules for the classification of hull in composite materials and plywood;

So thats 300% more than calculated according to this society, with respect to just the structural adhesive used in structural bonding applications!

So how deep does the rabbit hole go Neo? Im taking the blue pill... you can keep your red pill and return to the matrix...

 

As you have asked: My personal view (has little to do with laminating though)
It is partly a psychological problem to boat owners. The recent fifty years have somewhat generated a feeling that everyone is entitled for boating - even the unemployed. We find more people boating nowadays than is good for the oceans. But it is good for business. So the industry has reacted in giving people what they want.
However, buying or making ones own boat has become quite a financial strain to a majority of boaters (where i.e. Sir Lipton could feel much more relaxed...) and no one of those wants to lose his significant savings by entering a 'doubtful experiment'.
I would not say that the marine industry is behind per se. Think of Ellen's 'B&Q Castorama', think of 'OneAustralia', think of 'L'Hydroptere', think of the 'Moth'-class: there are efforts of setting new marks and finding new limits. And you will always see enthusiastic people from the marine industry as close as we are allowed!
Only, the MAJORITY of boat owners does not have this mind set.
To build the 'better boat' requires to step out of common paths. And it requires to accept a certain risk and certainly: courage.
Many others do not have this courage. If you have it: go on. I am one of the first to cheer. (Perhaps I will also learn something)

 

Yet again you’re showing your ignorance on the subject. This is very easy, all that is required is the load. So...Where do you get the loads from?

You have some beef about FoS, for some reason. Well, since you are building your own vessel for your own means why bother with FoS of 4 or 5 or whatever….why bother using Class rules, you clearly do not like/trust them. You appear to think that once an applied load is known, why bother with a FoS at all, or at the very least a large one? Assuming you can even calculate what loads to apply without Class rule assistance.

All you are doing is continuously and consistently showing your ignorance on design and fabrication of structures in a marine environment.

You should design to a bare minimum, lower than Class say, design to what you consider to be “acceptable”. Take your boat out and then tell me how safe you feel and then take her out into the offshore open ocean and again, tell me how safe you feel with your minimal FoS. And tell me it is a "better" quality boat because you have shaved off so much weight with minimal FoS.

Why do you seek advice/guidance when you have made up you own mind that what you read/hear is not acceptable, because you don’t like it? No one is forcing you to use such FoS…so why bother using them? Seriously why harp on about it if you don't like it?

If you are being “forced” and do not like it, then propose your own. That is what engineering is about. Show where everyone is wrong and that your way is better.

Structural design with longevity is more than one simple formula to which you are constantly seeking to justify your own thoughts/ideas on such.

 

I just started reading this subject thread, but I just had to comment on this excellent reply by Groper. Where is there ANY advancement in the way we build boats if all we do is follow the old ways.

We wouldn't have had Maltese Falcon if all we did is follow the old ways and never venture boldly in new directions.

In fact we might never have had fiberglass boats had we just followed the old ways.....

 

Aren't these two conflicting statements?

 

Engr Composites & Nigel Iren's observation

Agreed Groper, I have yet to run into an engineer that can pre-tell me what EXACTLY is happening inside a mult-layer of fiberglass material, particularly considering the different resins utilized to put that layer together. It is more of a 'build it and test it', or compare it to previous lay-ups that were successful.

I'll just reference two sites I happen to read rather quickly in past few days.
http://www.yachtsurvey.com/core_materials.htm
....excerpt

Nigel Iren's observation (OK, I could no longer find the webpage reference to this 'interview', but I had kept a hard copy. So here is a scan (attached). Hope it can be read.
...little excerpt

There was another piece I read from Nigel taking about the 'improper reinforcement' of some stressful areas on vessels with some of the newer hi-tech fibers overlayed on more conventional ones, and the false sense of security that presented to the designer/builder.

 

Having designed and manufactured both aircraft and race cars I can answer this in two words.

Weight sensitivity.

An aircraft or race car built to such a high FOS will fail. They can't afford the weight penalty of such luxury. But that is OK because aircraft can fly around storms or just stay on the ground. Boats can and will find themselves in dire situations that no one could have expected. In those cases the only chance of survival is the highest strength possible. So the designers put in as much beef as possible balanced by loss of performance. Since a boat can tolerate some weight buidup better than an airplane it works out ok. But even with the higher FOS occasionally boats still break and sink.