watertight bulkhead

But I am talking about pressure on sandwich panels, this is 1.1.2 of Part 3, Chapter 1, Section 3. Check the rules and get sense of them first, before lecturing someone.

 

Well you gave no reference to the part of the rules, only the 4 points which is, as noted, the only reference to it; that which i posted

However, your ref, now you cite it, doesn't make sense??:



Where does it mention about sandwich panels and 4 points???

 

I don't think class gives too much additional safety for small craft (below 24m). Moreover, often the opposite - there is degradation of safety. Example: for 10m patrol powerboat RS required 1.0m high handrails, three rows of pipe. This is just in front of pilothouse windows. Will it increase safety, specially at night when one is using searchlight? Isn't in this case requirement of ISO standard better, just handholds on pilothouse roof? I can give You dozens of example like this... Often the cost spent to 'classification' can be used for real improvements/maintenance of the craft. We design boats to both class and ISO. Class costs are often an overkill for small craft owner/operator; ISO is the way to go for non-passenger craft. 'Choose the right tool for the job'.

[/QUOTE]
This is well known: surveyor of Notified Body does that. Say, we worked with IMCI, BV, RINa, etc. surveyors, and they all required structural drawings for craft above 12m in length. They do not formally approve any drawings, but they do certify the craft, so first stage is review of technical documentation.

We as designers need to be fair with the Customers and do not push them to costly classification if ISO standards can be applied. Depends on the project.

 

In 2018 rules (which I have with me) it is:
For stiffened panels of steel, aluminium or single skin FRP:
Horizontally stiffened:
— midpoint of plate.
Vertically stiffened:
— 50 % of stiffener spacing above the lower edge of the plate,
— when the plate thickness is changed within the plate, at the lower edge of the plate.
For FRP sandwich panels:
— the design load shall be equal to the mean pressure on the panel. For large panels the true pressure distribution shall be used if resulting in a higher stress level.
For stiffeners and girders:
— the larger of pm and (pa+pb)/2 where pm, pa, and pb are the pressures at the middle of the span and at each end of the stiffener respectively.

This means that we need to find design pressures in the corners of sandwich panel, and each of them will have its own WL angle and deadrise/flare angle. I say this is not practical for design, don't You think so? My engineers are spending hours measuring these useless angles from 3D model, for each bottom panel.

 

I totally agree, the designer must choose the right tool and not the one he knows best. We have to be honest.
There is no reason, none, to enforce the class to a boat that does not need to meet it. And there are many boats sailing, not only recreational boats, which have been designed and sail without class assigned, with all the guarantees of safety, navigability, etc. Many more in number than those classified by any CS.

 

I support this statement. Often boat under class comes out overbuilt and heavy. Often 'ship minded' surveyors demand impractical solutions. Sometimes it becomes anecdotic.

Say, we do a lot of small boats for Russian market, and RS does require 'hulls of non-combustible materials'. They took it from IACS recommendations, but apply to all boats, including small composite craft. So, class? Cover all boat with 4mm steel plates over all composite structures, as they demanded from us and other designers? Is this for additional safety?? We just told them to fukoff, and designing good boats under small craft certification (ISO and similar)

 

Sorry Alik, you're showing ignorance of the rules.
Protection of crew is a SOLAS/ILLC rule i.e satutory, not classification society rule!

You still haven't cleared the Pt.3Ch.1. Sec.3, 1.1.2 you quoted...nothing about 4 points and pressures in DNV-GL?

So who does formally approve them then?

Then please quote the correct reference to the rule.

Who says it must be practical? Do you get a reduction in the scantlings if you can do it in 5mins?

ISO rules and its annex are just as bad if not worse!....but, whatever you may think, or disagree with, you must take into account the fixity of the edges, otherwise the structure strength is compromised!

No one says you have to. It is your choice which rules you wish to apply.

 

Statuary requirement to have 1.0m railings on 10m boat? Are You kidding?

About 4 points: for sandwich panel is mean pressure, so we need 4 points if it is bottom or side.

 

Notified Body (can be classification society or other institution) certifies the craft, based on submitted technical documentation, filled checklists/forms and testing of the craft. Everyone who did boats to CE over 12m is aware of that.

 

Try telling that the those on the Duck Boat that!..."..you're kidding!!!.."

Class only deal with safety of the boat and its system
Statutory deals with safety of personnel/crew and system associate with that.

Im sorry Alik, you're showing great ignorance here with regards to safety of personal onboard!!

Pls quote the rule as you're not making any sense now. As this is not in 1.1.2.

 

Errr..why use ISO then if you have to use Classification for its approval?...kind of shoots down the whole argument of not use Class and ISO easier/cheaper?!!

 

This is good question. Classification and certification are not the same. Classification societies such as RINa, DNV-GL, BV (not now), LR are appointed by European Commission to certify small craft to RCD (i.e to ISO standards). As well as other organizations, there are about 30 of them. Those all together are called 'notified bodies'. This is not a classification, the procedure is developed for small craft and less heavy ('small craft - small money').

 

This 1m railing is not applicable to 10m patrol speedboat. You might understand that, if You pretend to be practicing naval architect.

 

Already quoted above, again:
1.2.2 When applying the rule formulas for scantlings the load point where the design pressure shall be
calculated is defined for various strength members as follows:
For stiffened panels of steel, aluminium or single skin FRP:
Horizontally stiffened:
— midpoint of plate.
Vertically stiffened:
— 50 % of stiffener spacing above the lower edge of the plate,
— when the plate thickness is changed within the plate, at the lower edge of the plate.
For FRP sandwich panels:
— the design load shall be equal to the mean pressure on the panel. For large panels the true pressure
distribution shall be used if resulting in a higher stress level.
For stiffeners and girders:
— the larger of pm and (pa+pb)/2 where pm, pa, and pb are the pressures at the middle of the span and at
each end of the stiffener respectively.

 

Any competent/qualified engineer is allowed under ISO rules.
I can....

Like any naval architect, you learn the rules...and where it says, if you wish to use a lesser standard, you can apply for dispensations, so long as the philosophy is maintained.

Ahhh ok..now you're quoting the correct rules.
These rules have been part of the rules and in existence since i used the DNV Rules back in 1991.????... Don't understand the point?.