Structural glass on hull sides - ISO Harmonised rules

Discussion in 'Class Societies' started by ToMeK, Mar 12, 2021.

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ToMeKYoung naval architect

Hello everyone!

Please help me with an advice and guidance where to look for the rules for scantling of large hull side windows. Project is small planing boat 45ft GRP.

According to ISO 12216 in Area I (on the hull side below hs) smaller dimension of appliance must not be larger then 300m (b<300mm).

My conclusion is that this glass must be taken as structural, but I am having difficulty finding adequate rules glass calculation should be made according to. Does anyone have any experience or an advice? If possible it would be good to keep boat under ISO class.

Similar example is GALEON 700 SKYDECK 2021 with obviously large glass areas on sides close to WL.

Many thanks,

Best,

Tom

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TANSLSenior Member

Use the theory of thin sheets, with four recessed sides, and with a thickness such that the maximum deflection of the plate is not greater than its thickness.
The maximum dimension of each window should not be greater than 1 m, or two times the value of frame spacing (the less value)

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ToMeKYoung naval architect

Thank you. It is not a problem to calculate it that ways, but the questions is if the surveyor will accept it since the smaller dimension is longer then 300mm (not acc to ISO 12216).
I found ISO 1336-2 which is for large yachts considering glazing as structural part but taking into account only local loads on glazing plates. Do you have any experience with that?
In the end, FEM calculation can be made for this (as you said under 1m span and deflection less then 1/2 of thickness it can be considered as linear static)

Regards,

Tom

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TANSLSenior Member

I have done several projects of passenger ships with windows in the bottom. I have followed the rules of the Spanish Administration which, in terms of the calculation method, are reduced to what I have told you. These standards also speak of a maximum width of 0.5 m but I have presented openings of 1 m, justified by the calculation, with an extra reinforcement in the hull (double thickness of the laminate) in the area where the openings are placed, and metal frames . With all this, they have accepted the projects without any comment to the contrary.
All the rules, even those of the Classification Societies, may no longer be met, if you justify your calculations properly.

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jehardimanSenior Member

I support TANSL on this, as most societies have an "or engineered equivalent" clause. The rules are made to make plan inspection easy, not be a technical limit. However, the one rule you can't get around is that the glass cannot be proud of the line of the hull however it is measured. So you need to be diligent in way of curved hull sections.

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TANSLSenior Member

I forgot to add that, in the hull, glasses, and the area where they are or implanted, must be perfectly flat. Although I suppose this is obvious.

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fallguySenior Member

I believe that no element, including metal, can be proud of the hull line.

@TANSL How does one make all elements flat? Or is the metal frame proud of the glass, but not proud of the hull? Hard to tell by the picture above, but it appears to be double recesses. So the entire area is recessed? and then the windows are recessed? behind the metal framing.

I am only curious and not trying to answer the original question. I imagine those windows are a bugger to keep salts spots off!

When I built my small boat, my ports are behind the hull line, but the flange is proud of the hull and so I was rather stressed about it for a bit. That is nothing compared to these windows.

If they recess it all, then the fiberglass can be thickened. Perhaps this is all a no brainer for you fellas. If so, carry on and with my apologies.

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ScarfNew Member

The ISO 11336 standard you refer to allows a maximum clear opening size of 0.85m^2 and it is intended for large yachts > 24m, design loads on the side shell may be higher than ISO 12216 though. Large glazed openings are also sometimes accepted if they are constructed of laminated glass with a PVB interlayer between the panes which improves the impact resistance and also provides residual strength if one of the panes is broken. Glass thickness should be determined by the formulae in the standard, FEM is not really necessary for a simply supported monolithic pane but if you do decide to use FEM then a safety factor of 4 should be applied on the characteristic failure stress of the glass.

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