Shape of extrusions

[Celine]

Hi eveybody !

I try to understand how the extrusion shapes are chosen during the design of a ship. I know how to do simple calculations in using rules like DNV or LR but I noticed that the choice of the shape is usually based on personal preferences and habits for the majority of the naval architects I met.
Do you prefer Tee or Bulb flat? What are the typical sizes for what kind of boat?
All comments are welcome!
All available examples of calculations are welcome!

Many thanks in advance to who can help me.

By

[D'ARTOIS]

Apparament vous travaillez au métier de nous. Très bien. Et bienvenue!

First of all, when we talk .e.g. about aluminium construction - and that is in France the major metal used for boat production, less and less extruded body parts in way of struingers and frames are used in favor of cutted ones. Althoug for stringers a certain use will remain.

Regarding deckhardware, toerails, tracks etc. stainless steel is the preferred material becaus of the abrasion-sensitiveity of aluminium, unless it is surface treated, for example teflon impregnated.

If you work for a Aluminium industry alike Goiot, please indicate what you range of products is and the applications you might manufacture.

[Celine]

Merci beaucoup !
No, I am not working for a aluminium industry alike GOIOT.
My question deals with the stringers in aluminium. Are you using them in your design?

[D'ARTOIS]

Of course, mostly t-bar of 50x50x4 or 50x50x5 for the regular designs in alu till 13-14 mtrs.
However, now more flat strips are used, although I prefer the t-bar.

To be honest, stringers are not a big issue, most used are t-bar or flat. If you want details of strength etc. I can mail you a technical brochure.

[Celine]

Oh yes, thank you !

[FAST FRED]

For a steel boat the flat is usually prefered as the interior can be completly sand blasted ,and properly painted,

really hard to do do with L or T stock.

Probably doesn't matter on aluminum , except for hunting for stray copper wire cutoffs from a dumb electrican.

FAST FRED

[water addict]

Originally Posted by Celine

Hi eveybody !

I try to understand how the extrusion shapes are chosen during the design of a ship. I know how to do simple calculations in using rules like DNV or LR but I noticed that the choice of the shape is usually based on personal preferences and habits for the majority of the naval architects I met.
Do you prefer Tee or Bulb flat? What are the typical sizes for what kind of boat?
All comments are welcome!
All available examples of calculations are welcome!

Many thanks in advance to who can help me.

By

Generally you want the lightest stiffener that will satisfy the structural requirements. If you crunch through the rules, you are probably ok, provided you are doing it right. I have set up design spreadsheets with multiple stiffener catalogs, and with the few input parameters as requirements, the spreadsheets can sort through the stiffeners and pick the lightest one, based on the design criteria of choice. Of course I cannot release it over the net, sorry. But if you have a few days, it's not too difficult to program.

As far as tee or bulb- tees will give lighter structures, but bulbs are much easier to maintain (repaint). Having had to clean and paint both in prior jobs, I would prefer bulbs, but if weight is critical and you need to save that extra 1-3% for performance, then use a tee.