Stiffeners spacing

[DUCRUY Jacques]

Hello,

The ISO or ABS ORY don't impose a maximum space between longitudinal or transverse frame : if you choose a great spacing, you must choose a plating more thick (or a SM more important for stiffeners).

But I am surprised by the difference between a plywood hull (classic, not epoxy) and a GRP hull.

For example, on a plywood hull :
longitudinal spacing : 30 cm
traverse frame spacing : 60 cm

On a GRP hull, you can see sometimes only 3 or 4 longitudinals by side, supported only by bulkhead (spacing 2 m).

Do you know why ?

Thank you by advance

Best Regards


Jacques

[jehardiman]

Monocoque construction. Rather than compare coventional plywood to GRP, look at a hot molded plywood boat like a wood Thistle.

[victorship]

for deck/shell plating, beam, frame, girders and longitudinal... the rules take into account the stiffener spacing to calculate the thickness and section modulus, in order to evaluate buckling/yield criteria. on the other hand the modulus of elasticity and strength of each material make the difference.