Stuarttait,
Consider Shell Base Coat together with Shell Slip coat, that is also used to launch ships.
It is water resistent can can withstand pressures up to .5 Mpa.Regards
Wim
Kay,
If the tank has a direct opening to the atmosphere, the pressure will be atmospheric, provided the opening is big enough.
Concerning the diameter of the venthole, this depends on the fillingrate of the tank. Normally the velocity of liquids being pumped is limited to 1 à 2m/s, but...
Mr. Bucklebran,
I think you are right in saying that the stiffness is a material and geometrical related property.
The axial stiffness for instance can be defined as k;
where k=(E*A)/L; E for elastic modulus;Area;L length
or Torsional stiffness;
k=(G*Ip)/L, G is shear modulus of eleasticity;Ip...