RobertsonN wrote:.....In this case, the bomb was probably disarmed on penetrating the armor (as occurred on Scharnhorst (3 times) and Tirtipz (once)). By way of comparison, Friedman (US battleships) gives the Iowas as immune to 1600 AP bombs below 12200 ft. Does any one know if AP bombs had caps?
I have found original data on the US 1600 lb AP bomb. The terminal velocity was 270m/s. At 270m/s and striking at the normal, the penetration is ~205mm homogenous armour. It looks like Friedman was a bit optimistic here. In the case of the Tirpitz, the bomb should have just been able to penetrate 140mm effective homogenous armour with all the energy consumed, and this is just what happened. As for a cap or not, I don't know. The fact that these bombs showed a probability to being broken or rendered inert by de-capping arrays may indicate de-capping, but it may also indicate the center of gravity not being near enough to the head, and base slap was probably a factor as well.