i've seen pics of hms dreadnought in drydock with wood piles and those poles. there were probably 50 piles and 100 poles, this would make me suspect that the dockyard folks knew the stress points and tolerances of wood and ship well enought to make it safe. the only knocked over ship in drydock i've seen was a german tincan bombed in drudock. it was a freakin mess..