Re: bismark-after torpedo hit
Posted: Mon Mar 29, 2021 10:34 am
Hello Hans,
Struggling as I am with an internet translation of A S-H's article it would help if you can clarify a few points and confirm whether I understand his points correctly.
His Hessen example refers to trials with a much shorter, smaller 3 shaft ship with a single central rudder. He compares length/beam ratio but fails (I believe) to compare the lever arms of the two ship's outer screws where Hessen's are farther apart relative to her length than Bismarck's. He seems to indicate that running the centre screw in reverse in Hessen effectively disables the rudder effect and the vessel can be steered with the outer screws. I am unclear whether this is with the rudder only in the fore and aft condition or whether the centre screw would overcome the effect of a rudder over at say 15 degrees. He then goes on to point out that this example is completely different to Bismarck's installation. I believe he says of Bismarck "nothing is known of such trials". However we believe that during Bismarck's trials attempts were made to steer with engines alone, presumably with rudders in the fore and aft position ie not exerting any deleterious effect, and yet was impossible to steer the ship. No mention is made of weather conditions during either set of these trials but I suspect they were nothing like those out in the Atlantic at the time in question.
Then there is a comment about dragging an anchorless chain from the bow when leaving port, apparently going astern. 25m of chain are mentioned, by which I assume given shallow water a considerable length is dragging along the seabed, which would indeed be an extremely powerful heading stabiliser, since as we have established, ships do not steer well going astern. However for the water depth in which Bismarck was operating there was no possibility of dragging on the seabed, so I do not see the applicability of this technique. Maybe he is just suggesting that dangling a bow chain would act as a drogue, through water drag, but whether this could counteract the very powerful port turn effect of the jammed rudder when going astern is to my mind pure speculation. He also seems to make no mention of windage on the hull which would tend to make the ship swing round until beam-on.
His lack of consideration to prevailing weather conditions on his tentative proposal steering Bismarck astern becomes very confusing when he describes the constraints caused to the shadowing destroyers by the wild conditions that night.
If I have gathered this gentlemen's points correctly, I do not believe they are very applicable at all, and the Baron's dismissal of them seems fully justified. If the ship could not be steered with engines going forward in the calm low wind conditions of the Baltic, there is little reason to practice or trial going in reverse in bad weather on the assumption that such a situation would somehow make things better. I, like you do not understand the Baron's observations which ignore the fully operational gyrocompasses etc. I consider that since there is no sensible argument to be made against such fanciful speculations, which could never be trialled, he felt he needed to come up with some reasons of his own. There are no real-world precedents for A S-H speculative techniques which are just thought experiments extrapolated from very shaky foundations IMHO. Thus I do not see him providing any valid evidence at all about ships with a jammed rudder at 12/15 degrees travelling astern in very bad weather.
All the best
wadinga
Struggling as I am with an internet translation of A S-H's article it would help if you can clarify a few points and confirm whether I understand his points correctly.
His Hessen example refers to trials with a much shorter, smaller 3 shaft ship with a single central rudder. He compares length/beam ratio but fails (I believe) to compare the lever arms of the two ship's outer screws where Hessen's are farther apart relative to her length than Bismarck's. He seems to indicate that running the centre screw in reverse in Hessen effectively disables the rudder effect and the vessel can be steered with the outer screws. I am unclear whether this is with the rudder only in the fore and aft condition or whether the centre screw would overcome the effect of a rudder over at say 15 degrees. He then goes on to point out that this example is completely different to Bismarck's installation. I believe he says of Bismarck "nothing is known of such trials". However we believe that during Bismarck's trials attempts were made to steer with engines alone, presumably with rudders in the fore and aft position ie not exerting any deleterious effect, and yet was impossible to steer the ship. No mention is made of weather conditions during either set of these trials but I suspect they were nothing like those out in the Atlantic at the time in question.
Then there is a comment about dragging an anchorless chain from the bow when leaving port, apparently going astern. 25m of chain are mentioned, by which I assume given shallow water a considerable length is dragging along the seabed, which would indeed be an extremely powerful heading stabiliser, since as we have established, ships do not steer well going astern. However for the water depth in which Bismarck was operating there was no possibility of dragging on the seabed, so I do not see the applicability of this technique. Maybe he is just suggesting that dangling a bow chain would act as a drogue, through water drag, but whether this could counteract the very powerful port turn effect of the jammed rudder when going astern is to my mind pure speculation. He also seems to make no mention of windage on the hull which would tend to make the ship swing round until beam-on.
His lack of consideration to prevailing weather conditions on his tentative proposal steering Bismarck astern becomes very confusing when he describes the constraints caused to the shadowing destroyers by the wild conditions that night.
If I have gathered this gentlemen's points correctly, I do not believe they are very applicable at all, and the Baron's dismissal of them seems fully justified. If the ship could not be steered with engines going forward in the calm low wind conditions of the Baltic, there is little reason to practice or trial going in reverse in bad weather on the assumption that such a situation would somehow make things better. I, like you do not understand the Baron's observations which ignore the fully operational gyrocompasses etc. I consider that since there is no sensible argument to be made against such fanciful speculations, which could never be trialled, he felt he needed to come up with some reasons of his own. There are no real-world precedents for A S-H speculative techniques which are just thought experiments extrapolated from very shaky foundations IMHO. Thus I do not see him providing any valid evidence at all about ships with a jammed rudder at 12/15 degrees travelling astern in very bad weather.
All the best
wadinga