[Aktungbby]

QUESTION: does wolfpack incorporate reality into use of the U-boat periscope as occurred in WWII? http://www.uboataces.com/periscopes.shtml

At 6 knots, (out of 7 knots max when submerged) it caused excessive vibration which rendered it almost impossible to use. This was dampened by using an extension bracket to reduce the unsupported length and the pointed end was redesigned to minimize the forward hydrodynamic resistance. Nevertheless, vibrations still occurred, but to a much lesser degree. The other problem was fogging of the lenses. Since the damp atmosphere of the U-boat caused fogging, it was especially important that the tube was not only watertight, but was airtight as well. Any fracture on the airtight casing caused by a depth charge attack would result in fogging of the tubes.

https://www.subsim.com/radioroom/sho...d.php?t=189585

Originally Posted by Sailor Steve

On the other hand there is anecdotal evidence that raising the periscope at more than 3 knots would cause enough vibration to render the image unviewable. As I said, it's my understanding that damage wasn't the problem so much as not being able to see anything due to vibration. That said, I really don't know the exact parameters and problems.
I always slow down to use the periscopes, but that may just be me.

https://maritime.org/doc/uboat/index.htm

125.) The "sparing" use of the periscope (see Section I, B, No. 31); i.e., the raising of the periscope, at frequent intervals and for a brief space of time, to surface level, So that the periscope appears no bigger than a fist, and almost constantly awash, begins at a distance of approximately 4,000-5,000 m from the enemy, according to the state of the weather and the conditions of light. It is a mistake to keep the periscope down for any length time when the enemy is near. In that case the submarine is not less visible an during the "sparing" use of the periscope; but it can itself see nothing, and is therefore in greater danger. Consequently, the submarine should carry out frequent observations of short duration; but, in all circumstances, they should be repeated again and again.

126.) The periscope should only be raised when the submarine is traveling at low speed. Before raising the periscope, it is therefore necessary to reduce the speed. Otherwise, if the sea is calm, the wake of the periscope can easily be seen, besides which the periscope of a submarine traveling at speed will cause splashes, and a conspicuous feather ["Wasserfahne"].

127.) If special reasons require that the speed be temporarily increased, for example, in order to reach a position more suitable for launching an attack, the periscope must be lowered until the top of it is at least 1 m under the surface. When the submarine is at the depth for attack, the periscope should not, however, be further lowered to an extent greater than it is absolutely necessary, in order not unnecessarily to lose time in raising it again.