Imperial German Navy Research Thread

Colombamike

Post subject: Re: Request for photos on SMS Baden or even Bayern

Posted: June 4th, 2017, 10:27 pm

Posts: 1359
Joined: July 27th, 2010, 6:18 am
Location: France, Marseille

Tempest wrote: *

June 1st, 2017, 9:12 pm

From what I can tell battleships and battlecruisers had these fitted during trials, I am beginning to wonder if they have anything to do with speed trials over a measured distance, with bowspirit and sternspirit used to aid measuring somehow.
1) Does anyone know why they were fitted?

Probably to check ship-speed (& wind ?) & compare them with horsepower-machinery & draught.
Think "deep-water mile trial at Neukrug" => for the Konig class battleship
Think "Belt mile trial" => for the Bayern class battleship
For the Derfflinger class battlecruiser, the usual deep water mile at neukrug was considered unsafe in war and the 115ft deep mile was used instead.
For Hindenburg battlecruiser, the 10 may 1917 trial on the belt mile (26,6 knots & 9 meters draught) were considered equal to 28,5 knots at normal displacement at deep water

For german warships, speed & horsepower data were obtained on a mile run.

Tempest wrote: *

June 1st, 2017, 9:12 pm

2) Does anyone know if the pennants are merchant marine or something to do with trials, there appears to be two different ones amongst the photos, could they be shipyard related?

Probably merchant flag & shipyard flag

Tempest wrote: *

June 1st, 2017, 9:12 pm

3) Does anyone know what colours they were?

I don't know (for the moment

)

Tempest wrote: *

June 1st, 2017, 9:12 pm

4) During trials, the merchant flag would be flown if I remember rightly, is that so?

Yes, until the ship was formally commissioned I think

Others stuffs about german-ships trials :
- speed trials for Derfflinger and Lutzow could only be carried out in shallower water, they would be about 2 knots less than a deep sea trial.
http://www.jstor.org/stable/93825?seq=1 ... b_contents
http://hydrocompinc.com/library/white-papers
http://www.learnerstv.com/video/Free-vi ... eering.htm
very interesting
http://www.navweaps.com/index_tech/tech-091.htm

The original discussion is entailed in the K-office papers responding to the trials conducted under peacetime and wartime rules. In fact, the vast difference in speed achieved by these trials are based on three major differences:

[1] pre-war trials were run at the deep water measured mile off the North Sea island of Borkum. When the war made save trial conditions impossible, the wartime trials were conducted at Neukrug close to the Eckernförde Bay in the confined waters at the western Baltic Sea. The measured mile there had two calibrated ranges, one at 24 to 25m waterdepth, the other at 34 to 35m waterdepth. The original range at Borkum had a waterdepth in excess of 90m.

[2] the amount of power squeeched out from the engines in prewartimes was following the praxis "as much as possible without endangering the engines". This was also helped with by the aviability of high quality Whelsch steaming coal. In wartimes, domestic coal had to be used instead and the trial conditions were reduced to deliberately reduce the poweroutput to 120% in overload conditions, even while the engines were designed with higher overload capacities.

[3] During peacetime trials the displacement was somehow different than in wartime trials, which required a full crew complement and full ammunition and provisions (but not full fuel) to be carried. Thus the displacement was in part significantly larger in wartime trials.

In fact, when You compare pre-war and wartime trial speed results the differences are approaching the 2kts figure. SMS KAISER in her prewar trials achieved a speed of 23.6 kts off Borkum but the faster (in service) SMS KÖNIG achieved just over 21.5kts off Neukrug in their respective wartime trial conditions.
Similarely, the differences between SMS SEYDLITZ from prewar trials and SMS DERFFLINGER in her wartrials. The K-office recalculated the speed of DERFFLINGER in deep water following calibrations done with MOLTKE at Neukrug to be 28.0kts at 76,000 SHP.
The late war trials conducted with the battleship SMS BADEN off Neukrug were done in the 34m and the 24m range and again the 24m range yielded less speed than the 34m range. K-office consequently recalculated the speed of SMS BADEN in deep water from 22.08kts at full load and 34m waterdepth (=21.78kts at 24m) to 24.0 kts at 54,000 SHP if they had been done at the proper deep water trial range off Borkum.

Data from this primary source: Werft F. Seehahn, "Für die Prüfung des Schlachtschiffes Baden" (1916).

As mentioned previously calibration runs with MOLTKE in deep and shallow measured miles and with BADEN in shallow and very shallow measured miles have shown the relationship.
K-office notes that for the given shiplength the depth of the measured mile off Neukrug was not sufficient to yield correct speed results, if I remember correctly, it was said that beginning with 18 kts there is a light and at 21 kts a stronger increase in power required to achieve any given speed. The ~38,000SHP runs compared to the 54,000 SHP runs showed a very low increase in speed (from 21.548 kts at 37,430 SHP to 22.301 kts at 52,815 SHP) with more than 41% more power added. This represents an extreme power increase by x^10 instead of the expected x^5 to x^6 at this speed. When You plot the power notions, you can see where the hump set´s in. It´s at about 18 kts, just as calculated by K-office. The effect was more pronounced in 25m than in 35m and of course more pronounced at lighter displacements than with heavier ones (less speed of course). K-office required measured miles in excess of 70m water depth for the BAYERN-class ships with a length of ca. 180m to give exact speed trial results.

The Japanese found something similar, Haguro ran her trials at Mie on December 17, 1928 in 60 meters of water(197 feet) and reached 34.6 knots at full power. She ran the trials again at Koshikijima four days later in 180 meters of water(590 feet) and achieved 35.789 knots at full and 36.185 at overload.

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