WesWorld

Yep, for a breif while the Japanese had all kinds of stability issues with their ships mostly due to efforts to limit the designs to Washington treaty standards.

http://en.wikipedia.org/wiki/Tomozuru_In…mozuru_Incident

Quoted

Originally posted by thesmilingassassin
Yep, for a breif while the Japanese had all kinds of stability issues with their ships mostly due to efforts to limit the designs to Washington treaty standards.

http://en.wikipedia.org/wiki/Tomozuru_In…mozuru_Incident

Well so far I've found out that Japanese ships in the 30s had to be rebuilt bc of lack of stability/strength, but I've found nothing that relates that directly to high l:b ratios.

It seems that the stability/strength problems were caused mainly by overloading the ships and overuse of wielding, not bc of high l:b ratios. After the incidents that folks mentioned here, it appears that the Japanese had remedied the problems after rebuilts, and as far as I know the l:b ratios of the ships were unchanged.

The Japanese destroyer Shimakaze built in the 40s btw, has a l:b ratio of over 11:1. Although it is true that she had a short service life, I've found nothing that suggests she has the stability/strenght issues of her predecessors.

As for my designs, I believe my stability and strength are reasonably good, at least in terms of the stats that SS provides.

Well, it´s a mix.

During the 4th Fleet Incident (see i.e. http://shippai.jst.go.jp/en/Detail?fn=0&id=CB1011022& or http://forum.axishistory.com/viewtopic.php?f=65&t=110056 even though these sources are not very detailled) several IJN vessels, especially DDs of the Fubuki class, were heavily damaged. Some even lost part of their hull (snap in two) while many other units had their hulls buckled and rivets cracked away becaude of hull deformation. The reason was insufficient hull strength, not top weight and massive improvements were necessary to prevent such incidents to happen again.

SS may allow long hulls but it does not take into account the special stress to such hulls and their behaviour in heavy seas (wave length is critical). Meassures to strengthen the hulls would eat up weight that is not part of SS calculations.

Quoted

Originally posted by HoOmAn
Well, it´s a mix.

During the 4th Fleet Incident (see i.e. http://shippai.jst.go.jp/en/Detail?fn=0&id=CB1011022& or http://forum.axishistory.com/viewtopic.php?f=65&t=110056 even though these sources are not very detailled) several IJN vessels, especially DDs of the Fubuki class, were heavily damaged. Some even lost part of their hull (snap in two) while many other units had their hulls buckled and rivets cracked away becaude of hull deformation. The reason was insufficient hull strength, not top weight and massive improvements were necessary to prevent such incidents to happen again.

SS may allow long hulls but it does not take into account the special stress to such hulls and their behaviour in heavy seas (wave length is critical). Meassures to strengthen the hulls would eat up weight that is not part of SS calculations.

Well, according to the source you gave, and one that I've found myself, the main cause of the lack of strenght is still construction/overuse of wielding. That can certainly be avoided. The stability problems are caused by top weight problems. The Japanese just like to cram as much weaponry as possible.

Still, me thinks that high l:b doesn't come into much play. TF38 and Typhoon Kobra show that even if you have l:b below 10:1 you can still get bashed up by heavy seas.

Last version I can think of: one armed with 16 torpedoes!


Enter ship name, Siam Large Destroyer laid down 1938

Displacement:
2,841 t light; 3,000 t standard; 3,472 t normal; 3,849 t full load

Dimensions: Length (overall / waterline) x beam x draught (normal/deep)
(519.74 ft / 505.25 ft) x 45.93 ft x (13.78 / 14.68 ft)
(158.42 m / 154.00 m) x 14.00 m x (4.20 / 4.48 m)

Armament:
8 - 4.92" / 125 mm 50.0 cal guns - 55.12lbs / 25.00kg shells, 250 per gun
Dual purpose guns in deck and hoist mounts, 1938 Model
2 x Twin mounts on centreline, forward deck forward
1 raised mount - superfiring
2 x Twin mounts on centreline, aft deck aft
1 raised mount aft - superfiring
8 - 2.17" / 55.0 mm 55.0 cal guns - 5.51lbs / 2.50kg shells, 1,000 per gun
Anti-air guns in deck mounts, 1938 Model
4 x Twin mounts on centreline, evenly spread
4 raised mounts
8 - 0.98" / 25.0 mm 75.0 cal guns - 0.55lbs / 0.25kg shells, 1,500 per gun
Anti-air guns in deck mounts, 1938 Model
4 x Twin mounts on sides, evenly spread
4 raised mounts
Weight of broadside 489 lbs / 222 kg
Main Torpedoes
16 - 23.6" / 600 mm, 29.53 ft / 9.00 m torpedoes - 2.402 t each, 38.427 t total
In 4 sets of deck mounted side rotating tubes
Main DC/AS Mortars
40 - 440.92 lbs / 200.00 kg Depth Charges - 7.874 t total
in Stern depth charge racks

Armour:
- Gun armour: Face (max) Other gunhouse (avg) Barbette/hoist (max)
Main: 1.97" / 50 mm 0.79" / 20 mm 0.79" / 20 mm
2nd: 0.79" / 20 mm - -
3rd: 0.39" / 10 mm - -

- Conning towers: Forward 1.97" / 50 mm, Aft 0.79" / 20 mm

Machinery:
Oil fired boilers, steam turbines,
Geared drive, 2 shafts, 61,529 shp / 45,901 Kw = 36.25 kts
Range 3,800nm at 20.00 kts
Bunker at max displacement = 849 tons

Complement:
225 - 293

Cost:
£2.155 million / $8.622 million

Distribution of weights at normal displacement:
Armament: 227 tons, 6.5%
- Guns: 140 tons, 4.0%
- Weapons: 87 tons, 2.5%
Armour: 44 tons, 1.3%
- Armament: 30 tons, 0.9%
- Conning Towers: 14 tons, 0.4%
Machinery: 1,614 tons, 46.5%
Hull, fittings & equipment: 917 tons, 26.4%
Fuel, ammunition & stores: 631 tons, 18.2%
Miscellaneous weights: 40 tons, 1.2%
- On freeboard deck: 20 tons
- Above deck: 20 tons

Overall survivability and seakeeping ability:
Survivability (Non-critical penetrating hits needed to sink ship):
1,095 lbs / 497 Kg = 18.4 x 4.9 " / 125 mm shells or 0.3 torpedoes
Stability (Unstable if below 1.00): 1.40
Metacentric height 2.8 ft / 0.9 m
Roll period: 11.5 seconds
Steadiness - As gun platform (Average = 50 %): 51 %
- Recoil effect (Restricted arc if above 1.00): 0.27
Seaboat quality (Average = 1.00): 1.03

Hull form characteristics:
Hull has rise forward of midbreak,
a normal bow and large transom stern
Block coefficient (normal/deep): 0.380 / 0.395
Length to Beam Ratio: 11.00 : 1
'Natural speed' for length: 25.88 kts
Power going to wave formation at top speed: 60 %
Trim (Max stability = 0, Max steadiness = 100): 50
Bow angle (Positive = bow angles forward): 25.00 degrees
Stern overhang: 1.64 ft / 0.50 m
Freeboard (% = length of deck as a percentage of waterline length):
Fore end, Aft end
- Forecastle: 20.00%, 27.56 ft / 8.40 m, 20.01 ft / 6.10 m
- Forward deck: 20.00%, 20.01 ft / 6.10 m, 20.01 ft / 6.10 m
- Aft deck: 45.00%, 13.12 ft / 4.00 m, 13.12 ft / 4.00 m
- Quarter deck: 15.00%, 13.12 ft / 4.00 m, 13.12 ft / 4.00 m
- Average freeboard: 16.48 ft / 5.02 m

Ship space, strength and comments:
Space - Hull below water (magazines/engines, low = better): 166.5%
- Above water (accommodation/working, high = better): 177.4%
Waterplane Area: 14,636 Square feet or 1,360 Square metres
Displacement factor (Displacement / loading): 87%
Structure weight / hull surface area: 42 lbs/sq ft or 203 Kg/sq metre
Hull strength (Relative):
- Cross-sectional: 0.50
- Longitudinal: 0.83
- Overall: 0.52
Cramped machinery, storage, compartmentation space
Excellent accommodation and workspace room

Quoted

Originally posted by gaiasabre11
Still, me thinks that high l:b doesn't come into much play. TF38 and Typhoon Kobra show that even if you have l:b below 10:1 you can still get bashed up by heavy seas.

Having just recently read Halsey's Typhoon, I'd have to disagree; It was the overloaded high L:B Destroyers that foundered, and snapped in half in some cases, not relatively fatter DEs, auxilliaires, and other ships. In fact, Tabberer and other DEs took a pretty savage beating, but did not founder and were under control once the weather subsided.

Quoted

Originally posted by ShinRa_Inc
Having just recently read Halsey's Typhoon, I'd have to disagree; It was the overloaded high L:B Destroyers that foundered, and snapped in half in some cases, not relatively fatter DEs, auxilliaires, and other ships. In fact, Tabberer and other DEs took a pretty savage beating, but did not founder and were under control once the weather subsided.

Well, nevertheless, I feel that the current design is good enough. I've looked at other deisng people have and found plenty of them having l:b ratios between 10.5~11, including some Japanese ones, so I suppose my design still works out.

Quoted

Originally posted by gaiasabre11
I've looked at other deisng people have and found plenty of them having l:b ratios between 10.5~11, including some Japanese ones, so I suppose my design still works out.

So just because somebody jumps off the Golden Gate Bridge he´s a good example for you to do the same? Good luck. ;o)

As I said, it´s an old discussion and should you start searching for it you may note there have been many similar remarks on l:b ratio on these 11:1 designs too. The reason I came up with this (again) is that you´re new to the board and from the very beginning all your ships are designed to the very extreme.

Don´t get me wrong - our gentlemen rules allow ships with a ratio of max 11:1. But those who build those know the risk....

Quoted

Originally posted by gaiasabre11
Well, according to the source you gave, and one that I've found myself, the main cause of the lack of strenght is still construction/overuse of wielding. That can certainly be avoided. The stability problems are caused by top weight problems. The Japanese just like to cram as much weaponry as possible.

Still, me thinks that high l:b doesn't come into much play. TF38 and Typhoon Kobra show that even if you have l:b below 10:1 you can still get bashed up by heavy seas.

Well, the question was not if a typhoon can cause havoc to a ship but if it can cause havoc to a ship with a high l:b ratio more easily. And that´s obviously the case.

Regarding TOMOZURU:

The vessel capsized in storm. An investigation committee headed by Admiral Nomura Kichisaburo examined the wreck. The accident was attributed to the storm waves and to the Tomozuru´s lack of daynamic stability. Between April and June 34 another investigation committee headed by Admiral Kato Kanji, former chief of the Navy General Staff, investigated the cause of the lack of stability on the recent Japansise units and set up a serier of measures to improve their seaworthiness.

It was already known from tests with the CHIDORI (first unit of the class and sister to TOMOZURU) that the metacentric height (GM) was reduced and the dynamic stability impaired. As a result all ships of the class including TOMOZURU got bulges before commissioning that widened the hull to improve stability. However, because of too much weight put on the small hull that was obviously not enough. Each increase in displacement lowered the metacenter unless the ship had been widened even more.

As a result of the committees investigeation measures were taken for existing units of the First Replenishment Programm (and others) that include

- Removal of nonessential or less important fittings and change of location of main armament
- Fit ballast keels and/or load ballast
- Increase the ships beams (by fitting bulges for those already constructed)
- Install seawater tanks and adequate pumping capacity to compensate for the use of fuel, ammo etc.

So to sum it up - the TOMOZURU incident provides a good example of what happens to an overloaded long and slender hull. In case of the TOMOZUTU l:b ratio was 10,67:1 and she was overloaded by about 90 tons over her calculated 2/3 trials displacement (under battle conditions with a full load of ammo, fuel and men stability was even worse).

Regarding the Forth Fleet Incident:

The main body ran through the storms eye at about 1430 on the 26th September 1935. Before waves had been of a height of about 10m and of triangular shape but suddenly they rose to a height of about 15-18 meters. They smashed the flight deck and bridge of the HOSHO and RYUJO. Joints amidship on the sides of the hulls of MYOKO, MOGAMI and TAIGEI and othe runits of the MYOKO class and MIKUMA loosened or ruptured. In addition the forward part of the MOGAMI´s hull was distorted.

About 100nm further east the DD squadrons also encountered triangular waves of about 10m height. At about 1400 the waves reached as high as 15 meters. The DDs of the MUTSUKI class rolled to 75° and those of the FUBUKI-class to 70°. At 1602 the entire bow forward of her bridge broke off the YUGIRI. At 1729, while atop a triangular wave, the bow of the HATSUYUKI also broke off in front of the bridge. Other ships were badly damaged too but towards evening the destroyers came into quiter water and, at dawn, where joined by the units of No. 5 Sentai. Many DDs but especially those of the FUBUKI-class (l:b ratio 11,12:1) suffered buckled plates, especially in the forward part of the hull. The bows and sterns of the MURAKUMO, AKEBONO and USHIO were distorted and developed multiple cracks and tears. Many had ruptured or loosened joints in the upper deck amidship as well.

In April 1936 the investigation committee lead by Admiral Nomura Kichisaburo presented results. From the investigation it appeared that the ships of the main body had been subject of waves 100-150m long and 10-15m high, that is, waves with a L:h ratio of 10. In the area where the destroyers operated the waves had reached a length of 200m and height of 15m, or a length-to-height ratio of 13,3. Studies by the Hydrographic Department had revealed that in home waters ratios mainly varied between 20 and 30, and seldomly less than 20. Calculations of hull strength by the Bavy Technical Department were based on trochoidal waves with a ratio of 20. Moreover, the longitudinal strength of the most recent units, and of the FUBIKI-class destroyers in particular, was insufficiant to withstand waves with a ratio of 10. The sagging produced by such waves, with the bow and stern atop a wave crest, resulted in the buckling of the deck at the bow and stern (top compression) and the extension of the bottom (bottom tension).

As a result of the investigation the longitudinal strength of all units, except for battleships and large carriers, was increased by adding stell plates to the existing plates along the bottom, the upper deck and sides. Moreover, the designs under construction or in planning were altered to incooperate the lessons learned.

The damage to the ships during the typhoon also revealed the weakness of the nonoverlapping butt joints in the FUBUKI class DDs, and of some wields, particular in the hull of the TAIGAI and the larged welded hulls of the MOGAMI and MIKUMA.

Quoted

the main cause of the lack of strenght is still construction/overuse of wielding. That can certainly be avoided.

In answer to your claim above, wielding was not a problem on the FUBUKI-class DDs. The reference on insufficient wielding aims for the cruisers. And how will you avoid it? SS does not take care of this, AFAIK. One option might be to devote some extra weight to it or do NOT go down with hull strength to the very limit of 0,5 in very long and slender hulls. But you´ve not done so in your designs.

Furthermore, if a high l:b ratio only offers advantages (i.e. in case of high speed hulls), why wasn´t it used more often? Why had 3/4 or more of all DD designs ever build a ratio much lower?

Just curious..... :o)

Ships with higher length:beam ratios are subjected to higher stresses. Hence, to build them to the same strength there needs to be more material i the structure which leads to higher hull weights. With low block coefficients you also run into buoyancy related problems as the sections of hull have to be able to support what is on top of them. This gives problems when mounting heavy turrets at the ends of ships. Length:depth is ratio to take note of as well. A simple comparison is to treat the hull as beam. In that case the stress decreases with the cube of the depth.

What is the best length:beam ratio? Really it just depends on the circumstances. Recently there's been a move towards lower values in order to compensate for heavy topweight items and for greater seakeeping ability.

Given Siam's limited operational radius, I don't think that a l:b ratio of 11:1 is over the top. At the same time, Siam doesn't have the greatest experience in building ships so it's probably wise to build to a higher strength to give more margin for error, say 0.60.

I still think you're going to have problems mounting duple 55mm guns on the centreline along with everything else.

Offed a few days for misc shit. Been trying to draw something on my own without too much of a success. Will try more.

Quoted

Originally posted by Red Admiral

Given Siam's limited operational radius, I don't think that a l:b ratio of 11:1 is over the top. At the same time, Siam doesn't have the greatest experience in building ships so it's probably wise to build to a higher strength to give more margin for error, say 0.60.

Me hoping to get some foreign partners into this design? Preferably those with similiar designs.

Quoted

Originally posted by Red AdmiralI still think you're going to have problems mounting duple 55mm guns on the centreline along with everything else.

Well, perhaps they can be mounted to the sides?