Japan A-150 follower design

[Awenger]

Hi all

I am trying reconstruct a japanese A-150 follower

I make a hull lines and now need some critics. Hull characteristics included in image

Hull lines plan (11271 x 3006 pix, 1621 Kb )
http://i018.radikal.ru/0802/75/93f5ff40b560.jpg

Overall dimensions
http://i047.radikal.ru/0802/c6/13e95b8aa79a.jpg

stern part
http://i032.radikal.ru/0802/ea/b8a60f28effa.jpg

Rough midship section
http://i038.radikal.ru/0802/7d/660ada5c21d0.jpg

[harold]

Welcome aboard, Avenger!

Be shure that your interesting idea will find some enthousiasts to discuss with, as I did tell you some days ago!

First of all, would you be so kind and give us deplacement data, and a rough calculation of horsepower and speed for your project?
For discussing hull lines, this would be the most interesting fact to know.

Harold

[Awenger]

Displacement (Full) - 126829,7 metric tonns
Length (overral) - 356,73 m
Length (waterline) - 350,25 m
Beam (max) - 46 m
Beam (waterline max) - 42,72 m
Draft (at full displacement) -  13 m
Block coefficient - 0,652
Prismatic coefficient - 0,623

Midship section coefficient - 1,045
Waterplane coefficient  - 0,685
Admiralty coefficient ( at 32 knt)  - 294,7
Froude number ( at 32 knt)  - 0,297

Speed (design) - 32 knt  at 280000 shp (32 knt based completely on empirical considerations)
Machinery - 16 boilers (400C / 40 atm) and 4 direct impulse turbines (1939 year type).  280000 shp at full load (designed to withstand 10% overload)

I am now working under internal 510mm  turrets design. I meet a big troubles in arranging charge handling rooms because weight of charge (8x60 kg) almost exclude hand operations and in the same time big mechanization are prohibited.

[Jefgte]

Welcome aboard Awenger



Your monstruous BB is an interresting project

Here is a link for the internal of the Yamato turret

http://www.modelshipgallery.com/gallery/bb/ijn/yamato-100-jd/jd-index.html



If you want, you could post in "Warships Projects Forum", much Guys are also expert in the BBs concept

http://www.phpbbplanet.com/forum/index.php?mforum=warshipprojects


Jef 

[Awenger]

Here is a link for the internal of the Yamato turret

http://www.modelshipgallery.com/gallery/bb/ijn/yamato-100-jd/jd-index.html

Thanks for link. But i preffer a lttle more detailed sources Anyway i buld from scratch and only things that left from original turret structure are push-pull gear for shells that strored outside turret structure.

much Guys are also expert in the BBs concept

99,9% experts in springsharp. It's good toy but have very little resemblance with something real. Knowledge in  BB design can be gained only by prototyping based on study of original drawing.

[harold]

First of all, thank you for sharing your project with the community!
You will find it not so easy to read german comments, so keep in mind that figures and pics, math and geometry are the real international language ...
... Übersetzungsprobleme hin oder her, Zahlen, Bilder, Mathematik und Geometrie sind allgemeinverständlich (also bitte auch Stellungnahmen auf Deutsch, ich übersetz es gerne in eine der genannten internationalen Sprachen!).

So here's that what you did ask me for, some considerations on hydrodynamics.



Let's start with tha main frame - to keep wetted surface low, give a slightly more curved form, and avoid the sharp concave knuckle just below waterline (a very very bad trap for vortices, and thus more friction).
Hauptspant: gekurvte Seiten anstelle der geraden Platten, und die starke Einschnürung knapp unter der Wasserlinie überplatten (wäre sonst ein ziemlicher Wirbelgenerator, und damit Widerstandserhöher).

Next are the hull lines at stern (frame 27 onwards) - avoid the V-shaped form, give them a more voluminous and rounder shape, make the transom below waterline not that deep (otherwise you will have bad sucking effects); and if you really insist on screw diameters of 6(!) meters, duct the flow by adding skegs and keep the inner bottom between them quite shallow (no central fin).
Rumpfform am Heck: weg mit dem V-förmigen Querschnitt, auch hier rundere Ausbildung; das Spiegelheck nicht so tief eintauchen lassen (gibt sonst eine ziemliche Saugschleppe!); und wenn's denn wirklich 6-Meter-Schrauben (also Langsamläufer) sein müssen, dann bitte die Strömung mit schlanken Wellenhosen vorleiten. Dazwischen ganz sachte den Boden hochziehen, keine Mittelflosse.

Rudders: foresee 4 of them, each one in the prop flow, to give enough momentum to steer the beast.
Ruder: jeweils im Schraubenstrom, 4 Stück - anders lässt sich der Riesenkahn kaum steuern.

Framing at the bows: give her a more decisive fall outwards, to have a quick increase and righting angle of buoyancy, at pitching moves. To avoid too sharp lines coming up to broaden the deck, give a knuckle atop.
Spantausbildung Bug: stärkerer und tieferer Ausfall, um die Hebelwirkung der Auftriebszunahme beim Einstampfen zu vergrößern; damit sie nicht zu breit und scharf aufs Deck kommen, Knickspant.

Next to come, some considerations on skeg geometry, screw arrangement, and speed (have to do some math's for this) / es folgen dann noch ein paar Anmerkungen zur Anordnung der Schrauben, Geometrie der Wellenhosen, und zu möglichen Geschwindigkeiten.

Harold

[Awenger]

Thanks for your reply. But you take a little outdated image of hull form

Let's start with tha main frame - to keep wetted surface low, give a slightly more curved form, and avoid the sharp concave knuckle just below waterline (a very very bad trap for vortices, and thus more friction).

This is a strange decision in my opinion. This part will be subject to constant impacts  with a waves so it must be made from thick plates and will be unnecessary heavy. It's don't carry any usefull function (don't act as a part of TDS and don't protect main belt) Only additional weight. And i dont seen such solution on any real ship.  Will be better just give bilge a slightly more curved form i think but that weaken TDS a bit, especialy around magazines

Next are the hull lines at stern (frame 27 onwards) - avoid the V-shaped form, give them a more voluminous and rounder shape

If i make stern part like you draw there is will be no place for screws even if a make them 5m in diameter.

Make the transom below waterline not that deep (otherwise you will have bad sucking effects)

Currently deep at transom stern 1,5 m.  Possibly it will have some bad effects in calmly sea, but how about rough sea conditions and not under Full load?

and if you really insist on screw diameters of 6(!) meters, duct the flow by adding skegs and keep the inner bottom between them quite shallow (no central fin).

From the view of flow and speed skegs are inferior to conventional stern form.
For example this is quote from US Montana hull characteristics:
"The twin sceg form was retained although model basin test, conducted for the first time since the design of the North Carolina, indicated that the conventional stern form was superior to the twin skeg version, a complete reversal of the North Carolina tests. The new tests indicated a superiority of about 7 per cent through the entrie speed range and 9,5 per cent at the design speed of 28 knots. The retension of the twin skegs, despite these tests results, was a consequence of their undeniable structural and protective advantages over conventional form"

Also in japan twin scegs was tested on one of yamato scale models tests and recognized them as harmful.
As i  understand you suggest even four skegs  insted of standard twin?
Central die cast fin with 1.2m thinkness at lowel part work as part of TDS localizing damage in case if torpedo hit screws or hull on one side of ship, also i expected that it must resist direct hit of torpedo with 300kg TNT charge.

Rudders: foresee 4 of them, each one in the prop flow, to give enough momentum to steer the beast.

I already examine this solutions and reject this. Almost any hit in stern in this case will hit one of steering gear and this will be excessively complicated. In worst condition two steering devices can be disabled by flooding from one hit torpedo because of they arrangement  As i know no one ship in history have four rudders (but maybe i am wrong). Tactical diameter of 2,5 ship length can be archive and with three rudders.

Next to come, some considerations on skeg geometry, screw arrangement

Inner screws placed on 1 degree outward , outers screws placed without any angle.  Only horizontal arrangement possible bacause tripple bottom cover all citadel and dosn't allow any vertical deflection of screw shafts.

[Awenger]

Anyone can help with calculation of propellant charge for 20,1"/50 ?

How it's possible calculate muzzle velocity for given propellant charge, shell weight and gun barrel length. I know that correct calculation reqire great amount of characteristics but maybe exist a more simple rough calculation ?

By comparision propellant charges for various guns i found that amount of 480 kg DC₁ (even if this is DC₂) that given in "Campbell's Naval weapons of WWII" is looks small for such gun. So i am trying recalculate charge and receive muzzle velocity. Also i want replace cordite to tubite because cordite give too small barrel life.

I have chemical composition for propellant, it's calorific value, explosion temperature and force of explosion.

[Awenger]

I finishmy design of 20"/50 gun

some characteristics:

Designation 50/510 Type 0 ("KO" HO)



All data in metric

Gun Weight - 261750 kg (without breech)
Gun Length oa - 26105 mm (51,18 cal)
Bore Length - 25585 mm
Rifling Length - 22140 mm

Grooves - (90) 6,2 x 12 mm
Lands - 8,67 mm
Twist - Uniform RH 1 in 33
Chamber volume - 814 cubic. dm

Build-up construction , 5 layers. Inner tubes 2A,2B,2C autofretted.
Gun made from standart chrome-nickel gun steels Mark G0 and G1

Propellant Charge 512 kg DT3
Length of complete charge - 470 x 2940 mm

Center of gravity 8,41 m from breech

Muzzle energy for 2010 kg AP shell Type 1 - 70645 t.m. (at muzzle velocity 830 m/s)

Maximum range for Type 1 AP with full charge at 830m/s - 49,6 km
Maximum range for Type 1 AP with reduced charge at 726m/s - 38,4 km