Next generation escort cruiser?

[P3D]

I'd be thinking at least a 1:1 ratio between crane and boat.  Suspending that much weight from above is going require a very sturdy structure.

And also sturdy boats, if you plan lifting them at two points. But you don't need 100t weight cranes to lift a boat.

[The Rock Doctor]

I was under the impression that a crane must be heavier than its load - folks with a better knowledge of physics can correct me.

least assuming that I can't yet build forty to fifty knot planing boats

I think we're decades away from that yet.

Regardless, now that I know there won't be screaming tantrums over a fantail design, I'm going to go back to the drawing board and go with that. Stay tuned!

Er...hang on.  What does the tumblehome have to do with suspending light craft over the sides of the ship?  Why's the draft so deep?  A cross-sectional sketch might help supplement the top view.

[Valles]

End on layout? Something like this:

  __ 
_[  ]_
[    ]
\    /
\__/

...but like I said that wasn't the plan I'd considered most favorable, just the most likely to be accepted by the mods. Now that a better one is known to be workable, I'm going with...

Enter ship name, Enter country Enter ship type laid down 1913 (Engine 1912)

Displacement:
   6,940 t light; 7,174 t standard; 8,687 t normal; 9,897 t full load

Dimensions: Length overall / water x beam x draught
   392.83 ft / 387.14 ft x 52.49 ft x 26.25 ft (normal load)
   119.74 m / 118.00 m x 16.00 m  x 8.00 m

Armament:
      3 - 5.91" / 150 mm guns in single mounts, 102.98lbs / 46.71kg shells, 1913 Model
     Quick firing guns in deck mounts with hoists
     on centreline, all forward, 2 raised mounts - superfiring
      2 - 5.91" / 150 mm guns in single mounts, 102.98lbs / 46.71kg shells, 1913 Model
     Quick firing guns in deck mounts with hoists
     on centreline, all amidships
      4 - 2.95" / 75.0 mm guns in single mounts, 12.87lbs / 5.84kg shells, 1913 Model
     Quick firing guns in casemate mounts
     on side, evenly spread
      6 - 2.95" / 75.0 mm guns in single mounts, 12.87lbs / 5.84kg shells, 1913 Model
     Quick firing guns in casemate mounts
     on side, evenly spread
     6 guns in hull casemates - Limited use in heavy seas
   Weight of broadside 644 lbs / 292 kg
   Shells per gun, main battery: 150

Armour:
   - Belts:      Width (max)   Length (avg)      Height (avg)
   Main:   7.87" / 200 mm   232.28 ft / 70.80 m   13.12 ft / 4.00 m
   Ends:   1.97" / 50 mm   154.82 ft / 47.19 m   13.12 ft / 4.00 m
   Upper:   1.97" / 50 mm   232.28 ft / 70.80 m   13.12 ft / 4.00 m
     Main Belt covers 92 % of normal length

   - Gun armour:   Face (max)   Other gunhouse (avg)   Barbette/hoist (max)
   Main:   2.36" / 60 mm   1.57" / 40 mm      1.57" / 40 mm
   2nd:   2.36" / 60 mm   1.57" / 40 mm      1.57" / 40 mm
   3rd:   1.97" / 50 mm         -               -
   4th:   3.94" / 100 mm         -               -

   - Armour deck: 1.97" / 50 mm, Conning tower: 7.87" / 200 mm

Machinery:
   Oil fired boilers, steam turbines,
   Electric motors, 2 shafts, 43,359 shp / 32,346 Kw = 26.00 kts
   Range 10,000nm at 14.00 kts
   Bunker at max displacement = 2,723 tons

Complement:
   449 - 584

Cost:
   £0.603 million / $2.411 million

Distribution of weights at normal displacement:
   Armament: 80 tons, 0.9 %
   Armour: 2,156 tons, 24.8 %
      - Belts: 1,460 tons, 16.8 %
      - Torpedo bulkhead: 0 tons, 0.0 %
      - Armament: 98 tons, 1.1 %
      - Armour Deck: 526 tons, 6.1 %
      - Conning Tower: 72 tons, 0.8 %
   Machinery: 1,729 tons, 19.9 %
   Hull, fittings & equipment: 2,224 tons, 25.6 %
   Fuel, ammunition & stores: 1,747 tons, 20.1 %
   Miscellaneous weights: 750 tons, 8.6 %

Overall survivability and seakeeping ability:
   Survivability (Non-critical penetrating hits needed to sink ship):
     10,677 lbs / 4,843 Kg = 103.7 x 5.9 " / 150 mm shells or 1.6 torpedoes
   Stability (Unstable if below 1.00): 1.08
   Metacentric height 2.2 ft / 0.7 m
   Roll period: 14.8 seconds
   Steadiness   - As gun platform (Average = 50 %): 53 %
         - Recoil effect (Restricted arc if above 1.00): 0.22
   Seaboat quality  (Average = 1.00): 1.17

Hull form characteristics:
   Hull has a flush deck
   Block coefficient: 0.570
   Length to Beam Ratio: 7.38 : 1
   'Natural speed' for length: 19.68 kts
   Power going to wave formation at top speed: 63 %
   Trim (Max stability = 0, Max steadiness = 100): 45
   Bow angle (Positive = bow angles forward): 6.00 degrees
   Stern overhang: 3.28 ft / 1.00 m
   Freeboard (% = measuring location as a percentage of overall length):
      - Stem:      22.97 ft / 7.00 m
      - Forecastle (20 %):   19.69 ft / 6.00 m
      - Mid (50 %):      19.69 ft / 6.00 m
      - Quarterdeck (20 %):   19.69 ft / 6.00 m
      - Stern:      19.69 ft / 6.00 m
      - Average freeboard:   19.95 ft / 6.08 m

Ship space, strength and comments:
   Space   - Hull below water (magazines/engines, low = better): 81.9 %
      - Above water (accommodation/working, high = better): 120.7 %
   Waterplane Area: 14,451 Square feet or 1,343 Square metres
   Displacement factor (Displacement / loading): 124 %
   Structure weight / hull surface area: 82 lbs/sq ft or 399 Kg/sq metre
   Hull strength (Relative):
      - Cross-sectional: 0.88
      - Longitudinal: 3.24
      - Overall: 1.00
   Hull space for machinery, storage, compartmentation is excellent
   Room for accommodation and workspaces is excellent

I think we're decades away from that yet.

I figured.

[Borys]

Ahoj!
The crane is one thing. Machinery to run it, another. And the strengthening of the structure yet another. AFAIK MAddox is the closest thing to an engineer this board has ...
As to tumblehome - the benefit is that the boats suspeneded along the sides are closer to the centre of gravity - they are not entirely over the sea, but partly above the hull of the mother vessel. Lesser motion/momentum.
Also, they can be made secure against the hull (maybe even be on some sort of slides?) Or secured more easily.

Borys

[P3D]

I am a mechanical engineer (at least have a paper telling that)  >:(.

The crane must be heavier than the load to counterbalance. And that extra 100t on a ship would make the ship list a lot, hm...

After a bit calculation, Lifting a 100t boat would cause 15 degrees of list. (ShipWeight*GM*sinALPHA=LiftingArm*BoatWeight).

Due to the bulges, 15 degree list would wet 2m freeboard (Beam/2*sinAlpha). The bulges must have at least that high freeboard or the ship might roll over due to the lack of stability margin. Add natural roll to it and you are already at 4m freeboard.

Theoretical solutions to this problem are:
- Increase metacentric height (helps some but not much)
- lift/lower two boats at the same time on the sides. Would only work during trials.
- have pumps move fuel to counter it. This would make each lifting/lowering operation taking hours.
- lower the ships on a slide at the stern, close to the centerline.

All of these would limit the utility as a gun platform.

[Ithekro]

I'm reminded of Wesworld's Loki for some reason.

[Borys]

I am a mechanical engineer (at least have a paper telling that)  >:(.

Sorry for missing that part of your bio!

Quickly sacrifices black rooster to appease P3D's wrath ...
Borys

[The Rock Doctor]

Commodore Green built Loki as a freighter, lifting MTBs out of a central hold, over the side and into the water while at low or no speed (I believe).  I don't recall what engineering considerations went into the design, but it'd be in the Wesworld : Denmark encyclopedia somewhere.

[Borys]

The crane must be heavier than the load to counterbalance. And that extra 100t on a ship would make the ship list a lot, hm...

Wouldn't the ship's mass serve as counterweight?

After a bit calculation, Lifting a 100t boat would cause 15 degrees of list. (ShipWeight*GM*sinALPHA=LiftingArm*BoatWeight).

After reading this bit, Borys was last seen with steaming brains oozing out of ears ....