WW1-era Troop Transport

[Darman]

I spent this evening trying to sim the USS Henderson, a WW1-era USMC troop transport/amphibious assault ship. 
I did run into the problem of not being able to find the exact displacement of the ship's boats, and other odds and ends.  Wondered if I made any mistakes in simming a transport. 

USS Henderson (AP-1), USA Troop Transport laid down 1920 (Engine 1912)

Displacement:
   8,779 t light; 9,056 t standard; 10,000 t normal; 10,755 t full load

Dimensions: Length overall / water x beam x draught
   483.80 ft / 483.80 ft x 61.10 ft x 16.10 ft (normal load)
   147.46 m / 147.46 m x 18.62 m  x 4.91 m

Armament:
      4 - 5.00" / 127 mm guns in single mounts, 62.50lbs / 28.35kg shells, 1920 Model
     Quick firing guns in deck mounts
     on side, all forward
      2 - 5.00" / 127 mm guns in single mounts, 62.50lbs / 28.35kg shells, 1920 Model
     Quick firing guns in deck mounts
     on side, all aft
      2 - 5.00" / 127 mm guns in single mounts, 62.50lbs / 28.35kg shells, 1920 Model
     Quick firing guns in deck mounts
     on side, all amidships, all raised mounts - superfiring
   Weight of broadside 500 lbs / 227 kg
   Shells per gun, main battery: 250

Machinery:
   Oil fired boilers, complex reciprocating steam engines,
   Direct drive, 1 shaft, 4,543 ihp / 3,389 Kw = 14.00 kts
   Range 5,000nm at 14.00 kts
   Bunker at max displacement = 1,700 tons

Complement:
   499 - 650

Cost:
   £0.941 million / $3.764 million

Distribution of weights at normal displacement:
   Armament: 63 tons, 0.6 %
   Machinery: 274 tons, 2.7 %
   Hull, fittings & equipment: 3,013 tons, 30.1 %
   Fuel, ammunition & stores: 1,221 tons, 12.2 %
   Miscellaneous weights: 5,430 tons, 54.3 %

Overall survivability and seakeeping ability:
   Survivability (Non-critical penetrating hits needed to sink ship):
     14,329 lbs / 6,500 Kg = 229.3 x 5.0 " / 127 mm shells or 2.2 torpedoes
   Stability (Unstable if below 1.00): 1.04
   Metacentric height 2.6 ft / 0.8 m
   Roll period: 16.0 seconds
   Steadiness   - As gun platform (Average = 50 %): 58 %
         - Recoil effect (Restricted arc if above 1.00): 0.05
   Seaboat quality  (Average = 1.00): 1.56

Hull form characteristics:
   Hull has a flush deck
   Block coefficient: 0.735
   Length to Beam Ratio: 7.92 : 1
   'Natural speed' for length: 22.00 kts
   Power going to wave formation at top speed: 27 %
   Trim (Max stability = 0, Max steadiness = 100): 37
   Bow angle (Positive = bow angles forward): 0.00 degrees
   Stern overhang: 0.00 ft / 0.00 m
   Freeboard (% = measuring location as a percentage of overall length):
      - Stem:      24.20 ft / 7.38 m
      - Forecastle (20 %):   15.40 ft / 4.69 m
      - Mid (50 %):      15.40 ft / 4.69 m
      - Quarterdeck (15 %):   15.40 ft / 4.69 m
      - Stern:      15.40 ft / 4.69 m
      - Average freeboard:   16.10 ft / 4.91 m

Ship space, strength and comments:
   Space   - Hull below water (magazines/engines, low = better): 73.7 %
      - Above water (accommodation/working, high = better): 143.4 %
   Waterplane Area: 24,401 Square feet or 2,267 Square metres
   Displacement factor (Displacement / loading): 154 %
   Structure weight / hull surface area: 90 lbs/sq ft or 440 Kg/sq metre
   Hull strength (Relative):
      - Cross-sectional: 1.19
      - Longitudinal: 1.13
      - Overall: 1.15
   Hull space for machinery, storage, compartmentation is excellent
   Room for accommodation and workspaces is excellent
   Excellent seaboat, comfortable, can fire her guns in the heaviest weather

506t = 11 boats/barges (35 footers, appr. 23 tons each)
224t = 4 unpowered lighters (45 footers, appr. 28 tons each)
120t = 2 motor picket boats (50 footers with light guns, displacement appr. 30 tons each)
4,400t = 2,200 passengers (long term)
100t = fire control
80t = gyro-stabilizing fins

[snip]

First question, is this for SS practice or are you working on a similar one for the game?

[Darman]

Practice.  I wanted to sim one that actually existed from that time period before I started on one for Egypt.  As it is Egypt doesn't have the technology necessary to perform intricate amphibious landings at this time. 

[snip]

Ok, just checking before I launch into a reciprocating vs turbine thing, and why the former is completed out of date.

[Darman]

Yes I noticed that specifically about this ship.  It was sort of cobbled together between a joint Navy/Marine commission. 

[Sachmle]

Ok, just checking before I launch into a reciprocating vs turbine thing, and why the former is completed out of date.

Actually, for a ship built to 'lesser' standards then most warships, like a landing ship...especially one that's ONLY 14kts, a VTE is quite reasonable. It would cost less, be easier to maintain, and simpler to run.

[maddox]

The thing that makes a VTE cheaper is than a turbine, even if the turbine is mechanicaly simpler, it's a lot loser on tolerances, and can be build in an avarage, large enough machine shop of that era.

It's one of the reasons N. tesla had such high hopes for his bladeless turbine. It was about as simple to build as a VTE with the non complexity of the Turbine. Unfortunatly, it seems that the Tesla turbine isn't easely scaled up

Even in WWII shipbuilders ran into problems aquiring enough turbines and gears to reduce the RPM to the shafts.

[Darman]

Out of curiosity, does anyone know how much the ship's boats should displace?  I used the LCM specifications of 45ft boat displacing 28-29 tons (depending on source) and tried to scale from there. 

And yes, this ship wasn't intended as a front-line battle vessel.  4 of its 8 guns were built to be removed and emplaced onshore during landing operations to provide fire support. 

It also had a gyroscope stabilizer (accounts for 80 tons miscellaneous) and fire control.  The stabilizer made it a very good gun platform.  Were these used on warships? 

[damocles]

The LCM values were about right. Tilt tables, to account for beam roll as deck-mounts were fired, everyone attempted as two axis stabilization. They did not work.

What did work was timed fire on the roll moment with gyro stabilization of the sights so the aimer could follow the target in local control. He had to fire on the roll by the clock.

D.   

[P3D]

Springsharp is even more conservative determining machinery weight for VTEs than for turbines. OTL destroyer/TB VTEs of the late 1890s were in the 50SHP/ton range (equivalent to year 1950 turbines in SS2).

I don't believe that turbines were that difficult to make. Reduction gears might have been a bigger early problem (gears needing case hardening and such) - and they are necessary for any economical speeds.

About the Tesla turbine: did not know about it, but the wiki article is pretty good. However, it requires high tolerances for efficient work (0.4mm gap between disks!) and thin disks that warps easily. You need to make the disks effectively internal stress free - but if you anneal them you loose any strength.

The main issue I see is fouling and corrosion, getting worse as temperature and pressure is increased. Sub-mm gaps between disks, with a water that will have impurities.

On the ship: I'd forget fire control and gyro, the ship should ferry troops, not to provide a huge target during fire support.
Increase freeboard, the holds are just not deep enough for volume-constrained cargo like passengers.

[Darman]

Right now I'm trying to sim the Henderson but yes, for the troop transport I'm planning I'm going to forgo armament. 
I tried increasing the freeboard, but its hard when I'm not sure how to sim the upper works on a ship, especially since it appears that all of the Henderson's passengers' quarters were above-deck.  I did try to sim a higher freeboard amidships to make up for that. 

USS Henderson (AP-1), USA Troop Transport laid down 1920 (Engine 1912)

Displacement:
   8,779 t light; 9,056 t standard; 10,000 t normal; 10,755 t full load

Dimensions: Length overall / water x beam x draught
   483.80 ft / 483.80 ft x 61.10 ft x 16.10 ft (normal load)
   147.46 m / 147.46 m x 18.62 m  x 4.91 m

Armament:
      4 - 5.00" / 127 mm guns in single mounts, 62.50lbs / 28.35kg shells, 1920 Model
     Quick firing guns in deck mounts
     on side, all forward
      2 - 5.00" / 127 mm guns in single mounts, 62.50lbs / 28.35kg shells, 1920 Model
     Quick firing guns in deck mounts
     on side, all aft
      2 - 5.00" / 127 mm guns in single mounts, 62.50lbs / 28.35kg shells, 1920 Model
     Quick firing guns in deck mounts
     on side, all amidships, all raised mounts - superfiring
   Weight of broadside 500 lbs / 227 kg
   Shells per gun, main battery: 250

Armour:

   - Conning tower: 1.00" / 25 mm

Machinery:
   Oil fired boilers, complex reciprocating steam engines,
   Direct drive, 1 shaft, 4,543 ihp / 3,389 Kw = 14.00 kts
   Range 5,000nm at 14.00 kts
   Bunker at max displacement = 1,700 tons

Complement:
   499 - 650

Cost:
   £0.941 million / $3.764 million

Distribution of weights at normal displacement:
   Armament: 63 tons, 0.6 %
   Armour: 10 tons, 0.1 %
      - Belts: 0 tons, 0.0 %
      - Torpedo bulkhead: 0 tons, 0.0 %
      - Armament: 0 tons, 0.0 %
      - Armour Deck: 0 tons, 0.0 %
      - Conning Tower: 10 tons, 0.1 %
   Machinery: 274 tons, 2.7 %
   Hull, fittings & equipment: 3,003 tons, 30.0 %
   Fuel, ammunition & stores: 1,221 tons, 12.2 %
   Miscellaneous weights: 5,430 tons, 54.3 %

Overall survivability and seakeeping ability:
   Survivability (Non-critical penetrating hits needed to sink ship):
     17,696 lbs / 8,027 Kg = 283.1 x 5.0 " / 127 mm shells or 2.2 torpedoes
   Stability (Unstable if below 1.00): 0.99
   Metacentric height 2.4 ft / 0.7 m
   Roll period: 16.7 seconds
   Steadiness   - As gun platform (Average = 50 %): 74 %
         - Recoil effect (Restricted arc if above 1.00): 0.10
   Seaboat quality  (Average = 1.00): 2.00

Hull form characteristics:
   Hull has low forecastle
   Block coefficient: 0.735
   Length to Beam Ratio: 7.92 : 1
   'Natural speed' for length: 22.00 kts
   Power going to wave formation at top speed: 27 %
   Trim (Max stability = 0, Max steadiness = 100): 37
   Bow angle (Positive = bow angles forward): 0.00 degrees
   Stern overhang: 0.00 ft / 0.00 m
   Freeboard (% = measuring location as a percentage of overall length):
      - Stem:      24.20 ft / 7.38 m
      - Forecastle (15 %):   15.40 ft / 4.69 m (25.00 ft / 7.62 m aft of break)
      - Mid (60 %):      25.00 ft / 7.62 m
      - Quarterdeck (10 %):   20.00 ft / 6.10 m
      - Stern:      15.40 ft / 4.69 m
      - Average freeboard:   22.61 ft / 6.89 m

Ship space, strength and comments:
   Space   - Hull below water (magazines/engines, low = better): 73.7 %
      - Above water (accommodation/working, high = better): 223.5 %
   Waterplane Area: 24,401 Square feet or 2,267 Square metres
   Displacement factor (Displacement / loading): 154 %
   Structure weight / hull surface area: 80 lbs/sq ft or 393 Kg/sq metre
   Hull strength (Relative):
      - Cross-sectional: 0.94
      - Longitudinal: 1.84
      - Overall: 1.01
   Caution: Poor stability - excessive risk of capsizing
   Hull space for machinery, storage, compartmentation is excellent
   Room for accommodation and workspaces is excellent
   Ship has slow, easy roll, a good, steady gun platform
   Excellent seaboat, comfortable, can fire her guns in the heaviest weather

506t = 11 boats/barges (35 footers, appr. 23 tons each)
224t = 4 unpowered lighters (45 footers, appr. 28 tons each)
120t = 2 motor picket boats (50 footers with light guns, displacement appr. 30 tons each)
4,400t = 2,200 passengers (long term)
100t = fire control
80t = gyro-stabilizing fins

[maddox]

Springsharp is even more conservative determining machinery weight for VTEs than for turbines. OTL destroyer/TB VTEs of the late 1890s were in the 50SHP/ton range (equivalent to year 1950 turbines in SS2).

That's the Nverse for you.

I don't believe that turbines were that difficult to make.

Actualy, those still are.  It's not only the tolerances, but also the shapes. A VTE can be build on a simple lathe and standaard milling machine. For the turbine blades you need a compound 4 or 5 axis mill. And that's for the rough and dirty setup.
Even now, most "home grown turbines" use scavenged turbine blades from car turbos or simular.

Reduction gears might have been a bigger early problem (gears needing case hardening and such) - and they are necessary for any economical speeds.

Again, it's the machines to make 'm. With my tools I can mill small diameter gears, about 6", 8" long at max.

About the Tesla turbine: did not know about it, but the wiki article is pretty good. However, it requires high tolerances for efficient work (0.4mm gap between disks!) and thin disks that warps easily. You need to make the disks effectively internal stress free - but if you anneal them you loose any strength.

Just what I did write, it didn't scale up easely, but it's easier to make with simpler machines.

The main issue I see is fouling and corrosion, getting worse as temperature and pressure is increased. Sub-mm gaps between disks, with a water that will have impurities.

Actualy, corrosion can be avoided here, bronze is not a bad material for the disks. But the problem is the power involved to drive ships.  A 2 HP tesla turbine is buildable. A 5000 HP will require very fancy materials to withstand the forces on the disks without deforming those.

On the ship: I'd forget fire control and gyro, the ship should ferry troops, not to provide a huge target during fire support.
Increase freeboard, the holds are just not deep enough for volume-constrained cargo like passengers.

Agree

[P3D]

Most large (naval) shipyards could build turbines. My favourite example - Danubius in Fiume could build turbines.

IMHO the largest issue is capacity. One need no fancy mill to machine the simple-shape blades (WWI-era) for a handful of vessels, but they won't be adequate for mass producing merchant ships.