I've been working for a week now on my own version of Springsharp. As is my tendency, the file/formulas are stored in an Excel sheet while I tinker with all the formula before I compile it into an executable. The file is available on request but the formulas and jargon make it extremely convoluted and hard to decipher so I don't recommend looking at it.
This thread is for:
- Questions from me about certain formula specifics , useful literature, etc.
- Questions from you about any aspect of the program.
- Questions about the progress of my work on the program.
- Etc.
First question - do any of you know what Holtrop-Mennen means in "An Approximate Power Prediction Method" when describing the formula for c8?
The formula they state is c8 = BS / (LDTA).
Now I know all the variables except for D (B is beam, S is wetted surface area, L is length, T is draft). So what exactly does D represent? There is no mention of the variable's meaning in the literature. Even a suggestion would be ok - this formula is preventing me from finishing the engine section of my file.
Never mind! I found the answer to my question in another book - "Marine Propellers and Propulsion" - D stands for propeller diameter.
uhm Logi you do realise that SS3 is the only ship siming tool oficialy recognised... if your using some custom version you created we have no way of verifying that it isnt tamperd with... as such any ship simed in it would be unusable in the sim.
I know you guys wouldn't use it - it's just a pet project of mine. While you may not be able to tell what I did, I can - and through that even understand how SS gets its values. For example, SS computes the Cwp and S(w) through using a default Cp of 0.691 which is actually incorrect. Cp is usually Cb + 0.1 rather than a single default value like SS suggests.
I wish you would take my word that I don't tamper with my programs for general use - but I realize that would be useless. I don't tamper with programs I make - especially stuff I put on my resume. To post a counter-point, it's also perfectly possible that SS was tampered with - it was written by a programmer like me.
If you wish you can look at my file - but I've only done basic hull calculations for Cwp, S(w), A(m), Cm, Cp, etc as well as hull and propeller resistance and I already have over 30 naval literature as sources.
logi you can have whatever pet projects you want, but honestly most of us dont give 2 shakes why SS works so long as it works (which is mostly the case). A couple years back I went through all of SS3s code and realised it had several errors, however they were consistant errors and Honestly I didnt want to take the time to rewrite it. I honestly dont care what you want to code, I just ask that you restrict yourself to using SS3 for ships in the sim (and honestly we have people complaining its to complex... so why ad more complexity)
Hello, my attempt at my own program has met smooth progress while keeping inputs minimized.
However, I am stuck with a problem in the reduction of variables, namely, the hull's center of gravity (CGhull) and propeller thrust (Tprop).
Mostly these are described by empirical testing, such as tilting the hull for CGhull and propeller tests for Tprop. The data itself is also hard to find.
As a result, there is no hard basis on which I can (directly) estimate the values of these two variables.
This, along with propeller diameter, pitch, and number of blades are the only things my program requires over SS to produce the hydro-statics of a hull. As you can imagine, this is quite annoying.
If any of you have any information on CGhull and Tprop of other ships, please let me know. It would be greatly appreciated.
I've solved the GM problem, I have to ask if anyone knows about the differences (volume, weight, etc.) between diesels, steam turbines, and other engine types of the period.
If I recall properly, I think Kaiser Kirk mentioned this topic before.
Quote from: Logi on August 03, 2013, 11:33:18 AM
...I have to ask if anyone knows about the differences (volume, weight, etc.) between diesels, steam turbines, and other engine types of the period.
Depends on what exactly you need to know. I have quite a bit of Data for Bismarck, Hood and the Deutschland-class.
I'd been interested in the machinery weight of those ships and their respective power.
In addition I'ld like to know the fuel consumption of each.
Quote from: Logi on August 08, 2013, 10:19:34 AM
I'd been interested in the machinery weight of those ships and their respective power.
In addition I'ld like to know the fuel consumption of each.
I'll look it up when I get back to my books (some time between Monday and Wednesday).
However the definition of machinery weight is a bit tricky, because every navy defined it differently what was part of the machinery. For example: does a generator belong the machinery or the ships equipment?
Indeed. In this case, the generator belongs to the machinery weight. I calculate the equipment weight as a function of the hull form and displacement so it wouldn't make much sense (in my case) to include the generator weight in the equipment weight.
Thanks.
Quote from: Logi on August 08, 2013, 10:19:34 AM
I'd been interested in the machinery weight of those ships and their respective power.
In addition I'ld like to know the fuel consumption of each.
Bismarck
| Total engine weight (including auxiliaries) | 4833 t |
| Design Power | 138000 WPS |
| specific weight | 20,3 kg/PS |
| Actual Power | 150170 WPS |
| fuel consuption | full (138000 PS) | 325 g/PSh |
| | 115050 PS | 320 g/PSh |
| | 69900 PS | 335 g/PSh |
| | 39000 PS | 370 g/PSh |
| | 24900 PS | 415 g/PSh |
| | 15000 PS | 500 g/PSh |
Supplement
Bismarck was originally supposed to have at turbo-electric drive. Only a few things are mentioned about it.
- better efficiency at cruising speeds
- 1300 t increased weight
- 25% heavier
Yes, those numbers don't match. Just like many others.
Fuel7400 m³ maximum (wartime 8249 m³), but not all of that can be used. Listed as 2x3030t + 1770t = 7830t in the weight distribution.
| | Speed [kn] | Range [nm] |
| | 16 | 9280 |
| | 17 | 8900 |
| | 19 | 8525 |
Hood
| Design Power | 144000 WPS |
| Actual Power | 151280 WPS |
| Fuel | 4615 ts |
| Range | 8500 nm @ 14 kn |
Unfortunately, that is all I could find.
PanzerschiffeMuch more complicated (yet incomplete), I'll have to make an extra post for them.
NOTES
t = metric tons
ts = long tons
PS = metric horsepower
WPS = metric shaft horsepower
Data mostly taken from S. Breyer's & G. Koop's "Schlachtschiff Bismarck"
As I said, the "pocket battleships" are even more complicated. Let's start with a table taken from deutschland-class.dk (http://www.deutschland-class.dk/technicallayout/generaldetails.html):
| Deutschland/Lützow | Admiral Scheer | Admiral Graf Spee |
| Laid down | 5. February 1929 | 25. June 1931 | 1. October 1932 |
| Standard Displacement | 12.630 metric tons | 13.660 metric tons | 14.890 metric tons |
| Maximum Displacement | 14.290 metric tons | 15.180 metric tons | 16.320 metric tons |
| Machinery output at 250 rpm | 48.390 shp | 52.050 shp | 54.000 (Pse) |
| Speed | 26-28 knots | 26-28,3 knots | 26-28,5 knots |
| Range | 10.000 naut. miles at 20 knots | 9.100 naut. miles at 20 knots | 8.900 naut. miles at 20 knots |
| 16.600 naut. miles at 14 knots | — | — |
| 17.400 naut. miles at 13 knots | — | — |
| Bunkers | 2.750 m³ | 2.410 m³ | 2.500 m³ |
And continue with some technical details about the engines found here (http://forum-marinearchiv.de/smf/index.php/topic,592.0.html):
| M9Z42/58 details | | Deutschland/Lützow | Admiral Scheer | Admiral Graf Spee |
| peak power | 7100 PSe | | | |
| continuous power | 6655 PSe | | | |
| fuel consumption | ~200 g/PSh | | | |
| engine weight [t] | | 900 | 982 | 1013 |
| specific weight (design/actual) [kg/PSe] | 11,5 | 12,4 | 13,53 | 13,96 |
| machinery weight | | | | 1716 t |
Although these three ships have the same engines (eight MAN model M9Z42/58, a double-acting 9 cylinder in-line two-stroke engine with 42cm bore and 58cm stroke), you can already see the technical progression in the power increase over time. Since the first engines proved to be too light, later ones were build sturdier and therefore heavier.
Now if you do the math, you'll probably scream at me because the data doesn't match. True enough. That's partly because you didn't take into account that for each two 9-cylinder main engines an additional 5-clinder engine of similar construction was required to drive pumps, compressors etc.
I don't know if the "machinery weight" includes/excludes the same stuff as in the Bismarck/Hood reference!
Thanks a lot. I'm much obliged.
Yes, very interresting work Nobody.
Thanks
Jef ;)
I remembered some more stuff, it is from Stefan Zima's "Ungewöhnliche Motoren" (in English: Unusual Engines)
The 12000 HP Engine (1917, SMS Prinzregent Luitpold)
A 6 cylinder double-acting two-stroke in-line engine. Aside from some nice, but not very useful details (nothing about weight and size - apart from a picture I'm almost certainly not allowed to post) the interesting part is this (loosely translated by me):
"At 12160 PS a fuel consumption of 214 g/PSh Carbolineum (http://en.wikipedia.org/wiki/Carbolineum) and 29 g/PSh ignition oil was measured." So that's a total of 243 g/PSh for near maximum output.
MAN MZ 42/58 family (Deutschland-Class)
Fuel consumption: 163 g/PSh, but requires auxiliary engine (see previous post)
MAN MZ 65/95 (1938, H-class)
http://www.deutsches-museum.de/en/collections/machines/power-engines/combustion-engines/diesel-engines/large-diesel-engines/marine-diesel-engine-1938/ (http://www.deutsches-museum.de/en/collections/machines/power-engines/combustion-engines/diesel-engines/large-diesel-engines/marine-diesel-engine-1938/)
MAN ZV24 32/44 (1942, "Spähkreuzer" Z51)
Sometimes also named "V12Z32/44". A 24 cylinder double-acting two-stroke V-engine.
| | | specific weight |
| continues power | 10000 |
| max power | 12500 to 12600 | 5.2 kg/PS |
| with ATL ("Turbo") | 15000 | 4 kg/PS |
The sole survivor is on display in Sinsheim (http://sinsheim.technik-museum.de/en)
Other places were stuff like this was discussed before:
http://warships1discussionboards.yuku.com/topic/20470/German-Capital-Diesel-Engines (http://warships1discussionboards.yuku.com/topic/20470/German-Capital-Diesel-Engines)
http://www.forum-marinearchiv.de/smf/index.php/topic,9602.320.html (http://www.forum-marinearchiv.de/smf/index.php/topic,9602.320.html)
http://www.kbismarck.org/forum/viewtopic.php?f=37&t=775&start=15 (http://www.kbismarck.org/forum/viewtopic.php?f=37&t=775&start=15)
A small clarification desired;
Quote from: Nobody on August 19, 2013, 08:29:32 AM
| Deutschland/Lützow | Admiral Scheer | Admiral Graf Spee |
| Machinery output at 250 rpm | 48.390 shp | 52.050 shp | 54.000 (Pse) |
| M9Z42/58 details | | Deutschland/Lützow | Admiral Scheer | Admiral Graf Spee |
| peak power | 7100 PSe | | | |
| continuous power | 6655 PSe | | | |
| fuel consumption | ~200 g/PSh | | | |
| engine weight [t] | | 900 | 982 | 1013 |
| specific weight (design/actual) [kg/PSe] | 11,5 | 12,4 | 13,53 | 13,96 |
| machinery weight | | | | 1716 t |
I assume the second table details the
per engine weight and power output and the first table details the total power output on the ship?
I've been working on a suggested formula published in a research paper. Unfortunately, the paper is modern, so most definitely the machinery weights are also modern estimates. I've been able to derive a formula using the suggested one to be accurate to ±10% during the period of interest. In general, I would not do this, preferring to rely on the standard methods of naval architecture, but the alternative is neither simple nor pretty. I also have to mod my existing modifier value for Geared/Direct/Turbo-electric drives.
Quote from: Logi on August 20, 2013, 05:05:56 PM
A small clarification desired;
Quote from: Nobody on August 19, 2013, 08:29:32 AM
| Deutschland/Lützow | Admiral Scheer | Admiral Graf Spee |
| Machinery output at 250 rpm | 48.390 shp | 52.050 shp | 54.000 (Pse) |
| M9Z42/58 details | | Deutschland/Lützow | Admiral Scheer | Admiral Graf Spee |
| peak power | 7100 PSe | | | |
| continuous power | 6655 PSe | | | |
| fuel consumption | ~200 g/PSh | | | |
| engine weight [t] | | 900 | 982 | 1013 |
| specific weight (design/actual) [kg/PSe] | 11,5 | 12,4 | 13,53 | 13,96 |
| machinery weight | | | | 1716 t |
I assume the second table details the per engine weight and power output and the first table details the total power output on the ship?
Yea more or less. First table is
per ship the second was supposed to be
per engine.
However, machinery and engine weight is also
per ship, while the
specific weight is basically "engine block" only.
On a side note: in the late 50s the specific weight of a civilian/merchant diesel engine was ten times higher (at 40 to 50 kg/PS) than that of the ZV 32/44 almost 20 years before!
Smaller engines have a better specific weight. For example aircraft and airship diesel weighted about 2 kg/PS. The submarine engines on the other hand are no better the ones used on Admiral Graf Speed or the H-class, achieving 14.4 kg/PS in their latest incarnations (the highly charged M6V 40/46 used in the type XXI for example).
MAN W10V 26/33 (1926, K-class light cruisers)
A normal 4-stroke engine. About 730 kW, but only 900 WPS - so almost 10% loss trough the (hydraulic) gearing to the screw. Design target: 5 kg/PS.
Thanks to the data provided by Nobody, I've managed to resolve the Engine/Bunker issue.
The only details left to do are in order of difficulty:
- Weapons and Ammo Weight
- Subtract Deck Weight for Barbette Holes
- Deck & Hull Space Calculation
- Crew Size Estimation
Hopefully (fingers-crossed), I'll have enough time next weekend to finish all the math and move onto developing a usable GUI.
As a preview of added features to look forward to:
- Simple Superstructure Simulation
- Ship Parallel/Smooth Midbody Choice
- Ship Aftbody Shape Choice
- Tapering and Sloped Belt Armor
- Adjustable Depths (Below Waterline) Belts
- Individual Deck Thickness and Height
- Ship Speed in Trial and Actual Service by Region
- Weight and Fuel Variation by Direct/Geared/Turbo-Electric and Diesel/Reciprocating/Steam
Perhaps you would be happy to hear, Nobody, that all the entire file is in metric.
Edit: Belt Slopes completed
Edit2: Bulkhead (TDS) completed
Edit3: Conning Tower Armor Weight completed
I've converted the majority of the formulas and details into a simple command line C++ file.
Currently it does not include the option to add guns/armor and does not calculate hull strength, I'll have to spend some time (not this weekend most likely!) to wrangle it into user-friendly I/O.
If you want to test on the current file for kicks, download it here (http://www.mediafire.com/download/u2kci7lobx79sc7/ShipSim_0-1a.exe)
It'll output the detailed report to the console and write it to "Report.txt" in the same directory. The "Report.txt" is formatted into a nice table that this forum accepts, so it'll look neat and tidy like the sample below!
Also, here is a current sample Report:
| Length: | 160.00 m |
| Beam: | 16.00 m |
| Draft: | 7.50 m |
| Freeboard: | 6.00 m |
| Depth: | 13.50 m |
| Block Coefficient: | 0.527 |
| Midship Coefficient: | 0.951 |
| Prismatic Coefficient: | 0.554 |
| Waterplane Coefficient: | 0.675 |
| Displacement: | 10119 t |
| Wetted Surface Area: | 3440 sq. m |
| Waterplane Area: | 1727 sq. m |
| Max Speed: | 34.0 kn |
| Cruise Speed: | 18.0 kn / 10000.0 nm |
| Power Delivered: | 110738 hp |
| Power Effective: | 107141 hp |
| Froude Number: | 0.442 |
| Bunker Size: | 2966 t |
| Service Allowance: | 25% |
| Hull Weight: | 2277 t |
| Wood & Outfit Weight: | 557 t |
| Machinery Weight: | 3071 t |
| Equipment Weight: | 464 t |
| Superstructure Weight: | 279 t |
| Admiralty Coefficient: | 21.77 |
| Engine: | Geared Steam Turbine |
| Length of Superstructure: | 35.00 m |
| Aftbody Shape: | V |
| Longitudinal Center of Buoyancy: | -8.38% |
| Longitudinal Center of Gravity: | 2.80% |
| Vertical Center of Gravity: | 6.99 m |
| Metacentric Height: | 1.07 m |
| Roll Period: | 6.65 s |
| Tonnes per centimetre immersion: | 17.70 |
| Moment to change trim one centimetre: | 143.14 |
| Bow Entrance Angle: | 5.25 deg |
| Total Efficiency: | 0.97% |
| Length of Engine Room: | 70.04 m |
A small update:
After a while of on and off work on this I've managed to get high-speed vessels like the IJN Shimakaze working in this. Some stats:
User Inputs
| Length: | 126m |
| Beam: | 11.2m |
| Draft: | 4.15m |
| Avg Freeboard: | 4m |
|
| Std Displacement: | 2,610t |
| Power Delivered: | 75,000 shp |
| Design Speed: | 39kn |
| Shafting Type: | Geared |
| No. of Shafts: | 2 |
|
| Aft Body Shape: | V |
| Transom Stern? | Semi |
|
| Design Year: | 1941 |
| Engine Type: | Steam Turbine |
|
| Cruise Speed: | 18kn |
| Range: | 6000nm |
| Percentage Coal: | 0% |
Which spits out a corrected speed of 40.19kn. If I switch the engine power to 79,200 shp, which is the power at which Shimakaze achieved it's 40.9 trial speed, the corrected speed becomes 40.92kn.
I've tested the new calculation method for USN and IJN ships from ~1910 to 1950 and the results are very close - varying at most by less than 1 kn. I haven't tested it for older or newer ships though.
It's reliant on three correction factors: Power Density, Size, and Year
These are 0.913, 0.784, and 1.041- respectively for Shimakaze (it's not a linear equation though).
The only thing missing on propulsion is stuff like Nuclear, Gas, and Diesel powerplants - I had partially solved it at one point, but I seem to have lost my notes in the intermission.
The question I have though is whether the value of 2,352.63t for displacement consumed by the ship without weapons/armor is reasonable. Given what SS seems to think Shimakaze's armament weighed, it seems to be about 80t too light.