Logi's Springsharp

[Logi]

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 / (LDT_A).

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.

[Logi]

Never mind! I found the answer to my question in another book - "Marine Propellers and Propulsion" - D stands for propeller diameter.

[Tanthalas]

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.

[Logi]

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.

[Tanthalas]

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)

[Logi]

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 (CG_hull)  and propeller thrust (T_prop).

Mostly these are described by empirical testing, such as tilting the hull for CG_hull and propeller tests for T_prop. 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 CG_hull and T_prop of other ships, please let me know. It would be greatly appreciated.

[Logi]

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.

[Nobody]

...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.

[Logi]

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.

[Nobody]

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?

[Logi]

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.

[Nobody]

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.

Fuel
7400 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.

Panzerschiffe
Much 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"

[Nobody]

As I said, the "pocket battleships" are even more complicated. Let's start with a table taken from deutschland-class.dk:

	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:

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!

[Logi]

Thanks a lot. I'm much obliged.

[Jefgte]

Yes,  very interresting work Nobody.

Thanks

Jef  ;)