Loads Estimating

• crew and their effects (Group F10),
• ammunition (part of Group F20),
• provisions & stores (Group F30),
• fuel and other petroleum based liquids (Group F40),
• other non-petroleum based liquids including drinking water and hydraulic fluids (Group F50),
• cargo (Group F60), and
• aircraft/helicopters (part of Group F20) & their associated fuel (part of Group F40), etc.

• some repair parts, and
• some operating fluids (ie the fluids that are normally in a piece of equipment that is required to make it operate), etc

I may also refer to this as SWBSFlds or wFlds.  In general I had intended both Group F and SWBS Flds as being meant to refer to the category and wFlds is intended to refer to the actual weight of the items in this category.  I hope to go back and try to ensure that I have been consistent, as I get the time.  Similarly vFlds will refer to the vertical height of the center of the weight of the Group F items and cFlds will refer to the estimated cost of those items.

Below is a listing of the current methods proposed for estimating these loads.

Based on some information that I've collected on modern ship designs, an estimate for the weights for personnel and effects is as follows:

• Officers - 400 lb/man (0.18t/man)
• CPOs - 330 lb/man (0.15t/man)
• Crew - 230 lb/man (0.10t/man)

• Officers - 8% total crew size
• CPOs - 7% total crew size
• Crew - 85% total crew size

In general, these equations are probably appropriate for modern US designs, and it is possible that slightly different numbers may be more appropriate for vessels of other navies, or other time periods.  In the future, I hope to review this more fully and see if it might be possible to provide alternate equations for other navies or time periods (eg immediate post WWII, the 1950's, the 1960's, the 1970's, etc).

I intend to update the data tables provided in the Tables & Figures for the Pre-Processor  section to include not only the weight of the different weapon systems, but also the weight of the munitions for these weapons, so that it would be possible to quickly estimate the total weight of ammunition carried on the vessel by multiplying the weight of the munitions for each weapon by the total rounds carried for each type.

Based on some information that I've collected on modern ship designs, an estimate for the weights for provisions and stores is as follows:

• Dry Provisions - 3.2 lb/man/day of endurance (1.45 kg/man/day)
• Chilled Provisions - 1.7 lb/man/day of endurance (0.77 kg/man/day)
• Frozen Provisions - 1.1 lb/man/day of endurance (0.50 kg/man/day)
• Medical Stores - 3.9 lb/man (1.77 kg/man)
• Clothing & Small Stores - 3.1 lb/man (1.41 kg/man)

In general, these equations are probably appropriate for modern US designs, and it is possible that slightly different numbers may be more appropriate for vessels of other navies, or other time periods.  As with the estimate of the breakdown of the number of Officers, CPOs, and enlisted personnel in the crew, in the future I hope to review this more fully and see if it might be possible to provide alternate equations for other navies or time periods (eg immediate post WWII, the 1950's, the 1960's, the 1970's, etc).

The estimation of required fuel tankage is perhaps one of the more difficult areas to estimate weights because of the complexity and uncertainty associated with the calculations required.  Specifically, in order to make this calculation you will need to:

1. determine approximate desired cruise speed and range
2. better define the hullform shape
3. determine the power plant configuration
4. determine the power plant specific fuel consumption at the desired cruise speed (in terms of t/kW-Hr)
5. determine the estimated resistance at cruise speed
6. determine the estimated propulsive efficiciency at cruise speed, and
7. add in any appropriate margins, etc

When trying to approximate an existing design, my hope is that sources like "Janes Fighting Ships", "Combat Fleets of the World", or other such sources can be consulted for determine cruise speed, range, and propulsion plant configuration.  If you are investigating your own designs, my intent is that you would set the desired cruise speed and range in the pre-processor phase as part of "General Information".

I have incorporated some data relating hullform parameters such as block coefficient, midships coefficient, prismatic coefficient, waterplane coefficient, location of the longitudinal center of buoyancy, transom shape, waterline half entrance angle, and other such paramters that may be needed for resistance estimation into the Initial Hullform Definition  page.

Additionally, as part of the weight estimating routine when selecting a specific power plant, I intend to provide some additional information on notional estimated specific fuel consumptions for the different plant types.

With regards to resistance estimation, as noted on the Background page I am putting together a routine that is based on methods developed by Sui Fung and Larry Leibmann for transom hull vessels typical of most modern frigates and destoyers.

Similarly, I am currently investigating issues related to propulsive efficiency estimation, but this is still very much under development.

Finally, for now I intend to use the standard US Navy margins for fuel endurance calcultions but I also have some information on the margins used by some NATO navies (from a SNAME or ASNE paper from a few years ago) so I may eventually provide the option of using either the USN calcs or calcs for other navies.

Here is a plot of ship's fuel weight versus Full Load Displacement to give an idea of how a proposed design might compare to similar type ships.

Based on some information that I've collected on modern ship designs, an estimate for the weights for fresh water is as follows:

• 40 gal/man

Assuming a weight of fresh water of 8.32lb/gal @ 68 deg F, this equates to a weight per man requirement of 151kg/man (332.8lb/man).

Currently, I don't have a good estimate for the weight of hydraulic fluids, but I don't believe that this will be a large number, so for now I believe that you can assume 0t for this weight.

In general, these equations are probably appropriate for modern US designs, and it is possible that slightly different numbers may be more appropriate for vessels of other navies, or other time periods.  In the future, I hope to review this more fully and see if it might be possible to provide alternate equations for other navies or time periods (eg immediate post WWII, the 1950's, the 1960's, the 1970's, etc).

Group F60 - Cargo

Currently, I don't have a good estimate for cargo weights, or more specifically what would normally be included here on a combatant ship.  I am currently researching this, but for now I believe that you can assume 0t for this weight for most modern surface combatants.

Total Loads Weight

Below is a graph of total Loads weight versus Full Load displacement to help give an indication of how a ship's estimated load weight compares to similar vessels.  Please note that there are separate curves for conventionally powered ships as well as one for nuclear powered vessels.

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