The Fletcher Pratt Wargame Pt 2

I could describe the FP rules in some detail but since these are covered in the references [1][2]. What I will discuss is the FP surface gunnery system and the ship points value.

The FP system uses a range estimation paradigm for gunnery. On the firing phase of a move a player places a firing arrow at the bow of their ship with one or more estimates of the target range. The umpire or one of their assistants then measures the firing distance along the direction indicated by the firing arrow and hits are determined using some rule giving where the shots fall with respect to the nominal aim-point. Once again I am not to concerned with the detail of how the splash points are distributed, just that they are set up to give an acceptable level of playability. The splash points of the shells which do not hit are indicated with some suitable marker as are those which do hit thus providing some feedback to the firing player on the accuracy of their gunnery.

Damage done by a hit is basically the weight of the projectile with modifications for hits that are unable to penetrate any armour (belt thickness is used for near broadside hits and deck armour thickness for near endon hits). Also commercial shipping and other vessels built to commercial standards sustain double damage.

Torpedoes operate in a similar manner with the placing of markers, but in this case indicating the spread of the torpedoes. Hits are determined by measuring out the weapon tracks on each move on which they are running and if these pass through a ship that is deemed a hit. The number of moves for which a torpedo runs is determined from its rand for the speed setting indicated on the firing arrow.

That is the outline of the gunnery system, which I give because it one of (if not the) main focus of the game.

Damage accrues incrementally and a ship loses capability proportionately with damage as a proportion of the ship points value (other than for hits specifically on turrets which may knock the turret out independently of the accrued damage - this is a whole other topic for discussion, but won't be pursued here). A warship's points value is given by the formula:

PV=[C_M²N_M+C_S²N_S+10N_TT+10T_B²+10T_T²+10T_D²+25N_AC+N_M][(V/2)+10]+D

Where:

C_M: Calibre of main armament in inches
N_M: Number of barrels of main armament
C_S: Calibre of secondary armament
N_S: Number of barrels of secondary armament
N_TT: Number of torpedo tubes
T_B: Thickness (max) of armoured belt in inches
T_T: Thickness (max) of main turret armour in inches
T_D: Thickness (Max/total?) of deck armour in inches
N_AC: Number of aircraft carried
N_M: Number of mines carried
V: Maximum speed in knots
D: Displacement (standard) in tons

That is all for this article, I will have more to say about both the gunnery system and the ship points value in future articles.

References
1. Curry J., Fletcher Pratt's Naval Wargame, History of Wargaming Project, 2011
2. Featherstone D. Naval War Games, Stanley Paul, London, 1965, ISBN 0-09-076581-8

EndNote: The difficulty of getting Blogger to represent simple mathematics is seriously tempting me to move this blog back to WordPress where there is built-in LaTeX.

Staying Power Models and Naval Wargames

First let me define what I mean by staying power in the context of warship survivability. Staying Power is the ability of a ship to absorb hits and continue operating effectively (or sometimes just surviving). Thus we may measure staying power as the mean number of hits of some standard weapon needed to render the ship mission killed or more drastically sunk.

In many sets of naval wargame rules at least some aspect of staying power increases linearly with displacement. The question that I want to discuss here is how well is this assumption supported by historical data?

One of the main sponsors of the analysis of staying power on the basis of historical data is Captain Wayne Hughes of the Naval Postgraduate School at Monterey. His book [1] contains a summary of some of the results of investigations of historical data on staying power. These results may be summarised as: Staying power is proportional to the cube root of displacement. I have spent some time investigating the assumptions behind these results [2] and find them at least partially flawed, but even with the flaws corrected staying power still appears to vary as the 2/3rd power of displacement (at least for a number of significant forms of attack). There are limitations on the reliability of this modelling but the broad conclusion that staying power grows more slowly than displacement appears to be robust, and we are left with the conclusion that a force of two 20,000 ton ships has greater staying power than a force comprised of a single 40,000 ton ship, even when allowance is made for greater protection that may be built into the larger vessel.

References
1. Hughes W.P., Fleet Tactics and Coastal Combat, Naval Inst Press, 2000.
2. Larham R., Historical Data in Modelling Warship Battle Damage Survival Probability, 2nd IMA Conference on Mathematics in Defence, October 2011, link to copy on Academia.edu

The Fletcher Pratt Naval Wargame Pt1

In this first post I want to talk a bit about why I am interested in the Fletcher Pratt wargame/rules.

First some history. As children my brother and I always played with toy soldiers and eventually I bought a copy of Don Featherstone's Naval Wargames [1] and we moved on to playing naval wargames with scratch built (very rough) sailing men-of-war. After a while I devised a method of making reasonable models of WW2 warships out of card to a scale of 175 ft to the inch (about 1:2100) and we started using these in games using the version of the Fletcher Pratt rules in Feathersone's book. The problem was that I was more interested in naval wargames than my brother so eventually I mentioned the game to some friends at school. One in particular was interested and we started a small group with one or two others playing, but now using Triang minic ships at 1:1200 scale which were soon supplemented with scratch built models to this scale (using Ainsworth's plans from Model Boats). Anyway we continued with these arrangements for a while but eventually found a bigger group to join in the small adds of some model magazine. Unfortunately the group we found was the 1200 model ship society (unfortunately because we would have been better off with the Naval Wargames Soc) and moved away from the Fletcher Pratt rules.

The reason why I am writing about these rules today is the revival of interest in them with the publication of a couple of volumes in John Curry's History of Wargames Project [2][3].

References:
1. Featherstone D. Naval War Games,  Stanley Paul, London, 1965, ISBN 0-09-076581-8

2. Curry J., The Fletcher Pratt Naval Wargame, 1933, for Fighting Naval Battles 1900-1945, as Updated by John Curry et al (2006), 2006

3. Curry J., Fletcher Pratt's Naval Wargame, The History of Wargaming Project, 2011, ISBN 978-1-4475-1855-6

First Post

This blog is intended as an initial destination for thoughts on naval wargaming. I don't suppose there will be frequent posts but they will occur.

The header picture is HMS Vanguard in ~1917 shortly before her loss from an internal explosion.