Saturday, 16 July 2011

Jutland 2011 - A Design Rationale

SMS Seydlitz - A favourite warship of mine!

The rules are ready for the test I am running tomorrow and as usual, I am very excited at the prospect. The opposing forces will be the Greeks and the Turks and all I have to do now is to finalise the format of the damage cards. In advance of the test I thought it would be a good idea to explain how some of the rules choices were arrived at and why I have taken the approach I have.

Movement - This was pretty straightforward and all I have done is to take the actual speed of the individual ship in question and to convert this into hexes. I wanted a maximum speed of around 6 hexes (being around the 36 knot mark) and initially this caused a few problems because of the historical closeness in speeds between ships. It felt unrealistic having generic speeds for ship types and so I opted for a variant of the technique employed by Barry Carter in his book Naval Wargames (ISBN 0 7153 6812 5) of having 'long' and 'short' moves. For example, a ship rated as 2/3 can move 2 hexes on a short move and 3 on a long. My variation on that is to allow a ship rated as such as being able to move at the higher rate on any three game turns within the 6 turns making up a map move (1 game turn equals 10 minutes). This allows for an element of uncertainty over movement intentions on the tabletop. Turning is in increments of sixty degrees and costs a movement point to execute. Speed loss from hard turns could be very dramatic and so including this aspect of  seamanship was essential. I have increased the number of ships that can operate in a single hex to two for cruisers and four for destroyers - primarily for use with large actions.

Defence - Ships in the original game had a protection or flotation factor based on what looks like the maximum thickness of the belt armour of the ship under consideration. Ships could only be sunk by losing all their flotation value. In the game gunnery first had to destroy the target ships gun factors and then the excess hits went onto the flotation value. Initially I thought this was a little on the abstract side but after having carried out some research on the subject of the effects of naval gunfire on a ship I can see why this approach was used in the original game design. Warships are ordinarily very difficult to sink by gunfire alone - unless a lucky magazine hit occurred or there was an enormous disparity between the weight and effect of the incoming shells and the size and protection of the target ship. I decided therefore, to stick with this approach and so the protection/flotation/defence factor of the ship is equal to the maximum thickness of its belt armour. The original game assumed that a ship would have to have all its gunnery factors destroyed before they could be used on the flotation value. Given that a ship could be hit anywhere - including on or below the waterline - I am allowing the owning player to assign any hits received in any way he wishes. This will mean that hits will be well spread about which is historically accurate.

In the game the above approach was used for ships from armoured cruiser size and upwards. As I wanted to add in protected and light cruisers as well as destroyers I needed to consider an alternative method for assigning the defence factor to the ship. For the two cruiser types I opted to use the maximum deck amour whilst for the unarmoured destroyers I opted for defence factors based on tonnage.

Gunnery - In the original game firing is carried out by the simple but effective method of counting the number of factors available, checking the range, looking up the appropriate column on the gunnery table and rolling a d6. The maximum range in the game for gunfire was deemed to be 20,000 yards. Guns are rated by ship type so we have BB (battleships), BC (battle cruisers), B (pre dreadnought battleships), CA (armoured cruisers) and 'light ships' -  a generic heading for protected and light cruisers and destroyers. Whilst these headings were fine for the original game they were too generic for what I wanted to achieve. I would be adding a lot of additional ship types that would not be best served by his approach and so I needed to 'unpick' the generic nature of the firing types and replace this with something with much greater coverage.

The answer to this dilemma came from an old set of naval rules produced by Skytrex and written by John Hammond and called 'Rules for World War 1 Naval'. The cornerstone of the firing rules in this set is the use of F.T.Jane's gun ratings. In addition, the rules assumed a maximum gunnery range of, yes you've guessed it, 20,000 yards. Due to space limitations at home I opted for using a scale of one Hexon tile being 2,500 yards so the aforementioned 20, 000 yards became 8 hexes. With more space this could easily be converted to a 2,000 yard per hex or even greater in required. It was then a simple matter to assign maximum ranges to each of F.T. Jane's gun rates. I have had to combine these as follows:

  • A9 and A8 = 8 hexes (20,000 yards)
  • A7 and A6 = 7 hexes (17,500 yards)
  • A5 and A4 = 6 hexes (15,000 yards)
  • A3 and A2 = 5 hexes (12,500 yards)
  • A1 to C = 4 hexes (10,000 yards)
  • D to F = 3 hexes (7,500 yards)
I managed to 'crack' the method used to calculate the number of gun factors which is based around an 11 or 12" gun being worth one gunnery box. This means that a ship with a broadside of eight such weapons will have eight gunnery factors. Guns of 13 to 14" are worth 1.25 whilst 15" weapons are worth 1.50 so a QE class battleship would have a broadside of 12 being 8 x 1.5. I stepped this back from 1 for guns smaller than 10" which would allow for calibres from 1" to be assigned the appropriate factors. A good example would be the 6 x 6" secondary battery on the aforementioned QE. Guns rated at 5 to 6" are worth 0.5 each so the secondary factor of the QE would be equal to a gunnery value of 3.

The original game did not factor in secondary weapons at all other than to double all hits scored from a BB, BC, B or a CA at ranges between 3,000 and 10,000 yards and to triple hits scored below 3,000 yards. What I am considering doing is rather than having artificial gunnery factors is to have the actual number of barrels firing and to merely apply column shifts when firing depending on the calibre of the firing weapon. This would have the advantage of meaning that creating a ship card would be simply a case of converting the details of the ship from whatever reference is being used into gunnery boxes rather than having to calculate anything. 

What of armour penetration at a given range? What about increased rates of fire for smaller weapons etc?

These are abstractly built into the combat table/gunnery factor dynamic in that bigger guns have more factors which means more hits. Lighter guns cause the same amount of damage which could be seen to represent higher rates of fire. Ships also now have more hit boxes to mark off so longer range fire will take longer to produce a result. Interestingly the results at ranges below 10,000 yards having separated out the secondary gunnery factors but by dropping the doubling and trebling from the original rules are fairly similar.

Torpedo attacks have been left as they are in the rules - all I have needed to do is to assign the appropriate factor to individual ships. I have also given them a range of 3 hexes - 7,500 yards as opposed to the 6,000 of the original rules.

So that is the extent of my modifications/additions to the original rules for the Avalon Hill game Jutland. I think it must be a tribute to the soundness of James Dunnigan's original design that what I have so far attempted has been very straightforward to accommodate.

Of course all of this seems fine in theory but of course the real test of how successful (or not!) the adaptation is will be when I test them tomorrow and that will be the subject of my next post.


Peter Douglas said...


I'm liking what I'm seeing. Good stuff!


David Crook said...

Hi Peter,

I must confess that I wish I had thought of doing this sooner! The rules will not suit everybody but are ideal for my own purposes and will of course be great for a club night knockabout. They are not super detailed but are based on very sound historical foundations and much in the way of James Dunnigan's original research. The original rules have a very good flavour for the period and if I can retain that then I shall be very satisfied!

All the best,