On Ship Design

So my players want to build a ship. That flies. Cool.

This is the system I use when players want to create a vehicle of some type. This works for land, sea, and air vehicles with a little bit of common sense.

There are a lot of iterations of this type of construction system online.  I feel that most of them are lacking because they are overly fetishistic about ship minutia. This however, answers all the questions the players will have during play, while the other systems. . . don't. (How much, how long, etc.)

It should be fairly straightforward. It cannot be used in a vacuum, but requires some discussion between players and the Dungeon Master

What is a Ton?

Traditionally in Dungeons & Dragons, when you come across the word Ton, it refers to 100 cubic yards of volume. This is a space approximately the size of your living room—That is, 100 cubes with 1 yard per side, not a single cube 100 yards on each side. For shorthand, you can assume a ship can carry half its tonnage as cargo

Frame

The first step in designing a vehicle is to determine the frame. This is a combination of size (measured in abstract tons) and materials. The dimensions may take any reasonable shape and form. An engineer is required to build per 20 tons of the vehicle. The base construction time is 1 day per ton. Examples follow:

Ship Type	Tonnage	Dimensions
Fleet Flagship	100	70' Cube (343,000 cubic feet)
Large Warship	80	60' Cube (216,000 cubic feet)
Large Cargo Ship	60	55' Cube (166,375 cubic feet)
Medium Warship	50	50' Cube (125,000 cubic feet)
Medium Cargo Ship	40	45' Cube (91,125 cubic feet)
Small Warship	30	40' Cube (64,000 cubic feet)
Privateer/Trader	20	35' Cube (42,875 cubic feet)
Fighter	10	30' Cube (27,000 cubic feet)
Shuttle/Bus	5	25' Cube (15,625 cubic feet)
Carriage/Chariot	3	20' Cube (8,000 cubic feet)
Wagon	1	15' Cube (3,375 cubic feet)

Material 

It costs 300 gold pieces in man hours and labor per ton to build the vehicle. In addition to this cost, there is the cost of the raw material required to build the ship. Materials are straightforward, with their hardness reducing any damage. You can find hardness values in any srd. The Armor Rating provides the base AC of the ship.

Material	Cost Per Ton	Hull Point Modifier	Armor Rating
Thin Wood	75 gp	.5	+2
Thick Wood	500 gp	1	+3
Metal*	3,000 gp	2	+6
Stone**	2,000 gp	1.5	+5
Ceramic	6,000 gp	1	+4
Bone	250 gp	.5	+1
Other	Consult your Dungeon master	?	?

* Iron and Steel; special and precious metals will vary by type.
** Obviously not suitable for sea vehicles.

Calculate Variables

That's it, your vehicle is done. You have time, cost, and final size for your vehicle. Now you just need to calculate your maneuverability class, hull points, and various other factors.

Once you have these factors calculated, you can apply modifications below that will adjust these factors. Once that is completed, you can assign internal space of your vehicle using the module section.

Base Time: 1 day per ton
Base Cost: (300 gp in labor + Material cost) x Tonnage
Hull Points: Hull Point Modifier x Tonnage
Crew: 1 per 10 tons
Maneuverability Class:

Size	Class
1-9 Tons	A
10-19 Tons	B
20-40 Tons	C
41-60 Tons	D
61-100 Tons	E
101+	F

Modifications

If you'd like to make specific changes, then select any of the following options. These will affect the base time, cost, and other already calculated factors as listed after the modification.

Armored Hull
Cost: By Material per Ton
Space: 10% of tonnage value
This provides armored plating covering the exterior of the ship. This makes it more difficult to do damage to the hull by increasing the armor class. You can plate a ship with any material superior in protection to the hull material. (e.g. you can armor a hull of thick wood with metal, but not thin wood.) This modification can be repeated multiple times.

Material	Cost Per Ton	AC Bonus
Thin Wood	5 gp	+1
Thick Wood	50 gp	+2
Metal	300 gp	+5
Stone	200 gp	+4
Ceramic	600 gp	+3

Frame Modification
This allows you to modify the frame of the ship to alter its maneuverability and hull points. Space modifies the available tonnage for cargo and modules.

Frame Modification	Cost	Space	Hull Point Modifier	Maneuverability Modifier
Light	+20%	+5%	x.5	+1
Heavy	+5%	-10%	x1.5	-1
Extra Heavy	+20%	-20%	x2	-2
Super Heavy	+40%	-40%	x4	-3

Rigging Modification
Any vehicle, land, sea, or air is going to have some sort of steering mechanism. This is referred to as rigging. It's assumed any vehicle comes with standard rigging. Modifying the rigging can change both the maneuverability and the cost.

Minimal Rigging reduces the cost by 25% per ton, the crew requirements by 50% and penalizes the Maneuverability by 1.
Topped Out rigging increases the cost by 5%, the crew requirements by 25%, and increases the Maneuverability by 1.

Ram
The ship has a ram attached. The ship must have the heavy frame modification to mount a ram. This modification takes 5% of the hull space. Rams cost 100 gp per ton of the ship. Note that a variety of ram types exist, all with different effects (blunt, grappling, piercing, etc.)

Modules

These are the internal modules of the ship. Any unused space is considered cargo space. The module sizes include support structures for the module (hallways, structural supports, etc.) so tend to be slightly smaller in size then the tonnage required.

Rooms	Space	Cost
Crew Quarters	.25 tons per man	100 gp per man
Cramped Crew Quarters	.15 tons per man	75 gp per man
Bunk Only	.05 tons per 2 men	25 gp per man
Room	.75 tons	125 gp
Spacious Room	1 ton	150 gp
Larder*	1 ton	100 gp per ton
Cargo	1 ton	-
Hall (mess/recreation)	.5 tons per 2 men	150 gp per ton
Docking Bay, Internal, Specific Craft	Vessel tonnage + 10%	50 gp per ton
Docking Bay, Internal, General	Special**	100 gp per ton
External Passenger Dock	1 ton	200 gp
External Cargo Dock	2+ ton	200 gp per ton
Weapons***	As Weapon	As Weapon
Turret	1 ton	500 gp per class of the weapon****
XXX	1 ton	XXX gp
XXX	1 ton	XXX gp

*A fully stocked larder will feed 10 men for a month per ton. Poor rations cost 30 gp a month per ton, Common rations cost 100 gp a month per ton, Good rations cost 150 gp a month per ton.
** The tonnage of craft you wish to be able to dock, +30%. If you wish to have space for any 10 ton vehicle to dock, you must allocate 13 tons of space
*** Weapons, of course, depend on your campaign. Anything from catapults to greek fire throwers to submachine guns to lasers is possible.
**** Light weapon turrets cost 500 gp. Heavy weapon turrets cost 1,500, etc.

Note: The above system is just the most basic options available. It is Dungeons and Dragons after all, making your ship out of crystal and having cascading fire cloaks on the outside of the hull just requires some DM adjudication.

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Hack & Slash 

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