SHIP DESIGN AND CONSTRUCTION SYSTEM
(by: 'The Falcon')
Basic Ship Stats
Base Cost indicates the amount of money needed to construct 1/2 (one half) ton of ship of the listed material. Usually, ships will be sold for more than their actual building cost (including any adjustment above and beyond the bare hull cost), depending on circumstances, but never less. Used ships go for 50% to 100% ([1d6+4]x10%) of their total value, provided they are in good condition. Later modifications to a ship usually don't influence its price, unless they are magical. The Base Cost does not include any rams or standard armament  just the hull. Base Time is the number of days required for construction per ton of ship. Repair Cost gives a cost multiplier for repairs to a ship of the listed material. General Availability gives the chance of having access on a site to enough of the given material to build up to 100 tons of ship. Reduce the General Availability by one step for amounts of up to 200 tons, by two steps for up to 300 tons, and so on. Ships of combined materials use the average AR and MC (rounded to the most advantageous value), and the worst saving throws of the materials involved.
Material 
Base Cost 
AR 
MC 
Base Time 
Repair Cost 
General Availability 
Bone 
1,000 sp 
10 
D 
.25 day 
x2/3 
Uncommon (20%) 
Leather 
1,500 sp 
9 
D 
.5 day 
x1 
Uncommon (20%) 
Wood, Thin 
500 sp 
10 
B 
1 day 
x1 
Common (65%) 
Wood, Thick 
1,000 sp 
9 
C 
1 day 
x1 
Common (65%) 
Ceramic 
2,000 sp 
9 
C 
2 days 
x1/2 
Very rare (4%) 
Crystal 
5,000 sp 
8 
C 
2 days 
x1 
Rare (11%) 
Metal 
3,000 sp 
7 
D 
2 days 
x1 
Uncommon (20%) 
Stone 
2,000 sp 
6 
E 
2 days 
x2 
Common (65%) 
Base MC Modifiers 

Ship is over 60 tons 
1 MC 
Ship is under 5 tons 
+1 MC 
Base Minimum Crew Size: One sailor for every 10 tons of ship (round down), plus one officer for every 10 sailors (round up), plus one helmsman.
Base Cargo Space: Half the ship's tonnage.
General Limits 

Tonnage 
Crew 
MC 
Landing 
AR 
Cargo Space 

Minimums 
1/4 
1 
F/3 
No/No 
10/2 
100% 
Maximums 
200* 
+300% 
A/+3** 
Yes/Yes 
0/+7 
+100% 
* Larger ships can certainly be built, but for simplicity's sake, 200 tons is the maximum for PC designed ships. An NPC ship can be up to 700 tons, provided it is build out of a single piece of material; otherwise it is limited to 200 tons as well.
** Ships greater than 200 tons cannot have positive MC adjustments.
Design Improvements
The DM should check once for every step until a check is failed or the target improvement has been reached. The final improvement equals the number of successful checks. The results of the design should not be revealed until the actual ship is put to the test.
Crew: To man a spelljamming vessel, the base number of sailors needed is 1 per 10 tons of ship (rounded down). Add to this one officer for every 10 sailors (rounded up), and one helmsman. The total number of crewmembers can be increased by a maximum of 300%, or reduced to a minimum of 1. Adjustments to the crew succeed automatically when desired, but they do affect the ship's chances of MC adjustment as follows: Take the total amount by which the number of crewmembers is adjusted. Divide this number by the ship's tonnage. If the crew requirements were reduced, multiply the result by 300 to get the penalty to the MC adjustment chance; if the crew requirements were increased, multiply the result by 150 to get the bonus to the MC adjustment chance.
MC: The base MC can be improved by 1 step at a 45% chance. MC can be improved by a maximum of 2 steps, at a 30% chance per step. One step of targeted AR worsening increases the chance per step by 5%; each step of targeted AR improvement reduces the chance per step by 5%. MC can be kept as it is or worsened by at most 2 steps, to a maximum of F, with a base 100% chance of success; a failed check results in an additional 1 penalty to MC. Also check for MC worsening if improvement was targeted but failed completely; the ship might wind up with a penalty instead.
AR: The Base AR can be improved by 1 step at a 75% chance. Each step beyond that reduces the chance per step by 5%. AR can be improved by a maximum of 6 steps. Each step of targeted MC reduction increases the chance per step by 10%; each step of targeted MC improvement reduces the chance per step by 10%. Cargo capacity also influences the chance per step (see below). AR can be kept as it is or worsened by one step, to a maximum of 10, with a base 100% chance of success; a failed check results in an additional 1 penalty to AR. Also for additional AR worsening if improvement was targeted but failed completely, the ship might wind up with a penalty instead.
Cargo: The base cargo capacity is equal to half the ship's tonnage. It can be increased by a maximum of 100% (thus making the cargo tonnage equal to the ship's tonnage) or reduced to as little as 0 tons. Cargo capacity adjustments succeed automatically when desired, but they do affect the ship's chances of AR adjustment as follows: Take the total amount of tonnage by which the cargo capacity is adjusted. Divide this number by the ship's tonnage. If the cargo capacity was increased, multiply the result by 110 to get the penalty to the AR adjustment chance; if the cargo capacity was reduced, multiply the result by 50 to get the bonus to the AR adjustment chance. Remember that one Cargo Ton equals 1,000 cubic feet, while one Ship's Ton equals 2,700 cubic feet.
Rams
Before a ram can be used safely, the ship must be structurally reinforced at a cost of 50 sp per ton of ship. If a nonreinforced ship trying to ram makes an attack roll of 2 or less, the ram breaks off, and the ramming ship receives the damage instead of its target.
Ram Type 
Cost/Ton of Ship 
Blunt 
100 sp 
Piercing 
100 sp 
Grappling 
200 sp 
Standard Armament
Each large weapon installation (AKA. weapon pit or battle station) incorporated into the design of a ship adds one times the Base Cost of the hull material to the building cost. Note that a large weapon installation does not include the actual weapon, nor does it influence the ship's tonnage in any way. The maximum number of large weapon installations that can be safely build into a ship is equal to two thirds of the ship's tonnage (round to nearest whole number).
Landing
Assign a percentage chance for the ship's capabilities to successfully make planetfall (without crashing) on land and water, separately. Add both scores together, multiply by the ship's tonnage to the second power (the larger the ship, the more bracing it requires to survive planetfall), then multiply by the Base Cost of the hull material, and finally divide the total by 20,000. The result is the number of silver pieces added to the construction cost of the hull to incorporate the desired landing facilities into the design. Thus, a ship of one ton would have to add only 0.5% to its building cost for full landing facilities (100% land and 100% water), while a 200 ton ship would need to double its cost for full landing capabilities on water or land alone.
Design Bonus
Should the shipwrightengineer succeed both his shipwright and engineering proficiency checks by a margin of 5 or more, the ship gains a +1 bonus to both MC and AR. Should only one of the checks succeed by a margin of 5 or more, the ship gains a bonus to either its MC or its AR, but not both (designer's choice). A failed check results in a penalty of 1 on both MC and AR, within limits.
Should both checks fail, the chance of scoring a critical hit on the ship improves by one, in addition.