I've been writing these guides for my Alliance's FB page, and after they have had them up for 3 months, I'm putting some up here for the community to use. As they were written 3 months ago, some of the ship info is a bit dated, but still useful.
Introduction to Armor / Repair Time Ratios
My goal when designing a ship is not having to wait and/or coin as little as possible for repairs. Ideally, FREE and INSTANT is the best price.
There are two ways to achieve this. One of which everyone is familiar with, you take so little damage from the target that your ship(s) can repair in 5m or less, which is free and instant.
The second way has fallen out of favor because damage output from targets progressed enough to make it impossible. This involves using ships that repair instantly even if completely destroyed because their repair time is under 5m. Before the defense rework, this had become impossible vs almost all targets. After the rework not only is this possible again, but tiny ships can be made extremely resilient vs even highly damaging targets.
The original ships in the game had only one repair time to armor ratio. 1 second of repair = 1 point of armor repair. Ships with total armor from all sources repaired instantly if they had 300 armor or less (600 during raid, which is why the Sea Wolf became the king of raids back in the day)
Instant repair ships were very useful, but large ships taking less than 300 damage was much harder to pull off. Taking less than 300 damage when hitting a big target was rare.
Now all new ships have armor to repair time ratios that allow them to take much more damage before they pass the 5m repair mark. Typically a ship will have a repair time from 2hrs to 4hrs. Before the defense rework some had armor slightly in excess of 100,000. Now there are ships that have armor in the millions.
To make the most of your repair time or coins, you need the ratio of armor points to repair time in seconds to be as high as you can make it.
Look at the Punisher in Ship Designer. It has 830,673 armor and repairs in 1hr 36m 16s, which expands into 3600 + 2160 + 16 or 5776. 830,673 divided by 5776 is about 143. That means every 143 damage you take gives you 1 second of repair. This is definitely a lot nicer than 143 damage giving you 143 seconds of repair. A bare punisher can take 143 x 300 seconds of damage for 5m, which is 42,900. Pretty good actually, but there are bigger ships in the sea.
Look at the Eradicator in Ship Designer. HOLY CRAP. Almost 30 million armor. A bit longer repair time, but the ratio is extremely nice. This calculates out to an armor ratio of about 2762. A bare Eradicator can take 828,000 damage of any type and still repair in 5m! You can take over 1.6 million with half repair time from raid. This makes the Eradicator currently the most powerful ship in the game vs ANY kind of target, as long as the target allows the ship into it. I suspect Kixeye might nerf this or tighten class restrictions on even more targets, but there are ways around that too, which will be explained in future installments.