That would be the spelljamming duel section in that same chapter.

I agree that the current rules for repairing ships is pretty stupid it is mending or spend up to ~8,000gp to repair a ship at 20gp/point of damage which would take 400days with only 1 person working on repairs. Even if we assume mending by an NPC will only restore 5hp an hour over an 8 hour work day that is 40hp. As hiring to someone to cast a cantrip is 5gp if my memory is correct, then that would be approximately 1hp/gp spent for a workday... The nonmagical way is currently 20x less effective which is just stupid.

Personally in my spelljaming campaign, I am using a repair cost of 4gp a day per worker which includes the cost of the repair materials. With this it the manual method repairs 1d6+1 hit points restored a day. Bases on the bosun repair method from saltmarsh. Should average to 4.5hp repaired per worker at 1.125hp/gp. This way both options are viable but the nonmagical method is slightly cheaper and slower and if you want a ship repaired fast you can use multiple workers which can't be done with mending. I'd cap the number of workers to one twentieth the length of the ship. So typically at least 8 to 10 could be hired to work on a ship.

I do use the 8 hour work days so if you wanted you can hire even more people to work on repairs around the clock. And if you absolutely had to repair a ship as fast as possible use both means at the same time.

Repairing weapons costs half as much per worker for similar amount of health recovered per workday. I limit the number of people working on a siege weapon to be it's normal crew amount.

ultimately there was a spell that was a leveled version of mending, Repair Objects, but they decided not to include that spell for whatever reason https://www.reddit.com/r/dndnext/comments/wu19ff/the_spelljammer_adventure_light_of_xaryxis/ 

Quote from Kotath >>

And the ship has infinite acceleration up to its movement rate, cannot accelerate past that point, and can not just stop on a dime, but "On its turn, a ship can be turned and reoriented so that all its weapons can aim and fire at any target within range, regardless of where they’re situated on the deck." It can literally pivot in place at will. 

 Yep it is utterly unrealistic. But then that same goes for PC's having a constant 360 view/stance/held shield/whatever. Sometimes the game is better helped by simplicity than realism.

Quote from Kotath >>

And yes in Spelljammer, it is whoever is attuned to the helm. Silly me putting the Captain in that role on the theory that they would want to be the one with that power. While a spelljammer ship does not need an action to order the ship to move, it does require attunement, so if the helmsman goes down or is otherwise incapacitated, it would take an hour for someone else to attune to allow the ship to move, even if they have another spellcaster available to do so.

 I'd agree that this seems problematic. There is this titbit from the spelljamming helm that does somewhat help;

Transfer Attunement. You can use an action to touch a willing spellcaster. That creature attunes to the spelljamming helm immediately, and your attunement to it ends.

It wont help if they are suddenly incapacitated/unconscious though...

FWIW, here's my house rule on ship repairs.

Astral Adventurer's Guide, page 25, last paragraph, the one beginning with: "The mending spell is a cheaper, less time-consuming way to make repairs." Replace with the following:

The mending spell will help make repairs cheaper and less time consuming. Having access to a spellcaster able to cast mending restores a number of hit points to the target equal to 1d8 plus the spellcaster’s spellcasting ability modifier per day, instead of just 1 hit point. This requires several castings of the spell throughout the day, and ties up the spellcaster for the entire workday. Materials still cost 10 gp per hit point for ship repairs, or half that for shipboard weapons, but there is no need to pay the repair crew more than 10 gp per day until repairs are done, or 5 gp if you are repairing a shipboard weapon.

The fabricate spell will repair a ship and its shipboard weapon completely in a single day, provided that the ship is berthed, the spellcaster is proficient with either carpenter’s tools (for a wooden ship or weapon), tinker’s tools (for a metal ship or weapon), or smith’s tools (for a cannon, specifically), and that materials equal to 10 gp per hit point are provided. Shipboard weapons require half the materials. The caster is tied up for the entire day.

The wish spell will restore a damaged ship and all shipboard weapons to full hit points instantly without requiring any materials. All the consequences of casting wish apply.