In the enchanted item section of the book (which isn't at hand, so pardon the lack of a page number), exists a chart with size multipliers for enchanted item costs. At the top of this, and of particular interest to my lab rat, is "boat" in the x5 multiplier slot.
Boat to me implies a small vessel, perhaps capable of carrying half a dozen or so people in some small degree of comfort.
But where would other sizes of vessel fall? One must assume, given the great magi in the world both past and present, that surely something larger than a boat or cart can be enchanted. What if I wanted to enchant a small sailing vessel? Say one that could hold 20 or 30 people? Would that be x7? Times 10?
My maga has Magic Theory 7 (thanks to Affinity) and Puissant Magic Theory (thanks to being Bonisagus), so my total pawns in a season would be 18 by my thinking. A boat, made of wood (2), at the smallest boat size (x5) would take 10 pawns. How big would a boat be that would take all 18?
The vis capacity of an entire ship would , I suspect, be gargantuan (i thik that I'd go for * 40 for a large vessel - eight times what would be requied for a room/wagon/boat, other's might have different answers), perhaps beyond the ability of any by the book magus to enchant (we'll have to wait and see if the deeper Verditius mysteries can get them around this). However there is a section of text you should re-read in the right hand column of page 97 in the section on prepeation for enchantment.
"There are two ways... but you must select one... or with a number of pawns equal to the highest required by a single component"
So you'd just have to enchant the largest vis capacity component of the ship.
It's also not very efficient to enchant an entire ship when you can just as easily enchant one part of it that will affect the whole thing. If you want an enchantment to make the hull stronger for example, enchant the wheel and give it a target of Structure, which would effect the ship. You could enchant multiple things that way and really improve the ship.
If you just enchant the wheel a ship strengthening spell is range touch rather than range personal. You actually loose efficency if you only enchant part of the ship. While enchanting several items on the ship would gove you more capacity to instill effects than merely enchanting the highest capacity component of the ship this capacity could also be achieved by bringing in enchanted devices on to the ship that are not integral parts of the ship.
The only things that you would gain would be the ability to take these items on to a different ship at some later time (say after the original ship has been destroyed), and an eaisier time fitting the item into your laboratory.
P.S. Ship's steering wheels are anachronistic in 1220 Europe.
That would make enchanting it a multiplies of the order of x1000. Seems too high for me. On the other hand, what would be the cost of enchanting a wehole structure like a Mystical Tower? It is made of a single chunk of rock, so it is a singular item. According to the above post it would be easier to enchant it than to enchant a 50 ton cargo ship. Seems weird to me...
Hey! That'd work, I think. Except that people would be riding her talisman. Not sure what that'd mean. I also realized that if I enchant the thing piecemeal, I can do them as a string of lesser enchantments, which would eliminate the need to open the thing for enchantment and would allow it to be done over years.
Either way, the boat will be legendary, though also require some camouflaging, as it's not a boat for the seas, what with her specialty being Auram and all. I had actually thought of making the boat along the same lines as the tower spell, crafting a boat as a momentary ritual, which would be amusing and allow for some odd design elements. Things to think about...
If you enchant any one device with range of Touch and target of Structure, any structure it touches will be affected, whether it's on the hull or not. The wheel thing was the first I could come up with, it could just as easily be the decoration on the bow of the ship instead. Or it could be an amulet or other device touching the ship. Then they'd have the ability to be moved as you said. That's also a liability too, if it's moved the ship loses its powers.
Enchanting the ship seems to be inefficient, as it would be just too expensive vis wise, though you could put many effects on it. However you're putting all your eggs in one basket, if the ship goes down you lose a huge investment that probably can't be recovered or repaired.
So let's go then with your initial estimate, a boat that takes 18 pawns of Vim Vis to enchant. That allows you 180 levels of effects for another 18 pawns of effects for a total of 36 pawns.
Now instead you could invent several Lesser Invested items of single effect and save on the Vim Vis, allowing you 180 levels of effects and only 18 pawns of Vis. Altogether that would also save you a Season, as you wouldn't need to open the original enchantment. You are limited in that you wouldn't be able to put complex effects into one item, but could put several protective wards as well as effects that could pilot the boat.
Now then if you were to make each item as a fully enchanted device you're not saving vis, though not necessarily paying extra vis, depending on the material and size of each. But you are losing time because it would take extra seasons to open the enchantment on each.
The lesser enchanted device route is cheaper and more efficient in general, now if only I had actually mentioned Lesser enchanted devices before.
Happily we don't disagree on any of the facts here.
If you go with lesser enchanted devices exlusivley (and thereby limit the power of effects that you can enchant) you may come out slightly ahead in vis and time and you
If you even have one invested device among your lesser enchanted devices you loose your time advantage.
A possible advantage to enchanting the ship that I see is still enchanting effects at range personal rather than range touch, this is one magnetude from each effect. Suppose you have 10 lesser enchanted devices with an average level of 18. Of these ten devices six target the ship. Enchanting these into the ship itself saves you 30 levle of spells and from 0 to 6 pawns of vis depending upon how the levels of the individual effects end up.
The clear disadvantage is that with an enchanted ship your enchantments go down with the ship.
If you want a really enchanted ship you might eventually do both. If you don't enchant the ship to begin with you can always go back and do it later. If you do enchant the ship you can always add a few enchanted devices of other sorts later.
Hmmm... I like the notion of building a ship in miniature and then having the size increase. That's intriguing. Perhaps build it to 1/4 scale or so. That'd fit in a large lab and still hold enough vis to make it worth enchanting. It'd also allow for other items to be built into it (or would it?).
The other advantage is that this particular ship doesn't have to be seaworthy, as it won't sail the seas (my maga is an Auram specialist and has particular ideas about where she wants to sail )
For now, though, I'm just working on getting enough vis together, which is all going into a large golden bracelet (the Touch of Midas is great for making gold items, not just for destroying the local economy) that is size small and holds 20 pawns by my calculations.