Gurps vehicles to design boats?

[briansommers]

I’m using 4e but I’m so tempted to get 3e vehicles because I really want to design TL3 boats.

How detailed does this get?
I want to choose shape of sail, size of sail, length & width of boat, different levels, number of sails, where I place them, etc. can I do all of this with vehicles?

[mlangsdorf]

Vehicles provides statistics, not deckplans. So you can't really decide where any ship component is located except by fiat and then drawing a map.

For a ship in general, you choose overall volume and fineness (length to width ratio, more or less) of the hull. That implies ship length and width.

The number of decks isn't a design consideration. You can choose it, but it's cosmetic. The only possible exception is that some superstructures necessarily imply multiple decks.

You can choose the number of masts, their height and material, the rigging on each mast, the sail size in square feet, and the sail material. Vehicle Expansion 1 has more detail on sails.

[briansommers]

Oh that sounds exciting…
Thanks.

[Curmudgeon]

Originally Posted by briansommers

I’m using 4e but I’m so tempted to get 3e vehicles because I really want to design TL3 boats.

How detailed does this get?
I want to choose shape of sail, size of sail, length & width of boat, different levels, number of sails, where I place them, etc. can I do all of this with vehicles?

Yes and no. Some things mentioned by mlangsdorf aren't covered by GURPS Vehicles. However, two additional points should be made.

First, if you want to get into things like which ship can sail closer to the wind (i.e., "I'm still able to get some propulsion from my sails and he can't.") you will also need the supplement, Vehicles Expansion 1, which breaks the original three rigging types from Vehicles into seventeen sub-types, (two riggings get three sub-types each, and fore-and-aft rigging gets the other eleven). Vehicles Expansion 1 also has some new hull types for submarines and new calculations for submerged performance: a revised Crush Depth (the old Crush Depth now becomes Test Depth), together with the formulas for supercavitation performance. If you want to do more modern rigid sails, you'll also need Vehicles Expansion 2 as Vehicles doesn't cover them at all.

Second, there are two editions of GURPS Vehicles both for GURPS Third Edition. They're quite different in how you go about calculating your design. You definitely want the second edition. This is only an issue if you're looking at an original "dead tree" edition. If you're getting the PDF, it's second edition.

[mlangsdorf]

Originally Posted by Curmudgeon

Yes and no. Some things mentioned by mlangsdorf aren't covered by GURPS Vehicles.

How do you figure that? The sleekness/fineness of a flotation hull is covered on pp 10-11 (all page references are for the PDF of Vehicles 2e for GURPS 3e). Ship volume is on pp 15-17. Vehicle length and width aren't explicitly calculated, but surface area is on pp 17-18, and between volume, surface area, and draft (p 132), you can get an estimate of length and width.

Masts and their materials are on p 9. Sails, sail plans, sail material, and sail size are all over on p 30. And as I noted, Vehicle Expansion 1 has more detail.

So what did I mention as being in Vehicles that isn't Vehicles?

[Curmudgeon]

Originally Posted by mlangsdorf

How do you figure that? The sleekness/fineness of a flotation hull is covered on pp 10-11 (all page references are for the PDF of Vehicles 2e for GURPS 3e). Ship volume is on pp 15-17. Vehicle length and width aren't explicitly calculated, but surface area is on pp 17-18, and between volume, surface area, and draft (p 132), you can get an estimate of length and width.

Masts and their materials are on p 9. Sails, sail plans, sail material, and sail size are all over on p 30. And as I noted, Vehicle Expansion 1 has more detail.

So what did I mention as being in Vehicles that isn't Vehicles?

Poor wording on my part and terrible editing. I meant to say as mglansdorf said, some things aren't covered by GURPS Vehicles, such as deck plans, division into decks, etc. I'm terribly sorry for the unintended misrepresenation.

[whswhs]

The thing that has long perplexed me in GURPS Vehicles is figuring the volume of boats and ships.

GURPS Vehicles envisions a ship as a rectangular prism, which has length, width (beam), and height (draft). Total volume is the product of these three, and a ship's ability to float is based on its volume. But in reality, a ship's "height" is the sum of its draft (the part of its height that is below the waterline) and freeboard (the part that's above the waterline). I could never figure out how to represent the part of the ship's volume that's above the waterline. Of course a ship can have superstructures, such as its fore and aft castles; but the water never comes up to the top of the mail hull, unless it's a submarine (or the original Monitor, perhaps). And it just seems too arcane to say that a ship's main hull includes both a body and a superstructure that may not even be separated by a deck.

Secondary to this, how do you figure a ship's draft? It's simple for an actual rectangular prism. But what if the ship approximates an ellipsoid, or a pair of triangular prisms extending forward and backward, or something more complex?

I find all this so perplexing that I can't really feel at ease with ship design in GURPS Vehicles.

[Rolando]

As detailed as it is the vehicle design system in GURPS 3e is still an abstraction.

You will have to decide or research more specific details, but I think that for game purposes it is good enough.

[Polydamas]

Originally Posted by whswhs

The thing that has long perplexed me in GURPS Vehicles is figuring the volume of boats and ships.

GURPS Vehicles envisions a ship as a rectangular prism, which has length, width (beam), and height (draft). Total volume is the product of these three, and a ship's ability to float is based on its volume. But in reality, a ship's "height" is the sum of its draft (the part of its height that is below the waterline) and freeboard (the part that's above the waterline). I could never figure out how to represent the part of the ship's volume that's above the waterline. Of course a ship can have superstructures, such as its fore and aft castles; but the water never comes up to the top of the mail hull, unless it's a submarine (or the original Monitor, perhaps). And it just seems too arcane to say that a ship's main hull includes both a body and a superstructure that may not even be separated by a deck.

Isn't freeboard determined by the volume of hull which the weight of the ship forces underwater? On still water, if the loaded weight is the density of water times the volume of the hull then the deck will be just above water.

[mlangsdorf]

Originally Posted by Curmudgeon

Poor wording on my part and terrible editing. I meant to say as mlangsdorf said, some things aren't covered by GURPS Vehicles. I'm terribly sorry for the unintended misrepresenation.

Cool and apology accepted. Sorry for jumping down your throat, but it was just a weird statement.