Sailing ships at TL3

[temp]

Assuming a sailing ship is considered a machine for moving stuff and people around by capturing natural wind power. I suspect that you need to consider them.

Ship TL is quite broad. TL 5 is steamships. TL3 is medieval cogs and such. Clipper ships therefore are TL4, and we have some decent data.

At top stable speed,
Energy Generated/Captured for propulsion = Energy lost to drag.
Energy = Power * Time (T)
also
Energy = Work = Force (F)*Distance (D).
D = Velocity (V) * Time (T).
Energy for Propulsion = Power Available (P) * T = Work = Drag Force * V* T
Power Available = Drag Force * V

Drag Force = ½ * Area (A) * Coefficient of Drag (CD) * Density (Dens)*V^2

Power Available = ½ * Frontal Area (A) * CD * Dens *V^3

Assume the in air portion of the ship is generating the power, and the drag force comes from the in water portion. Take a clipper ship, http://www.sailpowersteammuseum.org/...d%20Jacket.htm

Important value, draft = 26 ft = 7.9 m
Important value, beam = 44ft

https://en.wikipedia.org/wiki/Red_Jacket_(clipper)
“with sustained bursts of 17 knots “ velocity = 17 Knots = 8.75 m/s

Assumption : her beam at the waterline is 35 ft = 10.7m (this is pretty much a guess)
Assumption her shape below the waterline is a triangle (almost assuredly not true, will result in an under estimation)
Frontal Area = ½ *7.9*10.7 = 42.27m^2
Density = 1000 kg.m^3 (approximately, it’s a bit different for salt water and varies mildly with temperature).
Assume a CD of 0.5 (I have no great faith in 1850’s hydrodynamics)
Power = 7.1 Megawatts.

1) A clipper ship is built for rapid cargo transport, not optimal power generation. You could undoubtedly trade cargo capacity for heavier masts and spars, able to support more canvas, to maximize power generation. Also, power generation is not necessarily fastest – a dump truck is not faster than a Mazda 3 compact, but it does have more horsepower.
2) A mage can ensure optimal sailing conditions, which should add some to the available power.
3) The trip described in the Wikipedia entry is practical sustained speed, not a peak power scenario – you aren’t loading on sail until the stays start creaking unless you’re being chased by pirates… You might if the owner is on board for a short enchantment and is crying out "Give me more power Scotty!"
4) Finally, it should be noted that even TL3 ships may approach this power generation, rather than speed. As I understand it, the much improved practical speed of a clipper relative to a cog, comes from a) better hull form, (lower CD) and better rigging (which lets it sail much closer to the wind when tacking, which is important when going to a destination, rather than where the wind takes you), not from a major improvement in raw power capturing potential.

Best guess, an optimized TL3-4 power generation sailing ship can probably generate something on the order of 10 Megawatts…

[Fred Brackin]

Originally Posted by temp

Assuming a sailing ship is considered a machine for moving stuff and people around by capturing natural wind power. I suspect that you need to consider them.

Ship TL is quite broad. TL 5 is steamships. TL3 is medieval cogs and such. Clipper ships therefore are TL4, and we have some decent data.
…

Clipper ships are not seen until well into the 1800s when TL5's start date is 1730. Clipper ships are therefore TL5 and a mostly late TL5 at that. Spanish galleons might be a better exemplar for TL4 ships.

Sailing ships probably not machines for purposes of the spell either. You'd have to be tapping into the kinetic energy of the ship and that's not power by the spell's definition any more than the raw heat of a fire is.

You'd need a tow line leading to a wheel or something like that and such an arrangement would probably fail due to material strength issues before it hit the MW capacities needed. It wouldn't really be any easier than building a big enough windmill. It just confuses the issue a good bit.

Pretty much all of these low TL schemes for creating a usable source for Draw Power start going astray by focusing on gathering the power and that's not the issue. Yes, there are large enough sources of energy out there but for this spell you need to be able to harness them into mechanically usable forms and you need TL6 steel to build key parts of those machines out of.

[roguebfl]

Originally Posted by Fred Brackin

Sailing ships probably not machines for purposes of the spell either. You'd have to be tapping into the kinetic energy of the ship and that's not power by the spell's definition any more than the raw heat of a fire is.

No I digress if the crash shaft of water wheel counts, and drive shaft of propeller counts, the shaft of windmill counts, a sail ship counts too.

The restriction of the spell is sole that NEED to be be a machine, and not a pure natural power source, being overly restrictive is probably not the intent

[Fred Brackin]

Originally Posted by roguebfl

No I digress if the crash shaft of water wheel counts, and drive shaft of propeller counts, the shaft of windmill counts, a sail ship counts too.

The restriction of the spell is sole that NEED to be be a machine, and not a pure natural power source, being overly restrictive is probably not the intent

I am certain of little of what you might be trying to say but the shaft of a water wheel or wind mill would count because you could hook up there to use he energy for some other purpose. It is the lack of such a point on the sailing ship that should disqualify it. That "take off" point is exactly where the spell should be targeted.

The only "work" the sailing ship does is integral to it's structure.

I'm pretty sure that the 4e description of this spell was re-written with the intent of being very restrictive. It restricted some of my favorite uses from 3e. :)

[AlexanderHowl]

A water mill and a wind mill are machines that transform momentum into mechanical energy. Sailing ships are unpowered vehicles that use the momentum of winds and currents to increase their own momentum. Since sailing ships do not transform energy but instead transfer energy, they would not be considered to be a machine according to the Mechanical Hierarchy and are considered to be tools because they are unpowered vehicles (Supers, p. 106).

[Daigoro]

Originally Posted by AlexanderHowl

A water mill and a wind mill are machines that transform momentum into mechanical energy. Sailing ships are unpowered vehicles that use the momentum of winds and currents to increase their own momentum. Since sailing ships do not transform energy but instead transfer energy, they would not be considered to be a machine according to the Mechanical Hierarchy and are considered to be tools because they are unpowered vehicles (Supers, p. 106).

What is "mechanical energy"?

Water mills and wind mills transfer kinetic energy from a linear direction to a rotary direction, but it's still kinetic energy. Sailing ships harness kinetic energy of the wind to gain their own kinetic energy.

Their sails can be classed as airfoils rather than simple machines though, so that might help with making a distinction.

[Ulzgoroth]

Originally Posted by Daigoro

What is "mechanical energy"?

Water mills and wind mills transfer kinetic energy from a linear direction to a rotary direction, but it's still kinetic energy. Sailing ships harness kinetic energy of the wind to gain their own kinetic energy.

The fact that they gain kinetic energy but have no means for usefully transferring that energy is I think the key consideration. A rotating axle is a source of power that can be used to run mechanisms. A moving sailboat isn't unless you stretch to suggest that its motion through the water means it could drive submerged turbines...

[Ulzgoroth]

Originally Posted by AlexanderHowl

Since sailing ships do not transform energy but instead transfer energy, they would not be considered to be a machine according to the Mechanical Hierarchy and are considered to be tools because they are unpowered vehicles (Supers, p. 106).

The bolded part appears to have no basis in the text that I can see.

[David Johnston2]

There is an inherent problem with this analysis quite apart from clippers being TL 5 sailing ships. (Clippers were not clearly inferior to steam ships. They were actually very competitive). You can't simultaneously get magic and electricity out of the same dynamo using the spell. The spell is converting the output into magic. The use of this spell to immobilize sailing ships while the wind blows would be just...goofy.

[temp]

1) With regards to all this discussion of which TL Clipper ships are, I am not sure that is the issue.
a)I used clipper ships for the math because I had decent data, thus they make a good example of how much power you can pull from a sailing rig. As near as I can make out from draw power, it is the amount of power in the machine, not how efficiently it outputs it, to what you can draw.
b) Has the TL chart been changed in 4th edition? In 3ed, (which are the books I own), basic pg 185, sidebar, Tech Levels - Transportation, 3. Sailing Ships 4. Fully-rigged ships 5. Steamships.
2) With regards to this business of "take-off points", if the ship was towing a barge that would otherwise be drifting, then the tow-rope would be a take off point and thus a suitable target for the spell? Seems physically odd, the barge starts slowing down, while the ship continues, and the rope does what? Magically stretches? This would boggle me much worse than David Johnson2's sailing ship immobilization effect...