Please help a wanabe writer

  • #26
459
7
True. It depends on the angle of the Earth to the Sun, the velocity of rotation and revolution of the planet. It also depends on how the water and land masses are arranged on the planet, assuming it is an Earth type planet.

Assuming the planet has an Earth-like atmosphere and is mostly covered with surface water at it's equatorial region and the planet has a similar tilt to the sun, then the trade winds over ocean regions would be similar. The velocity of rotaion and revolution would change the strength and frequency of the patterns.
 
  • #27
minger
Science Advisor
1,495
2
This is a great conversation, but I have a quick comment about the windmill thing. I think that the windmill would only work in very few instances. For me, when I'm thinking of a windmill on a boat, the first thing I think of it, well won't the wind actually push the boat back?

I mean, the blades redirect the wind giving the wind a sideways velocity as a straight forward velocity, this turns the blades. But, the majority of the force acting on the blades will be pushing them straight back. It just seems that you are trying to get more energy out of the system than what you are putting in.

Now obviously this is only the case when you have a headwind. If the wind is off enough to the side, then the wind would only be pushing you to the side. You must remember though that the blades will get the relative velocity of the wind (i.e. must add on the velocity of the boat).

It just seems like if this were to work, then it would be a perpetual motion machine. The boat gets going, and the propeller moves it making it faster, thus making the wind velocity faster moving the propeller faster making the the boat faster, etc, etc.
 
  • #28
459
7
I don't think sailing into the wind would work either minger. I don't even think windmills would be as efficient as sails in any case. The only things I've seen them on are a few photos of small catamarans.
 
  • #29
Danger
Gold Member
9,607
246
I feel your pain, man. It took me over 20 years to design a fighter plane that could do 8 Mach for my book, and by then everything else was obsolete.
I'm not going to refer to any specific quotes here, because this thread is way too long for that. Basically, a windmill would essentially be a very low-efficiency sail, and therefore counter-productive as Huck pointed out. If you really want to use the propellor set-up, rather than oars, I would suggest that you look into providing a bunch of pedal set-ups all geared or chain-driven together. Paddle wheels are not really all that lacking in efficiency, though, and side-wheelers give the advantage of differential steering.
It seems to me, with my poor memory stretching as far back as possible, that the 'wind turbines' referred to on a ship were in fact experimental self-adjusting sails rather than being hooked up to some mechanical system of torque transfer. The theoretical advantage was about allowing a sharper tack angle than a conventional sail does.
A couple of things that I should mention as a reader and writer of the genre: Don't use the term 'sci-fi'. It's considered a serious insult, taken by an SF fan to be equivalent to calling his wife a whore. 'Godzilla vs the Smog Monster' or 'The Butterfly Effect' was 'sci-fi'. And real SF, as opposed to fantasy, does rely upon the scientific aspects being at least theoretically possible, so you're definitely working in the right direction by seeking tech advice. Remember though, that it is above all about the people. Technical mistakes are forgiven as long as you have a good story going.
 
  • #31
Danger
Gold Member
9,607
246
Ivan Seeking said:
I didn't see this mentioned. Maybe a few ideas are found.

Here are some Google hits
Thanks for the links, Ivan. Well, the last one. I don't feel like running that first one through my German dictionary, and the second one looks like someone took a charcoal pencil to my monitor. The 3rd one is pretty cool, though. I'd forgotten all about that thing, since the only time I saw anything about it was in some kids' book that I had back in the 60's. The feature involved building a model boat with sewing-thread spools wound up with rubber bands. I don't think that there was an explanation of why the damned thing moved.
 
  • #32
8
0
wrong. you CAN go directly up the wind. This is because the boat stands at the interface btw water and air.
the max speed of the boat will be s=w.e/(1-e), where w is the wind speed and e is the efficiency of the system (windmill+water propeller)
So if e=80% you go 3 times the wind speed and directly up to it ! This is simple to calculate (equal wind and water forces, and energy)
In that way, if the task is to go upwind, the windmill is MORE efficient than a sail !
 
  • #33
Using windmills to propel ships has been studied for a long time. The main problem is that a windmill has high drag. So in practice, the speed in any direction is typically around 0.5 times the speed of the wind. Most ships travel at higher speeds than that. So windmills would be best applied to slower boats such as fishing boats. A few have been built and sailed, and they worked as expected. An interesting approach would be to use a vertical axis Giromill so as to keep the center of pressure low, and to keep the blades outboard of the ship. For higher speeds, the vertical blades could be used as sails.
 

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