rubber band propulsion

[d design]

So you have a big rubber band that goes up inside the mast and is conected to the prop shaft. You wind it up with shore power. and off you go. Almost no noise, no emissions, only a small amount of smoke, no oil changes, low maintinance, and no smell. No expensive heavy batteries. What do you reckon?

[Starbuck]

I guess if you got in trouble out there, you could reconfigure it into slingshot mode, and it would put you back on the beach.

[Panope]

A decent effort was put forth to create a man carrying, rubber powered aircraft. The goal was to fly the length of a runway. Sadly, the effort was not successful.

A Chance to Unwind – CAFE Foundation Blog

Steve

[seandepagnier]

the rubber band would have a very low energy storage, and add too much weight too high up. It would also wear out.


Instead consider a nickle titanium super spring low down in the boat (so you can remove some lead ballast to compensate) the energy capacity is still rather low, but the round trip efficiency is above 99% and this system could last hundreds of years, so cost is quite low. Because we don't need to generate a huge amount of power, just enough to navigate for a few miles, it is probably feasible, but the initial cost of the spring would be high as well as the customized systems required to efficiently utilize it.

Using lead acid batteries would likely be a more sensible storage option for a boat application. The spring is really only useful if you need to release/absorbe a huge amount of energy much faster than batteries can allow.

[d design]

Yeh but i like the idea of slingshot back to shore

[Terra Nova]

You were on the right track with the spring idea. But it is the rocking motion of the boat that causes a pendulum to advance one sprocket tooth, like in a huge clock, thus automatically winding the mainspring and storing energy for later release.

I once worked on a military project for a hand-operated generator; one straddled the frame and cranked it, somewhat like a bicycle, but by hand. Adapting this feature would allow you to operate a treadmill type device which would allow you to wind your spring or charge your boats batteries even when it was dead calm.

[Dale Hedtke]

How do you shoot yourselves anywhere with a sling shot? It's like blowing on your own sails. The physics don't work.

Since you're investigating alternative propulsion, why don't you consider a flywheel for energy storage? Regeneration could occur thru the use of a small IC engine or thru the prop. The mass could be kept low in the boat, displacing some of the ballast. Power companies are using them now and there have been workable designs for vehicles.

[Canibul]

Wouldn't there be a gyroscopic effect on a flywheel that would cause some issues when the platform it was attached to ( your hull) tries to move in three axis?

[atoll]

why not just get some sails and a mast

[HappyMdRSailor]

I thought for sure it was Jack who started this thread...

[HappyMdRSailor]

Originally Posted by atoll

why not just get some sails and a mast

Now that sounds pretty doable ???

[Dsanduril]

Check out:

The Windup Girl

and the others in Bacigalupi's future world. The whole world economy is based on food calories and high energy springs wound by giant elephants or waterwheels. And he has a pretty good (seems like) feel for the difficulties of getting a spring wound with significant energy.

I do like the idea for 20 minutes getting away from the dock, but suspect batteries and an electric motor are more practical.