Rudder Hydropower Generator & Solar Panels

[latestarter]

I find your ideas useful in making me get back to first principles.

I will try to be brief in reply to various points, I hope it does not come over as being curt.

Originally Posted by Bahama

For example, all these hybrid cars are grabbing elecricity from the starts and stops,

Stops only

Originally Posted by Bahama

but my quest to capture power lead me to think of all the friction (drag) that is associated with sailing--there is a lot of drag this is required to make sailing work...

Apart from a sea anchor or when running before the wind, I can not think of a case where friction/drag is needed or helpful. When close hauled or reaching and with keels and rudders you are using lift.

Originally Posted by Bahama

On this same thought, I find it curious to be able to lower a water turbine at night while moored to capture any current movement.

Very sensible, this is free energy, the only differences is the water downstream of the turbine will be moving slower and just upstream the water level is higher

See http://www.seageneration.co.uk/ as an example

Originally Posted by Bahama

And finally, as a side note, I have drawn up some sketches to capture energy from people who are walking on the streets

The flaw in your idea is that you are ignoring the movement that has to take place.

Assuming you step on the pavement and it moves down 5mm, you then need to step up 5mm to get on the next part of the pavement. It would feel like you were walking up a staircase with very small risers. Any energy at the turbine is being provided by the extra effort the walker has to put in, to effectively be walking up hill.




Just to add to DaveJ’s explanation

The parasitic drag is made up from the shape moving the water aside and skin friction due to the viscosity of the water flowing over the surface.
Wetted area is the part of the hull, keel, rudder etc in contact with the water, the more wetted area there is, the greater the resistance. Ideally the cross section of a rowing shell is semi-circular as it would have the least possible wetted area for a given displacement ( unfortunately it would also have no stability)

The object of a rudder is to create a side force at the stern, to turn the boat.

Lift is at right angles to the rudder.

Drag is parallel to the rudder.

If the rudder is turned 10 degrees to port; this generates lift which moves the stern to starboard.

As the rudder is 10 degrees to port, the drag force on the rudder mainly slows the boat down but also pulls the stern to port.

The lift/drag ratio of an efficient rudder at 10 degrees can be in excess of 17.

So which is more likely to move the stern the way we all experience, a large force pointing roughly in the correct direction (lift) or a small force slightly pointing in the wrong direction (drag). The more drag from the rudder the slower the boat turns.



If you don’t believe me, I quote from 'All about Powerboats' by Roger Marshall (technical editor for Soundings magazine)
“An efficient rudder operates just like an airplane’s wing. It is a lifting surface, and turning it increases lift on one side, forcing the boat into a turn.”

Rudders would still work if the fluid in which they moved had no viscosity.

You could visualize the drag on the rudder as being the equivalent of a rope tied to the back edge of the rudder and being pulled backwards in line with the rudder. In the above example, this will be tending to pull the the stern to port not starboard.

[Bahama]

Originally Posted by latestarter

>>Stops only<<

Yep, I was just trying to talk of the concept, but yes, stops only.

>>Apart from a sea anchor or when running before the wind, I can not think of a case where friction/drag is needed or helpful. When close hauled or reaching and with keels and rudders you are using lift.<<

Actually, no, you've forgotten the entire purpose of the keel or centerboards... they are there to fight against the wind from pushing the boat leeward... there is HUGE drag here and that's the energy that I'm focused on. But having said that, I'm guessing that the drag from the keel would cause the same problems as the rudder that has been talked about. Frustrating though, because there is tons of energy being pounded on laterally from the wind as it tries to shove this big boat leeward.

>>The flaw in your idea is that you are ignoring the movement that has to take place.<<

I wasn't trying to explain the whole idea in great detail since this is a boat site, I just wanted to show that I like thinking about capturing free energy, it's an interest of my. But, to be quick on this... if what you are saying is "there ain't no free lunch" you are right, which is why I don't propose this for the highways... because you would simply be "taxing" (stealing) energy from the cars as they go by... but for people, stealing a few calories here and there is not going to get complains as long as I'm not making people do a stairmaster to get to work... so yes, I'm stealing some calaries from hundreds of thousands of people walking over these tiny plates to create enough energy to actually do something larger like move a turbine.

The plates would be hexagon shaped, and would pivot a few millimeters 6 different ways. The weight would not be noticed, and they would just move around as people stepped on them. Sometimes people would step on a plate that's already been lowered on that side, and so zero energy capture, but other times the plate will move, and when it does, energy is capture. The energy is simply stored until there is enough store energy in a "cell group" to make their contribution worthy of releasing on to a turbine.

There would be many ways to store energy into a "cell" (a simple tank either pressurized or non-pressurized using only gravity feed). I just wanted to point out that cells can be used similar to engine cylinders to steady out the feed rate.

Capturing mass energy of large objects is much more efficient that simply storing the linear movement. For example, I have a train run by and each car on the train clicks a lever that creates some electricity... 100 cars, 100 clicks that create 1.5 volts each for a split second.... OR, i chose to capture all that mass in the movement... I use gears for example to make 1 click of a car spin a wheel 1000 times, so now, my 1.5V becomes 1500V per train car. I only use the train car analogy to talk about mass... yes, the train was stolen energy from, but pretent the train is now ocean waves, and the movement that we're capturing is the pivoting of those long float barges that pivot and create electricity. I've not look that them, but I assume they are trying to capture mass x movement, not just movement. Same thing with a boat, especially while moored, there is a lot of energy out there with this big beast rocking about. E.g. just blowing up a some floating bags, and hooking them up to some extendable arms, and hooking those up to the boat at night could generate enough electricity at night while you sleep as your solar panel does during the day. They don't have to be far from the boat, just a few feet... they just need to move about and you just capture the energy.

>>Just to add to DaveJ’s explanation

The parasitic drag is made up from the shape moving the water aside and skin friction due to the viscosity of the water flowing over the surface.
Wetted area is the part of the hull, keel, rudder etc in contact with the water, the more wetted area there is, the greater the resistance. Ideally the cross section of a rowing shell is semi-circular as it would have the least possible wetted area for a given displacement ( unfortunately it would also have no stability)<<

But I was curious about the keel... I'll assume that it would not work for the same reason.

You wrote down a lot of other stuff that I'll look into so that I can learn more. Thanks for your note, I found it to be kind, informative, and objective.

By the way, the reason for my pondering of energy is because I really like my electricity and I'd like to use it onboard without having to drink away at my diesel, which I can't manufacture... so grabbing energy is a good topic to ponder.

If you think about it, having a wind turbine on board is going to slow you down from sailing... there's no free lunch, here's an example where we are willing to trade speed for power. When I look at that, it make me ponder, what if I designed an efficient narrow (6" wide) pontoon that floated along side of the boat (attached to it) and simply bobbed up and down, tilted, and I captured all that tilting and bobbing energy. Yep, it would slow me down, but so does a wind turbine... which would be more energy efficient, the elctro-pontoon or the wind turbine? I think it would be possible to beat the efficiency of the wind turbine for the same reason that it's more efficient to do just about anything that is physically touching vs. the inefficiences found in air to capture energy. We'll I'll keep playing around with this an test some stuff out to see what I come up with.

Thanks again for your thoughts.

Thanks for the kind email, I hope my reply comes across kind as well. I posted in inside yours with red color.

[latestarter]

Originally Posted by Bahama

Thanks for the kind email, I hope my reply comes across kind as well.

Yes it does. There is no point turning these discussions into another Origami boats thread.

In my previous post I said

"Apart from a sea anchor or when running before the wind, I can not think of a case where friction/drag is needed or helpful. When close hauled or reaching and with keels and rudders you are using lift."

You replied

Originally Posted by Bahama

Actually, no, you've forgotten the entire purpose of the keel or centerboards... they are there to fight against the wind from pushing the boat leeward... there is HUGE drag here and that's the energy that I'm focused on. But having said that, I'm guessing that the drag from the keel would cause the same problems as the rudder that has been talked about. Frustrating though, because there is tons of energy being pounded on laterally from the wind as it tries to shove this big boat leeward.

I was confused why you keep to a view of how a keel works which is wrong, then it struck me that there was one condition where you are totally correct. When the boat is not moving through the water.
In that case, with no movement there is no lift.

I used to race dinghies many years ago. Waiting for the start I would just let the sails flap and stop moving. The dinghy used to drift sideways as the centre board was using inefficient drag to resist the movement.
Pulling the main sheet in, the dinghy started moving. Even moving slowly the much more efficient lift took over, and the drift seemed to disappear.

It is similar to an aircraft flying through air creating lift.
If it was not moving, there is no lift, it drops out of the sky, the wings would create drag upwards slowing the speed of descent.

[DaveJ]

Originally Posted by latestarter

I used to race dinghies many years ago. Waiting for the start I would just let the sails flap and stop moving. The dinghy used to drift sideways as the centre board was using inefficient drag to resist the movement.
Pulling the main sheet in, the dinghy started moving. Even moving slowly the much more efficient lift took over, and the drift seemed to disappear.

It is similar to an aircraft flying through air creating lift.
If it was not moving, there is no lift, it drops out of the sky, the wings would create drag upwards slowing the speed of descent.

This brings me to question why they don't they have Centre boards/Keels that can change there profile to help resist the push the leeward (create lift to windward) due to wind forces. Imagine at wing style centre board that is like the BMX Oracle mailsail they used during the american cup race with the goal in a closed haul position as the boat speed builds up its pofile changes to resist the push to leeward.

Maybe the drag created will drop the boat speed too much that a boat on normal track will still get to the top mark at the same time as a boat pinching with this style centre board.

[tspeer]

Originally Posted by DaveJ

This brings me to question why they don't they have Centre boards/Keels that can change there profile to help resist the push the leeward (create lift to windward) due to wind forces. Imagine at wing style centre board that is like the BMX Oracle mailsail they used during the american cup race with the goal in a closed haul position as the boat speed builds up its pofile changes to resist the push to leeward.

What you are talking about is a tab or flap on the centerboard/keel. Very commonly used. USA 17 had a tab on its central daggerboard, before they took out the daggerboard and went with foils in the amas. Even the 12 Meter boats had tabs on their keels.

However, it doesn't do what you think it does. It doesn't produce any more lift than a symmetrical board, because the lift on the board has to exactly oppose the side load from the sails. Anything different would have the boat going in circles.

Instead of producing more lift, it produces the same lift at a different leeway angle, as measured between the boat centerline and the course through the water. Deflecting the tab (or rotating a jibing symmetrical board) rotates the bow off the wind, while the boat continues to follow basically the same path through the water. This allows the hull to align itself with the direction of travel, and it also changes the angle of attack of the foretriangle - resulting in different sail trim.

Maybe the drag created will drop the boat speed too much that a boat on normal track will still get to the top mark at the same time as a boat pinching with this style centre board.

The tab can be used to reduce the profile drag of the board. It allows the low-drag region of the profile drag to be centered about the operating condition, instead of being centered about zero lift. It does not have a significant effect on the induced drag due to lift, however, which accounts for the majority of the drag of a board.

[latestarter]

I agree with Tom's analysis, my understanding is they are so effective that a lot of design rules ban them.

[DaveJ]

Originally Posted by tspeer

What you are talking about is a tab or flap on the centerboard/keel. Very commonly used. USA 17 had a tab on its central daggerboard, before they took out the daggerboard and went with foils in the amas. Even the 12 Meter boats had tabs on their keels.

However, it doesn't do what you think it does. It doesn't produce any more lift than a symmetrical board, because the lift on the board has to exactly oppose the side load from the sails. Anything different would have the boat going in circles.

Instead of producing more lift, it produces the same lift at a different leeway angle, as measured between the boat centerline and the course through the water. Deflecting the tab (or rotating a jibing symmetrical board) rotates the bow off the wind, while the boat continues to follow basically the same path through the water. This allows the hull to align itself with the direction of travel, and it also changes the angle of attack of the foretriangle - resulting in different sail trim.



The tab can be used to reduce the profile drag of the board. It allows the low-drag region of the profile drag to be centered about the operating condition, instead of being centered about zero lift. It does not have a significant effect on the induced drag due to lift, however, which accounts for the majority of the drag of a board.

I have never seen them or heard of them, i've heard of the self jibing centre board though. This justs disapoints me, if we have such a mechanism why don't today designers put them on the hulls of all boats that could benifit from them. Not everyone races, and at some point we have to beat to windward, anything that made it quicker crusier or racer would be better.

[Bahama]

Flexible solar panels are now being used on boats--but has anyone mouted them onto a blow up raft that can be dragged behind?

For smaller boats that are challenged for space, this seems like a nice option, and it would work out well for a life-raft as well I'd think.

I would have 3 blow up pontoons and mount them in between the pontoons. This design would help to keep them from being overturned. Perhaps what I've describe is already out there, I've just not seen one.

[CDK]

Flexible solar panels are very poor performers. They are not really flexible but built up from lots of small cells that get damaged over time, reducing the output even further. The ratio of both price and surface area vs. performance makes them virtually useless.