Collapsible Flettner Rotor Project

Actually, I prefer 3 phase AC over DC. I also, before we are finished, want to look at using wind power to produce SOME of the torque needed to spin the rotor by direct mechanical linkage. Faster the wind blows, faster the rotor spins. For free! If possible, this would reduce the required HP for motor, and reduce the electrical load.
I can imagine how a number of conventional windmill setups could be incorporated. The problem I haven't solved with this issue, is how to conveniently, mechanically, reverse direction with a windmill? Probably need to be CP props I guess.

 

You might end up with having the oddest (and possibly the most costly too) home-built wind contraption on this planet, but it might work. Tacking would be something to watch in amusement.

Now seriously, even the Flettner rotor alone will be a complex and costly thing to build. I really wouldn't bother adding the complexity of a wind turbine and the necessary connections to the Flettner rotor.

But, speaking hypothetically, in case of a wind turbine - driven rotor, wouldn't it be better to avoid mechanical connections and create an electrical power transmission? Wind turbine connected to a generator, and the generator creating voltage for the cylinder-mounted electric motor. In that case, changing the rotor direction would be just a simple inversion of polarity with a switch.

It would be more inefficient than a mechanical direct link, but I doubt that you can create a truly efficient home-made mechanical link between the two.

 

You are correct. That makes it simpler, but much less efficient. I don't know of any windmills that spin faster than the wind, but some % slower than. Then loses in torque conversion to electricity, and additional loss re-converting to torque. Seems more logical to apply the torque produced directly to where torque is needed. Over simplified, but logical.

As to an expensive rotor system, I'm hoping under $2000 installed and running. Am I unrealistic?

 

Per blade, if you are lucky.

Small wind turbines have the power efficiency of around 0.25, even less. The power potentially available in a uniform wind V is given by the following equation:

Pmax = (0.5 rho V^3 A) Eff = 0.12 V^3 D^2​

where V (in m/s) is the wind speed and D is the diameter of the wind turbine rotor.
So, assuming a pretty high wind of 20 kts (10.3 m/s) and a power requirement of around 3500 W (as calculated for the Magnus rotor in my example), you would need a wind turbine with a diameter of:

D = sq.root( 3500 / (0.12 * 10.3^3) ) = 5.16 m (17 ft).​

That would be more or less like this Windspot turbine: http://www.allsmallwindturbines.com...0/271/Windspot 3,5 KW/RS-Energietechnik GmbH/ which costs roughly $10,500 . Same for this turbine by Kestrel: http://www.ecodirect.com/Kestrel-e4...rid-Wind-Turbine-p/kestrel-e400n-250v-500.htm. So, that looks like the general commercial price for a 3.5 kW turbine.

Now, these are wind generators complete with inverter, controller and wiring. Take away those components (around $2,000) and you are left with the mechanical parts worth $8,500. Take away the manufacturer's cost margin (on average 35-45%) and you get around $6,000 of pure cost of the finished wind turbine (no installation).

It makes roughly $1,700 per kW of power. That will give you the ballpark of the costs you might expect for a well-made wind turbine. If it is not quality and lightly made, it is not worth making it at all, because it will not deliver the power you need, will weigh more and might dangerously unbalance your boat.

Oh by the way, we didn't check if your boat could handle all that weight so high above the deck.

 

I meant $2 grand for the Flettner rotor. and I never imagined driving the Flettner entirely by wind power, nor was I planning to buy off the shelf.

I came across this picture. The website it's from has viruses and my protection software won't load the page, so I have ZERO details, except SOMEHOW they are harvesting energy FROM Flettner rotors. It's got me curious if you can do BOTH, get energy from the wind and simultaneously propel the boat? I think they look like oil refinery components and only superficially resemble Flettner rotors, but the search blurb said windpower Flettner ect.

Then there is this second picture from
http://www.fundamentalform.com/html/involute_wind_turbine.html
(safe to visit)

One of these on top the Flettner might help some. Could use the space at apex of a tripod mast structure. Seems the airflow is upward. I have no idea how you could put one inside a Flettner rotor and direct air in at bottom and out the top, but it's an intriguing and charming mental picture.

 

Ok, we have had a misunderstanding regarding the purpose of the horizontal-axis (HA) wind turbine. But the numbers I gave you regarding the power-diameter-cost relationship of a HA wind turbine remain valid and can serve you for cost-benefit analysis. Only one side note - since you are considering a smaller-sized wind-turbine as a support to the motor which drives flettner, then you should use even smaller efficiency figure in the calcs. I'd use a value 0.22 or even somewhat less.

Regarding that conical vertical-axis rotor, I see that the idea and the technical paper are dated back in 70's. Ever seen one around? Me not...

 

Thanks, many thanks again.

 

Wow, this have come a long way from its humble beginnings.

If you use AC, and preferably 3 phase for torque, you will need a 3 phase inverter rated for regeneration as well as full current during acceleration of the motor. A 3 phase squirrel cage motor WILL regenerate as its frequency is reduced, a very old trick.

Your electrician is wrong, <50V is technically ‘low voltage’ but this is a very old definition. DC can be dangerous, especially at higher powers, and salt spray, as interrupting the DC current can cause an arc.

A successful wind power boat was built in Australia (i think) by a Danish engineer. His successful design had a 3 blade horizontal spindle (vertical blades) wind turbine about 20’ diameter turning at about 30 rpm. This was geared to a wooden screw propeller about 5ft in diameter turning at perhaps 5’ rpm. It would go about 1/2 wind speed dead to windward. His success was due to the very slow speed, high torque, of the transmission.

I think the design as sketched is excellent, and fairly practical. As a suggestion. Mount a trailer hub as suggested on a wooden frame attached to the roof of the boat, so mounting can be modified as needed. Go cart brakes work in both directions, as do most disk brakes. Check the caliper mounts, this will be the limitation for direction. The electric motor will be so low geared (to 200 rpm and less) that getting any energy out of this gearbox (into the motor) will be difficult, and i therefor i suspect braking will be a non issue.

Attach to this hub a series of plywood disks, alternately 42” and 40” in diameter. Place a “V” belt in each ‘grove’ so formed, and drive the whole assembly with a “V” belt pulley. You will need an idler wheel to increase the ‘wrap’ on the small pulley.

This is what i had in mind for the upper swivel.

http://www.directindustry.com/prod/...ings-360-swivels-180-pivots-24533-377508.html

Spinning that assembly at 200 rpm will be a trick. The slightest out of balance, or even perhaps heel of the boat will cause whirling and/or Coriolis effect to the detriment of the boat, its attachments etc.

Check out my suggested fabrication in post #26, it will need high tension, but be light.

Here is a link to another rotor system fabrication, and ‘west system’ may even offer to help you?

http://www.westsystem.com/ss/project-brighter-world/

Using diesel electric, and choosing 3 phase AC implies an inverter anyway, so there is little harm in adding a electric wind generator to this system. It is easier to integrate several different systems using electricity as the common link, but loses might get out of hand. We learned this on the 787 i might add. You don’t need very much battery, but you do need some. The DC bus voltage for 400V AC is about 560V DC.

The work i did at Boeing was wind power generation, no futher detail allowed.

There is a whole wind farm on the south coast of England which includes the vertical cone shaped rotors you show, though much larger. University of Southampton i think.

This is a situation where you could? blow (force) air up the inside of your rotor and have it impinge on vanes and drive the rotor though this. Unlike water, this might work. There would be some slight 'entraining' effect, but you would need a large 'bell mouth' at deck level.

 

thanks Allan

 

Allan, and anybody wants to throw rocks?
Only fairly practical design? How can I improve it?

 

That article about the cylinders for http://www.westsystem.com/ss/project-brighter-world/

is a terrific guide to the process. "Searunner 34. A 48 DC electric motor (golf cart motor) powered each rotor from a bank of batteries wired through a speed controller....."

Its like the system I suggested early on, building half sections in a mould. The layup details are terrific to have.

". foam/carbon fiber sandwich construction to keep the weight down. We made each cylinder in a cylinder mold in four longitudinal sections with joggle seams at the joint .... foam was beveled at the edges and omitted at the joints and bulkhead attachment areas. The 27'-long panels weighed about 25 lb and the 21'-long panel about 19 lb........ We chose MDF sheets and aluminum for the mold structure and surface to assure accuracy of the component parts. Using cutting fixtures, we made the MDF formers identical."

It might be worth trying to contact some of the guys from the project.

PS $2000 per rotor is a bit cheap. I would budget closer to $7000, with all the trial and error. You would want to buy some engineering calculations too, to make sure it wont kill someone too much. Mr D might be able to do you a good deal.

Even $7k is a good bargain considering a new rig/mast cost.

The 'upper swivel.' would be a waste of time - not nearly strong /effieicnt enough.


Also, take note of the comment at
http://www.fundamentalform.com/html/involute_wind_turbine.html

"flapping sails and severe imbalances. The cloth sails were too loose for the high winds, and the leading edge bowed in and out 3 or 4 inches as it spun, adding vibration & slowing it down considerably. The sails luffed badly on the upwind side, caving in and rippling the surface coming into the wind. "


This might be what you get trying to make a collapsible rotor.

Dont forget, a cylinder has little windage when stopped. It would be a pain to lower when trailering the boat around of course.

You might be able to design a part rigid, part fabric construction.




I second Mr D's comments of trying to power the rotor from the wind.

 

Alan
I do like the inflated tube in a sleeve. I scouted out those advertising balloons as off the shelf inner tubes.

I'd like to find a long toroid balloon, I could have a pole thru the middle and the toroid could crawl up or down as I needed.

I originally was going to use ridged drum shells. So ridged isn't verboten.

I'm trying to repurpose some off the shelf item as a rotor, to avoid expensive molds and fabrication.
But please continue to suggest Mr Rwatson.

 

Alan

Anything in this weird phenomenon applicable to Flettner rotors?
Looks like a Flettner rotor on steroids!




http://smallblimps.lefora.com/topic...tor-Focuses-Solar-Radiation-Prod#.U5ZRxHbMxdg

"Air Screw: A circular fuselage aerodynamics is well known in the aerospace industry and can be rapidly engineered into ultra-lightweight high speed aircraft that never need fuel. The outside diameter of this fuselage can be covered by a clear polymer to trap the heat and provide a smooth aerodynamic surface."

 

First a question needs to be asked. Is this a ‘proof of concept’ rig as i have assumed, or is it a full design effort, a reasonably permanent rig. If the former, exact size, the use of corroding elements (steel etc), wood supports, plywood endplates, and lashings would be completely acceptable. If not, not. There will be a substantial difference in the cost, and probably effectiveness, of these two different efforts. I personally prefer the former, a ‘proof of concept’ because failures allow learning, and rebuilding.

The basic arrangement, twin forward spars, and one rear spar is excellent. Reversing the stance, one forward, and two aft, may slightly improve the triangles stability, a wider base. You need to decide whether the upper ‘end plate’ rotates or not. If not, then it can become a structural part of the ‘bridge’ between the upper masts, like the Kiel Proa.

I am concerned about the level of compression on these mast(s) and their stability. I am also concerned about the detail design of the connection between these 3 masts.

The tension along the length of the rotor, whether it is ‘solid’ ie stiff, or ‘flexible’ ie soft, is going to be quite high, if only to ensure its stability. If ‘soft’ then the masts also need to react the thrust forces extant as well. All these forces turn up as compression on one or more of the masts, and in the upper fittings/bridge etc. The mast(s) therefor need to be quite robust, i.e. of good diameter to assume these compressive forces whilst holding column, and need suitable bases as well. Old mast sections are fine for this, but they might need to be substantial, i.e. quite large diameter, to withstand the compression forces and be stable.

Any significant out of round, or out of column, of the rotor, will induce whirling, and/or corollas forces. This will be hard to control and possibly destructive, especially at 200RPM..

In fact his alone may be a fatal flaw in any inflatable solution. Column stability in a tube relies on opposite sides being in differential tension and compression. As gas pressure is constant within our pressurized tube whether divided horizontally (inner tubes) or not (advertising tube), the compressive side of the tube receives no increase in support as the tube/column starts to bend or kink. Unfortunately, the inflatable rotors shown in the patent application, may simply be impractical at any speed of rotation.

 

I suspect the site in post above is some quack pseudo science