Collapsible Flettner Rotor Project

[Yobarnacle]

Collapsible Frettner Rotor Project

I'm interested in Frettner rotors as sails for small electric motorsailors.
I have the curiosity, have many of the parts, and desire and can afford an experimental drive.
Money is in short supply, but before anyone offers funding, thanks but no thanks. I prefer to not be held accountable how I spend money, except to my wife and myself.

This experiment has several hopeful outcomes:

An increase in knowledge, a benefit to the members of the forum. Many posts regarding various propulsion topics, lament the lack of comparison, one on one, with a similar vessel using different means. Since I have two identical boats, one has a diesel and conventional main and masthead jib, an opportunity exists to compare!
I'm asking for advice and engineering design help from the many expert members.
For myself, i'm hoping for an easily handled low power electric motorsailing rig. My intent is to attain a high degree of synergy with electric propeller and wind, the total benefit greater than the sum of the parts.
Now that already occurs with conventional sails and motors while motorsailing.
However, there is a difference; I intend to PUSH one Albin with the other as a composite tow, or integrated tow. Both vessels will have props and sails and can operate independently. But my wife and I are no longer teenagers. Having conventional sails deployed on two vessels simultaneously while hooked together bow to stern, sailing in tandem, sounds frightening. I wouldn't try it. Especially, just a man and wife crew and no other help. Hence the interest in Frettner rotors. I believe they can easily be remotely controlled if electric powered.
in addition, I read reversing the spin on the rotor reverses the vessel direction. BRAKES! A highly desirable feature! Thanks to Magnus effect.
Also there is another thing, the Barkley effect, that spinning the rotor at the same speed as the apparent wind, makes it INVISIBLE to the wind. No windage in a storm! Supposedly.
If so, that's advantageous. I plan on a collapsible rotor just in case.
I'd like to prove all these aspects on one boat, and then, with two in tandem.

I just happen to have a few dozen old drum shells. How and why I acquired so many is a long un-important story. I play drums, since beginning as a child of 8. That should suffice for explanation.
I also own the two Albin 25s. Because.
Because it's a well built great design and I like it. I got them at give away prices, and two boats provide twice the living space of one. And they only need one trailer, set up for one boat, to move them both, being identical hulls.

Okay, that pretty well covers the proposal. the rotor will be a stack of laminated wooden drum shells, smaller sizes capable of nesting in the larger drums. I have several or more drums, in each of these diameters: 16 inch, 15 inch, 14 inch, 13 inch, 12 inch.

Uploaded a rough sketch showing how three different diameters, each stacks of two or several segments, might appear. Using all 5 diameters, a rotor nearly twice as tall is possible.

And here is Flettners original ship 1925
https://www.youtube.com/watch?v=SXYjV2IpxGw

 

[Yobarnacle]

The cylinder is not tapered, that's just perspective. It IS stepped. Drew an outline alongside as clarification. The first upload didn't show up.

 

[rwatson]

I think thats a good approach.

To facilitate manufacture, I had often thought that you could make half drums in a mould, and join the two halves together. If you used recessed bolts to join the two halves, you could assemble the rotor on the deck of the boat, and not have to use a crane or try to raise the cylinder in one go.

In the attached illustration the half shell has reinforcing ridges inside, and this would support the narrower drum as it slides down inside.

I also attach a rotor calculator that came from the original Flettner Site

It allows you to put in the diameter of the rotor, and calculate the forces generated.

Once you have figured out how much power you need to have, this will allow you to calculate how big and fast you need your rotor to be.

 

[daiquiri]

That is an interesting project, Yobarnacle. I will be interested to follow its development and if you need an engineering help, just blow a whistle.

The telescopic part will be a challenge. In order to avoid adding weight up high above the deck, a closed-loop pulley system could be devised, actuated either manually or with an electric or hydraulic piston installed at or below the deck level. I think you will need an additional mast for this purpose, either internal or external to the rotor - but this is something which has to be verified and thought about.

And I would go with just two telescopic sections. Three sections will significantly increase the mechanical complexity, weight, costs and the possibility of malfunction.

Cheers


P.S.
It is Flettner, not Frettner.

 

[Yobarnacle]

thank you both. I've done a lot of thinking. now I need to find the words to describe the comic book in my head. Right brained.

 

[rwatson]

Mr D's comments are spot on. Collapsible is good, might I suggest a heavy duty fabric stretch on hoops as a starting point.

The design problems will be an interesting challenge.

The good news is that you dont have to worry about centre of effort for the rotor. Under reaching conditions, the majority of the drive is straight fore and aft. You wont end up with noticeable weather helm for example.


Added this link for future reference

 

[Yobarnacle]

Sailor Alan Sailor Alan is offline
Junior Member Join Date: Mar 2014
Rep: 53 Posts: 50
Location: Gig Harbor WA

Quote:
Originally Posted by Yobarnacle View Post
Bet you know a thing or two about magnus effect.
I'm considering building a Frettner cylinder from old drum sets I have stashed away.

Yes i know a bit about Magnus Effect, and a couple of attempts to implement them, Cousteau for example. I suspect you would be better off using old oil drums for the Frettner cylinder, and use the drum sets for collateral.

Why do we not see more boats/ships pumping air under their bows as a friction reducer?

Perhaps the same reason commercial airplanes do not use laminar flow, or ribletts, or e-beam, or surface heating to reduce drag.

Laminar flow does work, but requires such a smooth and clean surface that it is not practical. For instance, even a fly spot on the surface will destroy the laminar flow, so we, the manufacturer, cannot ‘guarantee’ the continuous existence of this flow during a flight. Hence the regulations will not allow the plane to depart with less fuel than needed for a ‘normal’ flight with the required reserves. One might get better fuel economy for some of the flight, but the real gain would be carrying less fuel (weight). Instead we concentrated on “aft loaded” wing sections, and the ‘potato chip’ wing where local curve is customized to exploit local flow.

Equally, ribblets, minute chevrons proud from the surface of the airfoil also work, but must be perfectly clean, hard and sharp, to work at all. Even when made from antistatic materials (self cleaning), they still weigh more than the fuel they save.

Finally, surface heating, and even active airflow control using e-beams, also work, but the energy required would need another engine, and lots more fuel than they save.

How about boats/ships.

Sound of joints creaking as he climbs on his ‘hobby horse’ or ‘soap box’; I think most of the development, and inventions, in the ‘pure' sciences, like engineering, chemistry, etc have been done. The next generation of such developments and inventions will come at the intercies of sciences, between chemical and electrical engineering, between mechanical and biological engineering etc. The exception being materials. These are being improved and developed all the time, and sometimes allow advances in current technology. Hence we should all be asking questions as did Yobarnacle, and Noah.

Someone on the forum suggested that Magellan had it right, and was the first successful circumnavigator using solar power. Equally, i build my boats out of wood, but even then they are not like Magellan's. They tend to be a wood core encased in long chain polymers, so though the wood bit is sort of sustainable, much of the rest is not. i suspect conservation is a good answer, and re-purposing a used FG boat a sound approach. Well done Yobarnacle, for re-using where you can, and reducing your use of other resources.

I “Invented’, found actually, bugs that eat diesel and produce electricity, but sometimes i wonder if i shouldn't have trained them to eat seawater and produce electricity.
end quote

I brought this over from another thread. Hope Alan doesn't mind and joins in this thread.

There is much to be learned about boats from studying airplanes. The RC fanatics are improving electric motors and controls almost too fast to keep up with.

I'm absolutely certain Alan knows the differences between boats and planes.
One important difference is a boat floats while a plane needs to work at staying aloft. Because of the critical load carrying ability of planes, less than optimum in efficiency isn't acceptable. I believe boats enjoy 'fudge' room planes can't. Not every pound is critical weight on a boat. if a bit of gear provides SOME benefit, isn't too large or too heavy, or too expensive, then why not have it?
The best example I can make regarding this philosophy is, boats carry spare parts. Planes store theirs in a hanger.

I respect Alan's input and wisdom and hope for more.

55 gal oil drums are flimsy when empty, and weaker yet once cut. Steel is also heavier than wood. These mahogany and maple laminated drum shells I have and so don't need to buy, are still glued together, still perfectly round, light and strong, 50 years after they were made.
They are pretty smooth as is, but several coats of epoxy or polyurethane and fine sandpaper will make them smoother still.
And IMHO varnished wood is prettier than oil drums.

There is no market for these shells. Though I did sell the fittings to restorers of other antique sets.

Totally off topic, but I retain 3 complete beautiful sets of Pearl fiberglass Cannons. Super thin, Super strong, Super resonant, Best sounding drums ever made and will last forever. And none made after early 80s. People frequently ask when hearing them if they are Gretch drums (also famous for voice). They are NOT getting donated to this Flettner project!

 

[daiquiri]

FLETTNER!!

 

[powerabout]

In the press I only see future trends on the high seas re costs/environment as gas and nothing else seems to interest the industry?

 

[rwatson]

.....

Yes i know a bit about Magnus Effect, and a couple of attempts to implement them, Cousteau for example.

he didnt use a Flettner rotor - they were non rotating aerofoil sections

 

[Yobarnacle]

FLETTNER!!

Flettner. thankyou.

 

[SamSam]

How about inflatable rotors using whatever they use in inflatable boats.

 

[Yobarnacle]

that might work!

anybody opined it wouldn't work?

 

[Yobarnacle]

playing with the magnus force calculator Rwatson posted, I'm only getting 100 to 250 newtons of driving force with small diameter rotors, even 10 meter tall skinny rotors.

that's only a few hundredths of a horsepower.
I could exert more thrust sculling an oar.

Am I doing something stupid?

 

[rwatson]

playing with the magnus force calculator Rwatson posted, I'm only getting 100 to 250 newtons of driving force with small diameter rotors, even 10 meter tall skinny rotors.

that's only a few hundredths of a horsepower.
I could exert more thrust sculling an oar.

Am I doing something stupid?

Jeremy isnt giving any guarantees for the spreadsheet.

First - have you done a sail calc for the marconi Rig ?? Remember ?

I called up
http://www.wb-sails.fi/Portals/209338/news/SailPowerCalc/SailPowerCalc.htm#Info & Theory

and made two sail 5 M high, and quite narrow in 19 knot breeze

( report attached )

It gave me around 80 Kgf - which converted to newtons = ~ 790


I then updated the Rotor calculator ( attached ) to a rotor 5m high, 1.5 meter wide with 200 rpm

On a beam reach, it got around 3300 newtons or 336 Kgf

Quite a big improvement over sail on the face of it.

Maybe we can get some others to check the results, as I am not an expert with the sail calculators.






http://www.translatorscafe.com/cafe/EN/units-converter/force/22-1/kilogram-force-newton/