Collapsible Flettner Rotor Project

I believe a toroid "advertising balloon" can and should be made. One of the sites I posted earlier offered custom sizes. If they make a balloon 32 ft long one metre in diameter, it can be turned over itself to a 16 ft toroid. An outer shell of sail cloth or ripstop nylon can be sewn up and lined with half inch structural foam. The aluminum foil covered stuff. Stainless wire bolt ropes can be whip stitched to the two open ends. In turn can be whip laced to end plates. This semi rigid foam and fabric shell can be shrugged up over the inflated toroid as it rolls up a center pole.
With the foam stiffened shell and a center 'SPIT', certainly the cylinder would be stiffer and more rigid. Question is, rigid and stable ENOUGH? Any responder.

Just happens I have a 17 ft long, 3.5 inch dia aluminum spinnaker pole off a large yacht. Nice taper on the ends. Re-purpose as the 'spit' I think.

 

Yes, it didn't make a lot of sense to me either. Looks like a suggestion i saw a while ago though, when tension was placed on the elements, the semi-circles turned into “V” shapes, so we might as well have built a ‘warren truss’ in the first place.

In the airplane business, we got deluged by similar ideas, most simply impractical, some simply too heavy. Im sure the marine industry rarely got outsiders suggesting innovative hull shapes or structural advances.
Most forms of structure have been evolved already, and we spent an inordinate amount of time re-visiting older, and obscure, structural principles to see if technology had changed in their favor. These included many biological forms as well i might add.

Honeycomb, or sandwich, structure is the latest, it has real promise, if we could only work out how to make it fail-safe. All Boeing structure is either ‘fail-safe’ or safe life. The latter being rather rare as it is expensive for the operator.

The other promising one was Barns Wallace’s Geodesic structure. Again a winner, but hard to reconcile with PAX transparencies, doors, and wing attachments. A couple of us spent a long time at Brooklands (UK) studying the Wellington Bomber there, and we have all his papers, but we still only use it for space craft, the international space station for instance.

 

Some of my "out-loud' musing in THIS thread might qualify as quackery I suppose. My excuse is, I'm not an engineer. Just a stupid old boat driver and people manager.

 

The advantage of a toroid is no zipper or other crack in the shell is needed. It can be a one piece complete tube. The toroid will crawl inside.
illustrations below. How the toroid is made then how it crawls inside shell as center pole is inserted.
With fairly high air pressure in the toroid, I can't imagine how to make a rigid rotor lighter. fabric, foam and air. Only the spinnaker pole has much weight and it's less than 40lbs. Haven't weighed it, but a 5 gal water bottle (40lbs) weighs more. So say my muscles.

 

Regarding the spars, the square top shears is seen on numerous shrimp boats, but I'm not obstinate. A triangle and apex could easily leave room for the rotor, if connected a little lower and further aft. leaves a bit longer unsupported section of aft mast top.
I do prefer the single leg aft.

 

Alan may be thinking I'm ignoring the issues in his post.
I wanted to well consider my answers to his questions before responding.
In thinking them thru, OTHER questions developed.

My wishes and reality need reconciliation. The cost estimates of the full sized rotor and subsystems, by everyone's assessment, exceeds what I planned to spend.
It's nice to dream I could find good operational components, perfect for their task, by dumpster diving. Not gonna happen.

Returning to my original statement of goal. I intend to push one Albin with it's mate. Motor sailing is more efficient than pure motoring. Multiple sails spread over two boats, is too much for my wife and I to handle.

My hope was/is Flettner rotors as sails or in lieu of, could be easily handled remotely by the two of us. Motor sailing. Not pure rotor powered.

The forces involved in a 5 metre tall rotating cylinder are a surprise to me.

I think as proof of concept project and caution suggesting reducing dangerous heeling forces, and reducing costs of rotor AND motors, spars ect, constructing an 8 foot tall rotor rather than a 16 footer, makes sense.

Later perhaps two 8 foot rotors could be stacked to test the 5.1 meter rotor.

I'm unsure cutting the rotor in half will cut the cost in half.

I need to think some more, but I didn't want to delay TOO long in responding.

 

http://store.winnicksupply.com/Detail/ProdDesc.CFM?itemid=spd3611&Description=36

36 inch dia, 11 ft long plastic culvert under $500.

Bet somebody makes a smooth plastic pipe this size or similar!

 

I guess it that a question "why do you and your wife need two boats, one towing the other?" is a bit too delicate to ask... So I won't.

 

Not a sensitive topic at all, senor.
I want the ideal live aboard boat, ideal for us. We have houses in Mexico that resemble forts in some ways. They are secure when we are away. American homes aren't designed or built as 'forts'. and I can't afford to be innovative and build one.
A boat can be put in dry storage behind guarded gates for a reasonable monthly fee. Total annual fees less than the property taxes on the average house.
Haul out and launching can be expensive, unless the boat is trailerable.
Trailerable also adds to range and access to landlocked bodies of water. In Florida, trailerable is an advantage because the Atlantic and Gulf of Mexico are just a few hours apart by highway but a long sail around thru Florida straits and the Keys. For that matter, from the Atlantic to the Pacific requires maybe a 3 day trip towing a boat.
Trailerable boats are limited in size to around 25 feet by 8.5 beam and 4000 lbs. You can go bigger but trailers, tow vehicles, road permits, everything starts getting REAL expensive.
My Albins are 25 X 8.5 and 3800 lbs. That's a little small to live aboard. Sure there is room to sit down and lie down for several people, but storage space is limited.
Solution: if one boat is perfect in all ways except a little undersized for our needs, two are twice as big!

Explaining a bit further: It is still legal in many states in the USA to file a gold claim on public lands. You are entitled to build a cabin on your claim. There is a law called "The Prudent Man Rule'. If within a short period of time (90 days most places), the claim has not produced enough gold that a "Prudent" man would continue to prospect there, then you have to move on. The claim didn't "PAN OUT". You have to leave it in the condition you originally found it.
Many old gold claims that didn't pan out when gold was $20 an ounce, might pan out at todays $2000 per ounce. Also, gold continues to wash down from the "mother load". Claims that produced some gold then dried up, might be restocked after 200 years of lying fallow. The final temptation to gold prospect, is advances in technology. The old prospectors a couple of centuries past, could only extract nuggets and flake gold. Anything too small to be tweezered they missed. Most gold, the highest % form of gold in streams and rivers is flour gold. Very fine dust. Extractable with a centrifuge the old fellows didn't have. And we have metal detectors.
A boat makes a good prospectors cabin, and when it's time, the boat leaves, and the site appears pristine and un-disturbed.
And many gold prospecting stream areas are remote, scenic and naturally beautiful, and provide good hunting and fishing opportunities. What's not to like?

 

Now i know you could do a ‘proof of concept’ design, here is a plan. You can throw darts at it, that is what it is for, and i expect violent criticism too. I expect the rotor to cost far less than $1000, and the masts etc to also cost far less than $1000.

I am very concerned that unless your rotor is a reasonable fraction of full size, its effect will be so small as to be useless for test purposes. I propose a spindle of approximately 1m diameter, and 15’ high, rotating at 200RPM. Was this the rough dimensions given?

The rotor will be from solid blue builders foam, the masts, scaffolding, and a belt drive to a large geared drill, from a Honda generator.

It will not be retractable, but as pointed out, will have minimal drag when stationary. It is not quite full size, and if i understand correctly, requires about 20kt to work properly.

Method:

Get some 4 X 4” timber stock, and make a frame across the cabin top where the spindle is going. These timbers can be contoured to match the cabin roof as necessary. Attach this to hand rails and the like so it is stable and secure, but preferably does not use new bolts through the cabin top. Use galvanized metal brackets, stock from Lowes et-al, and galvanized bolts if necessary to join timbers, and attach to the boat.

To this, in the proper position, attach a trailer spindle, complete with hub (no brake). This need not be stainless, a coat of greece will suffice. Make sure this is directly below the mast(s) apex.

Acquire 2 X 20’ scaffolding poles, galvanized, and 2.5” diameter, a standard size i believe. Acquire another such scaffolding pole, 24’ long.

Attach a 4” X 4” timber across the foredeck, attached to cleats, or lifeline stanchions using “U” bolts through the timber. This should protrude slightly over the gunwale, and is to attach the forward poles. Using standard steel (galvanized?) scaffolding fittings attach the forward ‘poles’ to the ends of the above 4X4. Attach the 24’ pole to the stern, possibly using another 4X4 as padding, or a buffer. Scaffolding poles and fittings are often readily available used, from used builders yards. Make sure the poles are straight to start.

Where these meet at a point, connect them using standard scaffolding connector, the ball and socket kind. Shackle on a 3-4 part pulley at this peak. At about 1/3rd, and 2/3rds of the way down each scaffolding pole, attach a horizontal pole/pipe tying the 3 mast poles together, to stabilize them in bend. You will have to leave one pair of these braces out to install the rotor.

Now cut 5 plywood disks, 3 off at 42” diameter, and 2 off at 40” diameter. Glue/screw these together making a large diameter "V" belt pulley, and to the bottom spindle. This should be the hub section, and it can then be removed for reinstallation later.

Now take some sheets of solid builders foam, the blue stuff, 6” or more thick, and cut it into strips about 12” wide. Cut these lengthwise with a ‘birds-mouth’, using the ‘hot wire’ technique, so they can be assembled into a cylinder, 1m in diameter, and 15’ long. They could be 16’, but i think this might be too tall for the 20’ scaffolding sections. Glue these sections using alternate lengths to space the joints, into a cylinder. I use PL Professional for this, and clamp solid using cable ties, webbing straps, or steel packing straps. Attach/glue to each end of the cylinder, a circular plywood disk, exactly 1m in diameter. Have 12 equidistant markers around these disks, and make sure they line up. These will be ‘talking points’ as you cut the cylinder using the hot wire. Now use a ‘hot wire’ cutter, a length of steel wire, stretched to to about 16’ long (it looks like an old wooden ‘bow’ saw), and connected each end to a 12V car battery, to cut around the cylinder using the marked plywood disks as a guide. The cutting wire should remain parallel to the centerline at all times during the cut.

http://www.public.iastate.edu/~orman/air/cutter/hotwire.html

Now bond/screw the bottom disk to the ‘stack’ of plywood disks prepared earlier. This is the bottom of the rotor. We will need to attach 3 steel wires with turnbuckles, from these bottom plywood disks to the top plywood disks, on the inside of the foam, to prevent the ends pulling off the rotor (from halyard tension)

At the top of the 3 masts, about 3’ from their apex, attach a 64” diameter (1m + 24”) plywood disk. Attach it using standard scaffolding fittings, cutting holes and/or slots in the plywood as necessary. These slots will be covered with duct tape to minimize airflow issues. This will be the top endplate. It will have a 4 part pulley descend down through a hole in its middle, with a swivel between the pulleys and the hook assembly. The top of the rotor will be hauled up ‘flush’ with this fixed endplate during operation.

Paint is optional, though painting the builders foam and plywood might be helpful. It is a 'proof of concept' after all.

Beg, borrow, or rent a large commercial electric drill, several horsepower, with a reduction gear on it. Variable speed would be nice. Put a two belt pulley in its chuck, and attach it to the cabin top 4X4 frame such that it aligns with the large (1m) pulley at the base of the rotor. Now beg, borrow, or rent a portable generator, Honda or similar, and mount it in the cockpit, again using 2 X 4’s as necessary. The drill supplies the power, with change of direction, and the gearbox, and belt reduction, the appropriate rotor RPM. As the drill slows down, the gearbox WILL brake the rotor, stop it ready for running in reverse. No separate brake needed. If only smaller drills are available, get two of them, and attach one belt to each one.

As a complete alternate, you could make the sailcloth tube, with full circular battens, as described earlier. This would be lashed to the bottom disk using grommets, and to a top disk with the hook/spindle in its middle. This could be reefed, or doused at will. The scaffolding, with braces, should withstand the resultant compression from tensioning this sailcloth tube.

 

Don't need the Honda gen set. Have a diesel gen set in the motor box. the drill might serve for a test, but not continuous operation very long I'm concerned. Used motors are inexpensive and plentiful, even 3 phase 220v in 3 HP and smaller. I know a rewind shop that sells them. Gears might be harder to come by. Maybe garden tractor or moped gearbox used.
Thanks for all the suggestions. I WILL build something. Change orders are always easier and cheaper on paper. doing the due diligence in advance maybe the MOST important part of any project!

 

I inspected an advertising balloon (beer can) yesterday evening about 4ft dia and 12 ft tall. It appeared to be made from the same heavy fabric as inflatable dinghys and ribs. The surface is a bit rough and the seams were quite prominent, but otherwise a sturdy and likely candidate for an inflatable rotor. Visqueen shrinkwrap used for waterproofing cargo on pallets, comes in rolls, and when a length is unrolled and cut off, it is a large flexible plastic transparent tube. I believe about 6 mil thick. A tube of visqueen could be shrink wrapped around an advertising balloon as a replaceable smooth surface.
Maybe some fiberglass battens could be encapsulated between the visqueen and the balloon fabric though that would hinder collapsing the rotor.. I wonder if such a rotor would be rigid enough?

 

Any suggestions how removable battens in pockets could be incorporated?
The inflatable beer can was quite heavy, but I think had water ballast.
To offset the weight of the rotor, helium is very expensive and hydrogen too explosive, but could the air inside be HEATED? A hot air balloon rotor?

 

To answer myself regards the hot air balloon, inflation with more than one atmosphere pressure means more air mass than ambient pressure thus weighing MORE not less, and heating would increase pressure but not reduce weight of balloon. Negative buoyancy in air. Darnit!

 

Keep thinking, one of these ideas will work. When our managers started to get snarky about reducing weight, we usually brought up filling the tires with helium, helium filled paint etc. Tires are currently filled with Nitrogen.

Note; hydrogen is not dangerous unless it is mixed about 15:1 with air. It cannot explode unless it is contained, and in the above mixture. It was the cellulose dope (paint) that burnt on the Hindenburg, the gas was long gone. The classic burning hydrogen in a test tube only works because as the hydrogen is escaping, for one instant it is in the correct proportions, and the lighted taper is still glowing.

I do not believe a simple inflated tube as described as an advertising balloon will be stable enough as an unsupported rotor. Even the versions in the various patents with a series of internal cones, like fish bones, or fir branches, would probably not be stable under lateral thrust. However, if such a balloon were cheap enough, perhaps even free from the beer company, you could try it. Assuming it has a fabric flange around the bottom, lash it to a plywood circle/pulley as described above, and spin it on the ground, as a test. I doubt anyone could actually read it at 200rpm, but don't tell the beer company.

Adding hoops or battens will probably not help in this configuration, so don't bother.

Adding a shrink wrap surface could help a little, but it would only smooth out the disturbances, not eradicate them. Im not sure, but i do not think even the present seams and other surface disturbances in the ‘balloon’ will bother the aerodynamics too much. In fact, they may help, creating vortex generators, though these should be discreet, not continuous. Just spin the ‘balloon’ and see how much thrust you get, and if its dynamically stable.

If it isn't, all is not lost. Assuming you can add a fabric flange to the top as well as the bottom, you can suspend it between two fixed points. Just use the advertising balloon as is, no shrink wrap surface.

Unfortunately the spinnaker pole as described will be a bit short, but with a shorter ‘balloon’ could be used. Make a frame (X form?) from 4” X 4” stock in the cockpit, and place the spinnaker pole, or another, longer, pole in the center. Rig it so it leaned forward so the top is exactly above the ‘base’ of the rotor, with its trailer hub, etc. Attach galvanized wire stays from the stern, and both forward quarters.

Attach a plywood disk to the top of the ‘balloon’ lashing it to this flange there. A flange can be bonded on easily enough, though bond it ‘plastic’ side to ‘plastic’ side for best results. Accuracy is needed though.
Note: these 'flanges' were invented during WW1 (at Farnbourgh) to attach airplane bodies to gas balloons as antisubmarine patrol vehicles. They were called ETA patches.

Strictly speaking you need a 6’ diameter fixed disk just above the rotor as an end plate, for this configuration to be effective, otherwise the top 1/4 (or more) of the rotor is effectively not there at all. You are already compromising length, and possibly aerodynamic efficiency, so we don't want to compromise the whole rig into non operation, so invalidating the test(s).

Note, the compression down the spinnaker pole in this configuration will at least twice that on the ‘tripod’ version, the forces from the aft stay and the rotor are additive.

Note; the shrink wrap surface would work very well on the foam rotor though, very effective, and sheds water too.

More ideas please.