Collapsible Flettner Rotor Project

Thank you for the morale support. I'm digging in my butt and scratchin my head and occasionally checking if there's anything of value up my nose worth pickin.

 

Hydrogen may be safe as a fill gas in the balloon, but marinas and coast guard and .. numerous others might have doubts and prefer to take no risks.
That not withstanding, would there be any advantage to a lighter than air rotor?

 

http://www.harborfreight.com/8-in-bench-mount-drill-press-5-speed-60238.html

With half HP motor for $63.
Unlike portable hand held electric drills, this IS rated for continuous operation.

Don't know if it would tolerate the power of a 2.5 to 3 HP 3phase 220 volt swap motor?

Why am I the ONLY one that thinks a friction drive would work?

Chuck up a little rubber tire and let it roll the end plate.
Works on those little gas engines that mount on a bicycle and friction drive the front tire. :?

 

I'm taking a moment to explain my preferences for the tripod mast and define some terms. Choice of mast affects type of rotor mounting.

The rotor isn't functional in light air. Sailors bane has always been being becalmed. A great many of the developments in sails past and present has been for light air sails. Studding sails on clipper ships and super thin mylar spinakers today.

I need sails in light air and a mast to set them on.

One of the prettiest rigs of all time is the lateen. Below is photo of a lovely model.
Some of the greatest voyages in the age of discovery were aboard Caravelles. Columbus had two, Nina and Pinta.

Caravelles were rigged caravelle lateena (lateen sail) or caravelle rodonda (square rigged).

None of the caravelles were preserved, nor were their sailors.

We have some paintings, but artists usually are not seamen and artists are notorious for 'mechanical absurdities' in their depictions of machinery.

I believe Caravelles didn't cary spars and sails for two rigs, but rotated the lateen yard horizontal, more or less.

as in last of the posted photos.

I suspect we don't give our fore fathers sufficient credit for intelligence.

 

I doubt caravelle captains would accept a lateen sail set as in the 1st of the photos below. I think they rotated the yard to tack. Just as I believe they rotated the yard horizontal before the wind. To tack, I think they hauled the peak down to the deck on opposite side and let the former tack end of the spar go aloft. A seesaw manuever. Probably required little strength, the yard was balanced. and the sail NEVER presses against the mast!

This would make a lateen sail easy to handle and pretty much self tending. Just tip the yard side to side.

In 2nd drawing I sketched sheer legs as explanation of why I call the A frame sheers.

in 3rd drawing, I added a lateen sail aft. It can be slid higher and further forward to achieve balanced helm. it can seesaw in tacks. It can rotate to rodondo, before the wind.

And MORE than one lateen yard can be set on same mast!

There you have it.

 

Yes, you are probably the only one thinking a friction drive of the kind you envisage will work, though a “V” belt is also a friction drive.
I’m concerned you will spend all your time getting the drive to work, and miss the essential experiment. A friction drive like this will put a lot of off center axial load on the drive disk, and even with an opposing (driven or non-driven) idler, will use a lot of energy in an already starved system.

The original French bicycle drives used a ~2” diameter knurled steel wheel held onto the bicycle tire by the weight of the motor. The motor was less than 1hp, and the torque at the point of contact (between steel wheel and bicycle tire) was very low. They were singularly useless in the wet, or a hill of any kind, but fortunately France, especially Paris, is fairly flat.
For a lot of information on the practical sailing of Lateen rigs, read Tim Severin’s “The Sinbad Voyage” a fantastic voyage.

http://www.amazon.com/The-Sindbad-Voyage-Tim-Severin/dp/0399127577

The next post is not for an “A” frame mast, but free standing.

 

Though reducing the absolute weight of the ‘rotor’ would help in theory, in practice it will make no difference. The structural issue here is keeping the rotor in column whilst spinning, and whilst accepting lateral force. The issue therefore is stiffness, a materials science issue.

We need either a light (relatively), stiff material, or a material ‘system’ that can be made stiff (and light).

As an example, were we to make a rotor from a series of concentric interlocking drum chassis’s, and held them taunt with air pressure, the pressure would be the same all round each joint. Were this column to be displaced sideways, into a curve, the pressure trying to close the seam on the shortening side of the column would be the same as that on the other side. Hence, no positive “straightening’ force.

Alternately, were the same column of interlocking, concentric, drum chassis, being held ‘straight’ by an externally applied tension in the center, the shortening side would feel a increase in tension, whilst the lengthening side would feel a reduction. It would be self regulating, and self straightening.

Note; though hydrogen is ‘safe’ enough, this is not the same as being benign, especially in the public eyes. The Coast Guard, and the FAA, deal with public perception as much as actual science. Though hydrogen is the most abundant material in the universe, it does not exist on earth in its native form. Manufacturing it by the ton for transport use, and having it leak all over, may be quite detrimental to our atmosphere, we simply don't know.

There are a couple of options we have not explored yet. If you obtained some sheets of corrugated aluminum, the kind used for roofing, and rolled them into a tube (approximately 1m X 5m), corrugations along the axis, then added another flat sheet of aluminum, curved to cover the outside of the corrugations, and attached them together, this would be a stiff, self supporting column.

Are these sheets of corrugated aluminum even available in America?

It would not be ‘reefing’ but should be strong and stiff enough to be self supporting. It would need to be attached to a mainly steel disk/base as the local loads will be quite high. I have never bought marine grade aluminum, but aircraft grade sheet stock is available from Aircraft Spruce http://www.aircraftspruce.com/menus/me/index.html 2024 probably. This is slightly susceptible to corrosion, though ‘Alclad’ and the 5,XXX series should be resistant to salt spray.

Alternately such corrugated and flat sheets are available in galvanized sheet steel (much heavier) and opaque fiber glass for roofing.

The corrugated sheets and the flat sheets will need to be fastened together, and “Blind”, Cherry, or ‘pop’ rivets will do fine. Do not use these rivets on the fiberglass unless you put a washer under each ‘blind’ end, fiberglass will not handle the lateral force needed to ‘pop’ the rivet. See patent http://www.google.com/patents/US7347641 for details, but do not use these rivets. They and the setting system will cost more than your boat.

This assembly will require a lot of care to make accurately, pre-assembly, pre-fitting, and so on. Make the bolt fastening the fiberglass version to its (steel) base at least 3” above the end of the fiberglass, this product has very poor edge margin.

I am still concerned about rotational speed, can you confirm we are discussing 200rpm?

 

I believe daiquiri's specs were 390 RPM for the 1 meter dia rotor.

 

Alans mention of the glass fibre roofing material is on the right track IMHO, but not the best way to go.

That stuff is made from cheap chop strand matt, and is inherently weak.

Its easy to make your own mirror finished flat glass sheet, with decent strength cloth.'

hey - and while you are at it, why not curve the melamine coated MDF into a 6 metre half circle before you lay it up. and hey, why not incorporate rebated, strengthened edges to facilitate joining the two halves.

hey - isn't this sounding so much like a proven, easy to build method like the rotor catamaran ?

 

yep, 390 RPM.

 

That may indeed be the method I eventually use. But that is NOT a collapsible rotor. Which is the title of this thread. September is still some way off and I won't be with the boat until September. We still have some time to discuss various possible means of collapsing a rigid rotor. Or making a collapsible rotor sufficiently rigid.
I'm postponing discussing rigid rotors for a short while, because I don't want to merely duplicate someone else's experiment.

 

If the rotor was a belt of vertical tubes inflated, resembling some very tall very tough air mattresses stood on end and fastened together in a one metre circle. Would that give opposing tension and compression to provide rigidity?

 

Yes, in principle your vertical tubes, especially inside your visqueen tube, should give a reasonable vertical rotor, BUT.

The vertical tubes would need to be ‘over stuffed’ i.e. rather more than needed for them to merely fill the circumference, so the outer tube skin was a circle and not a wavy multi-hedron. This would take a bit of fiddling, not to mention several people, to inflate. You would have to make sure each tube got exactly the same pressure, but not from a common manifold, ie not connected ‘live’. Though you could deflate this on the water, re-inflating it there would be quite a trick.

This structure would not be stable enough to stand alone, so would need a mast of some sort.

If you NEED a mast, then all sorts of options are available. One of the best masts could be an “A” frame, braced with wire fore and aft, and available for jibs etc, but no lateen. Were the “A” frame braced forward (a tripod) with a solid spar, then a Lateen spar could be set between the “A” frame legs. Your original sketch of a tripod would preclude a lateen spar, but would allow jibs etc. A single raked mast, braced 4 ways, could be used too, but the mast itself will carry a high end load.

I still like the sail cloth option. The “pure’ advertising tube is extremely viable. Given enough tension, you might be able to stretch visqueen between two 1m disks.
My personal favorite would still be the sailcloth option, even if it is blue tarp, with hoops and reefing, from your original tripod masts, scaffolding, or real 8” diameter, 1/4” wall, aluminum mast sections.

 

Thats fair enough - I will chime in when you eventually get to the conclusion that collapsible idea is too much trouble.

Maybe it should have been titled "dismantlementable rotor". I think that is probably the practical path.

Two halves sitting inside each other on the boat, the trailer ... or something like that.

I can wait .....

 

Do you suggest something like this? Just disks and a center mast and a sail cloth tube fastened to all and each disk? All taut by tension top and bottom? All collapse in an accordion fold at the bottom once tension released?
Because I understood or misunderstood you were suggesting an inflated inner tube inside the sailcloth tube. I got a little obsessed with inflatable.

this wouldn't be terribly expensive. My drawing is a cutaway. You wouldn't see the disks inside the sail cloth tube.