Collapsible Flettner Rotor Project

Discussion in 'Projects & Proposals' started by Yobarnacle, Jun 4, 2014.

  1. daiquiri
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    daiquiri Engineering and Design

    A good occasion to once again repeat what should be a the well-known fact by now:
    Wikipedia should not be used as a source of technical or scientific info. Its entries can be written and modified by anyone. Hence it is pretty vulnerable to errors, innacurate or non-verified claims, or even to straightforward intentional disinformation.
     
  2. Yobarnacle
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    Yobarnacle Senior Member holding true course

  3. rwatson
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    rwatson Senior Member

    Whoa boy. You are talking of thousands of dollars of research, when the job of single proven rotor is still a long way away.

    The BIG downside of that concept is that a cylinder is effective in any wind direction, while a flat rotor will be ineffective from several wind directions.

    The loss of deck area alone on an Albin would be catastrophic.

    get your mind back in the cockpit :)
     
  4. rwatson
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    rwatson Senior Member

    Not just Wikipedia. We have a lot of unverifiable 'opinions' on this thread already.

    Referring to actual research is fraught enough, let along 'thinking off the cuff'

    Now, if we can get Yoba to actually build one ........ :rolleyes:
     
  5. Yobarnacle
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    Yobarnacle Senior Member holding true course

    Thanks everyone.
    So far, I've learned a few certainties.
    The biggest dash of chill water was it needs to be a BIG diameter rotor. Drum shells need not apply.
    Also some hand-me-down roller furling gear won't serve for bearings.
    Darn. I thought I already had some of the parts needed.
    Rwatson recommends one n half meter (5 ft) diameter. Alan suggested 3 to 4 feet diameter. Rick remembers an 18 inch rotor an friend/engineer designed.
    In the photo below, the rotor is 2 ft diameter and 16 ft tall by eyeballing.
    So what size do I need. Off the shelf items that could be re-purposed are pretty scarce in 5 ft diameter size. I suspect kids inflatable wading pools would be insubstantial.
     

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  6. Yobarnacle
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    Yobarnacle Senior Member holding true course

    I have to have a plan first.
    Every September for the past 3 years, I head to Florida and work on my boats for about 3 months. I'm hoping to have the project details in hand when I get there.
    I will build a Flettner rotor or rotors of some sort. I'm figuring out the sort right now, with the aid of you gentlemen.
    Thinking off the cuff is innovation isn't it?
     
  7. rwatson
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    rwatson Senior Member

    Sorry - I dont recommend that size - it was an option on the calculator

    remember my attempt at sail power calculation ( still unchecked )

    "http://www.wb-sails.fi/Portals/20933...o%20&%20Theory
    19 knot breeze
    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 ."




    So, in another scenario in the calculator, you can get a theoretical 1000 newtons ( theoretical sail power ) in a 12 knot breeze. ( attached )

    for a 1 metre x 6 metre rotor




    So get your thinking cap on and your fingers typing
    OR
    employ a competent NA to do the theory for you.


    A few hundred dollars will save you a week of indecision.
     

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  8. Yobarnacle
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    Yobarnacle Senior Member holding true course

    Here is a possibility. only 44 inch dia instead of 5 ft.

    http://www.tubeproinc.com/products.php?view=114

    With 20 inch inner d and 44 inch outer d, by deduction, the tube inflated should be 1 ft thick.

    Plywood thom gates could be placed in between every two feet. 18 tubes reaching 18 feet high would be $600.

    Maybe wise to start with 12 ft stack and add on incrementally.
     

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  9. Yobarnacle
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    Yobarnacle Senior Member holding true course

    !2ft height compared to 18ft reduces the newtons to 2/3 of the higher stack. Purely linear.
     

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  10. Yobarnacle
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    Yobarnacle Senior Member holding true course

    I'm not asking anyone to do the work for me. Just help me stay on a logical practical path to a workable design.

    Both you and Alan nixed the multi rotor idea. I accept the critique.

    Shame though. I was thinking I might obtain BIG rotor performance with small rotors. Oh well.
     
  11. Yobarnacle
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    Yobarnacle Senior Member holding true course

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  12. SamSam
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    SamSam Senior Member

    That's from the patent posted by Nick.K.

    If you look at the 'references' to prior art in that patent, I'm sure there are lots of informational numbers and construction material suggestions.

    If you stack up a bunch of inner tubes, you'll get a lot more surface area compared to a straight sided tube, whether that's good or bad, I don't know.

    I don't see why a straight sided inflatable tube of some sort of modern fabric like rip-stop nylon, kevlar, maybe a gigantic condom or some other miracle stuff couldn't be made that wouldn't weigh much at all but still be tough and dimensionally stable.

    This is the 21st century, there ought to be something better than oil drums or truck inner tubes.
     
  13. Sailor Alan
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    Sailor Alan Senior Member

    Assuming Rwatson’s statement that the difference in L/D ratio between sails and the rotor was 1:13, then we would expect the new rotor to have a ‘size’ (whatever that is) slightly more than 10% of the sail area of the Albin 25. This is not an argument, merely a sanity check. Some of the independent calculations seem quite different to this. If the sail calculator got 100 newtons for the Albin, surely that is a goal to aim at. The “proa shown in the picture (at 2’ X 20’) from Kiel Week in Germany is a pretty slippery boat, so its total power required will be small compared to the Albin.

    I don't usually regard Wickipedia as an authority, but my ignorance of old rotor ships was profound. Our work on these rotors was to compare wind turbines of various kinds, kites and other lifting devices, wing-sails (like americas cup) and rotors etc for power generation purposes. It was a long time ago, and we were comparing slightly specialist applications.

    Please refer back to post #26, where i discuss/suggest a ‘pure’ sailmakers approach. Disregard the dimensions, they are clearly not yet correct, though the system itself should be cheapish.

    I would not recommend the stacked inner tubes, partly because no one else has mentioned a corrugated surface, and also i know those narrow “V” shapes between the tubes surfaces will have very high (interference) drag. Presumably enough to negate the extra surface area represented by the corrugations.

    I notice several proposals seem to have multiple “end plates’ on their rotors, but the actual ones built all seem to have only a top endplate. End plates, and fences, (end plates in the middle of a rotor) might be to reduce ‘spanwise flow’ as we call it, airflow toward the top of the rotor. The end plate at the top reduces the ‘tip effect’ of the rotor, meaning the top 1/4 is still ‘working’ and not subject to air flow sliding off the top.

    Disregard the dimensions here, they are assumptions, for demonstration only. If you wanted to pursue the NZ RIB structure, you would make an open ended tube, about 3’ diameter, and 20’ long, from truck tarpaulin or similar. Each end would have a ring of Cringles, or grommets around it.

    Now you would get a rubber bag, again about 3’ diameter and 20’ long, made from the identical materials as a truck inner tube complete with valve stem, and valve. A bit like the recovery ‘floats’ shown here.

    http://www.turtlepac.com

    The bottom of the ‘rotor’ would be a plywood platform, 3’ diameter, and arranged to rotate at the appropriate speed. It needs to be strong and stiff, as it carries the entire force of the rotor cantilevered above it. The tarpaulin tube is lashed to its perimeter, using the bottom Cringles.

    Now the ‘inner tube’ is placed inside the tarpaulin tube and a ‘lid attached. This could be a plywood disk about 5’ min diameter, 6-7’ better, as an ‘end plate’ This too is lashed to the tarpaulin tube using the cringles at the top.

    Now the inner tube is inflated to perhaps 100psi, which impinges against the upper and lower plywood end stops, and fills out the tarpaulin tube. Considerably more expensive than the sailcloth option, but completely collapsible, and repairable in the field too.

    You could perhaps fill a 44” diameter tarpaulin, or sailcloth, (or ‘blue tarpaulin?) tube with your proposed inner tubes, but they might be hard to keep stable, too many odd shapes as you blew them up individually.

    Please note; plenty of advanced technology materials we could use instead of truck tarpaulin, but they cost a lot. Sailcloth is pretty advanced material too, in its own right.
     
  14. Yobarnacle
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    Yobarnacle Senior Member holding true course

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  15. Yobarnacle
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    Yobarnacle Senior Member holding true course

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