Winsome the Pedal Launch

[David]

An alterative to the pedal system  would be the Hobie Mirage system.  This looks impressive with its folding wings for shallow water, and an easy action.

Regards

David

[Craic]

The Hobie Mirage Drive has already been adapted by several boatbuilders, even for bigsize Raid boats. Probably the first adaptation was done by Harm Rutten in the Netherlands, for his raid boat 'Willie von Tat'. http://www.youtube.com/watch?v=XAGpJRCWF-Y .
A very successful adaptation, we raced against them in the Dorestad Raid 2008 - and lost.
First Hobie sold the drive only in it's own kajaks, but when these adaptations started, they started to offer the mechanical unit as a module on its own.

[David]

For those asking, "What is a Mirage Drive?", it is a pedal powered set of penguin flipper fins that provide very efficient human power for small boats. Hobie has fitted Mirage Drives to a number of plastic shell kayaks, and they produce a lot of thrust and speed - more efficient than paddles or propellers. For more information, check out the following webpage:
http://www.hobiecat.com/kayaks/features/miragedrive/

DuckWorks Magazine features several articles by people who have retrofitted Mirage Drives to various kayaks and boats.

Mirage Installation Tutorial
http://www.duckworksmagazine.com/05/art ... e/free.cfm

Strider - A Mirage drive powered, two person launch
http://www.duckworksmagazine.com/09/des ... /index.htm

It's All in the Legs
http://www.duckworksmagazine.com/03/r/p ... /index.htm




David

[Julian Swindell]

There is an article about the Mirage drive in the latest edition of Woodenboat (or posibly Watercraft, I am not sure). The only very slight criticism of the system is that it only goes forward, no reverse. But it is very suited to shallow water as at the extremes the flippers are pressed up against the bottm of the boat. You can also just lift the whole unit out. I've never seen the system, but it has a lovely eccentricity about it, whilst actually working.

[Michael Rogers]

The article is in Water Craft, issue 84 (Nov/Dec 2010), p44.

I saw the Mirage Drive at the Beale Boat Show 3 years ago. It's beautifully engineered - genius rather than eccentricity. I didn't try it myself, but saw it being used on the lake, the little kayak absolutely stonking along without apparent undue effort by the pedaller. I believe it isn't cheap, but the R&D costs must have been high. My other query would be the long-term durability of the fins, but there must be information based on practical experience available now, because it's been around a few years.

A Mirage-propelled Winsome would be quite something. The WC article indicates that seat design is quite important.

If Mirage Drive were used for auxiliary, rather than primary, propulsion, the drag caused by the fins, even closely folded to the hull, would become an issue.

[Craic]

...If Mirage Drive were used for auxiliary, rather than primary, propulsion, the drag caused by the fins, even closely folded to the hull, would become an issue.

The module sits in a well and can be pulled up and out when not in use.

[Michael Rogers]

Claus, point taken, but doesn't that mean almost designing the boat round the drive? And water ballasting, for example, would presumably get rather in the way?

I wonder whether Jeremy has any comments about comparison with prop drives? One of the almost spooky things about the Mirage drive is that it doesn't seem to be unduly hard work. Clearly dolphins/seals etc 'know' a thing or two that we don't (until Hobie got to work).

David, the links you kindly provided to DuckWorks Magazine (what IS that, by the way?!) don't come up on my computer. Is that my Mac, or the links themselves?

[Craic]

Claus, point taken, but doesn't that mean almost designing the boat round the drive? And water ballasting, for example, would presumably get rather in the way?

Michael if you lookup the link I had given above to the installation on WILLIE VON TAT http://www.youtube.com/watch?v=XAGpJRCWF-Y . you would see that that was put into a waterballasted boat. And also, it was retrofitted into the existing boat. WILLIE did not have the drive the year before.

As to functioning 'seemingly effortlessly', believe me all the usual physics also apply for this drive.

[Jeremy]

I wonder whether Jeremy has any comments about comparison with prop drives? One of the almost spooky things about the Mirage drive is that it doesn't seem to be unduly hard work. Clearly dolphins/seals etc 'know' a thing or two that we don't (until Hobie got to work).

The Hobie Mirage drive is ingenious, fairly easy to fit to practically any small boat, has the advantage of being pretty immune from weed fouling and is pretty nicely engineered. 

Its only drawback is its relatively poor efficiency, it struggles to convert more than about 40 to 45% of the pedallers power into propulsive force.  This is a little bit less than a good rower, a fair bit less than a decent kayak paddler and a lot less than a good propeller.

Although efficiency is important, some of the other attributes of the Mirage drive make it a useful unit.  The ability to vary the flapper stroke allows it to be used into shallow water, a distinct advantage over the large diameter propeller needed to gain efficiency from a pedal boat system.  The way the flappers fold up close to the bottom of the hull to allow beaching is another useful feature.

Overall, it's a system best suited to the lightest possible hull, preferably one with a high L/D ratio and very low wetted area, as such a hull will be best suited to the relatively low thrust at speed (not the meaningless "bollard pull" static thrust in the Hobie hype) that the Mirage drive gives.  It's worth noting that the Mirage drive does give a more constant thrust than rowing or paddling, but less constant than a propeller.  It also doesn't create a significant pitching moment, so the hull ends can be finer than that needed for a rowing boat of a similar length.

As always with anything to do with boats, the Hobie Mirage is a compromise.  It trades propulsive efficiency for ease of use and fitment, but then so do designers of rowing boats and paddled canoes, or even sailing boats, come to that.

Jeremy

PS:  I know that I promised photos of my Electric Winsome, but life has intervened (I got retired a few years early) and I'm short of time to finish her until the Spring.

[Michael Rogers]

Thanks, Jeremy, as always an exceptionally erudite and succinct contribution. Very grateful. Incidentally, if your comments mean that you are, like me, now retired, you will not need me to remark that you are now busier than you've ever been! I hope (again like me) that at least some of the busy-ness is very enjoyable. Very best wishes.

Claus, I had indeed watched the clip before I wrote my previous piece, and I can assure you that, for someone who does not understand Dutch and has not previously seen the boat in question, it is not at all evident either that the boat is water ballasted or that the Mirage drive was retrofitted. Hence my comments. We did get little glimpses of beautiful workmanship, though.

[Jeremy]

Thanks for the kind words, Michael.  Unplanned early retirement has had a few adverse side effects, ranging from not having free time over the last of the Summer months until I retired a few weeks ago to being 'persuaded' that I now had time to fit the new kitchen (completed!) and new bathroom (about halfway done.......) leaving me no free time for the boat.

One thing worth noting about the Mirage drive is that its thrust drops fairly rapidly with increasing speed and it creates quite a lot of drag (many time greater than a propeller).  This means that it can produce quite a lot of thrust at low speeds, so could be used quite effectively as an in-harbour manoeuvring system on a moderately heavy boat at speeds up to maybe a knot or two.

Rick Willoughby, who used to contribute a great deal on pedal power systems on the Boat Design forum, and who has probably created the most efficient pedal propeller system I know of (well over 85% total system efficiency) did some comparative measurements of different human power propulsion systems and came up with pretty much the conclusions I've repeated here.  In particular, he noted that some of the claims that Hobie made for the unit, in terms of its efficiency and performance, were, shall we say, a little disingenuous.

Nevertheless, I like the unit and it certainly fulfils a particular niche in the market for human power systems.  I think if I were looking for a pedal power system though then I'd opt for something like the SpinFin (see here: http://microship.com/bobstuart/spinfin.html) largely because it can go forward and astern and can be fitted with a prop that's best suited to the characteristics of the boat it's propelling.

Jeremy

[Brian Pearson]

Hi Jeremy, I would love to see your electric Winsome if that were possible? Could the hull be used with little modification for a Mirage Drive. The Mirage drive is quite expensive but the SpinFin even more so.
I would have thought a ply panel kit from Swallow Boats for such a hull might be popular? If anyone else thinks so, and more importantly Swallow Boats think so, then I would be happy to donate 9 sheets of wonderful 4mm Bryunzeel ply to the project for the first hull kits. How many kits could we get from 9 sheets?

Brian