New Drive System for Pedal Boats - Feedback Needed!

[pmdproject]

Hi everyone,

We are three business students from the Judge Business School at the University of Cambridge, UK. We are currently working on a project for a small company called Pulse Marine Drives.

They have patented a unique drive system for pedal boats, but currently have little idea about whether there will be sufficient interest in the product to take it further.

The drive system follows nature’s design, allowing for speeds of up to 15km/h whilst being both manoeuvrable and safe.

We thought that because everyone on here is interested in boat design, the users of this forum might be particularly interested in the boat and able to provide us with some very valuable feedback. Therefore we’d really appreciate it if some of you would watch a very brief video of the boat before completing a very quick 5 minute online survey for us.

The link to the video and survey is below:

http://qtrial.qualtrics.com/SE?SID=S...CwSwhwqM&SVID=

If you have any other questions about the boat or want to hear more about it, you can contact us via the feedback section of the survey.

Thanks very much for your time and assistance!

James, Richard and Will

[Lurvio]

I'm a bit lazy to fill questionaires so I'll reply here.

I find the need for use for both feet and both hands to control the boat a bit troublesome. To me a pedal boat should have at least partial hand free operation so I can handle a fishing rod or what ever else is needed.

Lurvio

[Jeremy Harris]

I'm at a bit of a loss to understand the "unique" bit. Flapper systems like this have been built many times before and one company, Hobie, has been quite successful in selling their very similar twin flapper system for a while now.

To the best of my knowledge, every previous flapper design has been shown to be less efficient than other systems, like propellers. However, they do have the advantage of being relatively free from weed entanglement, usually.

I would guess the biggest single problem with this particular design is its size, if it can only be fitted on something as inherently drag-inducing as a low speed catamaran. Those who are looking for a bit of performance might prefer a system that can fit a narrow, long mono hull, but then I guess this won't be aimed at the performance pedal boat market, anyway, so this may be a moot point.

I hope that Rick Willoughby sees this thread and chips in, because he's, without a doubt, our resident pedal power guru.

Jeremy

[Squidly-Diddly]

for my 'fish tail' I was thinking of having all the motion below the surface with only a couple inches of 'back and forth' where the standard kayak rudder is, to cut energy loss from splashing.

I was wondering about the 'left, right, left, right....' motion, and was hoping to just use my body to balance that, if needed.

I was also undecided/untested as to the gear ratio, and well as the ratio of # of input strokes to output strokes.

Have you considered reducing the splashing by using a narrow, steam-lined means of connecting the paddle to the drive, so the paddles will be underwater at all times?

A connecting rod, flattened on the horizontal, should both reduce water resistance on the back and forth as well as provide more strength for the back and forth motion.

Best of luck in your new venture.



Squidly-Diddly
Senior Member


how about a one piece pedal/paddle wheel across a canoe?
Is that what those two across seater 'pedal boats' have?

I'm toying with attaching a long 'whip' to my kayak rudder, so when I work the rudder back and forth the whip should give me some propulsion, and steering at the same time.

That might be handy for kayak fishing-where you want to be able to maneuver a little bit once you got 'fish on!' but still keep both hands free.


05-04-2010, 09:36 AM
Senior Member
Join Date: Sep 2007
Rep: 32 Posts: 192
Location: SF bay


Space/Weight seems close to equal, with slight edge to Hobie
as far as space and keeping out of the way. The Native prop flips up and forward for beaching, the Hobie fins flatten to the hull with pedal in the fore&aft position(pedals together is fins both down). The big sales points for Native is that it goes in reverse, for the Hobie that it beaches easily.

As far as inflatiable VS hard Hobies, the inflatable seems a little quicker off the line, and in quick sharp turns, due to lighter weight and flatter hull.

All three pedals boats were extremely stable, and had a somewhat TOO recumbent seating position that would take so getting use to, and I use a recumbent exercise bike regularly and prefer it to upright(never rode a recumbent) thus I would try a raised seat as an after market mod for comfort on longer calm water voyages.

VVVVVVVVVVVVVVVVVVVVVVVVVVVVVVV
Me, personally? I'm toying with replacing a standard rudder with an elongated Fish Tail drive which would be driven by Foot Slides rather than bike pedals or levers. This would be on a larger SOT like Prowler 15, as the sit-ins don't have the knee-room needed.
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
I'd also be interested in a rudder for a solo, or larger, canoe. The only problem with a canoe is it catches a lot of wind and takes everything you got to make it head where you want it to go. Otherwise the canoe seems like a more efficient, cleaner, hull than SOTs with their various full length keels, scupper-holes, etc.

I couldn't get the Paddle-Board going, I was only able to get up on my knees before I felt sure I was going to fall over, but I'd had a few drinks and I'm over 250lbs. Smaller folks seemed to have no problem. The one person I saw fall in from standing was a med-large 190lb? young man.
[right]

[gonzo]

There is nothing really new about it. If you want an exercise machine it will do nicely. As a boat there is no advantage over more conventional designs. Different does not mean better.

[Chris Ostlind]

Gentlemen,

With some modifications, this product might be able to compete with the other mass marketed products of this type: Hobie Mirage drive and the Native Watercraft Propel unit.

On your site, I suggested that you bring a boat, or two, to the Outdoor Retailer Show this summer in Salt lake City to demo the drive system in front of the many thousands of show attendees.

Something to think about, anyway, if you are looking for powerful feedback from the kinds of folks who would be selling a product such as this.

[MatthewDS]

It appears that the arm levers control the flapper angle of the attack while the arm pedals just move the flappers back and forth. I'm assuming that by varying the flapper angle, you can go forward, back, in circles? Just like, oh I don't know, sculling?

This means that it requires quite a level of coordination and practice just to move the thing forward. I'm guessing that this would be too hard for most people to operate, and too expensive for the rest.

It is however, hilarious to watch. Give it some sort of amphibian themed name (Frogger Drive?) and turn a few wealthy yo-yos loose with it, and viola! Instant entertainment for the rest of us.

[portacruise]

Just a matter of time on the flapper designs, Jeremy?

http://web.mit.edu/towtank/www/Pike/pike.html

Porta

Originally Posted by Jeremy Harris

I'm at a bit of a loss to understand the "unique" bit. Flapper systems like this have been built many times before and one company, Hobie, has been quite successful in selling their very similar twin flapper system for a while now.

To the best of my knowledge, every previous flapper design has been shown to be less efficient than other systems, like propellers. However, they do have the advantage of being relatively free from weed entanglement, usually.


I would guess the biggest single problem with this particular design is its size, if it can only be fitted on something as inherently drag-inducing as a low speed catamaran. Those who are looking for a bit of performance might prefer a system that can fit a narrow, long mono hull, but then I guess this won't be aimed at the performance pedal boat market, anyway, so this may be a moot point.

I hope that Rick Willoughby sees this thread and chips in, because he's, without a doubt, our resident pedal power guru.

Jeremy

[Jeremy Harris]

Originally Posted by portacruise

Just a matter of time on the flapper designs, Jeremy?

http://web.mit.edu/towtank/www/Pike/pike.html

Porta

Maybe, but I'm not at all sure that flapping systems can ever really be as efficient as other methods of propulsion.

The physics of any system like this tend to work against efficiency, at least for displacement speed boats, as to get a large swept area (for good low speed efficiency) flapper designs tend to have a high wetted area. This inevitably leads to greater losses than a system with the same swept area but lower wetted area. Add in the tendency for most flapper designs to have quite high appendage drag from their supports and pivots and it's difficult to see how they could rival something like a large diameter, high aspect ratio, slow turning prop.

The idea of mimicking fish is an interesting one, but it's perhaps worth noting that, if biological systems were capable of having continuously rotating parts, fish would almost certainly have evolved to have propellers rather than fins.................

Jeremy

[portacruise]

Thought the links below might be interesting.

Porta

Originally Posted by Jeremy Harris

Maybe, but I'm not at all sure that flapping systems can ever really be as efficient as other methods of propulsion.




85% for rigid? flapper

http://dspace.mit.edu/bitstream/hand...pdf?sequence=1



The physics of any system like this tend to work against efficiency, at least for displacement speed boats, as to get a large swept area (for good low speed efficiency) flapper designs tend to have a high wetted area. This inevitably leads to greater losses than a system with the same swept area but lower wetted area. Add in the tendency for most flapper designs to have quite high appendage drag from their supports and pivots and it's difficult to see how they could rival something like a large diameter, high aspect ratio, slow turning prop.


Here's a company that had an unsuccessful run at it:

http://www.tailboats.com/propulsion_videos.html




The idea of mimicking fish is an interesting one, but it's perhaps worth noting that, if biological systems were capable of having continuously rotating parts, fish would almost certainly have evolved to have propellers rather than fins.................




I believe this organism is one of the fastest for its size:

http://dspace.mit.edu/bitstream/hand...pdf?sequence=1



Jeremy

[portacruise]

Oops, here's the last one:

http://www.technovelgy.com/ct/Scienc...sp?NewsNum=845

P.

[jehardiman]

This is a copy of the technology used by the Scripps HPV submarine SubDude circa 1993 when it went into the Guinness Book of World Records for the worlds fastest non-propeller HPV submarine. Nothing new from a technology standpoint.

[Jeremy Harris]

Thanks, I'd read some papers from around 10 - 15 years ago on high aspect ratio foil efficiency (I think it was related to the MIT RoboTuna work) but I hadn't realised they'd got up to 85% or so. That figure does exclude the fairly high support and appendage drag, though, plus it's for a high aspect ratio system. The flappers in this thread have a very, very low aspect ratio, rather like the Hobie system, so I wouldn't expect them to be better than maybe 40%, if that.

Personally, I'd love to see someone come up with a really efficient flapper drive, but solving the practical problems of supporting and driving high aspect ratio foils, ideally foils that predictably change shape as they flap, seems a hard nut to crack (certainly I can't think of an practical way to do it, and I have given it some thought over the years).

The Tailboat probably had a reasonably good configuration, as at least they understood the need to use high aspect foils with minimal drag from the support and drive system, although their surface-piercing design must create some wave-making drag. I think their major problem, though, may have been the fact that the thing just doesn't look right, some may say it even looks ugly. Boat buyers seem to be a conservative bunch; not many seem keen on buying something that look a bit unusual.

Jeremy

[jehardiman]

Originally Posted by Jeremy Harris

Personally, I'd love to see someone come up with a really efficient flapper drive,

Yes, that is the issue isn't it. I have some concepts, but not really more efficient compared too the smaller foils, just more power over the short run, which is rewarded by the in water demonstrations right now.

[Tiny Turnip]

Originally Posted by Jeremy Harris

The idea of mimicking fish is an interesting one, but it's perhaps worth noting that, if biological systems were capable of having continuously rotating parts, fish would almost certainly have evolved to have propellers rather than fins.................

Jeremy

Actually, the biological propeller does exist, as seenin the rotating helical flagella of E. coli, but I presume it is unlikely to evolve above the bacterial level. It also appears to achieve agonisingly poor levels of efficiency!

http://physics.bd.psu.edu/faculty/ye...rs/swimEff.pdf