My Dream, The Hydraulic Kayak (Hyak) is Over.

Miscellaneous and Personal Stuff I Must Share
1

Well, I’ll never develop it further. I failed. I just didn’t have what it takes in resources and know how and I’m getting too old and mentally tired to take it further.

Many years ago, while I was the production manager of Current Designs kayaks and interfacing with an American professor who was trying to develop a kayak with a human powered propeller, I learned in sea trials that a kayak could go faster with the leg powered propeller than paddling. Easier too. Of course the same holds for rowing. Leg power is far greater than arm power. Unfortunately, a prop operated kayak requires the recumbant position which I certainly didn’t find enjoyable and you have to be seated backwards to row.

That’s when I hit upon the idea of a using leg power to pump water through the kayak like a jet powered boat.

My first plan was two 4 inch diameter cylinders with pistons that were pushed alternatively right and left leg. They were connected so that when I pushed with the left leg, the right piston was pulled back as well for the follow up push. Water was extracted via a thru- hull at the bottom of the kayak and pumped into a chamber called an accumulater with air at the top of it (To modulate the flow) and discharged to the rear for thrust. Smaller lines to the bow and stern with valve controls at the cockpit for steering could be added. An open clam over the discharge which could be closed for reverse as well.

Problem was I could only assemble a crude propulsion unit. Too much water leakage. Efficiency of the crude prototype was way too low.

Then, to avoid leakage I tried to assemble a 16 inch diameter convex bowl shaped piston mounted on the back of my seat which rode on a track so that I could push the piston. The piston was pinned at the centre to a bowl shaped diaphram that I constructed out of fiberglass cloth and latex using the bowl as a mold. The diaphram was also conected to the rim of a concave 16 inch diameter bowl fixed to the kayak with opening at the centre to valves system. When a bungee chord pulled the seat/piston forward on the track, a check valve from the bottom of the boat opens and loads the volume enclosed by the fixed bowl,diaphram and piston , and when I push back, I load the accumulater and thrust systems.

Well I tried that, but once again the system was way too crude.

It has been several years now, but I’ve come to realize that the dream is over for me. I just don’t have what it takes to pursue it.

But I still strongly believe in the concept.

Leg power trumps arm power any day. To be able to sit facing forward with your ass firmly planted and starting with bended knee pushing till straight and resting while the bungee lifts your knees up is not all that hard. Imagine pushing a little lever with your finger to steer. Imagine you and your husband each in your own Hyak. Given that women are far closer to men in leg strength than arm strength, wouldn’t it be nice to keep up ?

It was a good dream. Its over.

Maybe not.

Maybe someone reads this lament and sees something in it and develops their own hydraulic kayak

2

I give you a ton of credit for trying.
I don’t have the patience to go after any of my cool dreams like that.
-D/a

3

Here is a major, though not unfixable problem.

A “jet drive” of sorts is fine as far as it goes. The problem is that it needs to be a large volume ejected slowly rather than a small volume ejected quickly.

Think of a paddle. When you are paddling efficiently, you are taking a large volume of water and just barely pushing it backwards. “Throwing” a small volume back at high speeds is NOT efficient.

For this jet setup to be efficient, you’d need to be pushing a similar volume backwards. The mechanics of HOW to do so is the trick obviously.

But you are right that legs are the way to go power wise. Then again, one of the main benifits I get from paddling is that it exercises my ARMS, which otherwise would get almost no exercise.

4

Could this one be improved on? If this product has made it to commercial status by now, it certainly isn’t well known in US markets.

5

The recumbant position in pedalling does not lend itself towards popular support. There are pedal powered water craft that do no require the recumbant position but then you have to sit so high you need a considerable beam or catamaran style floating platform that frankly has no appeal like touring with a kayak or a canoe.

6

I’ve forgotten the physics, but I remember the concern I had for comparing the momentum (mass times velocity) of the discharge against the momentum of a 250 lb person/kayak at low speed or just breaking inertia. I also was concerned about a comfortable frequency for pushing the piston which is why I made the diameter of the pump as large as possible (16 inches) and still look good under the deck of a kayak.

7

I like the general idea, and admire your attempt, though it does seem like a bit too much complexity (and weight?) for a kayak. But it does have one major advantage over the propeller and flipper leg-powered designs, and that’s the ability to run in shallow water and not having issues with getting tangled in weeds and fishing lines.

Speaking strictly of propulsion, legs are definitely the way to go, but IMO paddles are simply the natural fit for kayaks. The paddle not only provides the steering, but also aids with the stability and recovery from rollovers and near-rollovers. But for niche applications like kayak-fishing in shallow waters, something like your idea might just be the ticket.

8

They make a jet powered canoe that uses a small gas motor and pump. replace the motor with yourself and have at it.

9

I’m kinda tempted to be that someone. I have been chewing over the notion of a pedal-powered accessory for my own (absurd, experimental) boat - the Snow Pea

Being fairly deep-bodied, the Snow Pea supports a recumbent posture quite well. I was thinking I’d actually make a pedal-driven paddle-wheel accessory, designed to fit in between the main hull and the outrigger (knowing full well that paddle wheels are not optimal in efficiency - part of the rationale was deliberate choice of quirkiness), but one of the other design ideas I considered was a pedal-driven jet pump. I was thinking I’d cannibalise a bicycle for the pedal mechanism and rig this to run a water pump. The pump doesn’t need to be immersed, as long as it’s one that doesn’t require priming.

10

Paddle-wheels are efficient in still water. With the kind of waves in the pictures it should be fine. It creates drag while sailing thou.

11

Anything that’s recumbent, and narrow, and requires rapid leg movement is, IMO, bound to fail just through the bio-mechanical problems of a human body sustaining power output comfortably in that position while not tipping the boat over.

12

Isn’t the efficiency of a jet drive considerably lower then a screw drive?

13

It would be either-or. My boat ended up being accidentally quite modular - so I’d envisage deciding in advance whether I was taking it out for a day’s sailing, or paddling, as appropriate.

14

Not sure. Jet engines are more efficient than propellers on planes, but that may not be comparable to this, for all kinds of reasons, including the scale.

What about the pumping method though? I’m thinking a continuous rotary pump of some kind ought to be more efficient than a reciprocating piston pump, because in the latter, you have to overcome the inertia of the volume of pumped water twice - once on sucking it in (then a stop), then again to squirt it out.

15

Jet pumps operate very differently from a propeller drive. A propeller is a much better match for human powered devices, as it can develop significant thrust while running at a fairly low RPM. Jet pumps, with their need to force a high flow rate and discharge pressure rarely have any noticeable effect below 1000 RPM or so, and most require 4 to 8 thousand RPM to fully utilize the power being fed to them.

As for the problem of what direction you are facing, that should be a simply matter… Rather then any direct drive system, and it is what I thought first when I saw “They Hydraulic Kayak”, is that you would use two simple hydraulic motors. One connected to the pedals, one connected to the prop shaft. Then you just need two hoses between them to transfer the pedal force to the drive shaft. A bonus here, is with hydraulic motors, you can tailor the ratio to be what you want, but not be restricted in building a mechanical drive train.

ETA: Oh, and a jet engine is by no means anywhere close in design or function of a jet pump propelled water craft. One is an engine, one is a specific type of pump.

16

A further advantage could be the lack of need to maintain a closed-loop cycle for the hydraulic fluid (assuming it’s water).

17

What about some kind of turbine drive? Don’t those obnoxious PWC use something like that to achieve thrust from a water jet?

18

Did you consider a Tesla Turbine? Simple to construct, very effective with water, according to some. Not sure of the operating speed necessary in water, you probably need gearing.

19

This is roughly what I had in mind. But it does concern me. Given the complexity of the pump I suspect a relatively high degree of efficiency, To travel at 6 mph, the canoe requires A 3.75 hp motor. That is a lot more than the 0.1 to 0.15 hp that a reasonably fit person can muster over a 4 hour period. However I was only hoping for the ability to cruise at 4 mph, roughly a paddler’s cruising speed. The question is how much hp is required for the extra 2 mph

20

Go for it ! :slight_smile:

By the way I enjoyed reading your web site.