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Kayak Propulsion.

Kayak Propulsion.

Kayak Propulsion.

(OP)
Is anyone interested in brainstorming kayak propulsion methods?
Something got me started pondering possible methods of kayak propulsion.
Hand power or foot power?
I tend towards hand/arm power.
What will be the most usable?- Push-pull with handles near vertical, or up-down with the operating handles near horizontal?
What will be the best means of power transfer, mechanical, electric, hydraulic?
For cost and weight, air cylinders are attractive. What would be the best fluid for a hydraulic system using air cylinders?
Lots of other questions.
Any discussion?

Bill
--------------------
"Why not the best?"
Jimmy Carter

RE: Kayak Propulsion.

Stability and steering need to be considered not just the propulsion.

Any motion that involves moving your whole body, or significant portion there of, may be an issue for stability.

If you use some kind of a hydraulic system, you'll have to consider environmental contamination issues from leaks. i.e. water based fluid may be best choice despite some disadvantages.

Posting guidelines FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm? (probably not aimed specifically at you)
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?

RE: Kayak Propulsion.

Hand/feet? Why? Use the hands for balance, control, and steering.

Use a ducted jet just like the drives on every jet-ski this will prevent any accidental contact with blades of any kind. Power it with a flexible solar array wrapped over the front and rear decks.

Keith Cress
kcress - http://www.flaminsystems.com

RE: Kayak Propulsion.

Accordian style footrest, directly piped to a jet. Overcomplicate it from there if desired :)

RE: Kayak Propulsion.

At the risk of weighing the fun down with some numbers... Well, actually, WAG numbers. I've never actually kayaked on a dynamometer.

Lightly paddling propels me at about 5 mph. I define light paddling as 15 lb per stroke. Assuming that the force I apply to the paddle equals the force of drag on the kayak, and guessing that the the pulses of propulsion must be 50% higher than the continuous hydrodynamic drag to maintain a constant speed, then I can estimate the power required to keep my kayak moving at 5 mph. Which comes out to about 100 Watts.

For any mechanical device to drive the kayak, it will need a supply of >100 Watts to overcome its own efficiency losses. For a propeller I guess 50% efficiency, hence 100/0.5 = 200 Watts delivered by the drive. Most kinds of reciprocating paddle would get less than that, but not necessarily.

So the simplest (in my mind) is a 200 Watt electric motor driving a small propeller. I haven't worked out the appropriate speed of the prop yet because I haven't worked out the size of the prop, either. But I can tell that for this to last for 1 hour, the battery would need 200 Watt-hours, or, at 12 Volts, a 17 Amp-hour battery would be needed. Those are pretty compact (4 would fit in a typical lunch box). Without trying to make up my mind just HOW to make the propeller work, I can tell you that it CAN work, and that it won't need to be bulky or difficult to fit into a kayak.


OK
I'm sure you've already thought of a little electric motor - and you want to do something else. Otherwise you wouldn't have asked!

What energy source do you REALLY want to use? Human power? A human can generate 100 Watts pretty much continuously (at least, humans that tend to get into kayaks can) There are many ways to do it. Mechanical power? You're dispensing with the obvious paddle power, but what do you want in exchange? Speed or distance? Electric power? Solar panels suck as prime-movers for mechanical things, if you've ever tried it, but they could be used to charge a battery that is. Hydraulic power? There's a readily available source of hydraulic fluid surround the kayak, so I'd be tempted to look for ways to drive the water through or around the hull of the boat. There are many ways to drive a jet of water. But there's no way to store it on board or make complicated intrusions into the hull - not if you expect the kayaker to enjoy paddling it, too.


PS I make no excuses for intermixing metric and stone-age units.

STF

RE: Kayak Propulsion.

Bill, what a great idea to practice thinking outside the box! Now, let me see...
Peddle-powered propeller is already on the market..
How about a swishing tail or serpentine motion? Perhaps generated by a T-bar footrest (some now control a small rudder).
Issues to look at:
  • Stability (as KANAT mentioned) - maybe provide some outriggers?
  • Available room and comfort for constant leg motion.
Application may be limited to lakes and calm rivers.

Will be waiting to see what you come up with!

Gary Bangs
www.flowserve.com

RE: Kayak Propulsion.

Big picture: anything that can capture more energy from a full-body motion (like sculling). The Hobie yaks are interesting for this reason: you can pedal and paddle.

Maybe stability improvements to the hull to work more harmoniously with the paddle motion.

The problem with getting too fancy is that inefficiencies can quickly add up to negate the gains.

RE: Kayak Propulsion.

(OP)
Thanks for all the replies, friends.
A couple of points for discussion:
Hands vs. feet: Traditionally kayaks have been paddled by arms and upper body. Many solutions to alternate propulsion use foot power.
What thoughts on arms vs. legs, not just on maximum power but also on stamina?
A jet drive has been mentioned. What kind of efficiencies can we get with a jet type drive?

Bill
--------------------
"Why not the best?"
Jimmy Carter

RE: Kayak Propulsion.

There is a group near where I live helping wounded vets get into kayaking, they use a small paddle wheel type arrangement that can either be hand or foot powered. I've never seen them up close, but I do see them out in the bay and they seem to work pretty well. They adapt to an ocean kayak (brand) into some formed in holes in the hull. It looks like they also add a small rudder. I have seen some of the pieces on the beach, so it looks like it all is pretty easy to put on and take off, as it appears they use rental kayaks most of the time. I did a quick web search but couldn't find anything on the group.

I'll see if I can find out when they have their next event and get an idea of the details, maybe some pictures.

MikeL

RE: Kayak Propulsion.

(OP)
Thanks Mike. I like the portability aspect.

Bill
--------------------
"Why not the best?"
Jimmy Carter

RE: Kayak Propulsion.

Just bear in mind lead acid batteries + seawater=toxic gas. Having said that I did build and race a solar powered kayak with an electric trolling motor. It was OK, but easily defeated by something like this https://www.youtube.com/watch?v=lz6q74bdNnk

If you want to get into this I suggest reading the IHPV website, in between the loons there are a lot of people with experience.

also

http://www.gizmag.com/go/7402/

and

http://www.openwatercycling.com/


and my fave

http://lancet.mit.edu/decavitator/

and the granddaddy of them all

http://flyingfishhydrofoil.com/


There's no doubt that legs are better than arms/upper body alone, in terms of power vs endurance. A quick glance in the mirror before it cracks will show why.




Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?

RE: Kayak Propulsion.

(OP)
I have been pondering a suggestion made by Keith:

Quote (itsmoked)

Use a ducted jet just like the drives on every jet-ski
One commercial application of the ducted propeller is the Kort nozzle.
I wonder if a Kort type nozzle or ducting would supply any advantage at the low speeds and fairly low propeller loading of a man powered craft.
Comments?

Bill
--------------------
"Why not the best?"
Jimmy Carter

RE: Kayak Propulsion.

As I recall, in aircraft when using Jet propulsion having a biG delta between velocity of the engine output & speed of the aircraft is in efficient. i.e. Turbojet V High bypass turbofan.

I'd expect similar may be true in liquid jet propulsion.

Posting guidelines FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm? (probably not aimed specifically at you)
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?

RE: Kayak Propulsion.

The ducting on a waterjet has to cause some friction loss.
Nobody buys a jet boat for its fuel economy.
Most people are amazed and dismayed at the amount of fuel a jetski can burn in an hour of hooning around.

However, a Kort nozzle brings several advantages to an otherwise open propeller, including the ease of turning the nozzle into a guard to avoid unintended interaction with swimmers, and lawyers.

Kort nozzles are almost universal on tugboats, so there must be other advantages that accrue at low speeds.

Mike Halloran
Pembroke Pines, FL, USA

RE: Kayak Propulsion.

(OP)
Thanks Mike.
I agree with your assessment of jet ski efficiency.
Kort nozzles are interesting. My reading indicates that they are most effective below about 10 knt. Above about 10 knt the drag offsets the advantages.
For slow speed they are claimed to increase the bollard pull of a tug boat up to about 30%. That's at full power.
My concern is that at the relatively low power and speed of a human powered craft, the performance may become non-linear in a negative fashion.
We may have to test a model to find out for sure.
Any other comments?

Bill
--------------------
"Why not the best?"
Jimmy Carter

RE: Kayak Propulsion.

Besides the lawyer interaction issue was the compartmentalization of the system it would provide. Weren't not real clear on the final application here. If you want a retrofit to existing kayaks, that's a lot different and changes the market because far less people are going to want to 'destroy' their kayaks verse people who'd like to reversibly 'try' a boost. Hence, the unitized jet scheme and draped solar which could result in zero holes on a kayak.

Also the issues with dragging a kayak on/off shore. A propeller has no chance there.

It's also unclear if you're trying to go really fast or just leave one's hands free for steering, photog, fishing, etc.

Keith Cress
kcress - http://www.flaminsystems.com

RE: Kayak Propulsion.

(OP)
Hi Keith:
I am thinking recreational. Easy to use. No speed records. Easy to retrofit. What has a chance of working, what is a good idea, what is probably inefficient.
Kick ideas around.
Thanks to you and everyone else for participating.
Yours
Bill

Bill
--------------------
"Why not the best?"
Jimmy Carter

RE: Kayak Propulsion.

(OP)
Thanks Mike. Not ready to give up on human power yet.
That little electric outfit may be a valuable benchmark to compare human power schemes against.
It may eventually come out the winner.
I wonder about a pedal power generator to charge the battery?
How do we calculate the efficiency of charging a battery?
Yours
Bill

Bill
--------------------
"Why not the best?"
Jimmy Carter

RE: Kayak Propulsion.

Quote:

I am thinking recreational. Easy to use. No speed records. Easy to retrofit.

If you lose the retrofit aspect and don't mind bringing a full wallet, I still really favour Hobie's "penguin-fin" propulsion system; they make kayaks for two, leg-powered, fins self-clearing when it comes to weeds.

Unless of course there's a way to cobble up a similar retro-fit for less money, particularly if you already own a kayak...which you didn't specify in your OP, Bill...

CR

"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]

RE: Kayak Propulsion.

(OP)
Hi crshears: Yes I do own a kayak, single man person.
I like the "penguin-fin" propulsion system. Will that system allow you to coast, relatively drag free or do you have to pedal continuously? I wonder, if you find yourself in shoals, how difficult is it to get back into deep water with this system?
A system where the Kayak could be launched (single handedly) and then have the propulsion system pinned into place would be nice.
But this thread was intended to be a general discussion. I hope to explore as many types of propulsion as possible, and discuss the pros and cons of each.
Please don't try to please only me.
I am not the only one here with a kayak. Different folk may have different criteria.
Let's keep this a general discussion.
Thanks for all the suggestions.
Yours
Bill

Bill
--------------------
"Why not the best?"
Jimmy Carter

RE: Kayak Propulsion.

It's easy to spot my wife in a lake full of kayakers. Out there among the dopey-dippers and swishy-flailers is a siren moving twice as fast with half the effort.

Most of the problems with human-powered propulsion are human. Good paddling takes proper technique. It also requires sensitivity and awareness of one's interaction with the water. Most casual paddlers exercise neither.

RE: Kayak Propulsion.

A number of years ago I saw a design rendition of a canoe/kayak propulsion system that was modeled after the lateral and undulating motion of a caudal fin, but not sure if it ever got to the prototype stage. Cannot find a thing on the web about it.

It is better to have enough ideas for some of them to be wrong, than to be always right by having no ideas at all.

RE: Kayak Propulsion.

Fish have a huge advantage with their sensory systems. They can maximize the efficiency of their movements by responding to every little variance in their surroundings.

I find this is what separates the good paddlers from the dippers and flailers. The good paddlers are constantly aware of the feedback of their paddle. They waste less energy on splashing or other pointless motion.

Perhaps there is room to innovate on this front. Paddles that better transmit feedback? Propulsion systems that respond to and minimize inefficiencies?

RE: Kayak Propulsion.

I once discussed a concept for an undulating fin with a friend of mine. We were thinking of way to make a machine that could either swim like an eel, or have fins running continuously along its side that would undulate, propelling a "torpedo". It might be of interest here.
The ideal mechanism to drive the fin was not obvious to us, which is why we eventually abandoned the project.
It needed to be robust and watertight, but at the same time needed many reciprocating elements sticking out.
Maybe some ideas can come up here that we weren't able to think of then.

STF

RE: Kayak Propulsion.

This is a fascinating topic but I am reluctant to get too involved because it can diverge into endless branches without some specific requirements to target. By way of brainstorming I will offer these thoughts.

>Legs are far more powerful than arms.
>Human power is very limited so efficiency is of utmost importance. This rules out high velocity jets.
>As a scuba diver I can attest to the amazing efficiency and simplicity of swim fins. Applying them to a kayak may not be simple.
>Wind resistance is an important factor to consider. Kayak paddles are usually set for the paddles to be 90 degrees from each other so the paddle in the air does not act as a sail to retard forward motion.
>A paddle-wheel mechanism would be very efficient but heavy and with high air resistance.
>Water resistance needs to be considered, particularly when when not pedaling.

It is always best to learn from the experience of others before reinventing the wheel. Thus it pays to look at what others have tried before:

https://www.google.com/search?q=human+powered+wate...

RE: Kayak Propulsion.

Before everybody gets all lathered up about leg power, please note that the typical kayak structure is, er, not optimized, for concentrated forces, as would be seen at the pedal assembly, and especially at the backrest.

I.e., a retrofit may require its own exoskeleton (and associated weight) just to keep from breaking the basic kayak.

That will almost certainly raise the CG of the modified kayak, compromising its roll stability, which is also not helped by the up/down dynamic inertial forces of flexing legs, not ordinarily of much concern to a kayaker.

In the interest of roll stability, you may end up with a proa.

Mike Halloran
Pembroke Pines, FL, USA

RE: Kayak Propulsion.

(OP)
This is interesting. It looks like a good arrangement to make good use of arm and upper body strength.
BUT
As it is it would leave the person much too high in a kayak. That said, the pivot points are not that low, and it is the placement or location of the pivot points that determines the characteristics of the machine.
A thought; Instead of the work arms going down from the pivot, how about riding Between the persons legs and then curving out to both sides to end up in the same position for the handholds?
The hydraulic shock absorber could be swapped for a cylinder to extract energy. The cylinder would be mounted towards the front instead of towards the back.
I'm thinking that the mechanism, that is the seat, the seat rails and the handle bars may be able to be inserted into a conventional kayak without structural modifications. It would depend on the size of the cockpit.
But the other problem remains; how to efficiently get the energy transposed into forward motion.




Bill
--------------------
"Why not the best?"
Jimmy Carter

RE: Kayak Propulsion.

To get serious energy out you'll be moving your C of G a lot. If you add in a moving seat to get max leg input it only gets worse. Your idea about putting the actuators between your legs is mimicking an ergo rowing machine

So I return you to my first point in my first post.

"Stability and steering need to be considered not just the propulsion."

(By the way, am I the only one who finds it a little ironic that you're considering copying an exercise machine configuration that in is in turn mimicking a rowing motion from a scull or similar human powered waterborne vehicle. One might suggest going the other way, i.e. modify a scull to better do whatever it is the kayak is doing that a regular scull or 'row boat' doesn't.)

Posting guidelines FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm? (probably not aimed specifically at you)
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?

RE: Kayak Propulsion.

(OP)
My picture was causing issues and so I have removed it. It was a picture of a pretty girl on a very basic rowing machine that used only arm and upper body movement.

Quote (KENAT)

By the way, am I the only one who finds it a little ironic that you're considering copying an exercise machine configuration that in is in turn mimicking a rowing motion
Good point KENAT. GRIN
The method of harvesting energy shown in your animation is interesting. The flywheel and recoil device may possibly be mounted on the fore deck of a kayak. Thanks.
I agree with the advantages of arm and leg movement for maximum power, but my kayak and many others do not have room in the cockpit for leg movement.
We have two design areas yet to explore in depth;
Transmitting energy to the propulsion device, and the propulsion device itself.
TheTick's comments may be foreshadowing some challenging efficiency issues.

Quote (TheTick)

Out there among the dopey-dippers and swishy-flailers is a siren moving twice as fast with half the effort.

Most of the problems with human-powered propulsion are human. Good paddling takes proper technique. It also requires sensitivity and awareness of one's interaction with the water. Most casual paddlers exercise neither.
And
I find this is what separates the good paddlers from the dippers and flailers. The good paddlers are constantly aware of the feedback of their paddle. They waste less energy on splashing or other pointless motion.

Perhaps there is room to innovate on this front. Paddles that better transmit feedback? Propulsion systems that respond to and minimize inefficiencies?

Bill
--------------------
"Why not the best?"
Jimmy Carter

RE: Kayak Propulsion.

(OP)
Thanks again for all the contributions and suggestions.
Kind of putting it all together:
Ease of use, least effect on stability, easy to retrofit, fairly good efficiency (I hope), Use of mostly off the shelf components with not too much modification or building from scratch. This may not appeal to everyone for various personal reasons but for me it may well be the Biggest Bang for the Buck.
The first component would be one of those small electric motors suggested by MikeHalloran.
http://www.torqeedo.com/en/products/outboards/ultr...
We can add a pull rope type exerciser as suggested by KENAT with an alternator added to charge the battery. I believe that the for and aft motion will allow upper body strength to augment arm power while having the least negative effect on stability.
We can add a draped solar array as per itsmoked's suggestion and have the battery on charge even while taking a picnic break.
For some folk this may be the ideal solution.
A compromise between easy installation, ease of use, efficiency and overall usability.
This may also end up being one of the most economical solutions as well.
Comments are welcome.

Bill
--------------------
"Why not the best?"
Jimmy Carter

RE: Kayak Propulsion.

Those Torgeedo prices look absolutely abusive - insulting - gouging.

There are literally hundreds available for less than $200US. Where do they get off charging $1,700+??!!!

$900 for a 45W solar panel!! That's only about 8 times markup...
ebay flexible+solar+panel+boat

Keith Cress
kcress - http://www.flaminsystems.com

RE: Kayak Propulsion.

What's that got to do with it?

Quote (Gouging;


9. to extort from, swindle, or overcharge.)

Keith Cress
kcress - http://www.flaminsystems.com

RE: Kayak Propulsion.

Sorry, I'm used to hearing Gouging in the context of price rises after natural disaster etc. on items like food, water and gas. Didn't seem like it immediately transferred to a 'toy' but fair enough I guess the dictionary definition might apply.

Posting guidelines FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm? (probably not aimed specifically at you)
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?

RE: Kayak Propulsion.

I think I first heard of Torqeedo at least 10 years ago, ISTR in the New York Times.
... where the reviewer recognized that the prices were quite high.
... but asserted that you got German Engineering, when that was a good thing.
... and that there was nothing else like it for sale at the time,
i.e., an outboard motor with usable thrust, decent range and silent operation, that you could stash in a carry-on, and actually carry.

I'm not sure if there are direct competitors to the original product even now, but they have expanded their product line upward quite a bit.


Mike Halloran
Pembroke Pines, FL, USA

RE: Kayak Propulsion.

KENAT; "Gouging" is across-the-board overcharging as I used it.

However, "price gouging" The two words strung togehter, is usually associated with illegal prices tied to shortages. That's probably what you were thinking.

Keith Cress
kcress - http://www.flaminsystems.com

RE: Kayak Propulsion.

Since we brought out the dictionary, "overcharging" is only applicable when a transaction is taking place / has taken place. A big price tag is not "overcharging" unless someone buys it, presumably due to limited options. Or because they want to feel good when they see the logo.

Price gouging implies an "on the fly" price increase for whatever reason (people are waiting in line to buy your limited edition widget, 49 sold and the final 50th one you double the price and see if the rest of the line goes home, or someone buys it.)

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