I have been working on human powered watercraft

<The original content of this post was edited / removed by the OP on Tuesday. Thread will be closed now.>

 

One assumes you are referring to a single person craft?

Well, ask yourself this question. Firstly you need to look at the requirements to "beat" the record, in terms of the duration required to be a 'measured' and sustained speed. And then what follows next is, how much power can a human deliver and over that duration/time period? That fixes your power output - a key element in the speed. Then work backwards again, a floating vessel must not have its resistance than is required to achieve the desired speed with the given human power. Then design said floating boat that produces no more drag than the max allowable you have just established. That's it.

 

In what way - flawed?

 

Ahh...and that's the point. There are many ways to "skin that cat", in terms of optimising the power generated by a human into a means of propulsion.
But that is ostensibly a mechanical engineering problem, rather than a naval architecture problem, per se. But the true measure - is how much power is delivered at the prop.....how you achieve this, is up to you.

 

OK, a few thoughts.



It is not clear whether you are looking for a buyer for your record breaking vessel, or the design (and intellectual property rights)



Pretty much by definition, a record breaking HPV will require an athletic level of power input, beyond the ability of the majority of the population. Further, the design is likely to be tailored to the higher, athletic level of power output, and may not be readily operable by a non athlete.



For example, if the HPV used foils, the design of the foil to permit a record breaking speed will require a level of power to get the vessel onto the plane that is likely beyond the general populace. Foils designed in such a way that an average person could get the vessel onto the plane would be unlikely to achieve a record breaking speed.



It is feasible that an accumulator device, within the rules, could allow a non athlete to deliver the burst of power needed to get the hypothetical record breaking foiler flying, though increasing complexity of course.



Because of these factors, a record breaking boat will be likely to have an extremely limited application and market, and thus limited commercial value. This might explain a lack of response.



I understand your reluctance to offer any detail of your ideas, particularly if they are not protected; however I suspect members may be much more likely to engage if you can offer anything more concrete to discuss.



You mention the idea of essentially poling, or punting a vessel. My reading is that such a method of propulsion is excluded from the IHPVA record rules, although they might devise a separate sub class if there were interest.



There is a considerable amount of material on the forums on human powered boats, on a number of threads, notably the very extensive Pedal Powered Boats thread (Over 2000 posts.), which you may be aware of.

Pedal Powered Boats https://www.boatdesign.net/threads/pedal-powered-boats.23345/



The search function on the site works well.



There are some VERY knowledgeable and experienced designers who have contributed to the forum on this topic, (I am merely an interested amateur) including Mark Drela, and, notably Rick Willoughby (Guest625101138) and many others.

You will find some of this expertise at odds with your statements about propeller efficiencies and mechanical efficiencies for human power.



You may be aware of the Animal Dynamics Malolo record attempt project.



Very best of luck. I hope you are able to realise the project; It may have considerable value beyond and irrespective of breaking the record.

 

I think you’re presenting too many variables at once to stimulate meaningful discussion. Try breaking your concept into bite-sized pieces (hull, propulsion, human interface...). Incidentally, if you’ve developed a pedal system significantly more efficient than the existing systems out there, I recommend that you pursue development of that beyond this forum since its applicability is far greater, and arguably more valuable, than simply pushing boats through the water (heresy on this forum I admit!).

 

"...most things." What are the things nobody knows more than you about?

You gotta give up something: a sketch, a picture, a video, something other than talk.

'Cause you know what they say: "Talk is cheap, until you get the bill."

 

Some of your assumptions, that the record holding craft are seriously flawed, assume that the designers that hold the record were not brilliant. I would suggest that you rethink that. For instance, you've condemned an open prop and are assuming that a ducted prop would be far better. That is simply not true. At the speeds you're trying to go (above 20 knots) the drag from any prop ring would far outweigh any tip losses from a properly designed propeller. The efficiency of a higher aspect ratio propeller is very good. As to efficiency of power from a crank wheel, it's actually higher because the person exerting the force doesn't simply push with a constant force. Skilled performance cyclists exert more force when it is efficiently transmitted into wheel torque, (when the pedal force is effectively producing torque) and they don't push at the top and bottom of the stroke. Bottom line is that if it was easy it would have been done a long time ago.

 

The limiting factor in human propulsion is not leg strength or any maximum effort type thing. It is the rate at which a human can convert their chemical energy into mechanical motion. Modern bicycles are said to be more than 95% efficient at converting chemical energy into mechanical motion. Any improvements that can be made to the hardware must come out of that remaining 5%. You state that the standard pedal system is 67% efficient. I would like to know where you got that number, probably it is using a very simple model of only pushing the pedal down and not taking into account how cyclists actually use their muscles to spin the crank. To put it another way, they simply do not expend energy pushing on the pedal when it is not in a position to do any useful work.

In my opinion, anyone serious in improving human powered efficiency would be well versed in cycling biomechanics - since it is proven to be the most efficient. Such a person would not claim that pedals are only 67% efficient.

 

I think it is absurd that you accuse us (maybe just me) of being closed minded and hostile when you won't even engage in a discussion about one of your central assertions, a discussion which would reveal absolutely nothing about this great solution you supposedly have come up with. Additionally, you have no way of knowing if we are close minded or hostile to new ideas, you have presented none!

It is my understanding that cycling is the most efficient mode of transportation. The efficiency of converting human chemical energy into mechanical motion (modern high end road bike) is above 95%. There is very little efficiency lost in the pedal/crank method of transmitting energy - therefore a different technique of using muscles to move a mechanism cannot improve upon that except maybe by very small amounts. So yes, I am reluctant to believe that you have come up with something more efficient, something which gains this efficiency largely by replacing pedals.

You came to this forum to feed us clues, so that we could be part of your what, fan club?

I hope you will come back to this thread and let us know when your solution makes it's "day view".

 

So in essence you’ve figured out how to convert human output directly into rotational power, bypassing linear motion. I’ll invest in that and we can both become billionaires.

Incidentally, if you’ve already been granted a patent, is it still by definition a secret?

 

I am not replying to mr DHaggsway, but to anyone that could be mislead by his assertions.

What he is describing is using a very simplistic model of pedaling mechanics. What he is focused on is the amount of torque that can be applied to a crank at various points of rotation where the forces on the pedals are only downwards - as if weight were applied alternately to each pedal. He is treating this as if a person continuously exerts maximum effort (downward only) on the pedal through 180 degrees of rotation. Rather, in the real world a cyclist will apply force to a pedal tangentially to the circle that the motion of the pedals describe (always perpendicular to the cranks). So the forces turning the crank will not be zero at the top. No one that pedals wastes energy pushing on a pedal when it does no good.

There's more. Even if you are a pedal stomper with terrible pedaling technique it does not matter if there are zero forces at the top of the rotation and maximum torque when horizontal - because you would not be mindlessly expending your effort trying to push the pedal downwards when at the top of the stroke. You would spend your energy in small bursts when the pedals are in an appropriate position to make use of the effort. You exert your energy in short pulses and coast for the rest of the crank rotation - it is still very efficient.

It is widely accepted that cycling is the most efficient means of transport, it can be more than 95% efficient at converting human effort into mechanical motion. If that is true then it is absolutely impossible that pedaling is anything less than 95% efficient. If pedaling were only 67% efficient like DHaggsway asserts cycling would then have to be less than 67% efficient at converting human effort into mechanical motion. You can't take 100% of energy, run it through a 67% efficient mechanism and come out with an overall 95% efficiency - it is impossible.

 

A well designed chain drive can be as much as 99% efficient, when properly lubricated. Thus values of circa 95% are more for the "average" chain drive
Otherwise why else would systems such as motor bikes, conveyors etc with chain drives be driven this way if so inefficient....??

 

I assumed that the 95% efficiency claim was taking into account all parts of the system, such as the losses in the bearings and rolling friction - not just the driveline. But yes, I have heard that chain drives are close to 99% efficient many times.

 

Aahh..yes, indeed. More likely with most systems.
Going high-end, the value can approach 99% though.