Most compact watercraft for offshore touring

Dear all


Hello, I'm a design engineer from Korea. Mainly play in bicycle forums

I'm going to introduce my simple idea for the most compact human-powered-boat using a flapper-drive - eg. Mirage Drive -. I have an experience of working with an inflatable boat maker, Woosung I.B. in Korea. And rode a Mirage Inflatable Kayak, i12s(12inches, 53lbs) several times with much pleasure. But the inflatable Mirage boats were too heavy to move from a car to a shore even if the distance would be very short

So I started to imagine a combination of a flapper-drive(7lbs) and an inflatable surfboard(10inches, 15lbs). If the combination would be possible, I thought it could be the most compact watercraft for offshore touring. Very long range of sea-trip seemed to be possible!


Following my virtual experiments, the problem is the light weight of the inflatable surfboard. The light weight permits the up-down vibration of bow easily then the big vibration makes the propulsion thrust of flappers small.


In more large view, the only one useful component of the Flapper-force is the Backward-force. The Side-force is not critical because it is offset by a side-force of the Rear-flapper. But the UpDown-force just lifts up the bow of the boat and then takes down it. If you are on the boat, it is hard for you to feel the up-down vibration of bow easily because your position is on the center of gravity. It is why the vibration is critical for the light inflatable hull that the light bow makes the Twist-angle of the flappers SMALL. The small Twist-angle means the small Backward-force. If you hope to go fast, you should move your feet very fast. The speedy moving of feet will make you crazy on the deck.


So my solution is quite simple at this introduction. The one Inertia-tunnel under the bow in front of the drive.




The Inertia-tunnel uses the inertia of water inside itself to diminish boat's vibration without increasing the boat's weight. The boat still looks compact, light and cheap. Doesn't it?

But the originator of Mirage Drive, Hobie Cat company said, "The drag produced by your flap would be a drawback."

I agreed to the opinion because the seat position of rider is changeable. The Inertia-tunnel would work ideally when the hull's longitudinal axis is parallel to the water-surface. So I suggested an advanced idea below,

The next stabilizer idea named Inertia-dome. A streamlined design..


Its working principle has been from the wine glass under water. In the below drawing, every cup is filled with water under the water. Although the Cup-C has a small hole, it can have similar amount of inertia, compared with Cup-B. The benefit of Cup-C structure... there is no need to tilt the Cup when you put it into water.


Here is the following watercraft concept.



All of them have been rejected by the Hobie Cat
I think my ideas can add an useful amount of mass to the too light weight boat only when it requires additional mass to propel on the water without increasing the total weight of boat. But they don't like 'adding' ideas.

There is no patent of Mirage drive outside US. Even if I would manufacture a lighter version of it, that's not an illegal business in most of world market. The only one problem is that I respect its inventor, Gregory Ketterman

Any opinions or instructions are welcome.


Bintz

 

on the inertia tunnel or compartment; i once read chinese junks sometimes had a rudder in a bun witch filled up quick and slowly drained improving dynamic stability in sea waves
not so sure about inflatable surfboards and flappers but interesting and well illustrated and other flapper devellopers here may know a whole lot more on and have better answers than me

 

Wow Bintz....that is an EXCELENT post...GREAT graphics....thanks

 

Very interesting post, Thanks. Interesting comments you have on patents, some countries do not respect any foreign patents, or only pretend to. So I expect some very low cost counterfeits of the Hobie to appear at some point.

My hobby is tinkering with tiny, one man compact boats using electric drive for protected freshwater. The smallest can fit in regulation size airline travel bag including motor, battery and metal frame. I have considered adding lightweight human propulsion like the Hobie flapper, paddle wheels, props or fish tail drives. http://www.prophish.com/quickfin.html will give you some ideas of possible approaches. So far anything I have considered involving HP would appear to be more complex, heavier and slower over distance on the small scale I use.

Have you checked the stability with such a high center of gravity on your surfboard concept? Might tend to remain upside down when flipped. Also there is a lot more water friction and lower hull speed with a flat surface like a surfboard unless it can go up on plane. If you check the archives under Rick Willloughby, you can find some useful information. Hobie drives are considerably less efficient than props and neither can maintain any hull on plane for more than seconds, even with the best state of the art hulls-is what I read.

Hope this helps.

Porta

 

I'd just get a dolly if boat is too heavy to carry.

for kayaks I think the best kind is the bow/stern type, where it supports one end and you grab handle on the other end.

Those are small enough to carry on the boat without to much trouble.

 

Classification of inertia-tunnel and inertia-dome

Thank you, yipster
I didn't see the Chinese item yet but.. My ideas, so to classify..

• The inertia-tunnel is a kind of hydrofoils performing similarly to the Catamaran Raptor 16's outrigger of the respectable John Slattebo.
• The inertia-dome is a kind of bilge tanks having no Free Surface Effect.

I'm very happy to show drawings you like

 

Yes. The key to success is the quite cheap price for clone businesses But I won't sell it in US if I got a decision to manufacture it. I hope to remain as a good man

It is why I became to like you! Your hobby is my work Compact watercraft will possibly be the bicycle on water in the near future.

Great to see the Quickfin in action I tried to develop a similar fin-driven boat on October 2007. Its drawback was big energy loss.. hard to go really.. In my old concept drawing, you can see it could go forward

Following my experiences on inflatable surfboards, the big threat to rider is slip of hip when he sits on the board. A bit high centre of gravity could not be serious because the rider is a kind of animals. Anyway, the bow shape of my design should be changed into a lifted form

Rick Willoughby's YouTube channel is my favorite And I know well the most efficient Human-Power drive unit is a combination of pedal and propeller through my past development(YouTube video) on 2008.

Thank you for all your kind instructions, Porta
Bintz

 

If you get rid of all the complicated machinery and buy a paddle, it will save you a lot of pounds of weight and dollars too.

 

A bicycle is a human amplifier

The world-class bicycle designer Mark Sanders says, "A bicycle is a human amplifier."
You could get rid of your hull and paddle too

 

well put Bintz

 

Very nice!

To answer to the question of why it doesn't work for this particular design is because of the flatness of the 'boat'.
This results in a suction force from the local water, and since your movement isn't fast enough you can't overcome this.
It's similar to initial resistance of a car wheel. (adhesion)

If you use some transmission you could either create more force or faster movement, but it's better to use a more streamlined hull.

 

Thanks for your reply, haru.
But I didn't say that it didn't work or it didn't seem to work. Please check this YouTube video of an inflatable board driven by a paddle.

 

Thanks for the very interesting links! Here's one to the wavebike which I thought you might find of some use. http://www.roanoke.com/outdoors/biking/wb/xp-4890 (scroll down for picture). I prefer to stay as dry as possible in my creations, because of wetsuit an/or other associated hassles and this design is the best I have seen not having those issues. If this could be converted using an inflatable board and use CF support and drive parts, might meet some of your goals for light weight. Wavebike is a proven concept and faster than a pontoon because of the single hull, but I would think an recumbent version would do better in offshore wind and wave situations. Once wavebike is underway, no stabilizing outrigger device needed which might slow up or destablize things in heavy wind or waves.

The hammerhead is the smallest, most compact and stable HPB design I have seen over the years with good range and speed possibly exceeding paddles. See 4th picture down: http://www.humanpoweredboats.com/HydroFest/2000/P_TheBoatsAP.htm

Enjoy,

Porta

 

Sorry not to get back to you sooner. Recently I am busy in romancing a girl for the first time in my life
About the wavebike, thanks much for your kind helps.., I made a contact with one of its developers long time ago. And received two pics below with some notes.

It seems to me that the canard fin worked as a dynamic stabilizer.

Bintz