new kayak design took first place London Boat Show 2008

[john zimmerlee]

Now that I've won the concept award, I need help cleaning up the design of Stream Dancer.

This hands-free electric powered fishing kayak is controlled solely by your feet and operates in 6 inches of water without harming fragile underwater environments. Each heel rests in a sliding foot control which has linear potentiometers inputting pulse width modulation speed controllers which vary power to each of two submersible motors on either side of the kayak's centerline. The motors drive augers instead of props for less cavitation and stronger bite in the water, resulting in powerful turns and quick change in direction.

Stream Dancer's hull is now 10 ft long and about 38" wide. It's currently a tri-hull in the middle and kayak-like at each end. It seems to plough at high speed which leads me to believe I'm overspeeding the hull's max speed.

Should I make Stream Dancer's hull longer or modify to a blend of a planing hull? Any hints or software out there?

The augers are simple (no cupping) for equal performance forward and backward, but I'm challenged as to diameter and pitch for the 30 amp 12 volt motors i'm using.

The project can be seen at www.streamdancer.com

Four major kayak manufacturers have expressed interest but none can take on a new project this year. Guess I'm on my own to figure this out.

Appreciate your help,

John Zimmerlee
770-565-4420

[kach22i]

It seems to plough at high speed
I seem to recall the plough in the rapids video last year.

Are you sure other Kayaks don't do this as well?

I mean most of them have generous splash/spray aprons don't they?

Sample - collar type:
http://www.adventuresuppliesuk.com/boats_canoes.html
http://www.adventuresuppliesuk.com/adv_advanced_frame_kayak.jpg

How about adding a raise ridge to deflect water off the top of the bow and around the seated opening?

On a building an architect would call this a rain diverter, it's found over entry doors where there is no gable peak roof or gutter.

[john zimmerlee]

As a kayak or canoe breaks through waves, the bow splashes or goes through them creating drag and/or taking on water in the cockpit.

Under power, a displacement hull will reach max hull speed, then create waves which create a hill in front of the boat . . . ploughing.

I'm not worried so much about taking on water as I am cleaning up the efficiency of the hull to conserve battery power.

John
Stream Dancer

[Guest625101138]

The narrower you can make the middle portion of the hull the better it will perform at speed. You need to consider it as a trimaran with the central hull supporting most of the load and the outboard extensions normally just skimming the water until the hull rolls.

I cannot recall how the motors are mounted but they may need to be altered to work with a revised hull as suggested.

If you make the central hull say 10 inches wide and maybe 6 inches deep then it will have less drag at 5kts. Hull speed is still a constraint but it has much less influence on a narrower hull. If your target is 5kts then you need to be thinking around 15ft to get the best efficiency. Coming down to 10ft you will be getting inefficient above 4kts but impact is less adverse with the narrow middle hull.

The attached image shows a hull that is 8" wide and sits 8" deep when normally loaded. It is 12ft long. It requires 120W to do 8kph (5mph). Wave drag starts to build up over 12kph but it is reasonable up to the point.

This is the sort of central hull that will reduce drag and will not push as much water. You need to then mount the wing hulls so they just sit on the water with "normal" load. The wing hulls are best if they are say 4" wide and quite long so they give reasonable buoyancy without too much immersion. You want good roll stiffness.

It is possible to do proper analysis but it takes a bit of effort.

By the way congratulations on the award. You have done extremely well to get it to work with such shallow draft.

Rick W.

[john zimmerlee]

Thanks, Rick!

I've been thinking of a tri-hull . . . like the hulls on a Hobie Cat . . . long, skinny, and rockered . . . with a chair on top.

Two problems:
(1) Fishermen need a floor to stand on and to drop things in.
(2) The augers need a surface over them to prevent cavitation/ventilation.

Now, I'm thinking just two hulls 4" wide and 36" apart, maybe 8 feet long . . . with a tray and seat above. The hulls would have a shield attached to the inside wall to cover the augers at 6 inch depth. The shield would be strong enough to place the fisherman's foot on top, so that he may stand with feet at the waterline.

What do you think?

John
Stream Dancer

[kach22i]

Always leave something for a "new and improved" second generation model.

No boat is perfect.

[Chris Ostlind]

Hi John,

Rick W. is correct that skinnier hulls are generally faster. There are some caveats, however, and they play directly into what you are doing with your boat design.

For fishing in the areas you have intended, a boat with shallow draft and a short turning radius (as in turn nearly in its own length) will work best. Unfortunately, this plays directly to a minimized hull speed as you will be pushing a large frontal wave with a wide, flat, shallow hull. I don't see your boat doing enough speed to get it up on plane and I do not see that as an enhancement, in any event.

As with anything in boat design, you typically have to give something away in order to get the things that are most important to the overall design goals.

I would suggest that you make a very tight list of the design elements of the boat and list them in order of importance. I'm betting that top end speed is not one of the higher elements in the discussion.

If you do want to produce a boat that will move along at a good clip, then you’ll likely have to give away the maneuverability, or the shallow draft, or both, in order to get there.

I think you could take your boat out to a foot or two longer without messing with the turning ability and this will allow the main hull to be skinnier to some degree. The real trick is to balance the buoyancy of the main hull with the smaller flotation of the "amas", such as they are in the current design.

You could end up with a skinnier main hull, a pair of "outrigger" type hulls to the sides which are shaped and positioned for best purpose and still get the boat you describe on your web pages that has the turning responsiveness and shallow draft you seek. The result will be an improvement in speed overall with but a small compromise in the handling and utility.

At least, that's how I see it. Others may disagree.

This is a very tough design application with all the elements you seek being pulled into one package, so take your time and don't rush the solution. You already have a very interesting boat there, so marginal changes should be fairly easy to implement without destroying the present purpose and form.


Chris Ostlind

[Guest625101138]

Thanks, Rick!

I've been thinking of a tri-hull . . . like the hulls on a Hobie Cat . . . long, skinny, and rockered . . . with a chair on top.

Two problems:
(1) Fishermen need a floor to stand on and to drop things in.
(2) The augers need a surface over them to prevent cavitation/ventilation.

Now, I'm thinking just two hulls 4" wide and 36" apart, maybe 8 feet long . . . with a tray and seat above. The hulls would have a shield attached to the inside wall to cover the augers at 6 inch depth. The shield would be strong enough to place the fisherman's foot on top, so that he may stand with feet at the waterline.

What do you think?

John
Stream Dancer
John
I was not thinking of anything very different from what you already have. Make the centre hull narrower, deeper and longer. Lift the bridge to the side hulls higher. You can then put the augers inside tubes below the outer hulls or partially incorporated in these hulls. In fact I expect you would get better efficiency from a vaned prop in a tube but it would be more inclined to foul with weed.

The boat would look very similar to what you have now above the waterline but somewhat different below.

The tri will perform better than a cat if length of the main hull is over 10ft and the target is 5kts.

As Chris points out there are compromises. The most efficient hull with respect to power consumption will not turn the best.

If you post more detail on the weight and shape of the bottom of the existing hull I will compare a tri with overall beam of 3ft and the cat you describe aganst your existing hull. You need to nominate maximum length and desired speed.

Rick W.

[john zimmerlee]

Rick,

The current hull is different from the website. It now has sides that come down below the bottom of the augers. The center section is now a "V" hull with the bottom of the "V" at the same level as the sides. "V" is rounded at bottom and spreads to about 20 inches wide at a height 6" above the bottom.

I have photos, but can't figure out how to attach here. If you provide email address, I'll send them.

Turning is important. Speed is not as important as efficiency. Don't need to go faster than 6 mph.
If augers and motors can come off easily, the bare hull needs to be less than 65 lbs for car-topping.
Prefer not to get much longer than 10 ft for maneuvering and man-handling out of the water.

John
Stream Dancer

[Guest625101138]

John
I have attached a screen image of the reply window. If you place the curser over the paper clip icon then left click you get a new window that allows you to choose/select and upload files. Just select the photo from your computer file and upload. When you submit the reply it will have the photo shown reduced below the post. By clicking on the image it will come full size.

You can preview the post to see how the image looks when posted.

My email is given in my member detail. It is:
rickwill@bigpond.net.au

Rick W.

[kengrome]

Now that I've won the concept award, I need help cleaning up the design of Stream Dancer.

Hi John,

Whatever you do, be sure to keep your original design on the market, and add this "new and improved" design as a second model. There are all kinds of buyers out there, and some of them won't be interested in your 'improvements' because they will find the original model better suited to their needs.

It seems to plough at high speed which leads me to believe I'm overspeeding the hull's max speed.Well ... you could deal with this issue simply by using smaller or slower turning motors. Then the boat won't plow because its motors won't try to push it past hull speed. You'll probably get longer battery life out of it too. What percentage of buyers mention higher speeds as a desirable improvement? What other things do they talk about that are more important than higher speeds?

Should I make Stream Dancer's hull longer or modify to a blend of a planing hull?I's never going to be a planing boat. I think what you really need for more speed is additional length and an optimized hull form ...

Your idea of making it into a catamaran is good because it means each hull can be narrower, thus the overall resistance should be less. You'll need more than 4 inches of width though, unless you give up the shallow draft. Isn't shallow draft more important than speed to your buyers?

Or how about going with three hulls all the same size? I'm just guessing here, and Rick will know more about this than me, but since narrow hulls are the key to efficiency maybe three hulls -- each 10 feet long -- will come close to the same efficiency as one hull 30 foot hull of the same very narrow width?

[Guest625101138]

John
I have attached two images of what I regard as easily driven for 5kts. The main hull is 4m long.

This boat will achieve 5kts efficiently with all up displacement of 120kg. It requires 50W at each motor to do it. The prop shrouds shown have a diameter of 120mm and will give around 81% efficiency spinning at 2800rpm. The best prop speed for 120mm is 1400rpm but the motor will not give 50W on 12V.

I am reasonably confident shrouded props will be more efficient than augers and I believe you could make then work reasonably well in weed. They would need some sort of faired screen if weed was really bad. Such a screen would also provide an effective guard. It would add a little drag but it would not take much weed to add a lot of power demand.

A couple of motors like the D8095 would do the job:
http://www.transmotec.com/PDF/Catalogues/Motors_DC_Catalogue_25W-500W.pdf
Say the 24V motor will give 50W at around 80% efficiency. This should be big enough. Other option is to look at scooter motors but they are a bit big.

I would use an 8mm curved aluminium shaft with the motor mounted inside the stern of each outrigger. The prop shaft would be carried on two water lubricated acetal bearings with glass balls.

Rick

[kengrome]

Rick, what do you think of three identical slim hulls each 10' long and all submerged the same depth and therefore all supporting the same amount of weight? In terms of propulsion efficiency, would something like this come close to one 30' hull of the same width?

[Guest625101138]

Rick, what do you think of three identical slim hulls each 10' long and all submerged the same depth and therefore all supporting the same amount of weight? In terms of propulsion efficiency, would something like this come close to one 30' hull of the same width?

Ken
Unless you intend to go well in excess of hull speed then the wetted surface of three hulls kills it.

If you operate around hull speed then a single hull will be the best. That is why I chose 4m because the hull speed is 4.85kts so wave drag is just starting to kick in.

You only get an advantage with the really narrow hulls if you want to go faster than 5kts or 13ft is just too long.

Three hulls beside each other is quite different from one long hull of the same beam. You can think about it as each successive hull is drafting the leading hull. The rear one gets sucked along with the one in front benefiting from the moving boundary layer and the fact that the water is being pushed apart only once rather than three times. Hence you can have a longer bow and stern taper on the longer hull compared with the three shorter hulls.

Rick W.

[kengrome]

Thanks for your insights Rick.

In terms of John's goals here, I think he wants to keep the boat as short as possible. My thought was simply that three super-slim hulls carrying the weight equally might be better than two moderately slim hulls carrying the weight equally. If this is not the case then I guess the wetted surface of the three hulls drags more than the extra width and depth of only two hulls the same length.

Three hulls beside each other is quite different from one long hull of the same beam. You can think about it as each successive hull is drafting the leading hull. The rear one gets sucked along with the one in front benefiting from the moving boundary layer and the fact that the water is being pushed apart only once rather than three times. Hence you can have a longer bow and stern taper on the longer hull compared with the three shorter hulls.This is a very good explanation for why three short hulls of the same beam won't come close to the performance of a triple-length single hull, thanks!

I think John's customers are more interested in foot control than speed anyways. In fact, I think a plain old garvey or john boat hull would be a winner with his drive system in it!

:)

[Guest625101138]

Ken
I think the other images give a false impression of the size. I have placed a man on board to help scale it. This guy is big - maybe 90kg and 6ft tall.

Rick W.

[kengrome]

Aah, you said 4 meters above but I was thinking 5. Your new picture makes it clear the boat's not 5 meters long!

Your boat looks really nice by the way. It's only 3 feet longer than John's existing boat so maybe this one would actually fall into his updated performance requirements.

Edit: What's the displacement and draft at the waterline shown?

[Guest625101138]

.......

Edit: What's the displacement and draft at the waterline shown?

The displacement is 120kg and the draft is 150mm. From memory the WL beam of the main hull is 350mm. The boat is 1m overall beam.

Rick W.

[john zimmerlee]

Wow, you guys really know your stuff!
Thanks for all the drawing and comments.
Hands-free operation is the main focus. Shallow water operation is a close second. I have explored shrouded props. THought that would be very efficient. What I found was that smaller props didn't work very well; the prop needed to be an expensive fan type; if the kort nozzle was designed correctly, reverse was inefficient; weeds were a real problem; the depth required was too significant; and the propulsion was more like jetdrive, which didn't reverse quickly. Then I ditched the kort nozzle and created a tunnel in the hull that sloped down at each end. My thought was the water would be pressurized when it went up into the tunnel, lessening cavitation.

That was wrong. Cavitation was obnoxious. Performance was slow.

When I finally gave up on kort nozzles and lifting water up into tunnels, the performance increased by 25%.

Augers have surface area which grip the water for rapid turns and quick reversals. Simple augers work equally well forward and backwards. Props lose two-thirds of their performance in reverse.

I think the hull needs rocker. The bow and stern have rounded bottom edges which could be narrower. I'm thinking that the bow wants to rise while underway but the bouyancy of the stern is making it dig in.

The prototype has been butchered so many times for modifications, it is beginning to look very ratty!

John
Stream Dancer

[kengrome]

John, from your explanation it seems the augers are the best solution for your boat.

If speed is not one of your customer's big concerns (and I suspect it is not) you're probably better off keeping the hull as-is, and lowering the top speed of the augers if you don't want it to make a bow wave.

In fact, I think a plain old garvey or john boat hull would be a winner with his drive system in it!I said this in an earlier post and I still think you should create a second model based on a jonboat instead of modifying your existing design. Jonboats have universal appeal. Several people can ride in them easily and comfortably. They would be cheaper to manufacture as well. A jonboat will give the boat a much shallower draft too, and you said this is your second most important goal.

Or if you really want your second model to be faster instead of shallower -- and not push up a bow wave -- just use Rick's design for your second model, then make the jonboat your third commercial hull.

I think the hull needs rocker. The bow and stern have rounded bottom edges which could be narrower. I'm thinking that the bow wants to rise while underway but the bouyancy of the stern is making it dig in.Instead of trying to modify your current design, why not start from scratch? Adding rocker will shorten the water line and deepen the draft -- not exactly in line with your stated priorities.

I think your drive system is the real innovation here, and you should produce a number of different models with your drive system included. Then buyers will have a choice of several dramatically different boats -- all with the same drive system -- rather than another 'slightly improved' version of the same hull you're already making.

Thinking as a potential buyer, I would prefer a choice of different hull designs ... and I would go for the simple jonboat model regardless of the fact that it won't be as efficient as yours or Rick's designs. Why? Because it can carry my wife and son! You seem to be limiting yourself to one-person boats when a multi-person boat might actually sell better ... and a multi-person boat with a flat bottom will still have the shallow draft you're seeking, even when two or three people are in it.

Then again, this is only one man's opinion, others may have different priorities ...

:)

[john zimmerlee]

Thanks, Kenneth!
I've built ten prototypes . . . and modified each one about a dozen times.
I'm getting tired of building new hulls!
Surely, there is somebody out there who will take over this project.
Can't wait to find that person or company,

John

[Gilbert]

Congratulations John.
I saw one of your models a couple of years ago on the web. I thought it was about perfect. I think your biggest market is with people who are not especially agile, maybe up in years where they can't row or paddle for some reason, but just want to get out on the water and snoop around. Your shallow, wide stable model that doesn't go very fast seems perfect.
You should be thinking of market research instead of new models it seems to me.

[john zimmerlee]

Gilbert, Ken, Rick, and all who have contributed:

I'm 59 years old. I don't have it in me to start a new business or even to keep building prototypes. I have a good idea and a patent pending. I've spent $119,000 proving that a lot of stuff doesn't work. Gosh, it I had just known 3 years ago what I now know today, I could have saved $100,000.

I just can't afford any more education!

John
Stream Dancer

[charmc]

Now that I've won the concept award, I need help cleaning up the design of Stream Dancer.

This hands-free electric powered fishing kayak is controlled solely by your feet and operates in 6 inches of water without harming fragile underwater environments. Each heel rests in a sliding foot control which has linear potentiometers inputting pulse width modulation speed controllers which vary power to each of two submersible motors on either side of the kayak's centerline. The motors drive augers instead of props for less cavitation and stronger bite in the water, resulting in powerful turns and quick change in direction.

Stream Dancer's hull is now 10 ft long and about 38" wide. It's currently a tri-hull in the middle and kayak-like at each end. It seems to plough at high speed which leads me to believe I'm overspeeding the hull's max speed.

Four major kayak manufacturers have expressed interest but none can take on a new project this year. Guess I'm on my own to figure this out.

Appreciate your help,

John Zimmerlee
770-565-4420

John,

First, congratulations! You've taken a good idea and put your money where your mouth is, perservering through prototype construction. An international design award is something few small boat designers ever achieve.

You've had some good advice here. If I were you, I'd forget worrying about speed. From your video you have more than enough speed now. Reducing power a bit would reduce the bow wave/plowing and improve battery life without compromising current speed or manueverability.

The catamaran idea you have would make a good second model, but no need to develop it yet. IMHO, you have a saleable model now. Concentrate on marketing what you have. Once the money starts to come in, introducing a second model like the cat (different enough to attract new buyers without taking sales from the first model) should increase sales.

Keep at it. One problem now is the current shaky business climate; mfrs are probably reluctant to invest money, or may be having problems getting financing. On the other hand, your little boat is economical and environmentally friendly, which should make it very attractive to many buyers in the coming years.

No design will be perfect. I'm not criticizing any of the suggestions here, they are all valid. You've put a lot of yourself and your money to get this far, however, and I believe you have a saleable product now. I'd suggest you focus on marketing what you have. Sooner or later you'll find the right fit and you'll get the boat to the mass sales phase. Then you can decide if you want to revise it, introduce a second model, or sell out for the big bucks. :) That will be a pleasant decision.

[kengrome]

Hi John,

Here are some renderings of the type of boat I was thinking about when I suggested a 'jonboat'. I made this boat 7.8 feet long and 3.8 feet wide and 1.3 feet tall -- the perfect size to be shipped in a plywood crate with full sheets for the top and bottom and with 18 inch tall sides.

I figured 180 pounds for the boat weight and only 70 pounds for the smallest person to operate the boat. A 70 pound person will bring the boat down to its minimum draft of 6 inches ...

This boat is rather unusual. We usually want most boats that serve this type of purpose to float as high as possible, thus giving us the lowest possible draft and the most freeboard. But this boat has its own propulsion system built in, and it is not adjustable. This means the boat *must* sink into the water at least 6 inches -- even with the lightest person aboard -- or the augers will ventilate and be noisy and inefficient. At the same time the boat should carry several hundred pounds if asked to, without being in danger of swamping or taking on water.

The flat bottom of this boat, located 3 inches above the bottom of the sides, allows both light and heavy loading options with a very simple hull shape:

70 pound payload at 6 inches draft
440 pound payload at 9 inches draft

It also provides a clear and unobstructed flat bottom in the middle of the boat which makes passenger movement very easy and maximizes safety when moving around. The full wrap-around decks add strength and make the boat super-easy to get into and out of at any angle, too. The side decks are 10 inches wide and the end decks are 18 inches.

The waterlines shown in these drawings are at 6, 7, 8 and 9 inches. Freeboard at the heaviest loading is still 6+ inches if the boat is built with a deck and coaming as shown in one of these images. Everything looks smooth and curvy in these renderings because I designed this boat for roto-molded construction. This hull could very well be done in one piece.

Basically I ignored the appearance of the boat in favor of a relatively efficient design, given the dimensional constraints described earlier, and this is what I came up with. My thought here is that this shorter and wider boat:

1- will feel even more stable since it is nearly 4 feet wide;
2- fits into the back of a pickup truck more easily than a longer boat;
3- can still support one person very easily even though it is 2 feet shorter;
4- will maneuver more quickly and easily in tight spots on the water;
5- can comfortably carry a passenger on each end deck if/when the need arises; and ...
6- will easily fit into a cheap plywood crate for exceptional shipping protection.

:)

[john zimmerlee]

Very Impressive, Ken!
Wished I had your talent and abilities!
Now, do you have a couple hundred grand to get into production?

John

[kengrome]

John,

The software draws the pretty pictures, I just tell it what to draw ... :)

I think you could be selling these boats and taking orders for more by the end of the year for a total investment of say $25,000. If I were going to approach this project on a low budget basis I would:

1- build a set of female molds for the one model you prefer
2- have the first few boats built in fiberglass and resin
3- if made overseas, have them shipped to you
4- install the augers, motors, controls, seats, etc.
5- start selling them online from your website
6- start taking the boats to dealers and shows

There's an American boat designer/builder living overseas in the Philippines who would probably enjoy building the molds and producing the first batch of production fiberglass boats for you too ... :)