Shallow water propulsion

[john zimmerlee]

I need help!
My electric powered personal watercraft prototype was commended by the 2005 International Concept Boat Competition, but it was powered by trolling motors which require too much draft.

It appears that electric power is not sufficient enough to drive jet pumps and they don't work well at low speed anyway.

The craft currently drafts only 5" of water and I would prefer to have propulsion that will work in the same depth.

Paddle wheels make too much noise spalshing above the waterline.

But this is what I'm thinking: Build a catamaran with a tunnel down the centerline. Turn two paddlewheels on their side and embed one in each hull about half way in . . . exposing half of the wheels in the tunnel. The wheels will turn counter-rotating . . . much like a cake batter mixer . . . sucking the water through the tunnel. I think this is the way vane pumps are built.
If the width of the wheels are about the same as the depth of the tunnel, and the top of the tunnel is below the waterline, it should not cavitate and should have propulsion wherever the the boat can draft.

Obviously, I'm missing something. It seems too logical and I can't find where any one is using this, so please tell me where my thinking is flawed.

John Zimmerlee
Marietta GA
www.streamdancer.com

[FAST FRED]

Screw propellors replaced the less efficent padle wheels in the 1800's.

A trolling motor could be mounted behind a generous sized tunnel .

FAST FRED

[artemis]

Originally Posted by john zimmerlee

I need help!

...But this is what I'm thinking: Build a catamaran with a tunnel down the centerline. Turn two paddlewheels on their side and embed one in each hull about half way in . . . exposing half of the wheels in the tunnel. The wheels will turn counter-rotating . . . much like a cake batter mixer . . . sucking the water through the tunnel. I think this is the way vane pumps are built.
If the width of the wheels are about the same as the depth of the tunnel, and the top of the tunnel is below the waterline, it should not cavitate and should have propulsion wherever the the boat can draft.

Obviously, I'm missing something. It seems too logical and I can't find where any one is using this, so please tell me where my thinking is flawed.

John Zimmerlee
Marietta GA
www.streamdancer.com

During the 1820s through 1870s some really bizarre designs for propulsion machinery were put forward to both the US Navy and merchant shipping. The paddlewheels laid on the side and projecting from the hull was tried on three vessels in the 1830s by the US Navy. The performance was less than noteworthy.

[SamSam]

Originally Posted by FAST FRED

Screw propellors replaced the less efficent padle wheels in the 1800's.
FAST FRED

I don't think innefficiency was the cause so much as inconvienence. The wheels were topheavy and in the way for docking, loading, manuevering etc. The machinery was bulky, and took up a lot of space. They have a big disadvantage in waves. They were also vunerable to cannon fire. As far as transferring power to the water (in the right conditions) I think they were pretty efficient. One difference between John's idea and regular wheels is John's has the wheel totaly submerged where in a regular wheel only a very small portion is. John's version seems more like a primative jet drive in a way. A small bathtub sized model could could be easily made. Old crapped out automobile tape players or "Walkmans" and such can supply a real small 12v (6-18v depending on how fast you want it to go or how many batteries you have) motor along with numerous small belts ,pullies, gears and doodads. A bathtub boat with laser beams? Sam

[john zimmerlee]

Stream Dancer now has a catamaran hull with sump pump style impellers in each hull. The vanes are straight and the discharge is both forward and aft.
It will be tested this weekend.

This propulsion has been done in australia. See www.vortapowersystems.com

Wish me luck,

Tinker John (Stream Dancer)

[SheetWise]

How do you prevent the "unexposed" portion of the paddlewheel from doing unintended and unwanted work? On a horizontal axis with non-submerged area, gravity solves the problem. The hull form could expose a void once it had some lift -- but how would it ever get the lift? Maybe running exhaust to clear the blades? Just thinking out loud ...

[john zimmerlee]

Sheetwise,
Appreciate the response.
At one point, I used paddlewheels mostly sleeved in the hulls, with partial exposure in the tunnel between the hulls. That didn't work, probably because the paddles were too large, the diameter too big, and the motors too small.

I then switched to smaller flat backed, straight finned impellers, sleeved mostly in the hull with partial exposure in the tunnel and also a hole cut in the cover just over the center of the blades . . . to let water in. The centrifugal force spun the water out into the tunnel and moved the boat . . . though not very fast. The impeller diameter still too large.

I've now cut pockets in the hull for smaller impellers and a sloped discharge pathout the bottom of the hull.
Testing this weekend. You can visit my very rough website at www.streamdancer.com

Stream Dancer

[john zimmerlee]

Increasing success!

Just switched from 4" ducts to 6" ducts. That more than doubled the square inch discharge area. Amazing difference! . . . which proves the old adage "use the biggest prop possible for best performance."

Though the boat drafts only 4", the ducts rise to 6" above the bottom of the hull for about 12 inches horizontally where the prop resides. There is a slight bit of air initially, but discharges quickly when power is applied.

The propulsion system is now quiet and effective. The props are out of harms way. The boat now moves in 5 inches of water. It is truly the Stealth Boat for fisherman, duck hunters, and naturalists. We're rebuilding the prototype now with sleeker hulls and other refinements. We'll be seeking rotomold manufacturers and dealers soon. If anyone has contacts in those areas, we would appreciate an email. Thanks to all who have made Stream Dancer a success story!

Stream Dancer
John Zimmerlee
770-565-4420

[ted655]

There is a horizontal troling motor. It mounts on thr transom, much like a surface prop.
Ran across it last week. I didn't bookmark it.
Here (as best I remember) is how I ran across it.... It was a link off of a pontoon kit site I had Googled. Sorry, wish I remembered.
BUT... you know one is out there!

[john zimmerlee]

Ted,
thanks for thinking of me. I will look for the site. Meanwhile the prototype is nearly finished. I will be creating a demo taped (CD) soon to show the features. then I will look for rotomolders. if anyone knows of one in the southeast, let me know!

Stream Dancer