Building the Electric Sternwheeler Tesla's Revenge

[wildshore]

So, a little over three years ago we began work on our sternwheel shantyboat Floating Empire, conceived as a simple, easy to construct livaboard shanty that could be built of recycled and repurposed materials with ordinary hand tools. That began a three year experiment in onboard living, complete with revisions, repairs, product reviews, and general reflections of life on the water, all duely cataloged in our website thefloatingempire.com.

Now we're building a new vessel, one putting into practice what we've learned. The new boat will be a solar-electric sternwheeler; a snug, livaboard cruising shanty that can be built simply of ordinary materials with ordinary handtools by ordinary people. We'll be documenting the whole build on thefloatingempire.com website and have set up an indegogo site here to help finance the build.

As we get into doing this, we'd love ideas and feedback from the cruising community. The anticipation is that the boat will cruise portions of the great loop. What things should we be looking to include in the build? If you live the lifestyle, what things can you absolutely not do without.

Inquiring minds wanna know.

Don

[Red Herring]

Interesting. Luck to you!!

[Stumble]

In a word, don't. Paddlewheel efficiency is amazingly poor compared to a screw, requires hanging a lot of weight off the stern, and are very technically complicated to build well, particularly compared to a screw drive. Add in the additional cost and they frankly have no redeeming value other than nostalgia. It is actually more efficient to use the same power to turn a screw, then have a cosmetic freewheeling paddle that just turns withthe slip stream than to try and have it provide propulsion.

Finally there is the safety issue. Paddles are big, heavy, and complicated and when something goes wrong younow have a big, heavy complicated piece of machinery spinning rapidly attached to the boat.

Combine the lower effiency with the already low power availability of solar propulsion and everything just gets worse. Not only will you not be going anywhere quickly or very often (electric propulsion), you will be forced to go even slower, and use more power.

I get the reclaimed goal of your project, and think it is admirable. But you are up against some very hard engineering limits here.

[minaret]

Originally Posted by Stumble

In a word, don't. Paddlewheel efficiency is amazingly poor compared to a screw, requires hanging a lot of weight off the stern, and are very technically complicated to build well, particularly compared to a screw drive. Add in the additional cost and they frankly have no redeeming value other than nostalgia. It is actually more efficient to use the same power to turn a screw, then have a cosmetic freewheeling paddle that just turns withthe slip stream than to try and have it provide propulsion.

Finally there is the safety issue. Paddles are big, heavy, and complicated and when something goes wrong younow have a big, heavy complicated piece of machinery spinning rapidly attached to the boat.

Combine the lower effiency with the already low power availability of solar propulsion and everything just gets worse. Not only will you not be going anywhere quickly or very often (electric propulsion), you will be forced to go even slower, and use more power.

I get the reclaimed goal of your project, and think it is admirable. But you are up against some very hard engineering limits here.

I think perhaps what you are missing here is the extremely small size of this vessel and its propulsion unit.

Stern wheels can have merit in that they are the most shallow draft form of propulsion power. I think that may be the point here.

[SecondBase]

Paddlewheel is "low efficiency" on the other hand but at least a little easier for a home builder to construct than a lower unit or stuffing box and energy is "free" in this scenario. If this is a lake / inland boat electric trolling motor(s) might be a low cost middle ground for propulsion for limited duty. For the great circle I suspect you'll need a lot more push.

I would offer a base vessel good for daytime operating, day trips and overnight anchoring. Shelter, mobility, a counter, seating and berth.

Look at the Pardey's techniques for boating as simple as possible.

Then offer accessories:

- night time boat lighting

- 12v chest freezer (requires batteries and 2 extra panels)

- roof capturing and filtering water. Small water tank above counters for gravity feed. Large water tank lower (stability).

[wildshore]

Gotta disagree with ya there on some of that stuff, Stumble. This is our third paddlewheel experiment, and we're pretty acquainted with the engineering. At low speeds, due to the lower rate of slip, the paddlewheels are more efficient than screws. Its as the speed increases that the screw drives really shine.

There are three reasons we're approaching this with a paddlewheel design. First, this is a low speed application, never above hullspeed, which is largely in the sweetspot of the paddle drives. The torque-ey nature of electric motors make them work well in combination with the under 60 rpm speed of the wheel. Second, as a gunkholer, the extremely shallow draft and resistance to fouling is something for which we're looking. The very shallow draft of the barge hull, and the roughly 10" bite of the blades makes for a craft that could just about sail on a wet sponge, and that's one thing toward which we're working.

Third, of course, is aesthetics. Grindlebone is, first and foremost, and arts organization, a collection of eccentrics and oddballs, and if it wasn't different, interesting, and attention attracting enough, we probably wouldn't do it.

I do thank you for your concerns, though. We'll take those into account as we move toward the final design of the drive.

[Stumble]

If extremely shallow draft is the goal then I retract my objections. They do have to advantage of being able to operate in mere inches of water. But I am not sure that even at very slow speeds they are as efficient as a screw. I might buy that if the speed is low enough the actual power used is so minimal it doesn't matter much, but not the efficiency argument.

As for ease of building. I can knock up a simple electric screw drive in about an hour once I have the parts. And the parts list isn't exactly lengthy. All you need is an electric motor, a pipe, a prop, and two bolts. It's not the drive I would choose to build, but it will work. All you have to do is slip the pipe over the shaft of the motor and bolt it in place,
Then slot the prop onto the pipe and bolt it in place. Toss the prop in the water and add juice.

Of course in reality you would want a cutlass bearing of some sort, I would probably use a rod not a pipe, and a coupler not just bolt it together. But it would work.

Compare that to the complexity of a paddlewheel and there is no doubt which is easier to build.

[a64pilot]

I don't get the paddle wheel either, unless it's aesthetics.
Why do you want extreme shallow draft?

[minaret]

Originally Posted by wildshore

Gotta disagree with ya there on some of that stuff, Stumble. This is our third paddlewheel experiment, and we're pretty acquainted with the engineering. At low speeds, due to the lower rate of slip, the paddlewheels are more efficient than screws. Its as the speed increases that the screw drives really shine.

There are three reasons we're approaching this with a paddlewheel design. First, this is a low speed application, never above hullspeed, which is largely in the sweetspot of the paddle drives. The torque-ey nature of electric motors make them work well in combination with the under 60 rpm speed of the wheel. Second, as a gunkholer, the extremely shallow draft and resistance to fouling is something for which we're looking. The very shallow draft of the barge hull, and the roughly 10" bite of the blades makes for a craft that could just about sail on a wet sponge, and that's one thing toward which we're working.

Third, of course, is aesthetics. Grindlebone is, first and foremost, and arts organization, a collection of eccentrics and oddballs, and if it wasn't different, interesting, and attention attracting enough, we probably wouldn't do it.

I do thank you for your concerns, though. We'll take those into account as we move toward the final design of the drive.

I agree, extreme resistance to fouling is the other merit involved with wheel drives (aside from extreme shallow draft). There are reasons river boats were still using them long after screws were in use everywhere else...

[minaret]

Originally Posted by a64pilot

I don't get the paddle wheel either, unless it's aesthetics.
Why do you want extreme shallow draft?

I think we could compare the general aesthetic here with some of Phil Bolger's designs, to suggest a more known designer who has examples of the approach.

The general idea could IMHO be described as an "extreme gunkholer", ie a vessel able to fit into small bays, coves, even estuaries/marshes/rivers, that other vessels cannot, and then to comfortably spend time there.

[minaret]

Bolger and Bolger like designs with sail version of extreme gunkholer concept.

[minaret]

I think a stern wheel on a Bolger type hull design like this might make sense. It would certainly be able to beach itself and pull back off river boat style just fine.

[a64pilot]

The inertia, weight and additional frictional losses of a paddle wheel have to be large disadvantages.
Paddle wheels hung around for so long from tradition I think, if they worked better, they would still be around. Many of the paddle wheel boats you see on excursions etc. are screw driven, the paddle wheel just rotates freely.
I think a whole lot of unnecessary work and expense will be tied up in the paddle wheel design, and why electric propulsion?
What would it cost solar panel wise and battery bank wise to replace a 9.9 HP outboard for an eight hour run? How many days until you can do it again?
Use 750 W for a HP and for planing assume your only need 5 HP to replace that 9.9

[valhalla360]

First, the torque of an electric motor has nothing to do with the selection. Electric, diesel, gas, whatever, the torque is primarily controlled by the gearing and a paddle wheel will typically utilize gear reduction no matter what, just select an appropriate gear ratio. With equal HP, it just doesn't matter. This is basic physics. There is nothing magical about electric HP.


The simple solution would be to find a couple old outboards with blown motors and replace the gas motor with an electric motor (the old big-foot pontoon boat motors would be ideal donors as they typically are outfitted with large low pitch props ideal for this use case.) That will give you an efficient well designed drivetrain with far more maneuverability and still keep draft below 20" (Assuming you use adjustable motor mounts, you can raise the motors to get into even shallower water). Fouling isn't a major issue as you can tilt the motor up to get at the prop and with the low speed necessary for a solar powered boat, it's unlikely you will hit anything hard enough to do damage.


While you might wind up with a minimum depth of 15" as opposed to 10", the maneuverability of twin outboards should more than make up for the few inches of extra draft. (It's typically deeper 10-20' away from the shore anyway if you pull up onto the beach)


The only reason to go paddle wheel is nostalgia. Outside tour boats, every boat you see on the river system will be using screws and it's not an accident.

[Munoz]

Phil Bolger designed a couple of sternwheelers I think,

One is described in his book "Boats with an open mind"