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Stern-wheeler for shallow water by Boxbuilds - plan by C G Davis


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Researching steam powered ships, I came across a plan by Davis that was, to me, unique.  I found it in a 1913 book, Nine Motorboats And How To Build Them, published by the Motor Boat Publishing Co. No author, but Davis's plan is listed in contents as a "Light-draft Stern-wheel Boat".

 

The boat is a 2 cycle gasoline-powered, wooden launch that looks like a pleasure boat or simple water taxi. The hull is perpendicular to the flat bottom with wooden posts for support. It has a false keel, more like a rubbing strake down the middle of the bottom.  The superstructure is planked only to house a galley and head.  Propulsion is via two 3 foot diameter paddle wheels at the stern.   The engine amidships simply transmits power across a drive shaft to a worm drive that spins the paddle axles. 

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I just got a laser cutter and decided to make the parts with it. It has been a real learning curve but the parts are coming in.....after 3 or more tries.  The first challenge is to identify construction entities that will form the ship.  Then it's got to get into an engineering tool(s) to scale and size the items. Engraving versus cutting drawings are created and they are transferred to to laser controller for work. Here's a sample of the drawings and resulting parts.  Needless to say I am bumbling my way through this but I see promise in it.  

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The hull is simple and went together well  To  provide more freedom in detailing the interior I started framing one side. The side is one large piece and will be supported by vertical supports.  I chose to use walnut for the trim and posts.  Amidships is a pair of closets that housed gas, water and oil tanks. I am running water and fuel "lines".  I made a counter and sink for the galley.  The drive shaft runs from the center-mounted 2 cycle engine to the drive support through a space between two wall sections which are now installed.  I am fashioning a lavatory from FEMO for the head opposite the galley. 

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  • 2 weeks later...
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Starting again.  I/25 scale.  Burned the sides, bottom, deck and cabin sides. IMG_1223.JPG.a83f1e68c2e697776e6a6ee1eddf8589.JPG

Assembled the boat shell, added the cabin sides and the transom.

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The transom accommodates holes for the paddlewheel supports and the drive shaft.  Printed a new "engine" and toilet.  IMG_1233.JPG.e18556f4fc68b37acddfbb54e6a4af22.JPG(still needs cleaning)

The original engine attempt was one piece resulting in an item too rough and imprecise.  Instead of making the engine one piece, I got more precision and a cleaner look by breaking the small pieces down and gluing them together.  Some more prominent tubing, like the gas feed, is represented by dirtied wire.   

I burned the paddlewheel supports. A jig was essential to attaining the right width and mounting the 'buckets'. 

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The engine positioning, the paddlewheel positioning, the drive gear locations and all are requiring a lot of dry fitting and micro adjustments.  I managed to form a worm gear and matching drive gear for the axle. To get the spacing right, the engine mount, drive shaft and paddlewheel drive support were the most affected.  

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The drive train required custom parts that I printed. The gears forced a change in the height of the axle bearings which required changes in the wheel size to ensure water contact.  To ensure clearance from the rudders and transom a modification to the wheel supports was necessary.  The paddlewheels are finished and will be mounted after the painting is complete. The bearings are slices of styrene tubing mounted inside a brass housing. 


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Roof cross-supports are arches with a scale 4 inch curve.  They're mounted in slotted basswood laminated with walnut.  The curve of the sides of the boat was transposed to the longitudinal roof supports.  With the cross supports in place a thin wood roof  will make the basis of the roof.  The wood will be covered with a "tarp" and trimmed out.  

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There is no generator for electricity in the plans which made the galley and head very dark.  It made sense to add portholes for light.  Mica is used for the glazing. 

 

Where seating was indicated, I installed storage below despite the original, open plan.

 

The steering was new to me but makes sense.  I installed pullies, ran the lines through the bulkheads and out to the rudder assembly.  

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Edited by Boxbuilds
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2 hours ago, wefalck said:

Interesting power transmission. I have not seen a worm-wheel drive for a paddle-wheel before. I gather it makes sense, when you have a rather fast IC engine and adds torque at low speed for a small engine.

I've never seen a worm-drive for a paddle-wheel before, either. Those I've seen, which are not traditionally driven by connecting rods from horizontal steam engines, in small boats like this one, were all driven by chain or belt drives. The worm drive gear here seems way out of size to accomplish the reduction necessary with the RPM from a gasoline engine. I'd think that if the engine did not stall out, this design would have the paddles turning at much too high a speed. There's also the problem of what happens if the paddles ground out. I'd expect catastrophic failure to the gearing and shaft would result. I have a fair number of such old powered small boat designs in my library. The "backyard" engineering of many which employ the then-new internal combusion engines, most automotive conversions, is "quaint" to say the least! I assume this design was what was then called a "folly," a small boat for fun, though not especially practical. One would wonder why it was not simply propeller-driven from the gas engine. The only answer is that the paddle wheel was just more fun!

 

Interesting model! There were a lot of similar designs in the early Twentieth Century and the plans literature is fairly available. (See e.g.: http://shellbackslibrary.dngoodchild.com/ an excellent vendor!) They are great subjects for modeling, especially in the larger scales which allow great detail without resulting in a model that will chase you out of the room. They are rarely seen subjects for models, but, for some reason, most modelers seem to turn their noses up at models of small craft in favor of the challenges of a Nelson's Victory or a Constitution and the joy of trying to find a place to display them! :D 

 

Edited by Bob Cleek
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Say you live near water that is shallow....like, roll-up-your-pants- and-take-off-your-shoes shallow with plenty of plant life.  Davis was writing about how to build (not model) a shallow water boat with a ~7 inch draft to putz around in without fouling.  He was pretty detailed in his directions and provided meaningful explanations for the design.  I cannot do justice to his discussion of the drive rationale (including the dilemma of many chain-drives) so I just copied it here for you.

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I believe these engines employed a friction clutch, serving the dual purpose of engaging the drive and avoiding the "grounding" catastrophe you mention.  The worm and gear are supposed to be a 4/1 ratio. At 300 rpm, the output of the 3 cylinder, 2 cycle engine, and 25% slip the boat could achieve 8 mph, according to Davis.

 

The biggest issue I see with this design is that the engine control is a distance from the steering, making it imperative to have 2 people controlling the boat.

 

I pretty much followed his directions but in small scale and found it fun.  I did make some slight mods, as a builder would, but nothing affecting the executable plan.  After building mostly sailing ships, and being in the midst of the Soliel Royale and restoring the Great Harry, I try to find unique craft to build for a break....this is one of those. I'm happy it piqued your interest too.

 

Edited by Boxbuilds
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Davis' explanation of the advantages of the double paddle wheels was most interesting. I hadn't known that. I've never seen it mentioned in any of the classic works on steam propulsion, but then, having those old engineering books doesn't mean I've actually read them! :D  They're terribly slow going, as anybody who's delved into the subject soon finds out. 

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I appreciate the scrutiny and discourse. Finding old texts written in a time when lost technology existed or was fresh in the authors minds, is intriguing.  It's like being back there......eh, don't mean to be nostalgic.  Anyway, I get a kick out of finding these odd examples and imagining modeling them -- as though I had the time!  

 

I will reexamine the gearing.  The photos are unforgiving and screaming for improvement. We'll see 

 

 

Edited by Boxbuilds
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Prior to World War 1 most internal combustion engines were massive things turning at relatively slow RPM.

 

World War 1, particularly the aircraft industry, really spurred the development of powerful compact I/C engines.  Since power is a function of torque x RPM, these new engines turned at high speeds.  While this worked fine with propellers turning in air the marine propellers of the time performed poorly.  The problem was cavitation, the vaporizing of water around the propeller.

 

The big problem confronting marine engineers wishing to use these new engines was therefore developing a transmission system to connect the high speed power source to the slow speed propeller.  The obvious solution was  a gear drive that would also have the advantage of providing a means for easily reversing.  Gears were, however, expensive and at least in the US organizations able to make them were limited.

 

As metallurgy improved and automobile industry grew compact marine gear drives were developed.  Between the wars, naval architects and boatbuilders  developed improved hull forms to reduce the cavitation problem.  As a result, in the US by the late 1930’s boats with improved hull forms, propelled by light weight high RPM automotive type engines connected to propellers by efficient, compact geared transmissions were available to support the war effort.

 

Charles Davis was a conventionally trained naval architect with experience working on the mass production of large vessels during WW I.  My guess is that this was a brainstorm of his, typical of the ideas that are thrown out but do not stick for any new technology.

 

None of this is meant to imply that you shouldn’t build this model.  Practical or not it is an example of an idea that was seriously proposed at a particular time.

 

Roger

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I don't know about the US, but over here in Europe powering boats began with semi-diesel IC engines on the commercial side, while amateurs put petrol engines into boats already at the turn of the century. The semi-diesels were hefty chunks of cast iron. The Danish were pioneers at that, followed quickly by the Dutch and the Germans. These semi-diesels would eat anything from rancid butter (there was often a fuel pre-heater on top of the cylinder-head to reduce its viscosity) to petrol. They had a glow-bulb (similar to aircraft model IC engines) that had to be heated with a blow-torch before the engine could be started. Similar engines were used as agricultural power-plants and tractors. They ran at relatively low speed (perhaps as low as 100 rpm empty), but had a high torque - torque is also a function of cylinder displacement and mass inertia in the system.

 

Even at that low speed you would probably need at least a 1:20 to 1:40 ratio in the worm-drive.

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Very true, Eberhard. Unlike in Europe, over here, early marine engines were gasoline powered, large-cylindered, slow-turning behemoths. I've had the pleasure of being acquainted by a couple of them, which started by opening a compression-release lever, filling a small cup on a pet cock in the cylinder head with gasoline (or something "hotter" like starting fluid) and kicking a huge flywheel with your foot until you got it turning pretty well. Then one opened the pet cock to let the thimble-full of fuel run into the single cylinder, and quickly closed the pet cock and the compression-release lever. Hopefully, the engine would start with a "ka-thunk, ka-thunk, ka-thunk, ka-thunk,... turning a large, high-torque propeller, and off she'd go. There are still some of these old engines in a few preserved privately owned historic vessels and in museums. The most well-known of the type, the Hicks Engines, were manufactured in my home town, San Francisco. The technology of these high-torque early gasoline marine engines reflects their steam powered antecedents. 

 

 

 

 

And since this is a modeling forum, here's a 1:8 scale working model of a similar Hicks engine. I don't know this modeler, but I'd sure like to meet him. Talk about an amazing example of model engineering. Truly mind-boggling!

 

 

Edited by Bob Cleek
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The US was slow to adopt diesel technology.  The US Navy did not convert its motorized ships boats from gas to diesel until well into the 1930’s and the landing craft that fought in WW II were initially gasoline powered.  American PT boats remained gasoline powered by three Packard engines burning high octane aviation gas throughout the war.

 

 The US has never adopted the very large direct connected slow speed European diesels for marine propulsion.  Applications using large scale diesel power such as the 1000ft Great Lakes ore carriers and the few larger diesel powered US Navy ships use medium speed diesels driving controllable pitch propellers via gear box.

 

Semi diesels have been used in the US, the most famous being the Khalenberg engines built in Two Rivers Wisconsin.  Many of these were used to power Great Lakes fishing boats.  One of these was used to power an environmental research vessel owned by the Superior branch of the University of Wisconsin.  She continued to sail until she was recently sold to a private owner and I lost track of her.  

 

Roger

Edited by Roger Pellett
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