Some Technical Stuff
Several people (technical nerds all) have asked for some more details of the “River Snail (notopala solaris)” vessel and its systems…
The Design Process?
“Wouldn’t it be great to spend some time just floating down the river on a raft?”
“What about some sort of boat that we could throw together and that would just last long enough to get from Yarrawonga to the Murray Mouth, where we could step ashore from the sinking vessel just like Captain Jack Sparrow did in “Pirates of the Caribbean””?
“Be great if it was solar powered, wouldn’t it?”
“Hey, let’s make it a paddle wheeler.”
“Have to be a side wheeler – there weren’t many traditional stern wheelers on the Murray.”
The Size
The basic limit to size was that it had to fit on a trailer. Hire trailers max out with a car trailer at about 6 metres by 1.8 metres. So that seemed like a good place to start. In the final design, the trailer width constrained only the hull width as the paddles and paddle boxes were removeable – although that changed too!
Hull Design
I decided fairly early that pontoon systems were too expensive for a “one off trip” boat like this one – although there are some very nice looking plastic module type pontoon systems that would have minimised build time.
There are lots of interesting punt type boat designs on the web. See for example, “Dianne’s Rose”, “Triloboats”, “Shanty Boats”, “Gwen O’ The RIver (Atkins)” and so on. Phil Bolger also designed “Becky Thatcher” for sheltered water. That looked interesting and I spent much too long looking at this as an option. Funny, but in the end, the Bolger design had too many curves – not something usually associated with that designer! Also came across Phil Thiel’s “Escargot” which seemed to have a lot going for it. And the longer I looked at it, the cleverer it looked. We didn’t need a full on house boat for our trip, more a “camp aboard” design, but as “Escargot” was originally designed as a pedal powered boat, power wise, it seemed it might work on solar. I purchased a digital copy of Phil’s plans, extracted the basic lower hull shape, added a bit of rake to the bow and that was it!
What’s It Made Of?
As a “one trip wonder”, cost was a big consideration, so River Snail is made mostly of construction ply (pretty rough wood, but glues that will handle getting wet) and 70 x 35 M10 pine framing, with a bit of other sized pine – all sourced from the big green cathedral (where blokes go on Sundays), all hand-picked to try to get ply surfaces without too many defects and lengths of pine relatively knot free.
The side seams are also taped with epoxy and fibreglass and some epoxy “putty” was used to seal the bottom and side seams of the two “tubs” that form the trench down the middle of the benches on either side of the boat and the stern “poop deck”. The whole thing is painted with house paint.
Major laminating tasks (such as the 3 layers of 9mm ply on the bottom) were done using Titebond III – not normally associated with boat building, but waterproof long enough for us (we are keeping away from boiling water) and relatively inexpensive. Polyurethane glue was also used where it was more convenient.
Extensive use was made of a pneumatic nail gun for driving nails and staples (both galvanised) to hold things together while the glues dried. Non marine grade stainless decking screws and various galvanised bolts and screws were also used – on the assumption that for a short time at least, river water would not be too aggressive.
Hull Building
The base hull is made of interlocking ply panels – a bit like the dividers in a wine carton. The four longitudinal panels have a common top line, which meant we could start building upside down on a flat floor, with some chance of it ending up roughly square and straight. Interlocking lateral bulkheads at various places coincide with sheet ply dimensions. This placement has been used to make a box across the boat just forward of midship to provide lateral stiffness, house the motors and provide support for the paddle bearing system. A similar box across the boat a bit further aft provides stiffness in that area.
The four 12mm ply longitudinal panels are on 600mm centres. Two panels form the first layer of the sides and two more form spines 300mm either side of the centreline, becoming the inner surface of the side benches. Between the side benches and the lateral stiffening boxes are two trenches or tubs which allow a little more headroom. Each of these trenches has a false floor with 100mm of polyurethane foam flotation material inserted for reserve buoyancy. Both trenches drain into a common bilge box. Behind the aft stiffening box, another tub extends across the entire width of the boat. It also has a false bottom, filled under with foam. This tub is high enough to drain above the waterline, allowing self draining and a safer place to store our cooking gas bottles.
The lateral interlocking bulkheads divide each side bench into a series of boxes, which are topped with loose ply “lids” to provide somewhere to sit, set up swags for sleeping etc., while the boxes themselves form storage lockers. More flotation foam fills the front two boxes of each side bench.
I hope the above is clearer than the mud Chris landed us in while checking out how come pelicans can stand up in the river! Perhaps a couple of pictures will help.
The first one shows the longitudinal panels in place with the interlocking bulkheads. Looking from the stern, upside down before the bottom sheeting went on and before the side panels were added. The next shows it with side longitudinal panels in place and bottom sheeting ply going on.
The bottom picture shows the various interlocking panels and bulkheads with bottom sheeting in place. (View from the stern, right way up.)
Once the basic hull was completed (upside down), we rolled it over and glued in the “bitts” (end post things – 4 equally spaced across the bow, two on the stern corners, one centrally in the stern to hang the rudder and one offset in the stern to form the ladder access port).
Here the stern bitts are in place, with the rear “tub” glued up.
We then added the 700mm high, 9mm sheeting, giving a total of 21mm thick sheeting for the lower 450mm of the sides.
This one, a little later, right way up, shows side panels on, stiffening boxes across mid and aft, central tubs in place and masked up ready for epoxy putty in the corners. Side benches and basic storage boxes complete except for lids/covers.
A 35x70mm pine coaming was then rebated and screwed to the top of the side sheeting, which stiffened that up nicely. Another 200mm wide 12mm ply strip was also laminated to the bottom of the sides, giving a side total ply thickness of 33mm up to the waterline. The seam between bottom panels and side panels was then epoxy fibreglass taped. Each successive bottom and side layer overlapped the previous, so very little end grain was exposed.
After another hull rotation, the bottom was finished off with 4 rubbing strakes of 35x35mm pine (fairly knot free 35x70mm, slitted) and a base for the skeg (planned, but never actually bolted on – didn’t seem to need it!)
Then some painting and the basic hull was almost done! (Upside down view from bow. We built a “dolly” on castors to be able to move the hull around…)
Paddle Boxes and Solar Panel Supports
With the basic hull complete, we needed to build the paddle covers and sponsons along the side to protect them. Friend Ade came over from Perth for a week or so to help. (Thanks Ade, we owe you a longer river trip without the car and trailer ferrying this time!)
The paddle boxes are 7mm ply curved over 12mm sides. The sponsons are 12mm ply with some 70x35mm pine framing. Both the paddle boxes and the sponsons were originally removeable and bolted on to the coaming on the sides of the boat after launch. At 3 metres with the boxes in place, we were too wide to trailer with them permanently mounted.
Paddle boxes in various stages of construction.
The solar panel position was arranged to concide with the paddle boxes, so that a 35x70mm pine cross beam could do double duty – it supports one end of the panels and also ties the paddle boxes together.
Two other rectangular frames were also required to support the front and rear ends of the solar panels.
Progress at the end of Ade’s visit – boxes and sponsons complete, coaming and trim complete, solar panel supports complete.
Taking the paddle boxes on and off required lifting them over the top of the previously installed paddles, a task that proved arduous in the extreme!
One of those involved in this task on launch day (Chris Parker – that’s him at the front of the box trying to lift it over the paddle) suggested hinging the paddles boxes and sponsons. Brilliant
A bit late to do anything before the Goolwa Boat Show, but over the winter, the setup was modified so that the whole side unit folds up on hinges for towing.
Of course, it meant cutting away the outside of the paddle box and a few other rearrangements but turned out a much nicer solution all round.
Paddle Building
Building the paddles was a background task while the hull work was going on. Design was based on the “rule of three” some of the old paddle steamer texts refer to. i.e. Float length (the actual paddling part is called a “float”) is 1/3 of the paddle wheel diameter. Float width is 1/3 of float length. So for a 1.5m diameter wheel, the floats were to be 500mm x 170mm. Deciding how strong/robust/heavy to make the paddles was a problem. In the end I figured that if the original “Escargot” could be rowed, then paddles with similar strength to an oar would be adequate. So it became 2 arms of 19x70mm pine screwed and glued to pine plank 19x170mm floats. From some of the old texts, seven floats in a wheel of our size, operating at our hull speed (about 6kph max) would be about right. A few simple simulations seemed to confirm this, so that became the number.
To hold the paddles together and on to the paddle shaft, some mild steel hubs were designed and laser cut (at a very reasonable price). The hubs are welded to the shaft and the paddle arms bolted in place. The whole thing is the triangulated with aluminium strapping bolted to the paddles arms on both sides of each paddle.
Paddle making production line, the set of paddle arms with floats attached, ready for painting ( 2 lots of 7, plus 5 spares) and the first mockup of the paddles with one of the laser cut hubs.
Lots of paddles painted and hanging out to dry and a completed paddle.
Will It Sink?
The completed boat has approximately 600kg of pine and construction ply. Assuming an SG of 0.6 for the timber, with no shape buoyancy (i.e. fully flooded), it can support its own weight plus about 400kg of additional material.
There are three 50mm thick by 1200mm by 2400mm sheets of polyurethane foam in the various foam flotation compartments. This can also support its own weight (~20kg) plus 400kg of additional material.
Assuming batteries, solar panels, motors, motor frames, food, fridges, eskies, bedding, water, people, etc. weigh a total of 600kg in fully flooded condition, there is still 200kg of excess buoyancy.
In reality, people, fridges, eskies etc., will also contribute buoyancy, so the excess buoyancy is probably of the order of 500kg. It could certainly be swamped and end up with no propulsion, very wet and uncomfortable, but shouldn’t sink in a hurry. (“Hey Chris, look at the size of that iceberg!”)
The Power System
Once we’d decided on solar electric, it became a matter of how to get enough power and how to apply it to the paddles.
Initial thoughts involved axles and drives from electric 3-wheelers, but in the process of web searching, another option turned up. A small company in New Zealand, who were offering recycled Fisher & Paykel washing machine motors for use as generators in Pelton wheel water power units, were also offering the units as brushless DC (BLDC) motors for other uses. For more info, see http://shop.powerspout.com/categories/bldc-motor-applications and https://drive.google.com/file/d/0BzVDBix3S_qbNU1YWmZwTUFsQ2s/view
The motors are available in various re-configurations of the original windings, to suit required rpm and power. Operation at 48V and up to 750W looked in the ballpark for what was needed to drive the paddle wheels.
Eco-Innovation / Powerspout also described the use of a Kelly Controls e-bike controller to drive the motors from a DC battery source.
The Kelly KBS72051X unit (see http://kellycontroller.com/kbs72051x25a24-72v-mini-brushless-dc-controller-p-505.html) looked like a good match and appeared that it would be well within its limits in our application.
An offer on an online Gumtree advert realised eight, house type, Hanwha 250W solar panels, four of which were used on the boat. They are 30V panels, so two in series gives 60V, which is a good enough match for the 48V battery voltage that we could get away with relatively cheap solar controllers and didn’t need to go for a more sophisticated and expensive Maximum Power Point Tracking (MPPT) system.
Two sets of four, 12Volt, 33Amp Hour batteries completed the electrical side of the power train, which looks something like this, duplicated – one identical system on each side, operating completely independently:
Originally, the plan was to directly connect the F&P motor to the paddle shaft (just like a great big washing machine), but unfortunately, with the standard motor wiring configuration and the BLDC motor controller chosen, this did not seem possible. After a little testing, a pair of stators with windings configured to push the revs up to a more suitable range were ordered.
Of course, this meant a mismatch between the motor revs and the required paddle shaft revs. A 6:1 V-belt drive system was then needed to even it all up. This also had the advantage of giving us a sort of fail-safe, in that if the paddles got stuck on something, the belt could slip. In practice, this did happen on several occasions, with no damage to the paddles.
Of course, adding a speed reduction system meant more complication in the drive system. Here is a trial fit mockup during fabrication:
That’s the F&P motor, the grey disk in the lower far right, with its own bearing system and the small drive pulley on the original motor shaft, with a small plummer block and bearing supporting the end of the motor shaft. This part of the assembly is mounted on a swing frame to allow belt tensioning. The V-belt drives the larger pulley which is mounted on the end of the paddle shaft. The paddle shaft itself is supported in two plummer blocks and bearings, one inside the boat and one outside. This part of the system is all mounted on angle iron frames that bolt together through the sides of the boat as well as onto the sides of the mid ships transverse stiffening box. In the boat, the motor sits in its own compartment which is part of the stiffening box and a safety box with polycarbonate viewing window covers the larger pulley.
Of course, the available thick wall tubing required for the paddle shaft was of too large diameter for the bearings and the length required was too long for Dave’s little lathe. Our friend Neil, with his bigger lathe, to the rescue! Thanks mate, much appreciated.
Why Paddles?
Lots of reasons:
- “Degree of difficulty, Chris”.
- At the speed we are travelling, paddles are pretty efficient. And they look neat!
- Paddles are also good for a minimum draft craft such as the River Snail. Nothing protrudes below the bottom of the hull, so if we come to rest on a sandbar, we still have a good chance the paddles will work to allow us to back off.
- In the realm of firsts, Prince Alfred College students and staff designed, built and successfully cruised two solar boats (with propeller drive) down the navigable length of the River Murray in the mid 90’s. We had also heard reports of solar powered kayaks and catamarans completing the journey using trolling motors (at least one even going upstream). So apart from attempting to be perhaps becoming the oldest old f..ts to complete the journey under solar power, if we wanted a first, we needed something different. The Lock Masters certainly seemed to think we are the first solar powered paddle boat to attempt the trip!
- Paddles Sing!!! Something we have found during the trip is that the paddles make a great sound, one that really gets you in the relaxed groove! We love the sound of them!
An Iterative Design Process?
Of course, the design process wasn’t as simple as having everything fall into place, but wandered back and forth as one changed decision affected something else, which needed to be rectified and so on! But that was all part of the fun!
The Name
Given the shape of the finished boat when viewed from the side, as well as the projected hull speed of 6kph, something snail like seemed appropriate. And of course, the hull itself is based on Phil Thiel’s “Escargot”!
We web searched for river snails in the Murray system and found there had been at least two species identified, notopala sublineata and notopala hanleyi, both of which are thought to be threatened.
As unlikely circumstances would have it, while the threatened state was being assessed for possible listing, a river snail colony had been found breeding in a squatter’s tank at the winery where Dave’s brother Bob works. A resurgent threatened species? Seemed liked a good omen for a side wheel paddle boat.
Because we are a solar variant of the species, it became “River Snail (notopala solaris)”.
River Snail (notopala solaris) 