Pedal Boat Design

forward tube architecture

I believe we can help you with the architecture of your cat, BG; I started with design rather similar to yours, then evolved it until we settled with the forward tube arrangement. There are not so many architectures for small cats, and even less if you build it yoursef.
We found that the 'forward' tube is a sensible choice, becouse it gives you a strong and stiff connection that is out of the way but makes also a nice and useful footrest. A tube is easy to find and connect, and you can kick-up the drive unit around it if necessary. Adjusting the position of the drive unit is easy. We used standards connectors for plumbing at first, then developed some fast assembling connection like the one shown in the attached detail, it is a carbon fiber fast connector developed by a craftsman of the OW community and possibly one of the future 'OW components' available. But you don't need it if you are not interested in fast disassembling, a plumbing connector works well. I'm not sure how you call them, but they are shown later: you can see them it the picture of the lady in Venice, taken in 2000, that shows a previous step of the development. This was one of the first the experimental setting of the forward tube, all the connectors of the forward tube to hulls and drive unit are for plumbing. Not nice, but bery easy to build, strong and stiff, kick-up included. They worked well.
The geometry (you want to stay close to the cranks for strength and stiffness, but not too close, otherwise you can interfere with the rotation) is shown here:
http://www.openwaterbike.com/archit...rbike-drive-unit/the-forward-tube-connection/
You don't really need the nice connection for the seat shown in the lady's photo, it was meant for a different architecture and it's too heavy for the forward tube acrhiteture. A recumbent bike standard seat and a tube frame are probably lighter and easy to connect for back supporting. But buy a recumbent bike seat, it is easy to find and comfortable, it's worth the money.
I hope I have given you a little help, GP, and look forward to the development of your project.
Beppe

 

See post #161 this thread, page 11. Rick linked to a resource there.

Other than that, it's like how I compared it to daylight savings time.

 

Yup. Large diameter seems to be key, kinda like the front wheel on a penny farthing bike.

Or perhaps the simple designs were also the most effective. There were some designs, you recall, that were full of gears, chains, and linkages.

Given your talent for design, your kickbutt software, and what sounds like a world-class shop, I'm sure you'll come up with a very effective design. I fully intend to copy it for my own project. (But without the hi-tech hull. I picked up an old Aqua Lark hull, you see. Pic of the type below, although mine is very rough and in pieces.)

I've just moved, and have no shop yet, but I do have two hulls destined to be human-powered. One is a one-seater I want to power with a prop - the other is the two-seater to be powered by a sternwheel.

I was thinking of cupped paddles like the example below, not of round paddles.

 

beppe--

I am going in s slightly different direction because of shallow water and weeds. Forgoing the prop in place of a high performance paddle wheel. My boat will also seat two and have 18 to 20 foot hulls. All formed carbon built up construction for the frame, hulls, and dual stern drive paddle wheels using pre-preg. I am shooting for a 100 pound boat (it's good to have lofty dreams =)

Curtis--

I consulted that page at least 3-4 times a day since Rick posted it lol.

Tinhorn--

First the canal boat is a VERY interesting design. Like a half cat lol.
Second the little red boat must just blow the fancy stickers off the jet ski's.

Lastly, the best possible upside to taking the time to make molds and do built up construction on the sub assemblies is that you have molds. I mean you specifically. And Curtis, and Rick and anyone else who wants to do a paddle wheeler. Go back and look at the 2 molds for the paddle wheel lay up. They build a big strong reasonably light wheel from two rather small (and simple to use) molds that would be nothing to ship. We're talking a pair of shoe boxes almost.

Speaking of fancy tools =)

Just ordered a 120 watt laser that will swallow a full 4' x 8' sheet. You wont believe the rapids on this thing. Will cut 1.5" acrylic in a single pass (which I am a little skeptical about). Luan and plywood like it isn't even there. Edge is a tiny bit brown on wood though lol.

Fancy software I taught myself to use. Shop full of fancy tools most of which I actually built myself. The laser will be the first CNC machine I have that I didn't build--and I do a LOT of design work to pay for it. You can build a CNC router with 4' x 8' of bed for half of what a high quality table saw costs (mine was under 1K) and it frees up enormous amounts of floor space in the shop. Load your sheet and thats it. It will cut panels, drill all the holes and dados and even do dove tails etc. No in and out feed tables or space needed. I can also carve a mountain mural with elk and bears the size of a coffee table, an inch deep, in 3-4 hours. I could even add a wood glue dispenser to the table that applied the perfect amount of glue in the correct locations in seconds. The point is that my CNC router isn't really "fancy" but rather replaces other tools and frees up space. I build my own molds. My own hot boxes. I even built my plating bench (even welded the tanks =) for chrome, nickel, and copper. Anno too of course. As for the shop itself...I even built that lol. Didn't pour the slab but I helped. Built the entire building. And by built I mean cut every board, drove 38,000 4" screws (I HIGHLY recommend Milwaukee 1/2" drills) , ran all the wire, put in all the pipe. Not managed the subs. When Hurricane dolly scored a direct hit on us she lifted a small building up from down the street and slammed it into my building on the second floor hard enough to peel the metal roofing off. Building came through fine--mine, not the projectile (though it flooded cause said building ripped a hose bib off on the second floor)

As I see it, its not a fancy shop or fancy tools (and they are not believe me) IT'S A FANCY MAN !!!

 

For sure! There's a parallel to this:
"There are no dangerous weapons -- only dangerous people. To a dangerous person, anything is a weapon."

 

Yours sounds MUCH less gay too Curtis lol.

Not that there is anything wrong with being gay if that joke offended you. More chicks for the straight guys is my view =) ...It's those lesbians that ruin it lol.

 

Hey, you said it, not me, lol.
Nice thing about the laser, it won't leave splinters on the plywood edges -- cut and assemble, no sanding, no waste.

Machine tools are great, and I'd love to have some. I couldn't justify spending the money, though; maybe once or twice a year I could think up a part or two I wanted to make, and then they'd sit unused the rest of the time.

 

Cupped Paddle Wheels

Cupped paddle wheels have been mentioned several times in this thread. I highly recommend them as they permit smaller blades to be employed.

Rick and possibly another person suggested having them reversed, so that the cavity is forward rather than acting as a water scoop. This, too, seems to work better, though I have yet to gather hard data to prove it.

My test bed is a fairly heavy Old Town canoe, built from Royalex plastic. That material makes for the sort of "takes a licking and keeps on ticking" boat that is very nearly indestructible.

The paddle wheels were built from 27" 10-speed bicycle rims. The rims are welded via six 3/4" x 0.125" aluminum tubes to a 5" aluminum axle tube.

Evenly spaced around the rim are twelve 3" long 0.5" x 0.5" x 0.125" thick aluminum corner pieces, welded to the rim like mini paddles.

Bolted to the mini paddles, using two stainless #8 machine screws and bolts each, are 3" wide x 5" long x roughly 0.050" thick aluminum paddles. These paddles were from recycled office partition plates and have a 3/8" rib down the center of the back and 1/4" flanges down each side to give them some rigidity and strength.

Bolted to the mini paddles on the other side with those same machine screws and using the aluminum paddles for bracing, are scoop-like 5" x 5" PVC gutter sections.

A wheel with 6 of these paddles weighs about 5 pounds. Adding the other 6 paddles for the full complement adds at most another pound.

Most of the time I used two of these wheels, one per side of the canoe. The trim is such that the rim of the wheel barely touches the surface of the water.

In my tests with the wheel without the gutter sections and with all the blades in place I found that the wheels turned too easily for the range of pedaling cadences I found comfortable (0 to 85 rpm), even when using clipless pedals and bike shoes. Small fenders were required on this side wheeler to keep the pedaler dry.

My first thought was to add scoops to grab more water and create more thrust, and this is when the gutter sections were added.

With gutter sections I found that the thrust had increased dramatically, but much of the energy was expended in pushing water down at the front of the wheel, and in lifting water at the exit. Larger fenders were required to keep the boat occupants dry, and the scooped water hitting the rear end of the fender by the pedal station reduced the effective thrust considerably.

This configuration, called Dakanu, was entered in the Yreka World HPB Championships and, with a person using a normal paddle in the bow and another person pedaling in the rear, managed about 6 knots over 100 meters.

Quite some time later on a whim I decided to try the paddle wheel in the reverse direction; i.e., if one pedaled in reverse the wheels would do the scooping.

It appeared that the effort to pedal was significantly reduced, but the canoe was going about the same speed.

The idea behind having the scoops reversed is that the intent is to move water without lifting or pushing it in directions other than that which would cause the boat to move in the forward direction. One can do this with scoops, which can reduce the number of vortices created from two (one on either side of a moving standard flat blade to one, or by making a hole in the water that moves to the rear.

The "hole" approach means that the same mass of water is displaced, but there is minimal lifting involved as the water moves around the scoop.

As an aside, I have operated Dakanu in as little as 3 inches of water, through areas choked with lily pads (that photo of lily pads was open water as far as this boat was concerned!) or milfoil, and in moderate chop. The fenders are certainly wind catchers, and I'd recommend that any performance paddlewheel vessel be designed so that the spray and splashing occur in areas remote from the occupants.

Michael Lampi

 

M Lampi--

I am very curious because it sounds like you built a very minimal structure using the bicycle wheels at 27" diameter. Do I read it correctly that each paddle wheel is essentially only one rim? Like a wagon wheel with paddles attached to its perimeter?

We have been discussing the merits of using bicycle rims somehow welded together with paddles between them for a stern wheeler. If your pair weigh 12 pounds total...

Very interesting post all the way round. Paddle shape is really going to be important I suspect. Your post just gave me an idea for Rick to chew over. Let me go look for some pictures to explain. Will post shortly.

 

OK--

This might be of interest to you too tinhorn.

Maybe we are looking at the paddle wheel the wrong way? Michael's post turned on the light bulb. The wheel vs prop actually has another analogy. Wind turbines. Bellow are some images that more clearly demonstrate this, but what about a wheel with say six spiral airfoil shaped radial blades? Michael is right when he said the REAL goal is as simple as displacement...

Said another way we want to displace or make a hole or "toe hold" in the water to push against...the trick is to do it in a very hydro dynamic way--some resistance but not too much. A radial paddle blade with an airfoil cross section would enter the water without paddle slap, be much more aerodynamic (less wind resistance) for the much longer non submerged portion of its rotation, would NOT lift water, would be providing direct forward thrust for it's entire submersion, and would look cool =)

It would also be a pretty rigid structure...like a single weave basket.

As a bonus you would not have to have such a big diameter wheel because you could have deeper submersion too.

You could even just do flat airfoil sections that were hinged maybe...like Ricks self leveling prop but with horizontal blades.

By radial (as in the last image render) think of the radial mowers.

Hmmm....

 

Beppe--

I have been going over your OWB site and not to get you going again, but it "seems" to me that locking down virtually every aspect of the design to a form that looks like a virtual duplicate of your cat is pretty much going to limit the output to clones of...your cat.

I think the resistance your getting (at least in here) is simply to that. The people in here want to build their boat, not your boat. I mean that in general terms, not as a slight.

With any "club" the risk is always that the club or group becomes the focus rather then the original goal or activity that brought the group together in the first place. Unless your goal is to study the group dynamic, the very rigid form your taking all but kills truly original thinking.

Just my opinion, but if you really wanted to promote HPB or PPB an approach more like the X or Ansari prize would be more productive. Obviously I don't mean providing cash but rather usable information that designers can use as tools. Imagine if your group developed simple yet powerful software that could help with hull forms, propulsion models, weight calculations, balance etc etc. Amateur/garage Designers face huge challenges in the more basic elements that big design firms take for granted. We come up with our design (hypothesis) and do our testing by actually building prototypes. Often we have no way to measure our actual results and quantify and disseminate them to other designers. So we guess what is happening on our boats, make new designs to hopefully address shortcomings and find improvement, and start over. This is a long and tedious process with lots of overlap. And no, having everyone build your cat with tiny (and likely insignificant) variations does NOT address this. Invention is the science of branching trains of thought. In my scenario the branches go outward, in yours they go inward. Nice if you want a single tree (idea) not a forest (lots of ideas).

If you want standards, make them standards on gathering and disseminating all that data. I stand on the opinion that forcing designs to conform is not the path to innovation. Providing tools is however.

 

The paddle wheels each use just a single rim.

Three spokes are positioned at 120 degrees and welded to one end of the aluminum hub. Three other spokes are offset 60 degrees and welded to the other end of the hub. Overall, the wheel is dished much like the rear wheel of a bike so that the paddles are positioned outboard of the canoe.

Even so, the thing is vastly overbuilt. I have (inadvertantly) run my canoe over sandbars with these wheels, run over rocks, heaved bunches of milfoil, etc., and even bounced them on the ground a few times during assembly and disassembly. They are quite tough!

One thing that is nice about the mini-paddles is that this enables one to add or remove the larger paddles, or replace any paddles that break, or experiment with different sizes.

Lastly, I secure the hubs to steel tubular axles with a pair of 1/4" stainless steel bolts, using Nylok nuts to secure them.

Michael Lampi

 

Michael--

Thanks =)

Egg Beater Wheel--

Well I got started on the design but OBVIOUSLY am going to need Ricks help as calculating force angles is some unreal math lol. Its' like center of pressure but through 90 degrees (I am starting with 90 degrees of helix). I am thinking the airfoil (is it now a hydrofoil?) does not need to be uber fancy at these speeds, so one of the simpler Clark symmetrical foils should be fine, though maybe a tad fat.

I will have the first model in an hour or two.

 

One of the things I've been thinking of off and on is to turn the paddlewheel blades 90 degrees and give them an airfoil cross-section -- and then run the wheel opposite to normal paddlewheel motion.

See this page:

http://aa.nps.edu/~jones/research/unsteady/panel_methods/anim3/

Yes, it involves that damn feathering mechanism -- turned on its side.

But, if you did it just right, it really would mow the weeds!

 

. . . and that may not be needed either -- the hoop-style wind turbines don't have feathering blades.