Pedal Powered Boats

Very interesting, thanks for posting.

I think the flex shaft may be a little too thin and weak for the load. If you check the archives, Rick used 10mm or at least 8mm SPRING steel, which is much stronger, for just a single person boat. If you really lean into the pedals or accelerate rapidly, may get a failure using 1/4" ss. I also carry a backup shaft and props in case or failure, and have had to use it on a couple of occasions.

Hope this helps.

Porta

 

Coach Dave - What a great setup, you could start taking tourists. Even better, get all 8 people pedalling, would be interesting to see how fast it would go. It shows how much power can be generated by a pedal powered boat. A single person trying to paddle with the same load would get nowhere.

Now for my news, I've modified my boat yet again. I tried the dipping rudders but could not get them to work right. The boat would not turn any better and the rudders wouldn't always kick back up clear of the water. So now I've gone back to the directional prop but with a better setup. I made the shaft angle steeper to get more of the shaft in the water enabling me to swing it further side to side. Another bonus was being able to lower the seat, saving weight and getting a lower CG. I can turn a lot better now and if I lean into the turn and dig the outrigger in the boat comes round as good as with a rudder.

Ian

 

IM57

Looks like you are using the outrigger as a drag device. Those work pretty well as shown by dragging one oar on a row boat. But you are slowing yourself down quite a lot I imagine.
Since you are creating drag to turn the boat, shouldn't you reverse the outriggers? An asymmetric outrigger should provide "lift" towards the curved side. If you swap the outriggers side to side, the inboard one (on the turn) should also provide lift to the outside of the turn. Since the outrigger is aft of the center of the boat, it should also provide a additional direct turning power.

Nice looking boat. Can you keep both outriggers out of the water on a straight course?

Is there any reason not to dip a normal rudder? Pull it up when you don't need it, stick it in and turn it when you do. With 75 pages to this thread, I probably missed the answer.

Marc

 

Marc
I am using a steering arm to move the prop shaft side to side to steer the boat instead of using a rudder. Because the shaft will only turn so far the turning radius is a lot more than with a rudder. The outriggers are set so that they just touch the water. By leaning into the turn and digging in the outrigger the boat turns a lot tighter, just a way of turning a bit quicker if I need to. I see what you mean about reversing the outriggers, would give a greater force to turn the boat. The hull is narrow and deep and has always been slow on the turns, even when I was using a rudder. I did try Rick’s dipping rudders a couple of times but could never get them to work properly. The boat has minimal drag in the water, the skeg that moves the prop shaft is 25mm x 3mm aluminium. The boat is 5m long with a 200mm beam, on a straight run I can have one outrigger out and one skimming the water.

Ian

 

Ian, for low speeds or tight positioning such as in rivers or creeks, prop steering may be the only way to go, other than paddling. Prophish also uses this method for their craft, with some kind of swivel joint at the prop end http://www.prophish.com/home.html So you can pedal in places where rudders don't work. I think you have invented a clever setup for doing this type of steering.

Enjoy.

Porta

 

IM57

As I remember you are using a square cross section on the main hull. I'm sure you will get better than great directional stability, just not sure you need it all.

I also like the steering setup with the prop, so long as you don't need quicker response. The mechanism seems simple and clever. (Usually not combined in the same system).

If you were ever interested in a round bottomed boat that maintained the directional stability, increased the steering response and was relatively simple to build, please drop me an email. I built a similar hull (just too short for you) and had a way to strip plank the bottom that took very little time. At least I thought it was quick compared to other less simple shapes.

Too bad you are so far away, I would build you the bottoms just to show how it could be done. My idea was to use everything above the waterline as plywood, so you would maintain the majority of the simplicity and quickness of build. I would build the hull below the waterline as a symmetrical configuration (fore and aft), so that one mold 2.5M long would be enough. Basically a table top tool.

One of these days I am going to have to copy the drive mechanism and put my money where my mounth is.

Have fun.

Marc

 

Marc
Thanks for the offer of how to build with strip planking. It might be a while before I build another boat. I am still looking at ways to improve the current boat, not sure what yet. The boat started with flex shaft and dipping rudders then to a fixed rudder. After that it was a straight shaft trying a few different props, then back to a flexible shaft and then the directional prop. Back to the dipping rudders then back to the directional prop which is the current setup. Keeps the brain working and keeps me busy.
I am restricted in the length of 5 metre as that is the maximum length I can store in my garage. If I did the same thing as the rowing shells where sections are bolted together it would make transport and storage easier. Something to think about for the future.

Ian

 

Flexdrive on 28' outrigger kayak

Porta,

You are correct about the 1/4" stainless steel driveshaft. It does work and I've gone 57 miles with it so far. When I am cruising at 4.8 MPH the shaft seems to be adequate. When I push it up to 6.0 MPH the driveshaft feels very springy and prevents me from developing more thrust. I measured the flexshaft torsional compliance at 4.42 Nm/Rad. I'd like to tripple that by making it stiffer. I'm searching for the right materials and will post what I learn. Until then I posted

http://www.youtube.com/watch?v=uAUb47sUdjw

from may trip last weekend on the Ocklawaha River and Silver River. I pedaled the outrigger kayak 17 miles and paddled a solo kayak 11 miles. We had 10 people on the trip, 6 solo kayaks and the outrigger kayak served as the mother ship. I averaged 5 people in the outrigger kayak although at one point all 10 people were either in the mother ship or hanging onto it.

 

That's impressive that you can pedal such a big craft so well.

One way to stiffen the shaft might be to just lay up a carbon fibre/epoxy sleeve over it. This is pretty easy to do, as you can get hollow braided sleeves woven from carbon fibre that you just slip over the existing shaft, coat with epoxy resin and then bind with either electricians insulating tape or heat-shrink sleeving to temporarily pull it tight to the shaft (once the resin has cured you can take the tape/sleeving off).

Here's a link to a supplier across your side of the pond that shows the stuff I'm talking about - I don't know if these are the best people to buy it from over there though. http://www.cstsales.com/carbon_braid.html

Carbon fibre is a fair bit stiffer than stainless steel, so my guess is that one or two layers of this stuff will significantly increase the torsional stiffness of your shaft, without making it appreciably heavier or that much bigger in diameter.

Jeremy

 

Coach Dave,

Great video, you must have been an intense bicyclist previously to put in as many miles as you have. Probably still are I assume.

Any idea what causes the knocking noise as you pedal? That was the only surprise to me.

Jeremy, thanks for the web site, I never noticed the braid or thought of the application.

Marc

 

I'd hazard a guess that you could just use a bit of aluminium, or maybe even plastic, tube as the core for a carbon fibre sleeved drive shaft like this, as the carbon fibre would be taking pretty much all the load. It might be an idea to dangle the shaft vertically, perhaps with a weight on the end, whilst the resin is curing, just to ensure that the shaft remains as straight as possible.

Jeremy

 

A chap from the hpb list hpv-boats@hupi.org <hpv-boats@hupi.org> found powder coated sewer rod at this address http://www.flexmax.com/maxlife/cat1.html Not sure if it is spring steel, though it is available to 3/8" diameters.

The only spring steel I have been able to find easily in USA is electrician's drill bits but only in 1/4" maximum diameter. Still, I think it would be stiffer torsionally than SS, eliminating the rubbery feel....

Porta

 

Flexdrive on 28' outrigger kayak

Ian,
If I could get 8 people pedaling and actually develop 8 times as much power we could go twice as fast since speed increases with the cube root of power. Every time you double the power you can go 26% faster. Given the weight of my boat plus 4 passengers (1000 lbs total) and the hull dimensions Rick W. estimated 110W is required to move my hull at 4.8 MPH. That is a speed I can maintain for several hours. At 6.0 MPH Rick W. estimated 210W is required to move my hull. At that speed however my 1/4" ss driveshaft is very springy and limits my top speed.

Jeremy,
I want to try spiral wrapping 11 oz. unidirectional carbon fiber over a pultruded fiberglass core. The fiberglass can endure lots of flexing and the carbon fiber should boost the torsional compliance. In theory, the flexshaft should handle a larger load without fatiguing and my top speed will be limited by my legs.

Marc,
I am more of a runner than a cyclist. With my current schedule I typically get out and ride once a week. If I am taking the kayak out I pedal it instead of the bike. The big difference in position is that on my road bike the pedals are under me so I can put my weight on them. The kayak pedals are out in front of me like a recumbent bike so I can't stand on the pedals to get more torque.

 

Flexdrive on 28' outrigger kayak

Marc,
The knocking sound is the driveshaft hitting the strut that I use to adjust the height of the prop. If I let the prop get too close to the surface it will suck in air and the prop slips. If I run with the prop too deep I risk hitting obstructions or getting weeds tangled in the prop.

 

Directional Prop

Tried out the outrigger steering method today, it did turn tighter. I mounted the asymmetric outriggers the opposite way with the flat side outboard and the curved side inboard. The rudders were rigidly fixed to the aft end of the outriggers, 100mm deep x 150mm long set at 30 deg. Leaning into the turn I could only immerse the rudder about 10-15mm, if I had leaned any further I might have gone for a swim. The main turning force came from the shape of the outrigger, the rudder had little effect. The rudders were set 50mm above the waterline, any lower and they would have been causing drag from the waves. With the directional prop hard over and leaning into the turn it is the best I’ve had out of this boat. Tried turning using the outriggers only keeping the prop running straight and the boat was very slow to turn, seemed better to port than starboard. This may have something to do with the prop rotation.
It might work better with better designed outriggers but the main turning force came from the directional prop.

Ian