Human powered craft

My two main interests are boats and motorcycles. Swimming in the pool, I had an idea to join the two. I want to build a type of water bicycle that I can pedal around the pool, but I want the whole thing underwater. I want to float with just my head out of the water. I plan to make the basic craft out of PVC pipe, with foam noodles as flotation, with a forward rudder activated by handlebars, and a pedal crank turning a twisted chain driving a propeller I will make myself out of PVC and sheet metal. I need to know how far apart the two axis must be to work best. I plan on a 1:3 direct drive (one turn of the pedal crank will equal 3 turns of a prop I estimate will be about 12" diameter and of eyeball pitch. (A google search of twisted chain drives lead me to this site)

 

Why? Is this just to show off?
Great idea for that, but pedaling in the water will be hard.

You might look at this Thread http://www.boatdesign.net/forums/boat-design/pedal-powered-boats-23345.html You might start by looking at the posts by Guest625101138 although others have good inputs also.

It has 130 pages and might have a better idea for your propeller.

Fwd rudders are hard to control. IMO

 

I have a forward rudder on my steamboat, the rudder shaft sleeve is indeed the plumb stem pipe, right on the bow. The boat steers very well with the forward rudder, no problems whatsoever. Of course the steamer is slow at 5 MPH, but your imagined boat would have difficulty reaching even one MPH.

With most of your body submerged, the frame and floatation, it will be like you are propelling a small submarine with a displacement of around 1000 pounds. Not that your craft will weigh that much, but the hull "envelope" will take up space like a 1000 pound displacement hull, more or less. As a result, your available speed will be very low, performance far worse than common pedal boats which weigh far less.

Pedaling with your legs submerged in water will also be more difficult, moving all that water around. If you want to cruise around with just your head out of the water, a more practical approach would be to just rig up a small trolling motor with a battery pod, maybe 24 inches long and 8 inches diameter, hand held (don't forget the guards around the prop!!)

Of course, building strange craft is often a "just for fun" concept, and many of us build such stuff, so good luck with your project.

 

Thanks for the kind words. What is showing off about it?
Not looking for speed, looking for a little fun exercise in my own backyard pool. Got the idea while sitting on a foam noodle, hand-paddling.

 

I just meant showing off for fun - look at what I made!

Not a slam.

 

Yeah, I guess you could say it's a "check this out!" sort of thing.
I also want to bodge up a PVC tri with pedal power and a sail. I've thought about attaching some kind of sail to my bicycle and running it down the bike path at the beach. I've been around boats all my life; my parents were powerboaters with a classic Chris-Craft back in the early 60's, I was a marine engineer in the army during the 'Nam era, and I've owned several sailboats. Had to sell the last, a Beneteau OC400 a few years ago. I worked in the metal fabrication biz for several years, while in school and for some years after. I just miss boats and knocking stuff together, I guess.

 

Maybe a teeny tiny rudder is the answer.

I was pedaling my prop-driven pontoon boat while the sun was dropping low and reflecting off the water. I was being blinded so I turned around and pedalled backwards. I discovered that my rudder inputs had to be miniscule, compared to when I was operating normally.

 

I really just don't want to hassle a control system for a stern rudder when I will already have handle bars. I'm thinking a simple semi-balanced affair fabbed up from epoxied foam core board. The design brief is use only materials available at the local Ace hardware store.

 

The problem with a front rudder is that when you give an input, the rudder takes an angle to the water - which you want.
But when the boat starts to turn, you get an additional angle to the water which makes the boat turn harder than you intended.

It can work, and a smaller rudder will help, but it takes more concentration to make it work.

I don't know what happens when you move the input back to straight ahead. Since the boat is turning will it continue to turn with you thinking it should go straight?

 

I would think not. Maybe a bit of counter-steer will help keep things on course.

 

I would think that unless the 'bike' bit hangs from hulls/bouyancy which float on the surface, getting the weight vs buoyancy spot on to trim level with your head just out will be a royal pain, likewise the stability underwater.

 

Thanks for the input, Tiny Turnip- I plan to construct with 3 or 4 in. PVC pipe and end caps. I will be using limber holes to allow the whole shebang to fill with water, and will attach foam noodles to the top rail with zip-ties, a bit at a time to get the balance.

 

Limber holes will allow water to circulate through the inside of the pipe creating a huge amount of drag. Basically it is a parachute.

 

Thanks for the comments, gonzo. Think of a bicycle frame made of PVC pipe. Once it is full, with foam buoyancy attached to make it neutral, it should travel through the water like a submarine.

 

My backwards-pedaling-pontoon-boat experience is that when the rudder was held straight, I went straight.