Pedal Powered Boats

Ok, here's a close up of coach dave's peddle setup. I have a bike that I got sitting in my garage, it's upside down and looks just about the same! Did he not even cut and weld this? It does look a bit high though. What would be the proper geometries that I'd be looking for? Feet that far up looks uncomfortable for very long.

 

I think the rule of thumb for recumbent pedalling is that the pedals need to be lower than your heart. I'm pretty sure I read this somewhere back in this massive thread, and believe it was Rick W who stated it. He tends to be right about this stuff, so I'd guess it'd be a good rule to stick to if you can.

 

thanks! yeah, I seem to remember that now that you mention it. I should be able to hack together something that would resemble a model 1:1 unit. Maybe I can even find a bean bag chair and try that out as well? I'll also try out outher seat options as I come across them. I'll be looking at ergonomics for this, and then progressing the system into the drive unit. Gearing has me baffled so I guess it's just experimentation on that.

 

Gearbox

Spidennis
The gearbox I use is an Involute gearbox of 1:3.3 ratio. Every turn of the peddle turns the prop 3.3 times, the prop is a 430mm dia two blade folding prop. The prop was made by Rick and is made of stainless steel, the blades swing out when spinning and fold back if you hit a snag, log or whatever. The gearbox was made in India by a company called Involute, don't know if they still make them or where you could get one. They were originally made for a peddle boat which someone had developed and was selling. Advantage with this gearbox is its simplicity, no chains just the shaft coming directly off driving the prop.
Seats I've found are very much an individual thing, you have to use what suits you best. As for a bean bag its a great way to get a very sore back.

Ian

 

Is there any reason, that your boats have sharp sterns (going back together) instead of a "glider" stern? I have read an article about design of the german WW2 torpedoboats, which have been the fastest (semi-)displacement boats around back then. The article said, that they used an "as sharp as possible" bow and the widest point at the stern.

A boat with the widest point at the stern should at the same length have a decreased draft (=> decreased drag) and the speed should be high enough, that no drag results from turbulence. Also the wetted area should not change too much. Maybe someone has a simple explanation. Best regards, Andreas

 

that sure looks like a nice compact gearbox!
a quick google search brings this up:
http://www.involutetools.com/
with the shaft coming directly down the center would make for a difficult over the side mounting? I guess I should look at your boat again to see how this is mounted.

edit:
The folding prop looks really cool! and I bet a pain to manufacture? Rick has done some pretty cool stuff .... and after seeing your "gallery" of your boats I see you've been quite active in building as well! Nice job.

 

Andreas
Most peddle boats have sharp ends to get the lowest possible drag through the water. The semi displacement hull you mention is for a boat that can plane at high speed. The human engine has limited power and as far as I know no one has been able to get a HPB up and planing. Maybe a professional cyclist with a custom designed boat could do it but for the average person its getting the hull resistance to a minimum. I'm sure Rick and others would be able to give a detailed technical explanation.

Spidennis
My shaft goes through the centre of the boat inside a PVC tube. The shaft is 8mm flexible SS and kicks up when I hit a snag. One pic shows the new boat I am building, the other is my current boat. You can see the mounting frame and the shaft and prop. Hope this helps.

Ian

 

Wave Interference Boat

Andreas
Been having a look at your boat on the Open Waterbike website. I did a drawing to see how it would look with someone sitting in it peddling. The hull I have drawn is to the dimensions you have given the rest is a bit of guesswork based on your sketches shown in the website. The lower part of the hull is deep and narrow and at a guess probaly 250mm-300mm wide. You need at least 300mm from the centre of the crank to the deck to give your feet enough clearance. Pedal width requires at least 400mm clear. From this the person would be sitting very high up in the boat, what would the stability be like?

Ian

 

The width of the displacement hull actually has a trapezoidal form, with about 250mm on the upper side and below 200mm on the lower. The stability results from the glider hull, which has a width of over 650mm at waterline. The pedal clearance is my biggest concern at this time, as the upper side of the hull is closed and the drivetrain should be adjustable for riders between 1,5-1,9 meters height. In the current version, there are about 50mm missing space in all directions, but I am working on that and nearly finished doing that task. The next version (which hopefully will be the last one) also features a center of gravity of the rider at only 350mm above water level (currently 450mm). The gliding hull protrudes into water with a draft of 30mm-50mm, but dependent of the underlying water pressure, so that drag is minimized at higher speeds. The glider hull also has to lift only a very small part of the total weight.

According to calculations, the boat should be safe for angles of up to +30°. At a prismatic factor of 0,62, the longitudinal stability is also in a good area.

I like your pics, they are quite accurate. I will publish new pictures of the completed model (incl. drivetrain & seating) as soon as they are ready. The big amount of work results from the fact, that the whole boat will be developable in 2D, which means you can use plywood, composite, sandwich,... or whatever else you want to have. Also the parts of the drivetrain will be made out of lasercut 2D parts, which make them very cheap.

If my calculations for the APC prop are right, the 12x12 prop will have an efficiency of 82% compared to 85% for the 16x16, while enabling 100mm lower draft.

Andreas

 

If draft is important, I believe the torquedo props are reputed to be efficient and small. They can be bought as replacement part, though cost is considerably more than the APC.

Porta

 

I already had a look at these props. They are really the most efficient ones, but their smalles prop is designed for 10kph @1200rpm and needs above 180W at this speed. Also the price is a little bit high with 100$.

 

Scheny,

I take it you're planning on roughly 100 watts?

-Tom

 

Here's another much smaller, but don't know if you can get the specially modified 8X13 prop by itself:

http://www.electricpaddle.com/faq.html

Look at line #13 under PRODUCT FEATURES line 12.

P.

 

Looks more like a 13X8 tractor than an 8X13 in this clip, especially if it runs at 600 rpm..

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

P.

 

Andreas
Any details yet of the drivetrain you plan to use.
Quote:"I plan to use a HTD belt with a 90° twist, as this method is absolutely maintanence and corrosion free and very cheap, as it will use only one custom built part, which can be lasercut very cheap. The whole drivetrain with the best and only new premium parts will cost me only 150€ (but can be built for half or less)."
Do you know what distance is needed between the crank and the shaft to get the 90deg twist. Is the distance less than with a bike chain? Also what sort of gearing ratio are you looking at.

Ian