Pedal Powered Boats

You have a beautiful boat. What sort of cruising speed you achieving? I have been getting delayed by weather and the obligation of my day job but I am still plugging away at getting my boat to tests as quickly as I can. I was interested in your fiberglass prop. I am looking for innovative prop manufacture ideas. I want to experiment with pvc. I have currently outfitted my boat with twin aluminum props. Counter-rotating 7.75in. two bladed. Who knows what the pitch is? but they are symetrical and balanced well enough. I'll get it to the lake someday. Glad to see your success. It's a beautiful craft you have .

 

Props

Had the boat out today using the 4 blade prop with the cord width at 30mm, still felt heavy. If I was riding a bike I would have dropped a gear or two. 20mm was too light so might trim it to 25mm and see what happens.
Zipboater - My props are made of fibreglass around a square steel hub, the end of the shaft has a matching steel square rod. I use a piece of wire to stop the prop sliding off, easy to change over props. I glue a piece of ply around the tube and cut an angled slot for the thin aluminium sheet. This is cut to shape and curved, I then twist the sheets to the correct angles and then lay a sheet of fibreglass along one side. When this has hardened and I have the angles right I lay the rest of the fibreglass then sand and paint it.
My cruising speed is about 8kph, this speed I could maintain for an hour or so depending on how my back holds up.

Ian

 

Directional Prop

Have recently fitted a flex shaft and folding prop to the boat, courtesy of Rick. Then had the idea if a flex shaft can go up and down to avoid snags why not go from side to side to steer the boat. The flex shaft has a aluminium strut near the prop which slides in a slot in the steering arm. The arm is harder to move than a rudder so needs a bit more leverage. It works, tried it out today for the first time and turned better than with the rudder.
The flex shaft is at an angle of 11deg. the shaft has a shallow curve with a
flex section of 1.3m. The extra load when turning loads up the shaft a lot more so the steering arm needs to be quite solid.

Ian

 

Yes, there are certain situations where a rudder is not very responsive and this would be about the only way to turn. Like when going with the flow below the rapids on a river. You don't have the luxury of lag time when you want to avoid an overhanging branch or boulder in the middle of the stream. The flex shaft also allows travel in very shallow water as it swings up and around when hitting rocks or the bottom. http://www.boatdesign.net/forums/inboards/prop-shaft-systems-24636-4.html post 54 and 53.

P.

 

Sorry...been away from this site for a while building a new boat, etc.

No, the paddles were set up so only the 6" vanes were immersed in water. The vanes were mounted on the would-be tire edges of 27" bike rims, and were strong enough to lift the canoe to which they were mounted out of the water if necessary.

I traveled up streams with as little as 2 or 3 inches of water, and tidal areas choked with weeds. I never worried about rocks, weeds, shallows, etc.

Michael Lampi

 

Very cool, Ian!

So, how do you lift the prop when you get to the shallows?

Michael Lampi

 

Prop

Mike
It is one of Rick's folding props so when I hit shallow water the blades fold and the shaft bends up, the strut slides up its slot. On one of my earlier setups I had a vertical post near the stern with a cord attached to the top of the strut ( see post #979 on this thread). This worked to a point but the cord would sometimes jam and I had to wind up the cord and stow it. Where I go I am into deep enough water close to shore. It means carrying the boat a few metres but getting wet is not a problem where I live even in the winter.

Ian

 

Flexible shaft and Prop

Ian

Please bear with me as I'm a total newby to this stuff but I find it extremely interesting and looking forward to finding a new way to get some exercise.

After doing quite a bit of reading through these forums lately, particulary some of Rick W's from past years, I was wondering if I could get some addtional info. I came accross the post from Rick listing all the details about his boat (gear box, prop, etc) but I would like to know more about the flexible shaft (where to get it and how long it should be). Also, some of the links of where to get the prop where old so maybe you can suggest a place to get these also.

Any details/specifics (pictures) would be helpfull.

Thanks
John

 

Flex Shafts

JTA
Sizing a flexible shaft is beyond my technical ability, if you log into the
hpv boats website http://www.mail-archive.com/hpv-boats@bikelist.org/maillist.html . Someone on there can give you the details you are after.
The first step is to work out what sort of drive you are going to use. There is the twisted chain drive or a 90 deg gearbox. Depending upon the gearing will determine the prop size. For example my first boat had a bike chain turning a gearbox, the total gearing was 1:8. That is every turn of the crank turned the prop 8 times, the prop had a diameter of 250mm. My current setup is a 1:3 gearbox with the cranks fitted and the shaft running directly off the gearbox, prop size is 430mm diameter. The flexible shaft is 8mm spring steel, the tighter the curve the more strain and shorter lifespan. I make my own props out of fibreglass and use a program called Java Prop to size them.
With my latest boat I have fitted one of Ricks folding props which has steel blades. Are you building a boat or converting one? If you post some details I might be able to give you a hand. It involves the hull size(beam & length) and total load on the boat. What sort of speed you want and what conditions the boat is used (lake, river, bay). Hope all this waffle helps.

Ian

 

Awhile back, I did a lot of searching for the SPRING steel flex shaft in the larger diameters that Rick and Ian use and was not able to find a supplier in the USA. The flex part does not have to run the entire length if it will run through a support skeg as in Ian's design, the front portion can be rigid aluminum. The closest thing I have found that is available at just about any hardware (home depot, Lowes) store is 1/4" (6.3mm) electricians drills or extensions.

http://www.toolsofthetrade.net/industry-news.asp?sectionID=1490&articleID=1498824

I use 3/16" in my applications which are not human power related and they are way more than enough for my application. There are claims that 3mm diameter spring has enough torsional strength to handle the 250 watt human output, but like Rick, I doubt that 3mm would stand up to shock load and necessary stiffness. Using a magnetic pedal crank gearbox as Rick has developed would solve the shock load issue. But then the torsional compliance one remains with thinner diameter spring steel shaft, maybe can be minimized with shorter lengths of the flex section.

The easiest and cheapest way to go on the props for human power is to use 16X16 APC model airplane props, though this may require tall up gearing depending on how much power you are capable of for pedalling. http://www.amainhobbies.com/product...ts_id/36392/n/APC-16x16-140-Pattern-Propeller

Hope this helps.

Porta

 

Flex Shaft & Prop

Ian/Porta

Thanks for the input. I guess my initial thought was to follow what Rick W described here (http://www.boatdesign.net/forums/boat-design/converting-bicylce-pedal-boat-25486.html post #5). Using a bike crank connected to a Mitrpak 2:1 gear box thereby getting the 1:8 ratio, using the flex shaft described attached to a model air prop as described and shown in his photo. As far as the hull goes I'm still unsure but I think I would be leaning towards a sleek/thin catamaran design somewhere in the 12'-14' range. I know a monohull with stabilizers would be faster but I'm more concerned with stability and I thought with the cat option I could sit a little higher above the water (reducing spray). Again, the main purpose would be exercise, not racing. I would be using the boat in a coastal bay and back area canals/creeks. As far as load goes, well that's why I need it, the passenger load will be in the 225lb range, as for the hull/hulls (cat) I'm not too sure. I did a little research on stitch & glue technique and feel I could probably do something like that. Another thought I had, not sure if it would work, was to use some flotation foam billets to carve them into a shape of the hull and then glass over them. Again, not sure if you could glass directly to the foam or if you need to cover in wood first. Any thoughts/insights?

Thanks
John

 

Hull Construction

JTA aka John
Using a foam block and glassing over I reckon is the hardest and heaviest method of construction. Shaping the foam block is messy, all that foam shaving floating in the air and hard to clean up. After glassing over you have to coat it with gelcoat or some other sealant as fibreglass on its own is porous. No matter how well you seal it over time water does seep in and is absorbed by the foam, the water can't drain out and the boat just gets heavier. I'm probaly ranting a bit but I built a surfski like this once and it was a flop right from the start.
My current boat I built using 3mm plywood with internal framing every 200mm and internal fibreglass strips along the joins. It is a basic box construction but easy to make, the flat sides and bottom are ok for this type of hull. I sealed along the join on the outside and gave it three coats of paint. The result is a reasonably light strong hull.

Ian

 

Ian, I'm sorry your fiberglas experience was bad.

John, I would recommend fiberglas or fiber/epoxy, especially for a cat. You can make one mold and then lay-up two hulls. Brace them internally and shazam! You don't have to make a mold, you can lay-up on braced veneer, you'd have every success. You'll get a terrific strength to weight ratio.

-Tom

 

Ian thank you for the input about your prop fabrication. I have been dry running the drive system in my boat. It consists of a 10:1 direct drive pedal and sprocket which turns a 12.5" diameter, 1/4" thick aluminum disc. I use two 4" diameter non-skid industrial grade caster wheels fastened by a tensioner that induces each wheel to travel along opposing sides of the main aluminum disc. The caster wheels are each coupled to a pulley at both port and starboard sides of the main drive disc. I have this drive set up to yield about a 27.5:1 prop to pedal ratio. This configuration allows me to drive multiple props. In this boat I am running dual props. It also has given me the option of running much smaller diameter props and thus, has made it possible to reduce the minimum operating depth. I am about three months behind my projected finish date. Oh well, onward through the fog! Good luck to you.

 

Ian/Tom

Thanks for the responses.

Ian:
Is that the Hull from the pictures in your above post (#1053) that you are using the Flex shaft attached to your steering rudder arm? This is something I think I could tackle. So if I made two identical hulls (say 12' long) in a similar design/construction to what you are describing, would a bike crank to a gear box giving a ratio of 1:8 be sufficient to push the boat for exercise puposes? Again, I'm still unsure about the Flex shaft part (where to get), is it nothing more than what Porta described above (electricians flex drill attachment) or is this something that Rick W. has designed/produced for private use? I saw one of your earlier posts that shows your boat with the shaft (solid shaft) coming through the bottom of the hull. If I build the cat version and have a straight solid shaft coming down between the 2 hulls, I assume I would need a prop with a special pitch to compensate for the angle of the shaft right. I see you make your own props but that is beyond my abilities. This is why I was leaning towards the Flex shaft (if I could locate one) as it seems it comes right out of the gear box into the water, correct?

Tom:

Thanks but I don't think that I would be capable of doing a mold but I guess the Lay-up on braced veneer would be similar to glassing over a frame like Ian has shown, right? If you did this application, how many layers of fiberglass cloth would you need to use?

Thanks to all;
John