Pedal Powered Boats

Attached image shows an open nylon bevel gear drive. The PV30 should be more than adequate. The supplier is in Brisbane:
http://www.tea.net.au/welcome.aspx?page=12
I have never priced these.

You can get the gears from here:
http://www.smallparts.com.au/store/...odule250/bevelgearsstraightcutmetric/all/1/3/

I have got boxes from Transmission Australia in Rowville. They used to be a fair price with cost similar to Mitrpak.

If you have access to good milling and/or machining then you only need basic parts.

When you look at the little sealed boxes it is easy to recognise the value.

There are things like right angle drives for drills from Bunnings but they will not handle much power. Would be suitable for an initial trial.

Rick W

 

Rick, seems like someone mentioned an angle grinder on the HPB list years ago as having strong enough gears. What are these exactly, are they low cost and might they possibly work is the question...

Porta

 

I had a 4" grinder that had worn brushes that I stripped out for Ian to use. It was quite easy to set up and worked smoothly but did not last long.

The Involute boxes that George had made used the gear set from a 10" grinder. Both Ian and I have one of these boxes. I have never used mine but Ian's is nicely run in now and it is very smooth. The reduction is 3:1 so no chain required.

So an old grinder is a potential source of gears.

Rick

 

Frappacino

Read your post about a pedal powered kayak, have been down that road and still going down it. My first boat I was always putting holes in it when I tried different drive layouts, the angle grinder gear I got from Rick worked well and with a stronger gearbox would be a good setup. The alternative to a gearbox is a twisted chain drive but this means a hole in the boat unless you go for a catamaran. I have attached a drawing for an idea that might be what you're looking for, I don't know the size of the opening in your kayak but you will need a bit of leg room. Other thing to consider is outriggers if in rough water, with the peddle setup your CG goes up and you haven't a paddle to brace with. The flex shaft allows you to reach over and raise it out of the water for beaching.
Yes, I live in Melbourne as well (its a small world).

Ian

 

Hi all,

I'm planning on building a pedal powered catamaran for a raft race next year. It will be something along the lines of Warren Beauchamp's "Sidewinder", except that I will have two people driving the one prop. For those not familiar with the Sidewinder, you can check it out here...http://www.recumbents.com/home.asp?URL=wisil/hpb/boat.htm

I realise that a mono-hull would be faster but the extra stability of the catamaran is needed due to the nature of the race; there's a bit of moving about required.

I posted here because I will need some advice on prop design, but first of all I need to decide on a hull shape. I came across these instructions on how to cut a nicely shaped hull from foam http://www.instructables.com/id/SALXG8PF2ZML3LG/

This seems like a nice shape to me, but if you follow the instructions you'll see that it involves a fair bit of work. I'm wondering if there would be much difference in performance if I were to go for hulls like these instead? http://www.humanpoweredboats.com/Photos/OtherDisplacementHPBs/KweeKat.jpg

The latter would be much simpler to make, and if they were close in performance to the other then they may be good enough as the other rafts will be fairly basic.

Other than "the longer the better" I don't know anything about hull design, so I'd appreciate any advice on the difference between the hull shapes.

 

There will not be much difference. There will be a length to width of the hull that will give lowest drag. Any shaping beyond that will not make much difference.

Solid foam is not all that strong. If you make the hulls long enough to go as fast as you can then they will not support your weight. You need strengthening along the bottom of the hull.

It is not hard to make a very simply hull from ply. It would be lighter. There are photos of making a simple hull here:
http://www.boatdesign.net/forums/boat-design/camping-kid-build-raft-race-28311.html

A stabilised mono hull is also faster than a catamaran but it would need to be about 9m long to get the best speed from two people.

Rick W

 

Thanks Rick,

I had a look at that plywood hull. I had actually read that thread a while back but never checked back to see how they got on. Nice job.

I'm surprised that you think that the plywood would be lighter than foam. I suppose I never considered that 3mm ply would be strong enough. Really? If so, it's good news to me as I'm fairly comfortable working with wood.

I assume that the reason for flaring out the sides was to make more room for paddling. In my case the hulls would be fully sealed so I assume there's no great advantage to having the deck wider than the chine.

The raft will need to carry four adults; two men pedalling and two women paddling. Looking at the pics in that thread it seems we'd get away with two of these hulls to make our cat. What would you think of 15.5' long, 12" wide with 12" vertical sides?

This was roughly what I had in mind for the foam versions too. I intended adding a plywood deck for strength. I take it you think the plywood version would be better?

Ta.

 

The dimensions will work OK if you are not all in the 90kg weight range.

3mm will work if you place transverse bulkheads say every 600mm and a central longitudinal. These can be made from the 50mm blue foam. If you want something durable than 4mm ply would be better.

Cut the top and bottom panels with a nice curve for the bow and stern. Screw and glue the chine stringers - 20mm square works well for stringers. Glue the transverse and longitudinal bulkheads to the bottom. Glue the top to the bulkheads. Screw and glue the sides to the stringers with glue to the transverse bulkheads as well.

With a bit of planning you can use some internal timber stiffening in the hulls to bolt cross beam to.

You can get expanding polyurethane glue that bonds well to timber and foam. It will waterproof well as it is water cured. This is the stuff I get in Australia:
http://www.vise.com.au/

Just painting it will give a good finish. If you want something to last then glass tape along the seams and proper finishing with fairing filler and sanding before painting would produce something that will last a long time if stored out of the sun.

Rick W

 

This is great stuff. Just to be clear, I assume the central longitudinal would be a series of short bulkheads in between the transverse bulkheads?

Thats an interesting idea to use foam for the bulkheads. Foam would have more surface area to glue the sides to than plywood bulk heads. If ply is used I suppose it needs a little frame of 20mm square around the outside so that the sides, top and bottom have something to bond to.

I guess I'd need something more substantial at the transverse joint in the top/bottom/sides. Would you recommend overlapping the sheets or just creating a butt joint at the bulkhead? How wide would this bulkhead need to be to reliably join the sheets? Would you create 2 such bulkheads 6" - 12" apart so that the joints would be staggered? As you can see, I'm a bit worried about the joint.

 

Yes. There will be 550mm long longitudinal bulkheads between the transverse. You would not need them in the very ends. If you go back to post #295 on this thread you will see how I used 25mm thick foam for bulkheads. There is only one short longitudinal where I put my feet.

To join the sheets you cut them to size and screw/glue a splice plate of ply between them. The splice piece fits inside between the stringers. Need say 80mm overlap on either sheet. I would stagger the joins on adjacent sheets. I would ensure the chine and gunwale stringers were continuous through the joins.

You might end up with say 20mm thick timber bulkheads where you want to tie in the cross braces instead of the foam.

Once you make a box it ends up rigid and will be strong enough.

Rick W

 

Ok, that's the hulls sorted...... in my head anyway!

If you don't mind me pushing my luck I'll carry on. There's two other areas where I need some guidance; the rudder and the prop.

As an experiment to see how hard it would be, I've shaped and twisted some blades for an 18" prop I found linked on this page
http://www.recumbents.com/wisil/hpb/prop/default.htm. Thanks for the excellent instructions BTW.

"The design conditions for this prop were 2-bladed, 420rpm, 0.45m (18")
diameter, 3.5m/s speed and thrust of 88N. This was based on an input
power of 350W."

I'm not sure if this prop is appropriate for what I'm building. The drive train I've got has a 48:10 ratio so the rpm should be about right. I don't know what kind of power we put out though. We both do a bit of cycling so we're reasonably fit, and the race is only about 500 metres long.

Making the blades was pretty easy so I'd start from scratch if the blades I've made are wrong. I haven't even welded them yet anyway.

Last thing is the rudder. Would I need one behind each hull, or a central one behind the prop. What shape and size is best and how deep should it go?

Thanks for you help. Much appreciated.

 

Rudder is easy. I would go for one under one of the hulls. This leaves the other hull free to get closer to the beach. A rudder under the hull will be more effective. I would have a rudder say 250mm deep and 80mm long; a NACA0020 section.

Prop is a little more difficult. I am a little confused on the power input and weight. You say two are paddling and two are pedalling. Are the two pedallers on a single prop?

To arrive at the best prop you need to know the weight and power level. How heavy are the four people and how much can be expected from the paddlers?

Rick

 

The total weight of the four people would be about 285kg. The two pedalling are on a single prop.

The paddlers would not be practised at paddling but they will give it all they have for ten minutes. I wouldn't expect too much. They are only about 55kg each though so not the worst passengers.

 

The attached shows a 5m hull. I expect two fit men could push this along at 7kts for 500m. Maybe get 8kts if the passengers can add a bit.

A prop around 500mm diameter is OK. Blades made from 50mm wide by 4mm thick would easily be strong enough. It will vibrate if the shaft is inclined. Need to think about the drive set up.

When you get a bit further down the track with the hulls I can do a prop design that can be fabricated.

I am assuming you realise you could go considerably faster if you made longer hulls but do not want to handle long hulls

Rick

 

Yeah, I realise that longer hulls would be faster, but for building, transport, and storage reasons I think that 15.5' (2 sheets of ply) would be long enough.

So the prop I made already would be a bit small. The diameter is only 450mm and the chord is only 35mm at its widest point. http://www.recumbents.com/home.asp?URL=wisil/hpb/boat.htm

I assume we would be spinning too much if the prop is too small. If you don't mind, I'll be in touch again for a prop design when the hulls are built. I'm fairly sure I'll stick with the 15.5' plywood hulls with a shape similar to your attachment. What other info would I need to provide?

For the drive train I plan on using two universal joints so that the prop is driving in the direction of motion. I've seen your strutless prop but I've no idea where to get spring steel around here.

Thanks again.