Pedal Powered Boats

[I57]

Wonder what the limits are for a small multihull, I have had my proa out on Port Phillip Bay in 20 knot winds. The waves were half metre or so and even with the outrigger to windward it was still stable. The outrigger is narrow and deep and I think this helps, there is always boat in the water. Recently raised the bow on the hull and outrigger by 100mm and it makes a difference as the boat has stopped trying to dive like a submarine when going downwind.

Ian

[OldNick]

I think a lot relies on the design of the boat (you mention adding 100m to the hulls) and the skill and fitness of the operator(s), Ian and their ability and willingness to handle disaster. When you see what Pacific Islanders and Straits people did in tiny canoes....

In Perth, you can get a really nasty 2-3 ft chop at Pelican Point, where it shallows, after 4KM of being blown by a 25kt "Fremantle Doctor" Souwester. One of my more exciting sails was sailing a Moth, with two people on board, across there, downwind. It was a scow and even has a bow that was curved downward so that the actual scow bowline was almost half way down the profile of the boat. Nose-diving was its favourite pastime. But it handled that surprisingly well, if the two of us really kept on our toes.

Unfortunately one of us put their foot through the deck. But we kept sailing, until we tried to tack and realised that the poor old thing was completely full of water. It had literally kept afloat by sheer speed, like skipping a rock I had to jump off and provide stern ballast, being dragged through millions of (non-stinging) jellyfish, to the other shore.

People (not me) sail surfcats in...well...surf. The sails help, but can also hinder when the sail size gets to "sport ratio" to hull size and weight.

I do reckon that one big disadvantage of pedal power in difficult situations is going to be a lack of dynamic ability. You have no sails to trim, you cannot shift weight to provide trim, and you don't have the ability that a paddler does to use the paddles to provide dynamic support. Again I guess it comes back to the design of the boat for the purpose it was intended. I was relieved to read that Greg's boat, for his little jaunt across the Pacific, has a keel and will self-right!

Nick

[OldNick]

I discovered this\

http://shop.ebay.com.au/marcin5753/m...&_trksid=p4340

It's an English factory that turns out recumbent bike seats in a small way and they seem a reasonable price.

I would be interested in people's thoughts, and FYI for anyone looking for a seat.

Nick

[Guest625101138]

The seat is a good price if it is built well even allowing for the postage. It looks good. Mounting points might need to be resolved.

There are a few recumbent makers in Australia but I cannot recall a seat for less than AUD100.

This link gives an idea of what you can get in Melbourne.
http://www.trisled.com.au/shop/shopexd.asp?id=114
I made one of these from a tri-sled mould. I think they are carbon fibre as mine is. From memory mine weighs about 400g.


Rick W

[OldNick]

Thanks for the input Rick. I had seen the Tri-Sled and the price! That was why I was interested in the UK one. I like the $70 piece of foam from TS.

Mounting points: I had looked at the seat and wondered about those. I might ask the makers about that aspect.

A question. Do you reckon that a pedal boat's seat has to be the same as a recumbent cycle's? I would have thought that you could have a wider base, because you are not needing the manoeuvrability that a bike needs. I have wondered about something nice and comfy, bearing in mind that my application is not weight-oriented.

[Guest625101138]

If you are going to trailer the boat then the weight of the seat is really not at all critical. Before I realised how much easier life gets when the weight is low for car-topping I used a double skinned plastic seat that was made for fishing seats in tinnies. It was OK for sitting in but not ideal for pedalling.

The seat depends somewhat on the height of the pedals. In the very reclined position I use I have more weight on my back than my feet. If I pedal at full power I have very little weight on my backside. Most of the load is taken by my upper back.

There are issues in having feet high that most recumbent cyclist know about. If your aims are for a comfortable, relatively slow boat then you could use a nicely padded seat. The back support will depend on how reclined you actually sit.

The recumbent seat I use does not have drain holes so when in waves that wash over it my backside is in water. It is not a problem because I usually avoid long periods in this state. Most of the time it is just a little welcome cooling that evaporates. You do need to think about staying dry if you intend to travel and fish on a brisk morning.

You will also find that windage is significant sitting upright on the Hobie.

If you have not been in a recumbent it is worthwhile spending a bit of time in a gym on a machine. You can just walk in off the street and pay a few dollars for a session. These machines are more upright than I use but will give you an idea of the arrangement.

Rick

[Submarine Tom]

OldNick,

No need to apologize for your previous post about weight vs eating.

It's a common misconception I just couldn't let go by. Sounds like you

know better.

My comment today is have you considered making your seat(s) adjustable?

I have ridden a recumbent (stationary and on the road) and thought you

may find it beneficial to be able to slide fore and aft, and tilt. Vertical

adjustment may be nice too but complicated. I thought if you're fabricating

it all anyway, how much more work would it be and for what benefit - I

don't know.

-Tom

[OldNick]

Thanks Rick.

What made that seat not suitable for paddling? I was looking at a recumbent or semi-recumbent setup, as I can see that windage can be helped by it. It also lends itself to the wider larger seats of the recumbents. Was the seat simply at the wrong angle for its design? You mention having a lot of the force on your back. So the seat obviously needs to be strong and have good support the entire length of your spine, as well as the right shape. Some have headrests as well, I see.

I read about losing blood supply to your feet if they are too high. That is something I need to taker into account.

Good point about the drainage, although the seats will be set fairly high by the very nature of then fact that they are above the deck of the cat. Having said that I once sailed with a guy who deliberately dived the cat into a wave when I was facing aft. He swore it was an accident, but I am sorry, he was laughing too hard.

You really want to get me into that gym! No it makes sense.

Nick

[OldNick]

Tom.

I have given quite a bit of thought to making the seat-pedal distance adjustable as I know the importance of this from cycling MTB, where you usually use cadence / gearing and stay in the saddle.

I also thought about allowing both the seat and the entire unit to tilt to try to get the best angle for different situations and people.

I imagine that a useful height adjustment would need gas lifters or a screw.

I have to careful not to overbuild, both in terms of complexity and sheer weight. While weight is not super-critical, when you see what a normal bike is built like you realise how little you can do with.

I may do one or more of the above, but on a first try KISS seems a good approach!

Nick

[Submarine Tom]

I wasn't really picturing "on the fly" adjustment, nor infinite.

Just a few optional positions. Sounds like you've already considered it and

that was my point.

-Tom

[OldNick]

Thanks for chipping in, Tom.

What I consider and what actually gets done...

Actually my boat building has generally evolved with each boat, because I am fascinated by trying ideas and each setup leads to another. With boats (unlike some of my other endeavours ), I have always ended up actually using the final product!

[Guest625101138]

Originally Posted by OldNick

Thanks Rick.

What made that seat not suitable for paddling? I was looking at a recumbent or semi-recumbent setup, as I can see that windage can be helped by it. It also lends itself to the wider larger seats of the recumbents. Was the seat simply at the wrong angle for its design? You mention having a lot of the force on your back. So the seat obviously needs to be strong and have good support the entire length of your spine, as well as the right shape. Some have headrests as well, I see.

I read about losing blood supply to your feet if they are too high. That is something I need to taker into account.

Good point about the drainage, although the seats will be set fairly high by the very nature of then fact that they are above the deck of the cat. Having said that I once sailed with a guy who deliberately dived the cat into a wave when I was facing aft. He swore it was an accident, but I am sorry, he was laughing too hard.

You really want to get me into that gym! No it makes sense.

Nick

The plastic seat I used was much heavier than the carbon fibre ones. It did not have back support high up but this is tolerable if you are sitting upright. It had nice arm rests. The more upright you sit the less the back is required to be supported. The only time you really have much load from the pedals is when you are sprinting.

I have a head rest but I tend to use it only when I cup my head in my hands with hands against the backrest. After hours of pedalling it is nice to be able to move around. I have got close to going to sleep while pedalling. Certainly nodded off with feet still spinning.

The attached image is a side view of the Tri-sled seat I have. I use high density foam bathroom matting rather than the Tri-sled open foam as a cover. The seat gives even support and there are no road bumps like a bike. The original seat back support was 12mm OD tube. This failed after about 800km so I have upgraded to 14mm OD.

The problem with high feet is poor blood supply and tingly toes. It is worse in cool weather.

If you have power data it is quite easy to do decent prop design and accurate performance prediction. I have also used a GPS to get power data when running up hills. If you have a high building with accessible staircase you can climb you can get a good idea of sustainable power. You need to work for about 10 minutes to get an indication.

I have a Garmin Edge 305 GPS that has ability to accept heart rate, cadence and of course all the GPS data such as speed and average speed. I record this information as you would record engine data. I have attached data from December in 2008 and 2009. From this I can see my improvements or otherwise. The main difference is the fact that the folding props overcomes stopping to clean it. The average speed in 2009 is almost 1kph better than 2008. Distance travelled is 34km in 2008 compared with 40km in 2009, both in about 4 hours.

In my annual race it is surprising how easy it is to push out too hard early. The adrenalin reduces the senses whereas the GPS enables me to work at a steady level. There was I guy I chatted to last year during the race who was permitted to race by his heart specialist only if he kept heart rate below 120bpm. Most of the racers use GPSs these days. A few have heart rate monitors; they are common on bikes. If nothing else you know how much longer you must keep turning over.

Rick

[OldNick]

Ah what a picture. Pedalling along with your hands behind your head! That's called showing off! I can certainly see the advantages of pedal power though. I am not a fisherman but I will appreciated the ability to pick up a drink (WATER! ) or food etc while still getting along.

I can remember using stairs to do power tests at school as part of physics lessons. We did not do sustained power, beyond showing how it dropped if you climbed the stairs a few times. But you had to come down and that gave something of a break.

I will certainly look at optimising the prop, but I will then need at least two props. I suppose 95% use would be the same two people and rest will simply not be optimised.

I am pretty sure I can envisage what you say about the seat. It makes sense. I figure that as long as the back does not get in the way if I do decide to sit more upright, it's safer to have it.

I and my wife both have HRMs but not the GPS. Because we will be travelling mostly on the river, I can have a pretty good idea of distance and times and just use the HRM. Mind you, GPS is getting so cheap these days....

Appreciate the attachments very much. Thank you.

EDIT: This is a top thread and thanks for starting and contributing to it.

Nick

[SolomonGrundy]

Hi all, it is nearing the point I'll have to make a final decision on how to get power to a "puller" type prop for a 24' HP/V. As we are now, the aluminum prop will be mounted on a nacelle on the fin keel and connected to the chain drive by two 90 deg. bevel gears (1:1) and a 5/8" SS shaft in between. That was about as simple as I could manage, while still maintaining a high degree of reliability and robustness.
So my question is: Could a flexible shaft be appropriate in this application, if not, why?
I'm wondering if a flexible shaft would be simpler and more reliable by removing the shaft and one bevel gear.
Thanks, SG

[OldNick]

I am but an egg in all of this, and have not been able to find your setup. But if your pedal station is amidships above the fin keel, then to use a flexible shaft would require you to take the drive system right forward and then have the shaft flex down from the bow to your prop. If the setup is as your avatar, then the flex shaft would have to be very bent (not good) and you would need a vee-gearbox forward.

So AFAICS (and again I am but a noob) you are probably losing if you want to have the prop as a nacelle at the tip of the keel and try to use flex shaft. Pedals to 90 deg gearbox chain to vee-drive at bow to (very bent) shaft to prop.

If you want flex shaft, then 1 * 90 deg gear (with or without chain for gearing) and shaft with prop at stern or bow of boat. The shaft needs to be very gently flexed. Flexing causes both inefficiencies and destruction of the shaft over time.