A pedal powered catamaran with sail assistance

[Andrew Kirk]

A quick update on my progress. I tested my front mounted paddlewheel yesterday and averaged only 1.9 mph. The problem seems to be too little paddle in the water because my weight distribution is rear biased. This is raising the front of the hull, which I hadn't thought of. I need to lower the paddlewheel and will take the boat back to the canal to take accurate measurements.
The current paddlewheel position would be good for cappuccino making, with lots of slippage but little drive or resistance in the pedals.

 

[bajansailor]

Would it be possible to strap on some temporary ballast on the decks forward of amidships in order to try to immerse the paddle wheel some more, to see if this has an effect?
Are you happy with the actual blade area of your paddles, or do they still need to be increased some more?

 

[Robert Biegler]

If the motivation for the pedal drive is that you want to rely mostly on leg power, there is Ron Rantilla's front rower, which can be used with legs only, arms only, or any proportion in between that you desire:
Forward facing rowing for canoes, rowboats https://www.frontrower.com/

And here on a small catamaran:

The front rower is out of patent now, so you could build your own, and as long as you get the proportions right, you can be confident that you will get power transmitted to the water.

For hull shape, Phil Bolger advocated square-sectioned hulls with the same curvature on bottom and side panels, reasoning that made the water flow along the chine rather than across it.

For a very different hull shape that is claimed to be very efficient, and has mostly flat plates with a conical bend at the bilge, see http://www.din.unina.it/HSMV 2011 Proceedings/html/Papers/28.pdf

 

[Squidly-Diddly]

interesting concept. I think you could put the pedals on simple swing hingles so they would locked on the power-stroke but on return stroke would pivot and freely skim over the top of the water. Sorta like how on return stroke a sliding seat row boater will rotate the oars 85degs and they will skim on water for return stroke. He also does that for balance, which your cat wont need, but you get the idea.

 

[rwatson]

A quick update on my progress. I tested my front mounted paddlewheel yesterday and averaged only 1.9 mph. The problem seems to be too little paddle in the water because my weight distribution is rear biased. This is raising the front of the hull, which I hadn't thought of. I need to lower the paddlewheel and will take the boat back to the canal to take accurate measurements.
The current paddlewheel position would be good for cappuccino making, with lots of slippage but little drive or resistance in the pedals.

Try just pushing the paddlewheels just slightly faster than they would rotate by themselves in the passing water stream.
You lose a lot of propulsion ( and energy) pushing them till they cavitate, with very little extra forward speed.

I would also suggest investigating "self feathering" paddles.

You are still fighting the boxy, unstreamlined hull shape , too.

 

[Andrew Kirk]

Not yet perfect but I'm getting there!
I had a much better time on the canal, today. I have a couple of modifications to make but now think that I can achieve my design aims.
Real progress with the boat. https://mountainbiker.online/2023/06/08/real-progress-with-the-boat/

 

[Andrew Kirk]

After several more tests with the catamaran, I'm happy. I've been improving chain retention and adjusting the paddlewheel height and, hence, depth of immersion. I want to test one more position, in the expectation that I can improve my speed a little further. For a short hull my speed is acceptable. I'll easily be able to cruise a 60% of maximum hull speed and still have the exciting prospect of building sail power or at least assistance.
Successful Boat Test. http://mountainbiker.online/2023/06/22/successful-boat-test/

 

[Andrew Kirk]

I'd like to update my thread after 5 months of saying nothing. I think there must be someone out there who's at least a little interested because I often get links to my blog from this thread.
I decided that the catamaran was sitting at the wrong angle in the water. The stern was down and the bow up. The intention had been to have the flat bottomed hulls sitting level. This, I thought, would reduce drag to a minimum. I have started to move the heaviest part of the boat, myself, forwards by 22.5 cm which, according to my calculations, will be enough to level things up.
In the meantime I've had a heart valve fail, just like Arnold Schwartzeneger! This has surprised me since I've always kept myself rather fit. I'll get it fixed next year but may not be able to test the boat until after that. I will, however, be able to complete the work required.
Just before the heart problem revealed itself I had a good test, where I was very close to my modest target speed. A little more improvement should get me where I want to be.