Final drive - well for now anyway

Building this boat seems to be a continual process of design and redesign.
The last couple of days I've been focusing on the drive, gettoi the power
from my feet on the pedals to the propeller. I thought I'd found the ideal
with Rick Willoughby's swing-arm double roller clutch mechanism till he
pointed out that the prop freewheels when you're not pedalling, and that
means you can't back-pedal. Back-pedalling could be important for
manoeuvring and also for unwinding any weed so I had to think of another
idea. So then I thought of some form of belt drive using steel cable, but
how do you join it?

Yesterday though I had the breakthrough (well I hope it is). I got to
thinking about the flat belt drives of the old cotton mills. They'd twist
and turn around the place so why couldn't I do the same? But what to use for
the belt that wouldn't stretch or slip? Nylon webbing seemed to be the
answer to the stretching, but the slipping? Then it hit me, Velcro! It's
very flat so easy to join, it can be stitched even, and if I used the hooked
side as the belt I could put the fuzzy side on the pulleys. I can even melt
stripes into it so that it becomes a fuzzy cog. That means that the peeling
off part as the belt comes off the pulley will be easier too. And it's easy
enough to make up my own pulley wheels to get just the gearing I want.

No doubt there's downsides I've not thought of. Possibly it's not the most
efficient system in the world, but as I'm not worried about 100% efficiency
that's not a problem. Perhaps it'll stretch or slip too much, well it's easy
enough to make up a test rig to find out. For now though I'm happy.

Now on to the next problem.

PS I've blogged this from my mobile, so excuse the typos, please.

Finally!

Well I finally seem to have got a design that could work. Over on the boat
designs forum, people much wiser than me have plugged in the numbers and
worked out a whole series of numbers which show she'll be reasonably stable,
and should, at a normal pedal do about 10 km/h. That's pretty good, as I've
always thought I'd do about 6 km/h on this trip, which with six hour days
meant I'd take ten days from one end to the other. This way I've got some
flexibility. In all this I have to thank Rick Willoughby, in Australia,
whose patiently explained things.

It's Rick too, who showed me what I'm almost certain will be the final drive
solution. He's used pedals on swinging arms connected to two roller clutches
as a way to twist the drive through the 90 degrees. It looks like a good
reliable and cheap solution. All I have to do is find the roller clutches.

So that's where Voie Bleue stands at the moment, a finalised shape - which
will no doubt change as the build goes on, and a drive system where I have
to find the parts. Not too bad, now I really want to get on and build,
before summer really comes.

Surprising Support

Well the other day I mentioned my idea on the AngloInfo forum, asking if
anyone knew of a charity I could support as part of my trip, I'd already
asked once and had no replies so I didn't expect a lot. But I'm amazed,
people really seemed to get it and were full of interest and support, both
in their postings and in private messages. It's very encouraging.

Also I'm finally beginning to manage DelftShip, the boat design program. I
can't say I understand all the technicalities of boat design by a long way,
all these LCBs and CLAs, but I have at least managed to get it not to leak,
now I need to get it into a rendering program so I can animate it for this
website. I still think I'll use Kayak Foundry when it comes to building it
though, as it gives you nice simple to print out offset plans.

Mind you the whole design might end up different. I'd started off with a
slightly fat kayak, with a shaft driven propeller, but that seems to have as
many problems as it does advantages. For a start it's too fat to be able to
make the hull form out of single sheets of plastic, they'd have to be joined
at the keel. Also the shaft driven propeller seems to be causing no end of
problems, all down to having to turn the drive through ninety degrees.
Finding a gearbox is proving harder than I thought, partly down to the
vocabulary of it all partly down to the costs, if I can find a suitable
supplier in France then I'll be happy, but until then I'll be looking at a
conjoined catamaran, as I'm calling it. The advantages to this are that the
hulls can be made of a single width of PVC and I can go back to a twisted
chain propeller drive, which will pivot up between the two hulls, also it
could well be more stable, the downside is that the superstructure will all
have to be redesigned and might mean I end up sitting higher. We shall see.