Oh great fountain of knowledge of STW can you help?

I have a bit of a scrap heap challenge, the application is for a Human powered Yacht. It’s for the Three Peaks Yacht Race which I’ve done a few times before, I’m a runner/Cyclist not a sailor. As it’s racing, no engines are allowed. So if there’s no wind for periods of time, as there has been in previous years, we’ve used oars to at least try and keep moving. But as you might imagine a 7 ish tonne 30-40ft yacht isn’t exactly designed for rowing not exactly efficient or comfortable means of power. So after rowing the length of the Lock from nie on the Corran Narrows to the Corpah through the night to land for dawn and have to run up and down Ben Nevis I’m looking for a more efficient mode of human power
I’ve got the following frame all set up which fits the rear of our charter with 2 old rear hubs ready to go, suitable propellers are on order, 16×16 model aircraft props (apparently good off the shelf option for a HPB)

IMAG0101
Prop pole only lying down and mocked up in the photo + won’t be using u-clamps but BB shells to minimise drag/bearing load and all painted up in white now so it doesn’t look so out of place in the boat.

Now my last task is to get and mount suitable pulleys and belts, which I’m really struggling to find. Basically I need to get the larger pulley mounted to the hub (Disc mount or bodged onto spoke flange) and the smaller mounted onto a Squarr taper BB axle (prop on other end)
The prop’ pole will pivot around the hub, so they come out of the water, so as not to drag when we’re sailing.
The belts being twisted through 90Degrees to turn the prop.

I’m trying to find suitable belts and pulleys which will fit the following criteria:
-That will take a 1 Human power (geared 1:5 ish) and not slip
-Pulley sizes 2:5
with the smallest being not much more that a few inches in diameter to minimise drag in the water
aiming for 400-500rpm, chain sections @ 1:2 already so cadence of 90ish I need the pulleys at about 2:5 to get a total of 1:5
-OK to Run partially through salt water
-Allow a twist of 90degrees
-and be about 2ft in length (centre to centre of pulleys)
and if possible be cheap too (moon on a stick??)

I think Car ones will be to inflexible and heavy duty to allow the twist
washing machine ones to flimsy (pulleys seem wrong sizes generally too, too big and small)

any one got any constructive thoughts/ideas which work with what I’ve got?
a complete redesign is out of the question (Next year maybe), only a few weeks left and not much free time to do it in

we still have the oars as a back up if all else fails.

Thanks
All

Cooooooooooooooooooool

Have I missunderstood? you want to bend a belt drive through 90 degrees and get a 5:1 gearing out of it?

Have you considered using a bevel gear box and/or UJs?

Belt drives need tension and aren’t keen on twisting or bending….

Easier just to mount the two bikes sideways in the boat, and possibly shaft connect it, to remove the 90 twist? As above, without serious bracing your belt drives will just slip/fall off I fear.

Still not sure how this isn’t cheating, but they’re your rules 😀

http://www.recumbents.com/wisil/hpb/compact_drive.htm

not far off it yes
pretty much like this but with a belt run externally through the water

Viewed from above the pulleys need to form a cross directly above one another for best results, I have seen some stuff from googeling where it works ok, I just can’t find where the source them from
These people are on my list to try transmission development poole but depends on cost if it’s £££ then it might be too much

I had considered Gearboxes and UJs yes, sourcing suitable ones didn’t seem easy

It might not be perfect I know
I know I may need to add a couple of belt guides

Next years design might be very different, found a few ideas and things after being well under way

physically mounting the bikes that way was simpler, not very many mounting points and it’s a charter so we have to be careful not to damage the boat. getting 2 bikes and 2 props sideways was a PITA
bikes would have to be mounted so high/far off the stern to avoid the pedals strike, we went this way this year.

Rules are no engines, human power is allowed.
Oars are ok, also on a previous years a team of marines when in the Menai Straits landed via dingy and pulled the yacht Canal boat and horse style.

next year I was thinking of using Mike_D’s finding with a chair facing rearwards on the yachts stern recumbent style. but I found that a bit late on in the process. we live and learn…

Are you sure those 16×16 APC props are really suitable? Has someone tried these already?

I can’t imagine they would be much use in the role you are looking at. I can see they might be OK for something pedalo style but not to get a bloody big yacht moving.

The main point of that link was to suggest a twisted chain rather than a twisted belt — parts look easier to come by, and it’s tried and tested.

I’m sceptical about the props too — right choice for a kayak or a hydrofoil (light, low drag hull) is probably not the right choice for a 7 tonne yacht (heavy, draggy). I suspect that those props just won’t generate enough thrust.

We may have a great wind this year and it not be need but there’s usually some flat spots here and there

The Menai Straits and the Swellies are a pain as they’re so well protected if the wind’s in the the wrong direction it can all end in disaster there, several teams retired in there last year. One on rocks and 2 I think using engines to negate the same happening to them (light winds and strong tide)

I think the props will just slip at slow RPM and cavitate if you pedal like billyo. better of going to a chandlers and letting them know your expected RPM and letting them suggest something i rekon.

Mike+Uphill I have the same concerns on the props, but want to try something, normal boat props are no good either I don’t think as we’ll never get the RPM required even with a single prop’ powered by both bikes

nothing lost really if it doesn’t work
It’s only cost £50 ish + some scrap parts and spare metal I had in the garage

something similar has been done before, there’s an Australian 3Peaks and there are a few teams their which have done it with some success.
No details on the props used by them though. That’s where the initial idea came from, details were sketchy though
only other prop idea/design I’ve found is this from the same website above again it’s very much geared at smaller craft as you both point out

We can make 1-2knots from 2 oars but it’s back breaking for hours

uphill I’ll pop down to the chandlers and see what they think
maybe a very small outboard one???

the 16×16 props are out of stock at the mo’ so need a back up in case they don’t get in in time

I would think some of the electric outboards work on low RPM and power. Might be worth looking into what they use

http://www.demonick.com/kayak/HMR/HMR.Mirage.Drive.02.1024.jpg

These might be an idea for rear mounting in a recumbent position in future. They have loads of “Watergrip”. Lots of tales of hobie mirage kayaks rescuing and towing powerboats. You wouldnt need to worry about optimum RPM or prop size. I think with a prop you will end up with an egg whisk with no oomph on a boat that size.

With a flat or Open Transom you could adapt it to any future charter boats too.

The props on this look pretty big:

http://www.sail-world.com/UK/Australian-Three-Peaks-Race-2011-starts-off-at-a-cracking-pace/82737

Must be a couple of feet across judging by the seats. That boat displaces about what yours does, although two long thin hills might be less draggy than one fat one (don’t know what yacht you’re using).

I would stick a very small outboard motor on your yacht, to see if it will actually move… How much HP can one person make?

These people do lots of gears, chains, pulleys, bearing blocks etc.

TechnoBots looks like a good shout thanks Mike,
looks like T5 SyncFlex belt and Pulleys will work

the 16×16 props are out of stock so I’ll have a look at alternatives.
Maybe a small outboard type prop or a larger aircraft prop with a large pitch maybe, the photo Mike_D found from the Australian race looks like a larger diameter aircraft style thing than a boat prop

CBike’s find is an option too for future when funds aren’t as tight as this year

A friend of mine built something similar for his final year uni project. The prof was a mad keen sailor. He used a couple of old steering columns from the scrapyard. They came ready fitted with universal joints and rubber couplings. I don’t think it ever worked, though 🙂

What about bikes connected to a genny (aka car alternator), and then an electric motor (car starter)?

Gearing and power transfer problems solved. What you lose in generating/transmission of electricity you might gain in prop efficiency, and a twisted belt/chain is going to be far from efficient anyway.

The two of you should be able to generate 500W between you for a reasonable amount of time, which is about 0.7hp. With losses you’ll be lucky to get half a horsepower…

it may seem a little too obvious but how about a paddle stteamer style wheel?? doesnt have to be too big, could mount one for each bike?? would be able to generate a decent amouint of propulsion form them,
a 3-35ft yacht has typically a 30hp motor, which should poke it along at 6-7knots max,(hull displacement speed)
for a light weight racing yacht then i think your idea would be fine but dont think the propulsion will be enough for a large 30+footer?? i know the local marine engineers used to use their dory with a 15hp outboard on for moving boats aorund when needed but had to be worked quite hard,

on the subject of tides/ headwinds, is the use of a Kedge anchor allowed?? deployed when forward motion stops, – deployed over the side straight down rather than Launched off the bow and pulled in! i know they are still allowed to be used in racing for the purpose of holding yopu steady in heavy tidal situations over lack of wind, but! not allowed if forward propulsion is gained from retrieving it as such!??!

it may seem a little too obvious but how about a paddle stteamer style wheel?

My thoughts exactly – think pedalo.

Edit: In fact why not just buy one of these and stick it on the foredeck. it’s 7′ long so will fit fine and at 41kg isn’t that heavy (you could always move it to the windward rail if the breeze is up!). Just chuck it over the side and tow the boat if the wind drops.

it may seem a little too obvious but how about a paddle steamer style wheel?

^ this.

pullies and belts..

local / online bearing / industrial drive suppliers will have all sorts of belts and pullies

most industrial drive places can get fenner products or similar

http://www.fennerdrives.com/

or cheap:
90deg angle drill adapter and alter ration to it by altering your chainring size etc