Sounds like a good project. A cheap pedal drive using readily available components that can be easily retracted for beaching... and, no doubt, efficient with a good turn of speed with a weed cutting prop that can be used in reverse as well.
But that does sound like the holy grail of pedal drives and, if it was simple, there would probably be thousands of them by now!
I'm not the best one to help with details of prop pitch, size etc. But I can get the ball rolling with more questions! These should help with some design parameters.
Will the hull be a new build or are you adapting an existing one? Point of that is to understand the extent to which the hull is constrained to that design or can yet be adapted. Hulls that feel stable when paddling (the dip of the paddle providing support and the waist being free to flex with the movement of the boat) don't always feel as stable when sitting and pedalling (no paddle and reclining onto a seat back that effectively locks the upper body in relation to the hull so you can't let the boat rock beneath you in the same way.) If you already have the hull it's worth sitting in it reclined against the seat back without a paddle while being towed at your anticipated pedalling speed through some waves/wakes/etc. just to check you're comfortable. Though you can always paddle pedal, pedalling while using the paddle for direction and stablity. Also a good exercise in recognising the difference between the words. Have to turn auto spell check off for that, computer insists on changing paddling to pedalling and vice versa.
Do you have to have a prop shaft through the hull or could you consider a whip type prop shaft over the side? The whip type being easier to lift when beaching. Alternatively you could use a flexible drive shaft like these people:
http://h2proped.com/ordering-information.htm. That would allow you to create an 'outboard' type drive, again easier to design so it kicks up as you beach. But the power losses in the flexi shaft may be an issue.
What sort of cadence (pedalling rate) do you think you'll be able to maintain comfortably? Then what sort of speed do you hope to cruise at... and what's the hull speed of the boat (clever people can work that out from the plans, but not me)? I suspect that information will be important for propellor size and shape calculations.
The one thing you will need to do is turn the drive from the pedals through 90° to power a prop shaft. There is no standard cycle component that I know of to do that. A long enough bike chain can be persuaded to twist to drive sprockets at right angles but there's a cost in sprocket wear, chain wear and the ever present power losses. Drive belts may be more flexible, but not generally considered bicycle componentry. Jeremy has done good things using 90° drive adaptors for power drills which are readily available (but not bike components.) Again the question will be power losses.
So, lots of questions and no help whatsoever... must be a consultant!
Tim.
On 19 Mar 2017, at 13:46, BrianP [via UK HBBR Forum] <
[hidden email]> wrote:
Can you guys help me put together a SOT with affordable pedal drive, using bicycle drive components and rear drive which has correct size drive propeller, perhaps can be retracting for coming to the beach.
14' SOT like this one
Drive tower something like this
Rear drive, as an example, the Gartside Pedal Boat
Thanks
Brian
Locked
