I haven't added to this blog for a very long time and sadly, don't even own a G-32 anymore, but there are not many resources for someone designing and building a pedal drive system for an R2AK boat, so I'm posting some photos from last year's R2AK.
My attention is mostly focussed on units without right-angle gears. Why?, because these gears can rob something like 5 percent (per gear box) of the meager human output, while chains or belts take something like 1 percent. This means sitting sideways, but why not? Some production units with right-angle gears have not proven very reliable either, but I've only heard stories...
This keelboat system hooked up to the prop shaft (after the engine was removed) and took up most of the cabin. Just getting past it to take a photo was a challenge, but I think it worked okay.
This was my favorite keelboat system, but the photos I got were lousy and I know very little about it.
The red thing with the sprockets and chain rotates down to rest against the hull. The flexible drive shaft (see the prop at the end) is just dropped into the water. The pedaler leans back against the house side and it looked like good ergonomics.
Remember that flexible drive shafts work as long as the shaft is bent when operating. See Matt Johnson's system designed by Rick Willoughby in the previous post from 2018.
This was a very impressive, efficient system, but I'm not sure why the cranks and big sprocket weren't part of the "leg". The belt in this system would go slack when retracting the leg, but it looked like a well thought-out system. Mounting the unit on a separate beam allowed the cranks to be low (compared to the next system shown).
This is my favorite example of the "pedal drive-on-a-stick" system. I guess my only input would be to
not make the shaft diameter too small because it can flex with every pedal stroke and to not make the lower sprocket too small because of power loss and the possibility of the chain or belt "jumping".
13 teeth for the lower sprocket was what I used for a similar system that worked.
Upper and lower bearings on this system are bicycle bottom bracket bearings.
This was the drive system that was used on the winning boat. I don't think it was used more than a little bit (the boat went the offshore route) and I don't think it was on the boat when it finished in Ketchikan.
The only benefit I see is facing forward with no drive angle changes.
This system on Eric Pesty's F-24 seemed very good. The cranks folded down and mostly out of the way in the cockpit and the shaft lifted up with a control line. It required a universal joint (can be seen in 3rd photo), but Eric got very good speed with this system.
Eric's was one of at least 3 multi's that were knocked out of the race after serious damage from hitting logs in a year that had an unusual amount of floating logs. He was sailing solo.
I'm a fan of the "pedal-drive-on-a-stick" system, as you can probably tell. The following was my first system on the G-32. It was challenging to use because it was installed through the cockpit floor and was a bear to deploy (and especially to remove when a puff hit), but the construction is worth commenting on:
The "stick" was a piece of standard-diameter carbon windsurfer mast. The bottom bracket shells were epoxy bonded to the ends of the stick and laminated over.
The lower sprocket is 13 teeth, the upper is a custom 72 tooth sprocket driving a 16x16 propeller (from ACP).
A shell fairing at the lower end would have helped, but this unit provided good speed and was still going strong even after the trip home (the outboard died) and did another R2AK on another boat.
The lower bearing (and aluminum casing) was the longest I could find (for a wide bike frame), which allowed the best clearance between the prop and the "stick".
I don't even vaguely understand this system, but there's a lot going on and worth pondering.
It looks like 2 right-angle gears per unit and some very deep thought.
This was team Malolo's unit with a tandem bike frame driving a single custom unit.
The two blog posts previous to this one are about pedal drive systems, but I'm afraid that I have barely scratched the surface of this topic. I'll add to the blog with this year's R2AK systems if I can.
Please feel free to comment if you have relevant details that could be helpful to someone designing and building a pedal drive system.
