Rob
We are getting very close to a production version of a pedal frame per these renders:
There are two boats using the curved shaft and folding prop in the R2AK this year. They are not lightweight racers but are relatively small. Both have broken masts and took a long time to make repairs. Team Sea Runners have a Facebook page with some photos and comments on their rough and ready pedal drive:
Team Puffin is the other with a folding prop and curved shaft. These two boats have stuck together since they repaired their masts and sails. The pedal drives with the curved shafts have proven durable so far. Pedal drives with twisted chains used by other boats have not faired so well. One boat has Hobie flappers but I do not know how they have done.
The issues for a proa is deciding which end do you want to be the front for pedal power. In light conditions the HP sails higher with mast to windward and that would probably be good for motor sailing. In heavier conditions with just sail, lift the prop out of the water. In any case being able to get something like 4kts under power would give ability to pinch up with the lw hull to the lee.
One adult male in good shape can sustain 150W. That would get maybe 4kts if boat was trimmed to minimise drag for that speed. If the power is doubled to 300W then the speed gets to 5kts.
Both Team Sea Runners and Team Puffin have 2 crew. They have found they cannot sustain the effort 24 hours a day. A crew of 3 could likely sustain the effort. So 24 hours at 4kts covers 96nm. 16 hours at 5 knots covers 80nm. On that basis a single drive with 3 crew would be all that is needed.
The 8T cat with the twin pedal drives used slightly modified industrial gearboxes. They found that pedalling any time the boat dropped below 4kts was worthwhile. In fact those units are set up so they automatically lift once boat speed picks up so the pedaller is not trapped in the cleats trying to brake the monster prop. That was a problem with the first iteration.
The units in this photo are the final design. They are in the folded position with the prop sitting on the seat. There is a foam cushion about halfway along the leg that thrusts against the transom when pedalling. As the boat picks up speed under sail the leg just trails and there is no effort to stop the prop turning.
The folding props on the smaller boats just folds when the boat picks up speed although the prop would need to be lifted clear of the water when sailing prop first to reduce the drag.
Turn Point Design considered a pedal drive with curved shaft but their cockpit design did not suit a curved shaft so it pays to consider the pedal system at the design stage. Timing was too tight to engineer a drive with commercial gearboxes. They used a twisted chain drive - not certain how their pedal unit faired. Felix sailed well though.
Rick
On 17/06/2015, at 10:35 AM, "Rob Denney harryproa@gmail.com [harryproa]" <harryproa@yahoogroups.com.au> wrote:
There has been a fair bit of interest in the Race to Alaska. Looks like the next Cruiser will be built in Vancouver for a keen racer who suggested competing in the event before the boat is completely fitted out. His worry is that, in this notoriously light air area, would the boat be too big to people power. Given that Rick has designed a pedal system for a heavy Chris White cat which pushed it at 2 knots, I don't think it will be a problem. Question is, how many people would it be worth carrying, solely as propulsion providers? And what would be the best way to utilise them?rob
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Posted by: Rick Willoughby <rickwill@bigpond.net.au>
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