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[portacruise]

Originally Posted by OldNick

Sorry Porta and thanks for your time.

When I referred to the coiled stuff I was referring to the stanchion/skeg for the prop, not the driveshaft. I am still not sure how , but I am convinced that the curved spring steel shaft works, and is is the way to go. I just want to constrain it enough for reverse and as you say to prevent it banging the hulls.

The irony I saw was that the coiled stuff had pretty much eliminated as a driveshaft, but may have a use after all.

The coiled stuff strikes me as ideal as it can bend quite sharply without breaking or irreparable distortion. I was thinking of having it slide in a tube or narrow box, so I can lift for beaching/sailing, as well. DON'T QUITE FOLLOW THIS. THE STEEL INSIDE WEEDTRIMMER SHAFT HOUSING TYPE IS MORE LIKE FLEXIBLE STEEL CABLE THAN COILED LIKE A SPRING. IF YOU ARE THINKING OF USING SPRING LIKE MATERIAL, IT MIGHT STRETCH OR PERMANENTLY DISTORT UNDER STRESS?

I do see rust as being a problem though. I can of course completely sheath it in plastic soft tube with silicone....but given that it will lift in the narrow box, I may as well save myself the trouble and do as you say and use thin whippy fibreglass.

SPECIAL FIBERGLASS OR CARBON FIBER SHAFT THAT STANDS UP TO SEVERE TORSION IS NEEDED FOR THE FLEX SHAFT IN PEDALING APPLICATIONS. THE FIBERGLASS APPLICATION IN THE VIDEO IS UNDER 50 WATTS FOR MY 6' TRAVEL KICKBOAT AND WORKS GREAT FOR THAT PURPOSE . WHY NOT JUST USE PROVEN SPRING STEEL IF YOURE REALLY SET ON FLEX SHAFT?

My boat will be very like Tiny Turnip's: 18' cat for easy cruising, two people driving with various picnic gear. Definitely not a speed machine. However I realise the principles of good efficient design are still very important.
THERE ARE MANY POSSIBLE APPROACHES WHICH ARE EFFICIENT. IF YOU KNOW WHAT AN ASIAN LONGTAIL MOTOR IS, THAT APPROACH COULD BE USED AND STILL GIVE YOU REVERSE. YOU COULD USE AN OPEN BEVEL GEAR OR OTHER ARRANGEMENT THAT ALLOWS THE PROP TO MOVE UP AND DOWN AS NEEDED TO GET AROUND OBSTRUCTIONS. I DON'T NEED REVERSE OR RUDDER FOR MY 6' AS I CAN TURN IN MY OWN LENGTH, BUT WITH AN 18' YOU PROBABLY WOULD IF YOU DON'T CARRY A PADDLE.

Nick

Porta

[OldNick]

We seem to be talking at cross purposes here. I am going to use the spring steel for the drive shaft. As I said, I am convinced that it works.

My talk of thin whippy fibreglass is again for the support/skeg for the drive shaft.

Nick

[I57]

With my flex shaft I have a small skeg which slides up and down in a slot allowing the prop to find its own position. The cable enables me to pull up the shaft for beaching and also for reversing.

Ian

[OldNick]

Sorry Ian. I saw your shot from before, and I should have given credit where credit was due. That or something like it is what I have in mind.

Nick

[OldNick]

Has anyone tried the idea of having manual levers to supplement the pedal power? Or is the limit largely aerobic?

Thinks: Even so, over distance, more of your body is being used and it could help with muscle fatigue.

Nick

[Guest625101138]

Nick
The key objective is to keep it as simple as possible. Even that will have teething problems.

You see Hobie make reference to both paddling and pedalling but this is really awkward in practice. I have seen inexperienced people try and they go slower than pedalling alone.

After about 10 minutes of pedalling you settle in somewhere below your aerobic limit. It usually takes much longer before muscle fatigue sets in. Although it is a matter of training.

The most efficient cadence aerobically results in muscle fatigue with the duration depending on level of fitness. I have worked up from about 1 hour to about 4 hours now since October. Well trained cyclists trade efficiency against muscle fatigue because they have good aerobic capacity. Hence they spin a bit faster than their most efficient cadence to avoid muscles tiring. They usually have muscle reserve to cope with sprinting when needed.

My cadence is well balanced for aerobic level unless I am in a head wind. My weakest point under these conditions is my knees. I get to the point of dripping water on my knees to let evaporation provide some soothing cooling. In these conditions it would be nice to have a lower gear - but then more weight and more complexity.

In the past I carried a lower pitch prop so I could change if my legs were not recovering overnight however I have got to the point where I can pedal for more than 6 hours a day and still wake up the next day without any muscle soreness. A couple of years ago it took days to recover from that duration. The body adjusts with training. At this stage I have not suffered any damage from this sort of exercise. With jogging I get sore achilles tendon in a few minutes. My swing arm drive as used on V12 and jointly developed with ForwardFace is the nicest motion I have used:
http://www.boatdesign.net/forums/att...-warren_hc.wmv
http://www.youtube.com/watch?v=PYoW3...om=PL&index=49

Rick W

[OldNick]

Thanks for that Rick!

I agree with KISS. I can see that pedalling and paddling would be fun. Like a really deadly agem of patting your head and rubbing your tummy!

I was just thinking that if you had it all linked, that problem would not arise. Maybe later, after I have actually got something working! ...and worry about getting fit enough to make it all matter anyway!

I like the idea of an extra prop with lower pitch. As you say, gearing is complexity. I am pretty sure Ian suggested this as well.

Forwardface are the front rowing people? So that long straight stroke with the legs was very comfortable. Interesting. I figure it may be hard to match up to a prop though, rather than their rowing system, without some crazy flywheel system. Otherwise the prop would thrash about and then stop all the time...no...I know.....use a generator to charge a battery that...just kidding. I know all about how "simple' that is and also how inefficient.

Nick

[Guest625101138]

Nick
There are some good movies of the forwardface "rowing" system here:
http://www.forwardface.com/
You will see that between strokes the boat just coasts along. It is not much different to a rowing scull in this regard. The prop just freewheels. The drag from it is very low because it has very little friction. There are not even shaft seals because the components are designed to resist corrosion so work in water. No idea how long they would last in salt water.

My system used a curved shaft so the roller clutches were inside the boat. I avoided a shaft seal be elevating the shaft tube above the waterline.

The main problem with the system is lack of reverse. It is brilliant otherwise.

Rick

[OldNick]

Oh OK! I saw those films, but assumed that something other than a prop was used, when I saw how it was operated. The site had props shown, but I found it a little vague, somehow.

That was not helped by the fact that at my vid resolution I could only see half the still shots.

The guy (you?) certainly does look comfortable.

Nick

[Guest625101138]

Not me.

[Guest625101138]

I am back from my 2009 tilt at the Murray. I wrote the attached report for future reference while my memory of the race was still clear.

The folding prop was a great success and it has potential to underpin further design evolution that overcomes fouling problems with the shaft strut.

Rick

[I57]

Congratulations Rick on finishing the Murray Marathon, I see from the results you came 2nd in the UNR1/OV50. What sort of boat did the other guy have?
The heat would be a challenge on its own let alone the distance.
Maybe the next step is to build a boat that is designed just for the Murray Marathon, the only way to go faster is a longer narrower boat. Maybe a 10-12m long boat that bolts together in the middle. Anyway you have a year to design and build it, unfortunatley you will be a year older!

Ian

[OldNick]

Good one Rick! Great to hear the prop worked so well. I am going to have a read.

Nick

[Leo Lazauskas]

Originally Posted by Rick Willoughby

I am back from my 2009 tilt at the Murray. I wrote the attached report for future reference while my memory of the race was still clear.

Great effort and a lovely report, Rick.
Next year, shave your head and glue your ears back. Every little bit helps!

Leo.

[OldNick]

The goofy guy in white tights! Fascinating that one guy spotted your new gearbox! That is one aspect of a pedal boat that does not appeal to me. I am not one to handle attention.

Seriously that is some effort in that heat. My congratulations are sincere. I would simply have melted down in both the racing and real sense I think.

FWIW I read all your thoughts about mechanical improvements and they are all valid. Just remember the law of diminishing returns

I reckon that surely you are at a stage of development where you could hand a boat over to say, a triathlete, even if you still compete yourself. I know you are getting fitter, but those guys have both fitness and metal toughness to keep them going through pain and heat.

OOI, did the overall winner win on handicap, or outright?

Nick