A Pedalo instead of a rowing dinghy ? Why not ?

sarabande said:
Damn ! Spotted ...
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To be honest I've often thought the same thing. Oars have been in existence for literally thousands of years, totally unchanged, and facing backwards and rowing is totally daft and very much a case of "well, we've always done it this way". If you look at the cyclors on the NZ AC boat, the "bikes" on some of the offshore tris, human powered aircraft, vehicles, and of course hydrofoiling boats, clearly leg power is 100% the way to go. A big heavy rotomoulded hull with paddle wheels is ridiculous, but I suspect a folding carbon and inflatable thing with a self optimising prop could be absolutely brilliant.
 
Iain C said:
To be honest I've often thought the same thing. Oars have been in existence for literally thousands of years, totally unchanged, and facing backwards and rowing is totally daft and very much a case of "well, we've always done it this way". If you look at the cyclors on the NZ AC boat, the "bikes" on some of the offshore tris, human powered aircraft, vehicles, and of course hydrofoiling boats, clearly leg power is 100% the way to go. A big heavy rotomoulded hull with paddle wheels is ridiculous, but I suspect a folding carbon and inflatable thing with a self optimising prop could be absolutely brilliant.
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A rowing boat with sliding seats IS leg powered - as well as back and arm powered. Rowing with a sliding seat uses almost every large muscle group in your body, with the exception of the abdominal muscles. In fact, the arms make the least contribution; when rowing with a sliding seat, you can't bend the arms until near the end of the stroke, as the leg muscles are far stronger. Of course, that depends a) on having a sliding seat and b) knowing how to use it. But the whole point of a sliding seat is to allow you to use as much of your body as posible to power the boat. I can't imagine a way that you could obtain the same power from the body using pedals or whatever. You CAN row with a sliding seat facing forward (there are clever linkages that will allow it), but of course, there's an efficiency penalty.

I don't know what it works out at in horsepower, but a coxed eight can sustain speeds of up to about 15mph for at least several miles in a non-planing hull.
 
AntarcticPilot said:
A rowing boat with sliding seats IS leg powered - as well as back and arm powered. Rowing with a sliding seat uses almost every large muscle group in your body, with the exception of the abdominal muscles. In fact, the arms make the least contribution; when rowing with a sliding seat, you can't bend the arms until near the end of the stroke, as the leg muscles are far stronger. Of course, that depends a) on having a sliding seat and b) knowing how to use it. But the whole point of a sliding seat is to allow you to use as much of your body as posible to power the boat. I can't imagine a way that you could obtain the same power from the body using pedals or whatever. You CAN row with a sliding seat facing forward (there are clever linkages that will allow it), but of course, there's an efficiency penalty.

I don't know what it works out at in horsepower, but a coxed eight can sustain speeds of up to about 15mph for at least several miles in a non-planing hull.
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Fair point well made (and yes all of me hurts after a blast on the gym rowing machine, not just the arms!), however I think by the time you've engineered a sliding seat and some kind of oar direction reverser, you might as well dispense with oars entirely. I notice from any kind of "performance" rowing boat that the oars are very long and the fulcrum is very much towards the rower...most tender oars are short and usually pivot at around the 50% of the length mark. It would just be so much easier to have something under the hull, even if just for coming alongside etc.
 
JumbleDuck said:
Sustained output power for a trained athlete is generally put at ~1/2hp, which is confirmed by the results at https://www.semanticscholar.org/pap...sito/881264ccea251f6b7f01f9e2a75158007654ff00, so an eight does its stuff with about 4hp to push it along.
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Makes the 6.5 knots I get out of 28hp on Capricious look a bit sad! 7 times the power for less than half the speed. But it also highlights the efficiency of rowing with a sliding seat - it must couple those 4 hp to the boat very efficiently.
 
Half the story of fast maunally propelled craft, canoes sculling boats etc, is that the oars or paddles provide stability, allowing a very narrow, low drag hull.
A mate of mine used to have a K1 raying kayak, impossible to balance at a standstill, worked very well on the move.
If I was going to add any complication to a tender, it would be in the form of mast and sails.
 
There are many examples of bicycle powered catamarans, some foiling, some just reasonably quick. I saw one a few years ago and it looked to be powered by a road bike which looked demountable - presumably so that once ashore you could cycle to the nearest pub/supermarket/wherever you wanted to get.
 
PeteCooper said:
There are many examples of bicycle powered catamarans, some foiling, some just reasonably quick. I saw one a few years ago and it looked to be powered by a road bike which looked demountable - presumably so that once ashore you could cycle to the nearest pub/supermarket/wherever you wanted to get.
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There's a guy who rents bicycle-like catamarans on the river at Ely. The bike is not demountable, and the pedals drive a propeller (I think). They aren't quick! Fun, but definitely not quick.Sep08 204.jpg
 
JumbleDuck said:
Sustained output power for a trained athlete is generally put at ~1/2hp, which is confirmed by the results at https://www.semanticscholar.org/pap...sito/881264ccea251f6b7f01f9e2a75158007654ff00, so an eight does its stuff with about 4hp to push it along.
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I've rowed in an instrumented VIII, and one of the measurands was average output power. The biggest and strongest of us (#6 naturally - not me) did around 850 watts, and the mean was around 730. But we could only keep this level up for a few tens of strokes. So your 1/2 HP (~375W) is probably about right. A challenge to any pedalo in christendom: a pint says that over 500m I'll give you a 200m start and still beat you in my single scull.
 
There's a cafe near us, who has a pedalo for hire on a small loch. There is also a row boat tied up there. I asked if I could hire that instead of the pedalo. The answer was no, they could not get insurance to rent out the row boat, so it is for their use only. Go figure that one.
 
AntarcticPilot said:
Makes the 6.5 knots I get out of 28hp on Capricious look a bit sad! 7 times the power for less than half the speed. But it also highlights the efficiency of rowing with a sliding seat - it must couple those 4 hp to the boat very efficiently.
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The mechanics of a rowing eight are fascinating. When the pull is at its maximum, early in the stroke, the forces at the rower and rigger apply moments to the hull at each position, deflecting the whole boat - very slightly - into an undulating wriggly shape (~~~~~~~~) and storing a lot of strain energy while doing so.

As the force the rowers can exert decreases later in the stroke, when the legs are straight and the arms have to do the work, the hull unwiggles (technical term) and the strain energy stored in it is fired back through the rowers and the blades. As you say, very efficient coupling. You see exactly the same thing in modern racing gliders; long, flexible wings which bend waaaaay up when they enter lift and fire the fuselage up after them.

When carbon fibre came in as a material, almost the first large structures made of it were rowing eights made by Carbocraft (which I think was a commercial offshoot of the Rutherford or Harwell lab, where the material was made). They were initially very popular, but after a while were supplanted by wood again, because they were just too stiff and didn't absorb and release energy efficiently, so they were slower. I believe CFRP is now back in fashion, but used in boats designed to flex.
 
jdc said:
I've rowed in an instrumented VIII, and one of the measurands was average output power. The biggest and strongest of us (#6 naturally - not me) did around 850 watts, and the mean was around 730. But we could only keep this level up for a few tens of strokes. So your 1/2 HP (~375W) is probably about right.
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The guideline I've always used is that anybody - just about - can keep up 100W of mechanical work indefinitely while a trained athlete can manage 1/2 hp for 10 - 20 minutes or 1hp for a minute or so, which seem a pretty close match to your experience.
 
JumbleDuck said:
The mechanics of a rowing eight are fascinating. When the pull is at its maximum, early in the stroke, the forces at the rower and rigger apply moments to the hull at each position, deflecting the whole boat - very slightly - into an undulating wriggly shape (~~~~~~~~) and storing a lot of strain energy while doing so.

As the force the rowers can exert decreases later in the stroke, when the legs are straight and the arms have to do the work, the hull unwiggles (technical term) and the strain energy stored in it is fired back through the rowers and the blades. As you say, very efficient coupling. You see exactly the same thing in modern racing gliders; long, flexible wings which bend waaaaay up when they enter lift and fire the fuselage up after them.

When carbon fibre came in as a material, almost the first large structures made of it were rowing eights made by Carbocraft (which I think was a commercial offshoot of the Rutherford or Harwell lab, where the material was made). They were initially very popular, but after a while were supplanted by wood again, because they were just too stiff and didn't absorb and release energy efficiently, so they were slower. I believe CFRP is now back in fashion, but used in boats designed to flex.
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'Boats designed to flex' brings to mind Pete Goss's 'Team Ph-'
 
And rumour has it when Lord Ben of Ainslie gave up on his new "Rita" Finn for London 2012 and knocked on the door of the maritime museum in Falmouth saying "er, can I have my old Finn back please" it was because the new one was too stiff and therefore tried to batter waves out of the way rather than flexing with them a little and being more seakindly and faster.

I absolutely love the fact that he got his old boat back...partly because with the unstayed rig the Finn goes against the grain of a conventional dinghy where stiffness is paramount for speed, and also because when you look at the old Rita (now back in her place in Falmouth) she's actually a bit of a knacker...most of the cleat fairleads are worn through almost to breaking point, and it's just cool that for whatever reason he kept sailing with them...

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JumbleDuck said:
The mechanics of a rowing eight are fascinating. When the pull is at its maximum, early in the stroke, the forces at the rower and rigger apply moments to the hull at each position, deflecting the whole boat - very slightly - into an undulating wriggly shape (~~~~~~~~) and storing a lot of strain energy while doing so.

As the force the rowers can exert decreases later in the stroke, when the legs are straight and the arms have to do the work, the hull unwiggles (technical term) and the strain energy stored in it is fired back through the rowers and the blades. As you say, very efficient coupling. You see exactly the same thing in modern racing gliders; long, flexible wings which bend waaaaay up when they enter lift and fire the fuselage up after them.

When carbon fibre came in as a material, almost the first large structures made of it were rowing eights made by Carbocraft (which I think was a commercial offshoot of the Rutherford or Harwell lab, where the material was made). They were initially very popular, but after a while were supplanted by wood again, because they were just too stiff and didn't absorb and release energy efficiently, so they were slower. I believe CFRP is now back in fashion, but used in boats designed to flex.
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I'm not entirely convinced by this. I started in a Sims shell and then rowed in one of the earliest Carbocraft boats. The advantage was ageing: a wooden shell was stiffer when brand new but after <3 years use the Carbocraft (they became Aylings, then sold to Lola, I think) remained stiffer. And stiffness is good - no flexing at all is desirable in the shell itself. This is especially the case on the tideway (the Isis is so calm that it mattered less).

A new VIII will have hexagonal 3-d woven carbon fibre matting in it and have as near zero flexure as possible. And what flexure it has is damped to avoid all resonance so is very lossy - one recovers no energy at all. This approach applies even to modern 'wooden' boats: my single (made by Carl Douglas) is beautiful, and looks wooden, but is actually a high-tech fake: it's cold-moulded veneer on the outside, but kevlar rovings inside and is amazingly stiff and light. And of course uses carbon fibre blades. Which brings me to what we do flex, and recover energy from: the blades. We moved from wooden Macons to carbon fibre shafts, and then to 'cleavers' with composite spoons over 20 years ago now, and although it felt odd at first to be using stiffer blades one soon got used to a having to make a slightly subtler catch.

Not that this is entirely relevant to a pedalo!
 
JumbleDuck said:
The mechanics of a rowing eight are fascinating. When the pull is at its maximum, early in the stroke, the forces at the rower and rigger apply moments to the hull at each position, deflecting the whole boat - very slightly - into an undulating wriggly shape (~~~~~~~~) and storing a lot of strain energy while doing so.

As the force the rowers can exert decreases later in the stroke, when the legs are straight and the arms have to do the work, the hull unwiggles (technical term) and the strain energy stored in it is fired back through the rowers and the blades. As you say, very efficient coupling. You see exactly the same thing in modern racing gliders; long, flexible wings which bend waaaaay up when they enter lift and fire the fuselage up after them.

When carbon fibre came in as a material, almost the first large structures made of it were rowing eights made by Carbocraft (which I think was a commercial offshoot of the Rutherford or Harwell lab, where the material was made). They were initially very popular, but after a while were supplanted by wood again, because they were just too stiff and didn't absorb and release energy efficiently, so they were slower. I believe CFRP is now back in fashion, but used in boats designed to flex.
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jdc said:
I'm not entirely convinced by this. I started in a Sims shell and then rowed in one of the earliest Carbocraft boats. The advantage was ageing: a wooden shell was stiffer when brand new but after <3 years use the Carbocraft (they became Aylings, then sold to Lola, I think) remained stiffer. And stiffness is good - no flexing at all is desirable in the shell itself. This is especially the case on the tideway (the Isis is so calm that it mattered less).

A new VIII will have hexagonal 3-d woven carbon fibre matting in it and have as near zero flexure as possible. And what flexure it has is damped to avoid all resonance so is very lossy - one recovers no energy at all. This approach applies even to modern 'wooden' boats: my single (made by Carl Douglas) is beautiful, and looks wooden, but is actually a high-tech fake: it's cold-moulded veneer on the outside, but kevlar rovings inside and is amazingly stiff and light. And of course uses carbon fibre blades. Which brings me to what we do flex, and recover energy from: the blades. We moved from wooden Macons to carbon fibre shafts, and then to 'cleavers' with composite spoons over 20 years ago now, and although it felt odd at first to be using stiffer blades one soon got used to a having to make a slightly subtler catch.

Not that this is entirely relevant to a pedalo!
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My own experience of 45 years ago, FWIW, is that there is certainly a great deal of skill in getting the rythm of oar strokes and the natural rythm of the boat in step. Get it wrong and the boat goes slowly! But the boat's rythm is probably a complex mixture of the stiffness of the hull and the buoyancy of the hull. However, if you watch (say) the stern of an 8, you'll certainly notice that it deflects vertically during the stroke.

Again, things may have moved on, but we were exhorted to get as much force into the initial part of the stroke as possible - the ideal being to effectively give the cox a boot up the backside at every stroke! As I graduated from Bow oar to Cox (being really too light for the former), I know how it feels from both ends :)
 
JumbleDuck said:
The mechanics of a rowing eight are fascinating. When the pull is at its maximum, early in the stroke, the forces at the rower and rigger apply moments to the hull at each position, deflecting the whole boat - very slightly - into an undulating wriggly shape (~~~~~~~~) and storing a lot of strain energy while doing so.

As the force the rowers can exert decreases later in the stroke, when the legs are straight and the arms have to do the work, the hull unwiggles (technical term) and the strain energy stored in it is fired back through the rowers and the blades. As you say, very efficient coupling. You see exactly the same thing in modern racing gliders; long, flexible wings which bend waaaaay up when they enter lift and fire the fuselage up after them.

When carbon fibre came in as a material, almost the first large structures made of it were rowing eights made by Carbocraft (which I think was a commercial offshoot of the Rutherford or Harwell lab, where the material was made). They were initially very popular, but after a while were supplanted by wood again, because they were just too stiff and didn't absorb and release energy efficiently, so they were slower. I believe CFRP is now back in fashion, but used in boats designed to flex.
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Although I have been rowing for 50+ years, I have not heard the flexion theory before. In general it is regarded as an advantage to have a very stiff hull although flexion can absorb some of the competing strain of crew members not being perfectly in time.
Carbocraft went through a continuous development process and were very successful (latterly as Aylings) but have now disappeared. I suspect that part of the reason for their disappearance was the development of many competing brands. Leading brands include Empacher (Germany) Philippi (Italy) and Janousek/Stamfli (weybridge). Popular also are some economical Chinese brands. Longevity makes these boats economic for clubs to buy.
No competitive racing boats are now produced in wood apart from single sculls produced by Carl Douglas.
 
blenkinsop said:
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No competitive racing boats are now produced in wood apart from single sculls produced by Carl Douglas.
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See my post above: even they are actually composites made in part from kevlar with wood veneer.

PS: You might have mentioned Vespoli.
 
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