Paddles vs. Mirage Drive

[leong]

Take a look at this article about the Hobie MirageDrive propulsion gadget for a kayak (especially scroll down to the link showing a tug of war against Greg Barton).
Hmm, it shows that an ordinary mortal using the MirageDrive can beat Greg Barton (the two-time Olympic gold medalist in sprint kayaking) in a tug of war. I got to thinking about the efficiency of this device vs. kayak paddles. I came to a conclusion (I won't tell you yet) that needed to be verified.

So the other day when I saw a young guy in this Hobie SOT kayak I challenged him to two races:
A short race about ¼ mile and a longer race about two miles (he was thrilled for the opportunity to kick my butt). Note that I was using my usual Epic wing paddles and my 18-foot-long QCC700X.

Here are the results:

Short race: His initial acceleration was much greater than mine was and I never caught up. He beat me by about 20 yards.
Longer race: I had the same disadvantage in the beginning of the race but I caught up and beat him by about ¼ mile. I'm almost certain that I'd do even better against him in a much longer race (think Blackburn Challenge)


Question: Why do you think that I could beat him in the long race but not in the short race? I’m fairly certain that he has at least as much endurance as I do, so that’s not the reason for the race results.

PS
No, I don’t have delusions of being in Greg Barton's league. Racing against Greg in the Blackburn and NYC Mayor’s Cup surely took care of that impossible dream :-)

[cfolster]

I'm guessing his strength did it despite likely poor form and the lousy hull design of a sit on top. Younger faster muscles (no offense Leon) that can get a boat going faster initially, but he can't keep up that kind of output over the longer race, which his why you won that one.

[John Martinsen]

Ask to race backwards next time. Have also heard those things are garbage in current as well.

[leong]

>>I'm guessing his strength did it despite likely poor form

Unlike using a paddle, there's not much form needed for pedaling the MirageDrive. Yes, he might be stronger than me. Actually, it was his legs against my upper body and that was a big disadvantage for me.

>>and the lousy hull design of a sit on top.

Yes, his boat’s hull is not as efficient as my long and narrow QCC. Nevertheless, I still think I could beat him in a long race if the MirageDrive were installed on a similar sea kayak. In other words, I think there's something else that gives paddling an advantage over pedaling with the MirageDrive.

>>Younger faster muscles (no offense Leon) that can get a boat going faster initially,

But I'm only 37. Oh wait, I reversed the digits. I hope that that’s not another problem with aging brains.

>>but he can't keep up that kind of output over the longer race, which his why you won that one.

Yes, of course, but why? In fact, I think the race results would have been reversed if we had switched kayaks. That is, there's something about the MirageDrive that makes it that way. That's really the crux of my question.

Cathy, good insights. We in the NSPN community all know the MirageDrive would be pretty crummy for serious sea kayaking (waves, braces, surfing, rock play, backing up, etc.) and, of course, white water kayaking. I know you realize that that's not what I am addressing.

I'm really questioning Hobie's statement that their MirageDrive is more efficient than paddle drive. One part they got right is you can generate more power with your legs than with your upper body. Nevertheless, I hypothesized another part of efficiency that I believe Hobie overlooked (perhaps on purpose). My two races may have validated my hypothesis, but it's far from an absolute certainty.

[rfolster]

My thought is in regard to the design. The pedals have a very small range of travel, which can be compared to a bicycle in first gear. You can get a good start off the line, but not much speed.

[leong]

My thought is in regard to the design. The pedals have a very small range of travel, which can be compared to a bicycle in first gear. You can get a good start off the line, but not much speed.

Rob,

That’s one possible reason that I didn’t think of. It’s probably right, but I’m not sure. Nevertheless, I don’t think it tells the whole story.

Here’s my hypothesis:

First we need a definition: For kayaking, define human efficiency as useful power output (driving power needed to create the thrust to propel the kayak) divided by total power input (say the calories burned per second to generate the useful power output).

With this definition in mind:

Point 1. I think using a paddle has a greater efficiency than using a MirageDrive. However, your legs are obviously more powerful than your torso (even considering that a good paddler uses his legs for rotation). So for a short time period you can generate more useful power output with the MirageDrive, notwithstanding at a lower efficiency.

Point 2. I think that the MirageDrive’s blades add more drag to the kayak than normal paddles do. That, and the fact that for normal paddling there is a significant glide between strokes, and that makes normal paddling even more efficient. When I raced that guy I noticed that his legs were continuously pumping at a very high speed. Between strokes I glided and that gave my muscles a short rest period. Although some of my glide was due to a “faster” hull, I think the MirageDrive blades greatly reduced his potential glide.

I’m hoping to do another test with a MirageDrive whenever a “willing target of opportunity” comes by again.

For sure, the MirageDrive is better than a paddle for short “tug of war” contests. But is it better for actual kayaking? I hope Greg Barton got paid well for the demo he was in. I think it was an absolutely stupid way to demonstrate the advantage of the MirageDrive for kayaking. Good marketing for the masses I guess. But I do admit there are some advantages to the MirageDrive, especially for kayak fishing in a recreational type hull where you’re not interested in speed or anything else that sea kayakers like to do.

Respectfully,

-Leon

PS

I’m sailing a Sunfish some days now. Ironically, I get a pretty good paddling workout each time I take the Sunfish out. That’s because I need to paddle it through the narrow canal between my dock and the bay (it’s demanding to paddle a four foot wide hull that weighs 140 pounds against a strong wind)

This is an example of where a MirageDrive would be nice.

Edited March 29, 2014 by leong

[lhunt]

I'm thinking that tug of war and racing are very, very different things. Normal kayak paddles (and wings) are designed to "lock" into the water - the boat moves forward but the paddle stays still relative to the water. In a tug of war you are moving the paddle backward against the resistance of the water. It's much less aerobic, puts much more stress on the arm muscles, even if you rotate, because you have to hold the paddle. In fact, I think it might have been Greg Barton who said he doesn't expect to use rotation for propulsion in the first few seconds of starting in a race - it's like trying to start a car in 4th gear. You wouldn't do tug of war in a car in 4th gear either, for the same reasons. It's interesting that they didn't try to race Greg against the Mirage in the normal way.

-Lisa

[billvoss]

I remember being very surprised when I discovered that I can swim faster using just my arms and a swim pull buoy between my legs than I can swim using both my arms and legs together or for that matter a kick board. I eventually concluded that I was aerobically limited, and that using all my aerobic capacity to drive my more efficient arms resulted in the best times, assuming I could minimize drag by keeping my body level.

In your race Leon, the short sprint was apparently mostly anaerobic. So using the big muscles was an advantage compared to a paddle, at least initially. Basically another way of looking at your point #1, and Lisa also touched on the issue.

However, in the longer race I'll bet you were both aerobically limited so using those big legs was no longer an advantage. I could easily believe the MirageDrive introduces more drag than a paddle, and I'm confident that the drag for both will increase more than linearly as speed increases. So as speed increases the paddler would have a growing drag advantage. Basically your point #2 Leon.

I also think Rob is probably correct that adding gears would help the MirageDrive racer. Though I wonder if there would be a degradation in MirageDrive efficiency at greater power inputs, and if a human power source would ever be materially affected by such a degradation.

Of course for me, until someone shows me how to roll using a MirageDrive my interest is probably limited. :-)

[leong]

>>I'm thinking that tug of war and racing are very, very different things. Normal kayak paddles (and wings) are designed to "lock" into the water - the boat moves forward but the paddle stays still relative to the water. In a tug of war you are moving the paddle backward against the resistance of the water. It's much less aerobic, puts much more stress on the arm muscles, even if you rotate, because you have to hold the paddle.

Yes, of course. I didn't want to explain all that so I just said the demo was stupid.

>> In fact, I think it might have been Greg Barton who said he doesn't expect to use rotation for propulsion in the first few seconds of starting in a race - it's like trying to start a car in 4th gear. You wouldn't do tug of war in a car in 4th gear either, for the same reasons.

I think this also applies to surfing. You don't rotate when you need to accelerate from a standing start to catch a wave.

>>It's interesting that they didn't try to race Greg against the Mirage in the normal way.

I doubt that Hobie Cat would be so naive to try that. But if they did they surely wouldn't advertise the results.

-Lisa

[leong]

>>I remember being very surprised when I discovered that I can swim faster using just my arms and a swim pull buoy between my legs than I can swim using both my arms and legs together or for that matter a kick board. I eventually concluded that I was aerobically limited, and that using all my aerobic capacity to drive my more efficient arms resulted in the best times, assuming I could minimize drag by keeping my body level.

That's true for me too. But I think an Olympic swimmer has a much more efficient kick so he or she would be faster sans the pull buoy.

>>In your race Leon, the short sprint was apparently mostly anaerobic. So using the big muscles was an advantage compared to a paddle, at least initially. Basically another way of looking at your point #1, and Lisa also touched on the issue.

Agreed.

However, in the longer race I'll bet you were both aerobically limited so using those big legs was no longer an advantage. I could easily believe the MirageDrive introduces more drag than a paddle, and I'm confident that the drag for both will increase more than linearly as speed increases. So as speed increases the paddler would have a growing drag advantage. Basically your point #2 Leon.

Agreed.

>>I also think Rob is probably correct that adding gears would help the MirageDrive racer. Though I wonder if there would be a degradation in MirageDrive efficiency at greater power inputs, and if a human power source would ever be materially affected by such a degradation.

The MirageDrive doesn't have built-in variable gear ratios. However, they have three fin sets that can be installed, each providing a different effective gear ratio. I think built-in variable gear ratios would be very useful. Like the value of variable gear ratios on a bicycle.

>>Of course for me, until someone shows me how to roll using a MirageDrive my interest is probably limited. :-)

I suppose the Hobie people would say you can have it all; i.e. use paddles with the MirageDrive. But it would be a mechanical nightmare to install the MirageDrive in a SIK.

Bill, you and the others have good insights. I just wonder whether a MirageDrive type system could improve times for the same kayak vs. paddles for short sprints like in the Olympics. And, if so, would it be allowed? Wing paddles were quickly accepted by the Olympic authorities. After 1992, the America's Cup committee accepted catamarans and eventually hydrofoils. So rules do evolve with technology. Still, because I like classic kayaks, I hope that normal paddling turn out to be the best.

[leong]

A recycled topic from the past:

A neighbor just brought down a Hobie Kayak that uses the MirageDrive. I’ll probably try it soon. It got me thinking of this thread. I did some googling and found this well written review about the MirageDrive. The author (I used to be a member of his kayak fishing club in Fort Lauderdale) is very knowledgeable about kayak hydrodynamics. Read the article if you’re interested in lots of details about the MarageDrive and how manufacturers hype their products based on erroneous tests or no data at all. The review clearly explains why I lost the short distance race and easily won the long distance race (and the Barton/Chalupsky team lost the tug-of-war) to the Hobie with MirageDrive. The main reason for our losses is “With the MirageDrive there is very little pause between what amounts to very short strokes. Compare to the paddler(s) whose strokes are necessarily longer, and with a greater pause between strokes.”

That's why for a static race (tug of war) or very short distance race the MirageDrive has a big advantage over a paddled kayak. Several of us said essentially the same thing in this thread.

-Leon

[Pintail]

There is one aspect on which no one has touched: that of bracing. Forget, for a moment, that this race was staged between a proper kayak (Leon's QCC) and some obese specimen of an SOT (whatever that might be!) and imagine it, if possible, designed into a real kayak. What would happen in rough water or any sort of substantial waves? Answer: it would topple/capsize -- no bracing available! Every stroke with a real paddle is a brace -- not so? -- regardless of which plane the movement of the blade and this is simply not there for John Doe-Paddler when he is busy working his triceps and quadriceps as he pedals (not paddles).

So change the title of thread, Leon, to Peddling v Paddling? (Likewise, change that man's name to John Doe-Pedaler)

[leong]

Yes, Pintail, that's an excellent point. In fact, even the regular floating bathtubs called recreational (kayaks?) that use paddles are not sea-worthy. I found this out when I borrowed a wide 12-foot recreational sit-in kayak and took it out for an ocean spin. The initial stability was much greater than needed; however, I had to continually brace with each broadside wave. And, sans a sprayskirt, I had to eventually start pumping out water.

-Leon