http://microship.com/bobstuart/spinfin.html

For those who really want to go fast in a kayak...........

Santiago, I've been intrigued about foot propelled craft vs. paddled craft for some time. I do need to make some experiments by actually paddling a mirage drive boat vs. paddling technique using a gps.

Here's where my brain doesn't follow the logic: the argument of legs being more powerful than arms. In a PROPER kayak forward stroke using a paddle you don't use just your arms. You power a long shaft with power blade with your torso and leg on power side. The torque or distance the blade travels with one properly executed forward stroke is larger than what can be generated with one pedal stroke. Since the blade travels from foot to hip. How much does the foot propelled drive deliver in torque for one pump of the pedal?

I would have to set up an experiment one of these days at FBO to actually time the difference using a heart rate monitor and speed through a mile effort. Do you know if anyone has tested the mirage drive or other foot propelled device against a kayak paddled using an efficient forward stroke?

quote:

Originally posted by vivian:

Here's where my brain doesn't follow the logic: the argument of legs being more powerful than arms. In a PROPER kayak forward stroke using a paddle you don't use just your arms. You power a long shaft with power blade with your torso and leg on power side. The torque or distance the blade travels with one properly executed forward stroke is larger than what can be generated with one pedal stroke. Since the blade travels from foot to hip. How much does the foot propelled drive deliver in torque for one pump of the pedal?

I would have to set up an experiment one of these days at FBO to actually time the difference using a heart rate monitor and speed through a mile effort. Do you know if anyone has tested the mirage drive or other foot propelled device against a kayak paddled using an efficient forward stroke?

I can tell you from a physiology perspective that your legs are usually significantly stronger than your upper body, as well as having the capacity from much longer duration of use (for the average person).The foot propulsion should also give you more continuous forward force against current and wind.

I personally think you can find a decent paddler in a reasonably fast tourer to out run a Hobie, but all bets would be off if you used a more efficient prop system in a fast touring hull.

I'd really like to see a head to head, but I don't know anyone who's tried it yet.

quote:

Here's where my brain doesn't follow the logic: the argument of legs being more powerful than arms. In a PROPER kayak forward stroke using a paddle you don't use just your arms. You power a long shaft with power blade with your torso and leg on power side. The torque or distance the blade travels with one properly executed forward stroke is larger than what can be generated with one pedal stroke. Since the blade travels from foot to hip. How much does the foot propelled drive deliver in torque for one pump of the pedal?

That is still my question on paddle vs drive the torque delivered. But if you are interested in someone that has put a pedal drive in what I consider a very nice touring canoe that has won many a race. Look up Pelican in the challenge viewer on the watertribe site. He used this modified canoe in last years race so go to Everglades Challenge 2006 also note he did it in a very slow pace because he was continuing on to do the race around florida so Ultimate Challenge.

One of our very own Ron (shallowminded) used an AI this year and did very well. He is quite an accomplished paddler and you can compare his time this year to last years. He also commented on pro/con of drive vs. paddle in watertribe forum.

Anyway, I would think putting a drive in a long skinny fast kayak would not work because you would be very unstable. Those skinny boats need your lower body to control the boat and with the position you have to be in to pedal, it won't work. That's why Pelican chose that Kruger boat it's wide but very efficient.

I've seen first hand what a former competitive mountain biker can do in a HoBie... pass me the oxygen bottle...please.

those skinny boats need your lower body to control the boat and with the position you have to be in to pedal, it won't work

Work OK with an ama system. Your probably going to see something like this...sooner than later.

Is this to be a fishing kayak? I wouldn't want amas where I fish! I don't see the point of trying to modify an efficient and fast hull that was designed to be paddled for speed and stability just to make it work for a mirage drive. You probably have a market for that where you paddle/fish?

Candidates:

1.Custom ocean going 17-18 footer 26" width, no tank well, internal fish box storage with removable fish bag, internal rod storage, etc etc.- Being designed by JEM for me. Will have ama system for sailing. Until I try it I won't know if ama are required for Mirage Drive. I doubt it, but I might have them on 90% of the time anyway in event I use sail.

2. Possible high tech carbon SOT 18' from commecial manufacturer. Again high speed sailing capability with Mirage Drive.

3. A new longer Hobie Adventure type that has been on their design list and may be moved up. I suspect two year wait, but you never know.

Ama are not a detractant to ocean fishing. Guys here add them all the time. You never know what a large pelagic will do.

Also if you want to sail an ocean yak for trolling speeds of 6-8-10 knots in winds that can gust on you, a must have.

at what size does a yak become a boat?

You can distinguish a boat from a ship.

But I doubt you can distinguish a yak from a boat. They are boats.

Vivian, your question and observations are very astute. Effective paddling is primarily a combination of torso rotation and leg extension; the arms and shoulders play a much lesser part. Paddling in this fashion is decidedly closer to a whole body involvement.

However I know of no direct comparison paddle vs flapper. But your suggested approach is right on the money. Two leading HPB'ers have been testing the Hobie Turbo Flappers on an AI hull.
The hull was modeled as accurately as possible using Freeship to produce drag, resistance and wave patterns.

Certain speeds were tested to establish heart rate; power output for the same heartrates were established in a gym.

Here's the results:

Heart Rate (bpm) vs Boat Speed (mph)

106 - 3.75
117 - 4.45
131 - 5.25

By combining this data with power data they were able to determine the flapper's efficiency at various speeds. Their findings:

1. The turbo's have little advantage at cruising speeds.

2. Both are fairly inefficient (around 25%) at reasonable cruising speeds; their efficiency does not reach 50% until very high effort is exerted. Compare to most props at 70 - 90%.

I will endeavor to gain some paddling comparisons but have no data at this time. However, I'd have to guess that a good wing paddle is certainly more efficient than the flapper's and likely uses more of the whole body as noted above.

Actually, now that you have the bpm/mph figures, you could see what you can do paddling at these heart rates, remembering of course that these were derived by another person.

Heart rate efficiency is meaningless unless adjusted for age factor.

Heart rate is meaningless in a comparison between two people. The same heart rate in two people working at the same task will in all probability NOT produce the same work output as measured by thrust/torque or whatever.

If I may be so bold as to offer another observation.

1. In order to paddle harder and with more force you must sit up and lean forward. Result, more aerodynamic drag.

2. When pedaling in the recumbant position more force from the legs may be gained by slouching a bit. Result, lowering of aerodynamic drag a little for sitting slightly reclined produces a relatively low drag profile.

3. Yup, the well trained paddler has a longer stroke per dip, well maybe not if the flipper powered boat is up to cruising speed. Have to look into that one next time out.

4. I suppose we all evaluate the "DATA" presented by applying it to ourselves and how we react to that situation. I am 68 and have started goint to the Y for additional formal exercise. I start the warmup on a X training recumbant stair stepper. This machine has 10 levels of resistance and offers both upper, lower and combined body exercise. I use only the lower body mode. Setting the machine on level 4 is like pedaling the standard fins, 5 like the turbos at cruise and 6 pushing flat out. At level four I cannot get the heart rate over 115. At 5 its easy to get to 120 and at 6 I seem to max the heart rate at 130-135. All these exercised done at 80 - 100 ppm. These exercises will over time hopefully reduce the heart rate. On the boat I can only get my HR up if I intentionally push to go fast. Cruising along at 3.5 - 4.0 no perceptable increase over 90.

5. Now, what does all this stuff mean. If we were racing whatever effort we put into the boat we would demand maximum speed and glide. Bur for the most part we are not racing, but going fishing. This other requirement to be a good fishing craft modifies the design criteria so that we get a bit more stability and manuverability both of which detract from the design of your all out racing hull.

6. There you have it. Go fast fishing hull is a good dream. Add to this dream the requirement to have a hull that is purchasable by the average Joe or Joette and you add another factor which influences design probablyadding weight and slowint it up.

Gosh, nothing bu comprimises. Like most things.

Well it does appear that Vivian's question will not be answered until someone does a rough test, which would be very interesting indeed.

From a practical standpoint though it's obvious people don't buy Hobies to paddle em. And most of their hulls are simply not terribly efficient. At the same time good paddlers are riding hulls that are. That's the comparison.

I think that Vivian is actually questioning whether Hobie's marketing claim that "legs are stronger than arms" is accurate or fair, particularly considering her observation of use of legs, torso AND arms in proper paddling. Not surprisingly, if Hobie has the data, they aren't sharing it.

My guess: like their anti-prop list, just another unsupported and misleading marketing claim.

I would rather be punched in the face than kicked in the face any day of the week... and twice on Sunday.

Well actualy my preference would be neither.. but you catch my drift.

It is correct of course that Vivian cannot compare her bpm directly with those of another person (who may be more or less fit); however I included those to illustrate the researcher's methodology. As noted, she will have to run her own tests; however was some data that does translate regardless of the paddler/pedaler:

The Hobie AI demonstrated the following power requirements:

3.8 mph = 20 watts (hull power) = 85 watts (pedaler power) = 22% (cruising efficiency)
4.0 mph = 25 watts = 90 watts = 23%
5.0 mph = 60 watts = 130 watts = 40%
5.3 mph = 70 watts = 150 watts = 46% (max efficiency)

As you can see the power requirements of the AI are increasing exponentially as hull speed is approached. No surprise. So here's my suggestion:

Vivian may be able to find an exercise machine in which she can determine her heart rate to achieve say, 90 watts. With this in hand she can test a Hobie at this bpm and GPS her speed; then repeat at the same bpm but paddling and again GPS her speed. This will achieve two things:

1. It will test her observation that paddling is more of a whole body activity
2. It will reveal any possible differences due to paddle efficiency.

Actually a pretty interesting and reasonably easy test to perform. Frankly, I think a better test would be for Vivian to calculate her bpm to produce 90 watts, then apply this bpm to paddling her favorite kayak and GPS it, compare this to 90 watts in a Hobie. This more represents the decisions most buyers must make, ie. between a Hobie and a good paddled kayak.

Until you control every other variable, the "arms vs. legs" thing is an unknown. Using two totally different propulsion mechanisms in totally different hulls makes the question difficult to answer. Even if your legs are stronger than your arms, if ther leg propulsion system is dramatically less efficient, you can negate the raw power output advantage of legs over arms very easily.

Santy, did you miss Vivian's orginal question and observation, namely that advanced paddler technique uses mainly the torso and legs, and the arms? A whole body event. She is correctly noting that the comparison is actually between "legs (pedaling) vs legs/torso/arms (paddling).

The "arms vs legs" things is just another oversimplified, unsupported and self-serving Hobie marketing ploy. Like the "tug of war" it's meant to be dramatic (but not particularly informative or relevent).

As noted above putting together a good and roughly reliable test of her observation is not hard. One trip to the gym and two paddles/pedals in the water.

You are right on when you note it's about efficiency and actual performance on the water.

There are at least two things we tend to overlook when making these theoritical comparisons.

1. The drives being compaired are not in the same hull, so results seen must be different from that standpoint alone.

2. You can put a rank novice in a Mirage equipped Hobie and he/she will make it go as fast as he/she is able. Putting the same person in any high performance yak and ask him/her to paddle as fast as he/she can is a recipe for a capsize or at least lots of S-turns.

Folks it takes instruction, time and dedication to become a "whole body" paddler. Time spent practicing and NOT fishing.

Here is something for you "Soc" to try. Get a Hobie Sport. Paddle it as fast as you can with the Mirage removed and the hole plugged. Now remove the plug, install the Mirage equipped withthe standart flippers and go do your level/honest best to make it move. Keep speed records for each case. Report back.

Personally I bet the Mirage powered trial will be faster.

quote:

Originally posted by ValFitzAndrew:
There are at least two things we tend to overlook when making these theoritical comparisons.

1. The drives being compaired are not in the same hull, so results seen must be different from that standpoint alone.

2. You can put a rank novice in a Mirage equipped Hobie and he/she will make it go as fast as he/she is able. Putting the same person in any high performance yak and ask him/her to paddle as fast as he/she can is a recipe for a capsize or at least lots of S-turns.

Folks it takes instruction, time and dedication to become a "whole body" paddler. Time spent practicing and NOT fishing.

Here is something for you "Soc" to try. Get a Hobie Sport. Paddle it as fast as you can with the Mirage removed and the hole plugged. Now remove the plug, install the Mirage equipped withthe standart flippers and go do your level/honest best to make it move. Keep speed records for each case. Report back.

Personally I bet the Mirage powered trial will be faster.

There are a lot of ways to look at it, but even with maximal experience, it's likely virtually impossible to use a Hobie Mirage hull as a paddling/peddling demo. They just aren't designed for paddling for some reason or another. There are plenty of similar hulls that paddle much better. Even the Adventure glides like it has a chute out.

If there is a comparison, you'll always have to have dissimilar boats.

Hobies are great general purpose fishing boats. You'll never get an argument there. But there's plenty of BS surrounding them that makes a fair target for discussion.