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 Post subject: standard fins
PostPosted: Wed Dec 27, 2006 9:54 pm 
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Location: Minnesota
I find I am much more comfortable with the standard fins for pedaling distances with my Adventure. I like the faster pedaling cadence. I find myself moving a little faster unintentionally with the turbo fins and end up straining too much against the increased resistance. (I'm in very good shape since I'm an avid bicyclist and runner, so it's not a fitness issue) It's analogous to gearing down and spinning faster on a bicycle. Also, the standard fins are a lot easier on the hull, which makes me happy, since I am much more interested in consistent distance,reliability, and utility than speed.

That being said, the Adventure really moves along at a good clip, even with my older standard fins. I love it. I'd never go back to paddling. it pedals so well, I usually don't bother to bring the sail along, unless I'm planning to just play and splash about a little rather than getting anywhere. The pedal drive works so, so well, that the sail just isn't worth the fuss. And I sold my sailboat in favor of an Adventure. What a turn of events.


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 Post subject: Re: more fins
PostPosted: Thu Dec 28, 2006 2:00 pm 
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kepnutz wrote:
No matter which fin one does eventually use, unleaded, premium or the new premium light, the top hull speeds of our hobie kayaks tend to max out at between 5 to 8 mph, depending on the model, beyond which it will be near impossible to achieve faster rates using the mirage drive pedals alone. -kepnutz-
That was well said. Top speeds are dictated by hull length and width. I have no complaints about my 12 foot long, 34 inch wide kayak's speed because it keeps up with much longer and narrower kayaks, but mine is way more stable and keeps me dry.

The gearing system for a trained bicycle sprint racer will definately be different than that of a neighborhood bicyclist who rides for about 3 miles once a month. The key here is that Hobie recognizes the issue of different strengths of kayakers and now offers more than one option for a pedal system. We have much to be thankful for. Short of a gear transmission of some sort, what would be nice is if Greg Ketterman could design a quick release system of fins so we could carry a variety of different sized fins with us on trips that we could quickly swap out.

I have both the super easy drive unt (drive unit with composite sleeves), and a turbo drive unit. I can mash the turbos all day long with the only problem being it digs into the bare feet (wear water socks). I also find it rewarding to use the easier drive at times so I can crank the pedals to the faster cadences of music. It takes less than a minute to swap out the drive units. I have options and for that I am thankful.


Last edited by Rnykster on Thu Jan 04, 2007 8:27 pm, edited 1 time in total.

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 Post subject:
PostPosted: Sat Dec 30, 2006 2:19 pm 
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Roadrunner wrote:
As a cyclist, you should be able to run the Turbofins easily at 60 to 65 CPM for extended periods (once you get used to them).
Wow! Using Turbofins, at a 20 cadence I do 2 mph. At a 30 cadence it is 3 mph. At a 40 cadence it is 4 mph. At a 50 cadence it is 5 mph. At a 60 cadence, I can momentarily push the threshold of 6 mph.

I seriously doubt that anyone can easily run the Turbofins at a 65 cadence for extended periods of time. At least for me in the Outback - we're talking maximum hull speed - sprint mode.

I certainly hope Hobie starts offering some Mirage races in conjunction with all their sailing races. There are a whole lot of competitive people out there who would jump at a chance to start racing on the water in their kayaks - if only there were some incentives - like actual races - sprint races, long distance races, etc. :roll:


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 Post subject:
PostPosted: Sat Dec 30, 2006 11:14 pm 
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Hi Rnykster,

Interesting comments. I can't sustain 65 CPM either. Moreover, if you're getting 6 MPH in your Outback at 60 CPM, you're taking longer, more powerful strokes than I am (60 CPM gives me 5.7 MPH in the Adventure).

So stroke length (leg length?) must be a significant factor, since the Adventure is the faster, more efficient hull.

In a cycling event, I'd probably be last, so I just assumed that that the buff cycling crowd could whip me on the water just as well! When I suggested up to 65, I had not considered stroke length.

I agree that racing would be fun. I was severely humbled by an Olympic sprint kayaker last month (see below), but thoroughly enjoyed the process anyway! 8)
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 Post subject: Who knows
PostPosted: Sun Dec 31, 2006 8:48 am 
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Location: sacramento california
Hey Rinky Hey Roadie.. :oops:
You are probably correct Rinky..60 SPM..(strokes per minute) might be too high to sustain for long periods in a mirage drive. I really dont know for sure. I have never counted the strokes. Those figures might not crossover well at all to the mirage drive.
I just might try to count the strokes per minute next time out to see just what high and low or average could be.

I kinda like the idea of having some mirage kayak races but then again Im not really sure about it. When I took my recreational bike riding into outright road racing and began racing and training in the higher categories it stopped being recreation and turned into a second job. :cry: Winning was all that mattered everything else was just no fun anymore and every ride was working to the max to beat buddies , teamates or competitiors alike day in and day out... ride after ride... no breaks ..no gift's..no slack.. groan. After a while it became extremely to difficult for me to turn that off and do a pleasureable ride with friends anymore. no more fun..no more recreation...etc :twisted:

As for Roadie coming in last in a bike race.. Roadie that too has yet to be determined, for even a blind pig finds an acorn every now and then. :wink: A bike race is not always to the swiftest or strongest and every Roadrunner has his day. When I was bike racing some teamates would spend all their gas in our weekly race training rides and have an empty tank on race day.Then they would try to domintate the pace too early and blow up or would just not race smartly and have nothing left for the final sprint..etc ..etc.
In cycling being stronger and faster is not always a guaranteed first place finish.(but it is a good start) The smarter racer guys like you could always grab the victory on any given day. :wink: In the meantime just stay away from those skinny "Oly" guys with the faster skinny boats and no worries then. :roll:
-Kepnutz-


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 Post subject:
PostPosted: Sun Dec 31, 2006 9:46 am 
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Roadrunner wrote:
So stroke length (leg length?) must be a significant factor, since the Adventure is the faster, more efficient hull.
I have taken out an Adventure with Turbo Fins and found it about the same as the Outback at faster speeds. I believe this has to do with the amount of wetted surface area. While the Adventure is narrower and longer providing faster hull speed, there is a lot of wetted surface area slowing it down compared to the Outback. The Adventure's front end doesn't rise whereas the the front end of the Outback rises out of the water at fast speeds causing even less wetted surface area. It is an interesting phenomenon.

You are right about stroke length being a factor. Also, those Turbo Fins have adjustable tension screws which also affects the amount of water they push at a given cadence. Also, current plays a role is speed at a given cadence. There are definately many variables involved explaining why someone might not be getting the same results at a given pedal cadence.


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 Post subject: Re: Who knows
PostPosted: Sun Dec 31, 2006 10:14 am 
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kepnutz wrote:
I kinda like the idea of having some mirage kayak races but then again Im not really sure about it. When I took my recreational bike riding into outright road racing and began racing and training in the higher categories it stopped being recreation and turned into a second job.
In any sport, you will always have the people bent on winning who take their sport seriously competing with those who just want to go out and participate in an organized event to have fun.

There is no way for a Mirage kayak to compete with the multiude of long, narrow, unstable racing kayaks out there. Even racing with just Mirage kayaks, races would have to be broken down into model type, and fin type, not to mention ages - a 50 year old can't expect to compete fairly with a 20 year old. Mirage races would be more personal, a person racing against their previous best time for a given distance.

The whole key though would be to have an organized event where Mirage enthusiasts can get together, briefly blow it out in a short race, and then have some group fun together after the race exploring the area's waterways. Short of having Mirage only races, the other option would be for Mirage owners to start joining already existing kayak races.

http://bp2.blogger.com/_AX4dWd-lTGY/RZgRscczt4I/AAAAAAAAALQ/jr3MV7xEDfo/s1600-h/Kayaking+in+Mobile.gif


Last edited by Rnykster on Sun Dec 31, 2006 4:08 pm, edited 2 times in total.

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 Post subject: Hey Rinky that soundz ok
PostPosted: Sun Dec 31, 2006 2:03 pm 
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Location: sacramento california
Hi Ya Going Rinky.
This sounds good...

"The whole key though would be to have an organized event where Mirage enthusiasts can get together, briefly blow it out, and then have some group fun together after the race exploring the area's waterways."

I have fun exploring the waters..it would be fun to have other hobie miragers to do it with..go somewhere new.. and check stuff out. 8)
-Kepnutz


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 Post subject:
PostPosted: Tue Jan 02, 2007 5:13 pm 
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Location: Northern Neck, VA
I thought the adjustment on the TFs was there to change the thrust and therefore the pedaling resistance. No matter, out of the box with no adjustment at all I found that the resistance was a bit high (good thing) and speed was higher (great thing). The more I used them the less I thought about the resistande and the more I adjusted cadence to keep up with my fishing buddies. For very little effort I keep up with a standard drive Adventure in my Outback. What more do I need? It's not a race afterall.

I have biked also and find that there is little to compare between the two modes of powering a vehicle. Except thet the legs are the source of transmitting the thrust to the machine. Both have their place and I like both. Wouldn't change much there. Biking exercise doesn't seem to help durability with the Mirage and using the Mirage doesn't seem to help the biking effort. The more I use either the easier it becomes.

My thoughts on the Mirage drive are that it is the speed limiter in the boat. The fins produce drag, and a lot of it at high repitation rates. Then the fins are not able to produce sufficient thrust to fly you faster. Don't know how fast I go as I havn't had a GPS until this Christmas. I am anxious to do some experimentation, so weather and chores permitting I'll start on that this week.


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 Post subject:
PostPosted: Thu Jan 04, 2007 10:14 am 
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Kepnutz said:
Quote:
No matter which fin one does eventually use, unleaded, premium or the new premium light, the top hull speeds of our hobie kayaks tend to max out at between 5 to 8 mph, depending on the model, beyond which it will be near impossible to achieve faster rates using the mirage drive pedals alone.


As kepnutz suggested above, it doesn’t matter much if you are a master cyclist, superb athlete, or if you use the Turbos or not, you cannot get over a certain speed in a yak or other displacement craft because of the physics of the situation. This is pretty much determined by your hull length at the waterline. You can generally only achieve greater speeds with a longer yak, with the 16-foot BigA theoretically giving you the fastest speed of any of the Hobies. There is a general formula that gives the relationship of your hull length at the waterline to max speed: about 1.35 times the square root of the hull length at the water line of a loaded boat is the generally accepted relationship.

http://www.recumbents.com/WISIL/hpb/hpbcalculator.asp

http://www.solarnavigator.net/hull_speed.htm

This formula, as related to the wavelength of the water you are passing thru and your bow wave, will determine the maximum speed you can attain with a particular displacement hull design in a particular situation. A planing hull is a different ball game, and you can overcome the hull length at the water line max speed if you can get your yak on a plane (lotsa luck!). Now, there are several variations on this formula (and others) that sailboat sailors (mainly) have debated ad nauseam. Here is a link to some of this discussion, but I will leave this to the more mathematically inclined to figure out.

http://www.dynagen.co.za/eugene/hulls/

Soo—the bottom line is that for most practical purposes, the upper hull speed limit is present in each and every yak displacement hull design and there is not much any of us can do to overcome that top hull speed, even by adding an outboard. It is true, however, that a well-conditioned athlete will be able to come closest to that maximum hull speed, but will not be able to overcome it.

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 Post subject:
PostPosted: Thu Jan 04, 2007 10:56 am 
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Apalach wrote:
This formula, as related to the wavelength of the water you are passing thru and your bow wave, will determine the maximum speed you can attain with a particular displacement hull design in a particular situation. A planing hull is a different ball game, and you can overcome the hull length at the water line max speed if you can get your yak on a plane (lotsa luck!). Now, there are several variations on this formula (and others) that sailboat sailors (mainly) have debated ad nauseam. Here is a link to some of this discussion, but I will leave this to the more mathematically inclined to figure out.

Well, the trouble with the hull-speed calculations and Hobie sailboats (and to a degree kayaks) is that the hullspeed only applies to full-displacement hulls. A Hobie 16's hull speed in displacement mode is a paltry 5.36 kts - ask anyone if the 16 can't go faster than this, even in light winds. Even the kayaks are not full-displacement by any means.

Hull speed is gravity-driven; the resistance from this has to do with the height of the bow wave, which depends on the weight (displacement) of the craft. While a kayak with an average paddler and full of gear might seem heavy at 250lbs, or a Hobie 16 at minium boat and crew weight at nearly 600 lbs, a 22-foot monohull could have 600lbs in ballast alone, plus another 800lbs of boat, plus 500 in crew weight, plus several hunderd pounds of gear, water, and fuel - the displacement of these are massive for their length and power and most ballasted monohulls are indeed limited by hull speed (exceptions being purpose-built ultralight ballasted racing monos like the Melges 24 which can plane and thus are not limited by hull speed) (completely off subject, this is a good part of why "monohulls point higher into the wind" - it is not some magical property of the single hull, it is just that they won't gain any more speed even with the additional power of heading off).

Most small, light, long craft (Hobies) are far more limited by drag. With the cats, upwind can lift a hull to reduce the drag from the water; however, the wind also creates drag on the boat. Downwind, the wind drag no longer hurts speed (coming at 90-degrees to the direction of travel or behind the boat), but both hulls are now in the water, creating more drag there (unless you are doing "The Wild Thing" on a spinnaker boat (Tiger) or very light boat (A-Cat) and flying a hull downwind for less drag.

Paddle/pedal yaks have minimum effect from wind drag without a large sail above them. While I have no personal experience with it, I'm betting that the speeds of all of these boats are fairly close. My guess is that the longer boats track better (giving better power) and the shorter boats have a bit less wetted area; in the end, the longer boats are a bit faster because of a little more power, and at similar displacement but longer length, they provide a more hydrodynamic shape.

Wow, that was a lot longer than I thought. Hope it was on-topic enough!

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 Post subject:
PostPosted: Thu Jan 04, 2007 8:34 pm 
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tjp wrote:
...in the end, the longer boats are a bit faster because of a little more power, and at similar displacement but longer length, they provide a more hydrodynamic shape.
It will be interesting to start seeing some race results comparing the BigA against the Outback. Hey Apalach, whatcha doing on the 28 of January? Care to race an old man in an Outback on the Wakulla?


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 Post subject:
PostPosted: Thu Jan 04, 2007 9:58 pm 
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Rnykster asked:
Quote:
Hey Apalach, whatcha doing on the 28 of January? Care to race an old man in an Outback on the Wakulla?

Uh-Oh, things are getting dicey here! BTW, whatcha mean "race an old man"? That question should be "care to race a "young" man in an Outback on the Wakulla?"

I have to admit the thought did cross my mind, but considering that I have not even been out on the water for over 6 months due to the weddings of my daughter and son (not to each other, I should add!), as well as my recent surgery, I'm afraid it would not be much of a contest. In fact, I just got back into the gym today after a more than 6 month layoff. But I may come down to snap some pics and to meet you and the other folks! Where are you guys starting and ending the race? Sounds like a blast--I will be cheering on you Hobie dudes fer sure! Let me know the details, and good luck!
Best,
Dick

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PostPosted: Sat Jan 06, 2007 1:12 am 
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We recently watched the HPB (human powered boat) races and time trials at Long Beach Marine Stadium. I was wishing I'd brought my Classic or Sport....the hydrofoils could not complete the slalom without hanging bouys in the turns, or stopping to get in the water and clear weed from the foils. The paddle kayaks had a miserable time with the turns in the slalom. On that particular day....this old man could have beat them all in his Sport!

The point is...slalom type kayak events (these were about 400 meter and 1-2 KM) are a good potential venue for the Mirage drive boats. It appears there'd be some equality of the boats (due to easier turns for the short ones) and the physical side is closer (we saw young and old putting up similar times in the short events).

It could be interesting for the spectators, doesn't need much room, and can be done on flat water. Food for thought, anyway...
Happy New Year to all,
JimL


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 Post subject:
PostPosted: Sat Jan 06, 2007 10:55 am 
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Hey Jim,
Good to hear--I have been following those HPB events for several years now online, and would love to see one up close and personal. The Long Beach Stadium is very close to where I grew up in SoCal so I'm familiar with the layout. Hobie might want to enter some of their boats (like the Quest, Revo, Sport, or new OB)--I would love to see how these particular boats would do head to head. I think the BigA might be just that--too long to do well on the turns, but it would probably be great in the sprints.

I know the Sport would hug those markers pretty closely in the slalom events and probably gain some excellent advantage on the turns. It's always nice to have a boat that can turn wiithin its own length--never the fastest, but certainly the most maneueverable! Mebbe one of these days...
Thanks for the report.
Best,
Dick

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