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PostPosted: Sun Dec 27, 2009 1:32 pm 
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Location: Central Coast NSW Australia
p0uch76 wrote:
They bought the hobie in Australia and can't seem to get much info down there about replacing the standard fins with the ST Turbo fins...can you help me out please?

:?
Who did they ask p0uch76?
Any Hobie dealer will tell you the Turbo's will fit all models!


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PostPosted: Mon Dec 28, 2009 1:10 pm 
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Location: NSW Australia
stringy wrote:
p0uch76 wrote:
They bought the hobie in Australia and can't seem to get much info down there about replacing the standard fins with the ST Turbo fins...can you help me out please?


Any/All Hobie Dealers in Australia would have advised you that "yes" you can change fins. Contact the dealer in your region.
Steve
Hobie Aus


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 Post subject: Re:
PostPosted: Fri Apr 15, 2011 9:40 pm 
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Yakaholic wrote:

Yes, I prefer the SS over the plastic sprockets. My heavy turbo fin use, coupled with the ability to strike objects, re-straighten the mast and keep going are better than taking a chance of cracking a plastic sprocket.



Old Salt,

I have a new 2011 Kayak with Turbo fins, my first trip out I broke two teeth on the plastic sprocket and the chain jumped several teeth. I'm getting a new sprocket under warranty....I don't think this will happer again but I was wondering if stainless sprockets are available for the Mirage Drive 2's.

Thanks!


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PostPosted: Mon Apr 25, 2011 5:16 pm 
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Location: Auckland NZ
Islandretreat

I am sorry to hear that you have had a problem with the sprocket teeth breaking & the chain skipping cogs HOWEVER I would strongly suspect that the problem you have experienced relates to adjustment of the drive rather than something inherently wrong with the plastic sprockets or drive chain.

In my experience the plastic sprockets are very robust and reliable: the teeth do not routinely break and the chains do not slip on them even under heavy usage.

Chain slippage can occur on the older stainless steel sprockets if the cables are not correctly adjusted, especially the idler cable, but as far as I am aware the plastic sprockets do not suffer from this issue to anything like the same extent: unless the cables are really badly adjusted.

Stainless sprockets are available and should fit your drive, but if the problem that you are trying to resolve is one of broken teeth & chain skipping on a drive equipped with plastic sprockets I would be looking to cable adjustment before considering retro-fitting stainless sprockets.


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 Post subject: Re:
PostPosted: Fri Aug 22, 2014 1:18 pm 
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Location: Naples, Italy
Roadrunner, is there any chance you could repost the images that went with your earlier description quoted below of adding lock rings (and O rings?) to help the fins clear the outhaul on the v2 drive? I'd like to do this but am having difficulty understanding what you did without the photos.
Pretty please? :-)

Roadrunner wrote:
rx7vt wrote:
So - tried adjusting my ST turbo fins as suggested. I agree that it seems to require less effort at low to moderate speeds (up to about 4.5 mph).

However, it seems to me that it also requires a slightly higher cadence, especially as speeds get higher.


Yes, that's the case -- the faster the cadence, the faster the speed (given the same fins and stroke length).

Quote:
I think what we really need is an adjustment that tightens up the clew as speed increases - essentially a variable pitch prop.


I think we already have a variable pitch prop -- the harder you push, the more the twist, the bigger the bite. But unlike a conventional prop, you can't really over-twist it since the twist ratio is not rigidly built in. The question is, how much pitch should you start out with for best efficiency? IMO, more is better; loose clews put the root of the fin to work and add potential pitch to the entire fin.

The following mod is somewhat similar to JimL's. This can increase cruise speeds by about .1 to .2 MPH and still retain full power at sprint speeds.

Take a pair of lock rings and attach them to the clew adjustment screws as shown below. This clears the fins of the clew outhauls and allows them to articulate and swing more from side to side. This works with screws, but is a little smoother if you're able to use clevis pins:
Image

Then, slip the rings over the clevis pins (or screws if you're using them). This is what it looks like on the newer drives. Notice that the outhaul is free to pivot out more:
Image

And here it is on an older Drive:
Image

By adjusting the clew screw it can be set up for varying degrees of freedom. IMO, this is one of the rarely tapped potentials of the Mirage Drive. The only disadvantage I've noticed is that you can hear the fins clicking from side to side. JimL's rubber bumpers should fix that though! 8)

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PostPosted: Sat Aug 23, 2014 12:17 am 
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Location: Escondido
I see you've been getting some good info from some old posts! I've made some improvements in 6 years. Now I'm using "Jack Chain" -- I believe it is size #12 in stainless. Galvanized works and is much more common, but has to be replaced occasionally due to rust. Here's what it looks like:
Image

In order to open up this much gap, I rake the masts forward to about 7 degrees approximately (stock setting is about 15 degrees). I use a home made mast bender to keep the shaft straight. This does weaken the masts slightly though (will shorten their life span by about 1/2, depending on how hard you use the Drive and whether your masts have been bent before) You may need to lock the raked masts in place with "Loctite Red" (permanent locker) if Loctite Blue doesn't keep the masts from spinning (let the Blue dry for a few days to get to max strength). Notice the new hole for the outhaul due to the angular change.

Note: You can start out with less rake and see how you like it -- also wouldn't have to worry about Locktite Red or shorter mast life -- maybe 10 degrees?
Image

This gives you quite a bit of lateral separation as you can see.
Image

Your fins will now have a bigger sweep, more efficient aspect ratio, and more pitch options. Your outhaul clew adjustment ends up adjusting the pitch. I get about .1 MPH improvement with this set-up, use it mostly for races, not every day use. I've been using this "improved" set-up for about 5 years and am very happy with it -- need all the help I can get!

If you try it, let us know how it works out!! 8)


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PostPosted: Sat Aug 23, 2014 1:41 am 
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Location: Naples, Italy
Thanks Roadrunner, I like it!! (I also need all the help I can get :-))
As I'd rather not drill an extra set of holes and bend the masts I'll try the less raked option first once the hardware shops open again here after their long summer break so I can hunt down some 'jack chain'.

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PostPosted: Sun Aug 24, 2014 12:27 pm 
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Location: Sarasota,Key West FL
This is actually very interesting, I tried opening the adjusting screws further and pedaling does become easier yet I can detect very little loss in speed if any (interesting). However I suspect I have a different problem. As everyone knows I pedal my TI between 10 and 15 miles per week as my exercise program all year round.
However when sailing and pedaling at the same time (what I always do) my pedals now oscillate and shake quite a bit while underway with the adjustment screws turned out quite a ways. It's possible that my flippers are just all stretched out (which they appear to be from so many pedaling miles), and also my situation may be unique because the way my boat is rigged (ie wing sail and suplimental hybrid propulsion) and the typical very low wind conditions in my area my boat averages between 8 and 10 mph average speeds (regardless of wind conditions). Since I pedal 100% of the time always it's entirely possible that my fins are all stretched out and the fluttering is not a result if them being set loose but more because they are stretched out. As a testament to the mirage drive durability, I have never repaired or had to replace any part of any mirage drive I have ever owned (at least a dozen mirage drives), except to straighten a couple mirage shafts.
I guess my question is with your adjusting screw lengthened the way you have how do you prevent your fins from shaking violently.
Bob


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PostPosted: Sun Aug 24, 2014 1:38 pm 
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Bob, what is your typical pedaling cadence (cycles per minute where 2 strokes = one cycle)?


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PostPosted: Sun Aug 24, 2014 2:14 pm 
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Location: Sarasota,Key West FL
Roadrunner:
I always pedal at about the same cadence, about 40-50 cycles per minute (leisure pace), at that pace I can pedal for hours at a time. That's one feature of the TI that I really like, even with just one person pedaling at a moderate (leisure) pace the boat (in kayak mode or with the sails furled) glides along very well (we always had to have two people both pedaling at a moderate pace with our old oasis).
Note: I only get the violent shaking when we are sailing, so I expect my problem is self induced.
Bob


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PostPosted: Mon Aug 25, 2014 11:21 pm 
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siravingmon wrote:
As I'd rather not drill an extra set of holes and bend the masts I'll try the less raked option first once the hardware shops open again here after their long summer break so I can hunt down some 'jack chain'.
Jack chain may not be a good alternative for you then. The fins need to be some distance away from the outhaul so they can cross from side to side. Jack chain, being rigid, might jamb up against the outhaul rather than passing under it. At the very least you would get a lit of clicking and clacking.

OR, you could try mast extensions -- 1/4 inch wooden dowels that slip in the bottom of your masts. 1/4 inch length is about all you can do safely. In this picture, you can see the effect on the front fin:
Image
The last possibility is the "ring clips". I started with these. Problem is, if you are a strong pedaler, you can unravel them and have your fin slide off the mast. Fins don't float! Use them cautiously and with frequent inspection.
Image

fusioneng wrote:
This is actually very interesting, I tried opening the adjusting screws further and pedaling does become easier yet I can detect very little loss in speed if any (interesting).
As you know, the dynamics of propulsion have a lot to do with blade pitch, RPM (CPM in our case), boat speed and load. That's the amazing thing about the Mirage drive -- it's effectiveness across all these range factors!

If you loosen the clew outhaul, it does make it easier to pedal and your efficiency through the kayaking speed range improves. As speed increases though, your cadence must increase to maintain the best fin angle-of-attack (AOA) on the water. At your speeds though (8 to 10 MPH) your fins are more likely to slip-stream if the outhaul clew is too loose unless you're cadence is about 90+. So your case is a bit unusual -- you would possibly tighten the outhaul for a better high speed "bite", especially if you're pedaling in the 40 to 50 CPM range..

Quote:
However when sailing and pedaling at the same time (what I always do) my pedals now oscillate and shake quite a bit while underway with the adjustment screws turned out quite a ways. It's possible that my flippers are just all stretched out (which they appear to be from so many pedaling miles)... my boat averages between 8 and 10 mph average speeds (regardless of wind conditions). I guess my question is with your adjusting screw lengthened the way you have how do you prevent your fins from shaking violently.
If your fins have a warped leech like this (below), they likely are pulling to one side and may be causing your vibrations at those speeds. They could also be causing one leg to be more fatigued than the other , having to work against the fin bias. The current Turbos don't stretch like that and should perform much better.
Image

Also, if your Drive is that worn, your parts may well be causing vibrations, even though it functions perfectly well. Mine doesn't act that way, even at those speeds, so I'm not sure what specifically might be causing that effect. I have a bad habit of breaking parts that get worn, so I tend to preventively replace when something starts to show signs of wear or fatigue. 8)


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PostPosted: Tue Aug 26, 2014 6:44 am 
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Location: Sarasota,Key West FL
Roadrunner:
Thank you for all the advanced knowledge on mirage drives, I will put it to good use.
I have two sets of fins, one set I will put new fins on and keep the clews tight for high speed operation (8-10 mph) for when I'm using my motors and wing amplifier. This gets me to my destination with enough speed to provide a nice breeze on me when I'm out pedaling in the hot Florida sun in the typical 4-6 mph winds we have ten months out of the year.
Once I get to the new river or mangroves I want to explore I typically put my motors up furl the sails and pedal my way around, I will rig my other set of pedals with the very loose clew specifically for low speed pedaling ease and power (I did notice a huge difference in pedaling effort by following your suggestions) however was perplexed when my pedals began shaking violently at high speed. Yes the shaking subsides if I increase the force and cadence to 80-90cpm, but unfortunately I'm only good for a mile or so at that pace then I'm toast (I'll have to work on my endurance).
One thing I noticed about our TI verses our old oasis is when just pedaling the oasis up a long river it would take both of us pedaling to make good headway, where with our TI (without sails or motors) we only need one person pedaling and the boat still makes good headway (even with 3-4 people on board). So my wife and I take turns pedaling giving each other a rest once in a while (extending our range considerably).
Actually I have a pulley setup on my TI that allows me when solo to pedal both sets of pedals from the front seat. However the pedaling effort increased so much that I abandoned the system a couple yrs ago. Now with this new knowledge I'm going to set that system back up and try it again. One thing I gleaned from my original twin pedal effort was I could maintain 3-4 mph at a much slower cadence (about 30cps) where with just one set of fins my cadence had to be 40-50cps but the strain on my legs operating both sets of pedals was too great to maintain for any distance, with this new information I might finally succeed. This would be a huge accomplishment for me in my quest to build the ultimate human powered craft.
With my boat if I have two strong peddlers with the wing engaged we have always been able to get to our 8-10 mph cruising speed without the need for the supplemental engine power (motors tilted up). However the 80-90cps cadence would always wear us out in a mile or two. Which was a major flaw in my system, with this new info if I can decrease the pedaling force required to get my wing to operate (minimum 6mph forward speed) I might finally succeed on my original goal of a human powered boat that I can go my desired speed (8-10mph) in any wind conditions (including no natural wind) without having to use suplimental power. I'm so close I can taste it.
As soon as I get my new wing completed using an eppler 420 wing form (much higher lift from my current design), I'm gonna go for it.
Thank you for the advise.
Bob


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PostPosted: Tue Aug 26, 2014 10:37 pm 
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Roadrunner,
As an altenative compromise to your ring clips, how about replacing them AND the pin with a zip tie (with the locking end in the middle on the upper side)? They're incredibly strong and might give the fin more lateral play for the same height.

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PostPosted: Sat Aug 30, 2014 10:52 am 
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Like this :-)

Image

3.6 mm zip ties with 2 extra heads as spacers for each drive, screws set up with eyes in line with fins and with hole in eye centered on edge of fins

Hope to try it out next week, if not tomorrow

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PostPosted: Sun Aug 31, 2014 10:15 am 
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Tried it out today with fins tethered with light line just in case. Big difference in acceleration from standstill. Much easier. Cruising seemed to require less effort too. Didn't notice any increase in top speed.... No noticeable wear on the zip ties. Pressure required slightly different between the 2 strokes so perhaps some fine tuning to do still
:-)

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