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PostPosted: Fri Dec 17, 2010 6:19 am 
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Thanks, reconion. This is the first time I have felt lucky to have lost my mirage drive in the creek. Mine was a V1, and was replaced with a V2. On the left, my wife's original V1 drive, on the right, my V2:

Image

I assume the cut bevel rather than the rounded end means my shaft is splined and I'm good to go! :D


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PostPosted: Fri Dec 17, 2010 6:41 am 
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Yep, looks good.

It's amazing how well a Mirage drive without a leash can act like an anchor!

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PostPosted: Fri Dec 17, 2010 7:40 am 
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We think we are seeing our TI's ability to point to windward improving with both drives down along with the centerboard. I say 'we think' because we have only had it out twice, last weekend and it was pretty light wind.

But that would make sense, wouldn't it. With the drives in and the pedals aligned with each other, it's pretty low drag and acts as additional keel surface to give the boat some bite and reduce slippage when trying to sail close hauled.

I would assume sailing off the wind it would be better to have the drives up and reduce the centerboard.

We can't wait to get out and experiment some more. I'll take the GPS along next time to see about the speed.

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PostPosted: Fri Dec 17, 2010 8:49 am 
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The Mirage Drive in a solo Island does act a bit like a centerboard, but because the blades feather themselves into the current as the boat slips sideways, they don't reduce slippage all that much. Not creating much lift. For the same reason, they do not cause a lot of drag. Overall, I'd say the bigger advantage to leaving the drive in place is that you can pedal! :mrgreen:

I wonder if one or the other of the drives on a tandem will have more effect on sailing performance. They are likely to be on opposite sides of the center of lift. Try removing one, then the other, then both and report back (but not in this repair forum thread, on the main board or the tandem board).


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PostPosted: Fri Dec 17, 2010 9:34 am 
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reconlon wrote:
Yep, looks good.

It's amazing how well a Mirage drive without a leash can act like an anchor!


Yep. Since that incident, we got a fancy color fishfinder on our powerboat, and I tried scanning for a hard spot in the bottom, looking for my old Mirage Drive. No luck.

Just out of curiousity, what would happen if I tried to use my wife's V1 drive with my Click n Go boat? The shaft somehow releases the CnG? Does it just rotate the locking blade of the CnG right off?


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PostPosted: Fri Dec 17, 2010 9:47 am 
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Quote:
what would happen if I tried to use my wife's V1 drive with my Click n Go boat? The shaft somehow releases the CnG? Does it just rotate the locking blade of the CnG right off?


It will work if you take a break from time to time to allow the right hand CnG lever to reset.

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PostPosted: Fri Dec 17, 2010 1:12 pm 
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Thanks, Matt!


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PostPosted: Sat Dec 18, 2010 9:46 am 
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Gringo wrote:
We think we are seeing our TI's ability to point to windward improving with both drives down along with the centerboard. I say 'we think' because we have only had it out twice, last weekend and it was pretty light wind.


Have you tried sailing your TI with the drives removed? If you go out and time the differance between having them up or down I'd really appreciate you comparing the speed with them removed and the plugs installed.

I have only sailed my TI with the drives in it one time and that was because we had really light winds and I was with a group of kayakers who were paddling their boats and I needed to stay with the group. When we had two AI's my wife and I did speed comparisons and hands down the person sailing the AI with the drive removed was always noticably faster. I would sure like to see some objective data.

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PostPosted: Sat Dec 18, 2010 11:58 pm 
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Tom Ray wrote:
Just out of curiousity, what would happen if I tried to use my wife's V1 drive with my Click n Go boat? The shaft somehow releases the CnG? Does it just rotate the locking blade of the CnG right off?
It looks like your "V1" drive is an '08 model. I believe the splined drumshafts were actually phased in sometime during that model year, so it is possible that you have an early splined shaft. These early splined shafts had the round edges as well and are indistinguishable from the non-splined versions (without exposing the spline):
Image
Top to bottom drumshafts: non-spliined; early splined, rounded tips; later splined, beveled tips.

Additionally, not all non-splined shafts spin in the drivewell. You can find out by etching a reference line at the top of your "V1" drumshaft and see if it rotates under use. If not, you should have no issues.

Quote:
The Mirage Drive in a solo Island does act a bit like a centerboard, but because the blades feather themselves into the current as the boat slips sideways, they don't reduce slippage all that much.
Although the fins clearly aren't as efficient as the daggerboard, I would tend to agree with Gringo that they can make a contribution to tracking, depending on wind and boat speed. Remember on all the other sailing Hobies, the Mirage Drive IS the daggerboard equivalent and actually does a credible job. Even on the AI, you might be comforted by the fact that if you forget to bring your daggerboard, you can still go sailing with the fins alone acting as surrogate.

Disregarding pointing (and tacking), if the fins aren't being used at all, the AI/TI will go faster without them, as they are unnecessary drag (unless of course, you are becalmed). If you are using them though, I think they make a nice enhancement to speed and definitely help close-hauled and tacking without having to use them rigorously. IMO, an AI with Drive pulled is no match for an AI with Drive in use, but an idle Drive is no match for a pulled Drive. The same principles should apply to the TI. 8)


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PostPosted: Sun Dec 19, 2010 5:11 am 
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Thanks for the further clarification on the shaft thing, RR. I do not anticipate ever using my wife's drive in my boat, but I'll put a little mark on it and see if it moves. Her hull was manufactured in January of 08, so I'd guess the V1 drive dates to about then as well.

The drive does act a bit like a daggerboard, and much more so if the boat is stopped and drifting beam to the wind. The blades can't feather far enough for that, so they provide good resistance to being blown sideways.

Under sail, the drive fins do provide a bit of lateral resistance, just not nearly as much as the board. If I'm not pedaling, I leave the blades centered when going upwind, and leave one foot resting on a pedal to keep the blades against the hull on any off wind angle.

I would think that keeping the blades vertical would be more efficient for the same reason race cars draft each other, but have found that the boat is faster with the blades against the hull, but points better with them down. Points best with them in motion!


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