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PostPosted: Thu Jan 31, 2013 2:31 am 
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Joined: Wed Oct 19, 2011 6:02 am
Posts: 322
Location: Cape Coral, FL
yaknrugger wrote:
stringy wrote:
I came to hate a number of issues when sailing in good winds with the MD in:
-it was slower. The MD in either position adds drag.
-you could feel the fins fluttering at speed. I felt this might contribute to wear on the drive and unecessary extra force on the drivewell ledge.
-they would catch weed
-they were more prone to damage from hitting things.
-the cockpit felt cramped
So if I'm not pedaling then the drive is removed (but kept handy and leashed).


Sorry, not to hijack the thread, but a quick question about removing the MD's to increase performance in a good wind. Is there any additional benefit (speed or otherwise) by adding the drive well blanks when the MD's are not in?


I've noticed a slight increase in speed (.1~.3 knots) and faster, more bombproof tacking. Tacks like a machine. Of course, if you blow the tack without the MD installed, you're boned. I always pull the drive in winds between 5 & 20, above and below that the drive remains installed.

J

A PVC lock is a cool idea, I might make one for windy days.

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PostPosted: Thu Jan 31, 2013 4:39 am 
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Posts: 1870
Location: Central Coast NSW Australia
Tom Kirkman wrote:
I can't really speak to an increase of speed by removing the Mirage Drive. I haven't noticed it but then I haven't really bothered to check it against a GPS or anything. I will say that when the Mirage Drive is pulled you greatly reduce noise and splash by installing the well plug. Speedwise, I just can't say. I haven't done any legitimate comparisons. I'm sure somebody else has.


I haven't done legitimate comparisons either when sailing. Too many variables. It certainly feels faster and does tack better as K7 noted. (BTW if you miss the tack, reversing the rudder direction gets you out of 'irons' and sailing again)

I have done some GPS comparisons though, in kayak mode. Paddling without the drive in, rudder up and in flat conditions I can comfortably average around 7km/h. Putting the drive in and paddling, that average drops to around 6.5km/h. Interestingly that stays the same whether the fins are folded up against the hull or 'locked' down. Adding the drivewell plug makes no difference to speed but it does stop water surging up and over the 8" hatch cover.


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PostPosted: Tue Feb 05, 2013 3:20 pm 
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Joined: Mon Mar 26, 2012 10:37 pm
Posts: 79
Location: Puget Sound, Washington USA
Quote:
A velcro strap can indeed be used, but it won't hold the pedal arms as straight and parallel as this tool will. If it would, I wouldn't have bothered with this. Yes, I tried it.


Tom,

I suspected as much. You probably need all the stiffness you can get since the flippers were not designed to be a dagger board. I've often wondered if they added some dagger board function when sailing. There was a good discussion here a few months ago about that with strong and good arguments on both sides.

I can also understand the convenience of your approach. Sliding up on the hatch cover is not as easy for me now as it would have been 30 years ago.


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PostPosted: Tue Feb 05, 2013 4:32 pm 
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Joined: Tue May 18, 2010 2:31 pm
Posts: 2577
Location: Kailua 96734
Kman7, I lack a way to accurately meter speed changes that small, but when I remove both the dagger and Mdrive, I can tell that my mid-level speed ramps up some. In moderate conditions, the boat feels more slippery.

By slippery, I am referring to speed made good, rather than leeway.

Riding on the Hakas may have some influence here, because when I try this, I'm surprised at how well the boat points while close-hauled on a starboard tack.

Those of you riding the benches may want to try this. Let me know if your results agree with mine.

And I'll check to see if the tacking is improved without the drive, as you suggest.


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PostPosted: Tue Feb 05, 2013 7:08 pm 
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Joined: Fri Dec 05, 2008 2:32 am
Posts: 1769
Location: Calga NSW, Australia
NOHUHU, I certainly concur that hiking out seems to make the boat point higher - on either tack, but more so on a starboard tack. It makes sense, as the daggerboard is going to "bite" better with the boat flat.

I don't know to what extent it's my "roll-tacking" technique on the quarterdeck and to what extent it's the larger rudder, but I find the AI now tacks exceptionally well without the drive in - virtually zero failure rate.

Hiked out, with the drive pulled, is a very catamaran like experience.

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PostPosted: Sun Mar 17, 2013 11:04 am 
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Joined: Sat Dec 19, 2009 4:35 pm
Posts: 24
What if the miragedrive plug had a small daggerboard?


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PostPosted: Mon Mar 18, 2013 11:12 am 
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Joined: Tue Jul 19, 2005 6:29 pm
Posts: 1893
Location: High Point, NC
That's an interesting idea. Assuming it wouldn't put too much side pressure on the MD fasteners or the hull in that area, it might be an idea well worth considering.


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PostPosted: Fri Mar 22, 2013 7:31 pm 
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Joined: Sat Jul 28, 2012 4:21 am
Posts: 71
Location: DARWIN, NORTHERN TERRITORY, AUSTRALIA
Well thats a cool solution and simple to make Tom. I often feel as though i require the 'centreboard' effect from the fins straight down and in-line because sailing in Darwin as we have frustratingly high tides and strong tidal currents that often stuff up an otherwise perfect sailing day. :x
I like your simple solution too Slaughter, with your set-up the hook remains attached to the boat and can't get lost. Like I always say, we AI/TI owners are an innovative lot :wink:
Cheers Vintagereplica
If it works okay...modify it anyway!


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