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 Post subject: Fin Adjustment?
PostPosted: Wed Nov 03, 2010 1:55 pm 
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Location: High Point, NC
I understand that in one position you gain more low end acceleration but sacrifice some top end speed, and that in the other position you gain more top end speed but lose some low end acceleration.

My question is - which way do you turn the nut to gain which effect? Thanks.


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 Post subject: Re: Fin Adjustment?
PostPosted: Wed Nov 03, 2010 2:26 pm 
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Tighter for flatter fin and better top end.

Looser for full foil shape and better low end.

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 Post subject: Re: Fin Adjustment?
PostPosted: Wed Nov 03, 2010 2:39 pm 
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I assume tighter is with the nuts spun to the top?


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 Post subject: Re: Fin Adjustment?
PostPosted: Wed Nov 03, 2010 3:18 pm 
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Nuts tightened towards the drive would tighten the fin.

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 Post subject: Re: Fin Adjustment?
PostPosted: Wed Nov 03, 2010 4:49 pm 
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Thanks.


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 Post subject: Re: Fin Adjustment?
PostPosted: Wed Nov 03, 2010 10:45 pm 
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Location: Escondido
Sorry to disagree with Hobie on this. Tighter for slower and more work (similar to batting boards). Looser for more forward thrust, faster speed, better acceleration and easier pedaling. Those of us who race run them as loose as we can get them (including some of the Hobie employees). IMO. the "tighter goes faster" mis-concept should have been removed from the installation instructions about 4 years ago!

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You want about 1/8" of the trailing edge of the fin tucked in to the clew outhaul as shown here. This is the best setting for all stock applications, at all speeds.

Try it yourself. 8)


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 Post subject: Re: Fin Adjustment?
PostPosted: Thu Nov 04, 2010 9:12 am 
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Trust roadrunner he knows... I bow to you ol expert o the MirageDrive. My info is from the basic concept for a propeller. More twist for low end and less for top end. roadrunner has done a lot of testing of his own concepts on this using the MirageDrive.

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 Post subject: Re: Fin Adjustment?
PostPosted: Thu Nov 04, 2010 11:42 am 
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Thanks Matt. The idea of tightening the fins for faster speeds is a solid concept. As it turns out however, the speed range of kayaks is well below the threshold where that concept would be beneficial. The amount twist existent in the current Turbo and ST fin materials is most compatible with a looser clew arrangement for optimal thrust.

The adjustment feature is still great to have though, as it can compensate for slightly bent masts, any variation in mast length (early Turbo masts were 1/4" longer) and for use with customizing projects. 8)


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 Post subject: Re: Fin Adjustment?
PostPosted: Thu Nov 04, 2010 5:46 pm 
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Location: Kailua 96734
RR, don't you also recommend a tighter clew in the front fin, and looser in the trailing one?

FWIW, my rear fin's mast always slips first and needs the set screw retightned before the front one. Yet the front has taken the most abuse. (V1 with Turbo upgrade)

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 Post subject: Re: Fin Adjustment?
PostPosted: Thu Nov 04, 2010 9:54 pm 
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NOHUHU, I did find something like that, but the other way around. I stopped short of recommending it though. Here's the post you may be thinking about:
viewtopic.php?f=11&t=10176

For the small amount of difference it makes, I don't think most users are interested in spending the time on it. Now days, if I can feel any difference in flexing stiffness between the unmounted fins, the stiffer will go on the rear mast.
The only time I would go less than the max open position shown above, is if it causes an imbalance between the fins (virtually impossible if everything is properly aligned, lubed and tuned).

There are ways to open the clew further, but that goes beyond the scope of this discussion. 8)

PS: If your clew adjustment screw has gotten a little loose and won't hold its position, work a little Loctite Blue into it and that will stabilize it.


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 Post subject: Re: Fin Adjustment?
PostPosted: Thu Nov 04, 2010 11:40 pm 
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Location: Kailua 96734
Mahalo for the advice and link.

It's the mast screw working loose on mine.
Mast dropped off couple times.
And then the adjustment holes stripped.
Others are popping chains and breaking gears fairly often out here.

Hard life, being a mirage drive in the islands.

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 Post subject: Re: Fin Adjustment?
PostPosted: Fri Nov 05, 2010 8:31 am 
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Of course the V-2 sprockets/masts will take care of that. But as an alternative, you can epoxy the old mast and screw. I've had good luck with Loctite Marine Epoxy (some of the others like JB Weld will break down). The mast will eventually work its way loose again, but this should hold up for quite awhile. Make sure everything is squeaky clean first. For that, I like denatured alcohol on a swab.

Interesting about the chain and sprocket problems. Are these like broken links, cables, swedges, or cables popping off the drums? corrosion? I know the chain will kink up if it doesn't get lubed every once in awhile in a salt environment. I wonder if they're kinking and chewing up sprockets -- any common location (center, edge, random etc.)? 8)


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 Post subject: Re: Fin Adjustment?
PostPosted: Fri Nov 05, 2010 5:50 pm 
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Location: Kailua 96734
Broken links
Broken gear teeth.
Shredded cables near the idler drum.
Stripped peg holes :roll:
Non-corrosive issues for the most part.
All were youngish drives that were well cared for. All failures at sea.

(For me, it's the masts coming loose or popping-off while while sailing, tacking or surfing).

Of course there are the usual, "dragging the Mirage" fin tears and bending, but most of the unexpected events cause us to question the reliability of the Mirage in Hawaiian waters. Carrying spare drives is becoming a common practice here, for those who can afford it.

What would you list as the main source of failures in your waters?

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 Post subject: Re: Fin Adjustment?
PostPosted: Fri Nov 05, 2010 8:24 pm 
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Location: Maui, Hawaii
Carrying a spare seems to have fixed most of my problems. Since I've starting carrying it, I've only had 2 breakdowns on the water in over 2 years. Before then, I was breaking something on the drive every couple of months.

Two things that probably helped...

1) after buying a spare I realized the cost of a new drive! :o so I'm more careful with it (No beach landings with the drive in)

2) and after realizing the costs, I've done much more preventative maintenance of everything (Thanks Roadrunner!)

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 Post subject: Re: Fin Adjustment?
PostPosted: Fri Nov 05, 2010 9:07 pm 
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Location: Kailua 96734
Yes- Mahalo Nui to you and Yakass for the great maintenance guides.

And to Hobie for making us think twice about the cost of a NEW drive! :lol:

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