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PostPosted: Sun Jul 24, 2011 11:03 am 
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I used to beach the boat with the drive bungeed up because I heard that you "could". Well, I know better now!

So, I need to order new fins but I see a few different types. Are these ST fins or ST Turbo fins? Also, does the mast look damaged or bent? Is that gap of visible mast normal?

Image


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PostPosted: Sun Jul 24, 2011 8:47 pm 
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Those are Turbofins. What's the matter with them -- your picture doesn't show any visible problem.

It appears that you may have a 2008 Drive (V2 drums, V1 sprockets). Your sprockets would be the bottom style in the picture:
Image

In this case, your masts may be slightly bent, especially the front. OR, your masts could be loose and may have slid out a bit. To straighten, loosen the Allenhead, remove the masts, do a roll test and straighten with a vise or hammer. If the masts are straight, reinsert them (mark the flat spot, make sure hole is clean), tap them to seat them, tighten screw against flat area and secure with a thread locker.

If you have the V2 sprockets (top sprocket shown in picture; 2009 or newer), your masts appear to be slightly bent (the mast gap at the top of the fin should normally be about 1/4"). In this case, you should straighten them in place by bending them forward slightly. Measure them at the base and tips (fins off) to make sure they are parallel. On the other hand, the bend looks minor and you could just ignore it if you're not comfortable straightening it. 8)


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PostPosted: Mon Jul 25, 2011 5:19 am 
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Thanks RR!

This mirage drive the fins are ok. The others are damaged near the tip exposing the mast. Both sets appear to have too much mast at the top. I'll verfify the sprocket version tonight and get some replacements on order.


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 Post subject: Turbo fin tip tear also.
PostPosted: Tue Jul 26, 2011 6:47 am 
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I wish that there was a way for Hobie to attach a more wear resistant 'cap' on the end of the Turbo fins. The fins are made of a very soft material. ANY touching of the fin end seems to cause an immediate tear. Because the mast is solid SS the fin material tears away exposing the bottom of the mast. I have never hit anything hard enough to bend a mast but I have replaced a fin several times because of bottom rip outs.


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PostPosted: Tue Jul 26, 2011 3:12 pm 
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The fins are positioned way too low on the mast and should be adjusted up to a position where there is just a little play or looseness of the fin along the mast. I discovered some time back that too much slack allows the fin to drop on the mast which gives the bottom of the mast more opportunity to tear out of the fin. Repair of the fin can be made with a few drops of superglue and sprinkling talc powder or similar dust immediately onto the liquid glue before it hardens. It goes rock hard within a couple of minutes and cures overnight and holds onto the fin quite well. If you had a black talc it would totally disguise...Pirate

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PostPosted: Tue Jul 26, 2011 11:09 pm 
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Pirate wrote:
The fins are positioned way too low on the mast and should be adjusted up to a position where there is just a little play or looseness of the fin along the mast. I discovered some time back that too much slack allows the fin to drop on the mast which gives the bottom of the mast more opportunity to tear out of the fin.
IMO, this is not a fin adjustment problem, but likely a bent mast problem. A rearward bend on the mast will force the leading edge of the fin out along the mast.

On the other hand, fins should have some gap at the bottom of the masts to achieve the desired twist for good thrust. It's good to have about 1/4" to "wind up" the mast when the fins are static -- this gap disappears as you pedal.

Note also that all masts are not created equal. The early Turbo mast shown next on the far left is 1/4" longer than the others, extending the length of exposed mast significantly. Making assumptions based on the length of exposed mast, even if the mast is not bent, is risky.
Image

Here is a fin that is properly set:
Image
The clew outhaul is adjusted to keep the rear of the fin barely in the gap (about 1/8") so it doesn't pop out when twisted. Mast exposure is usually about 1/4" but can vary as noted above.

TIDALWAVE wrote:
ANY touching of the fin end seems to cause an immediate tear.
If your fins are tearing near the bottom without provocation, take a look at the bottom edge of your masts. In the mast picture above, the first three have squared edges; the third in particular is likely to have burrs on the bottom from screwdrivers that can cut the fins from the inside. Only the fourth example (current mast version) has eased bottom edges. If you have any of the other mast styles, you can bevel the bottom edges with a metal file to make them smooth and easier on the fins. Hopefully that will solve your problem. 8)


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PostPosted: Wed Jul 27, 2011 8:24 pm 
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I keep mine adjusted as RR suggests and just rebuilt my V1 drive with V2 sprockets and turbo masts. I have seen just about every Mirage part fail at some point, including having masts snap near the insertion point. Comes with the territory, I guess.

There is some logic in having a shorter mast and letting the leading edge of the sail sacrifice itself for the sake of the mast and sprockets.

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PostPosted: Wed Jul 27, 2011 9:40 pm 
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NOHUHU wrote:
I keep mine adjusted as RR suggests and just rebuilt my V1 drive with V2 sprockets and turbo masts. I have seen just about every Mirage part fail at some point, including having masts snap near the insertion point. Comes with the territory, I guess.

There is some logic in having a shorter mast and letting the leading edge of the sail sacrifice itself for the sake of the mast and sprockets.


Possibly some of the drive failures are directly caused by slack adjustment allowing tear outs near the unsupported bottom and broken masts by allowing the force to be generated down deeper. My money is still with tightening to the point where it only just functions then a little more for safety sake...Pirate

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PostPosted: Thu Jul 28, 2011 2:48 am 
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Pirate wrote:
NOHUHU wrote:
I have seen just about every Mirage part fail at some point, including having masts snap near the insertion point. Comes with the territory, I guess..

Possibly some of the drive failures are directly caused by slack adjustment allowing tear outs near the unsupported bottom and broken masts by allowing the force to be generated down deeper....Pirate

No- I just hit stuff ALL the time. :lol: :lol: :lol:

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PostPosted: Thu Jul 28, 2011 6:35 am 
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Great detailed feedback guys! Thanks a lot :)

I'm gonna take them apart and see what I got, and try that superglue and talc thing.


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