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 Post subject: Re: Mast Support Fail
PostPosted: Mon Aug 13, 2012 12:02 am 
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Location: Central Coast NSW Australia
NOHUHU wrote:
Stringy, I just poked my head in the AI with the old female-style mast cup and the V-frames seem the same to me, other than the scale, due to the different sizes of the AI/TI hulls.


Nohuhu,
I just checked my '11 AI (been away for week with just the TI) and there is a difference. Like your earlier AI the X-bar and mast cup are not connected. There is a gap of about 10mm. That explains the quick and easy V-Brace adjustment for mast drum height.

My TI is exactly the same as Tom's excellent drawing where the mast cup is connected to the X-Bar.

My AI is actually is an '11 hull with '09 X-bars (warranty claim)

So there have been significant changes made to this design, with the newer AI's that share the same aka as the TI, it seems.

I'd like to hear from Hobie on the correct adjustment procedure for the V-Brace.
Might have to email them.


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 Post subject: Re: Mast Support Fail
PostPosted: Mon Aug 13, 2012 5:22 pm 
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I had fun "playing" with the V-truss adjustment... and coating everything with Permaflex Anti-Seize. I definitely found out that my previous (and current) furling line jams (under the spool) were due to the deck height being too low. So, I was able to push up the deck height (by expanding the V-truss gradually on both sides) so that it is almost touching (but not rubbing up against) the spool. The hull bulge remains beneath along the keel-line, of course, but... oh, well.
Scott


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 Post subject: Re: Mast Support Fail
PostPosted: Mon Aug 13, 2012 8:41 pm 
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Location: Kailua 96734
I might suggest a little extra room be added for the times when the mast is fully torqued upwind. The aft side of the furling ring usually contacts first under pressure...


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 Post subject: Re: Mast Support Fail
PostPosted: Mon Aug 13, 2012 9:49 pm 
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That's a good point... I've got it at a bit less than the thickness of the furling line (1/8"?)... And maybe a thicker furling line would help, too...!?!
Thanks.
Scott


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 Post subject: Re: Mast Support Fail
PostPosted: Mon Aug 13, 2012 11:07 pm 
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Location: Maui, Hawaii
I adjust my AI's with a space of a little less than 1/2 the thickness of the furling line. Works well for me.

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 Post subject: Re: Mast Support Fail
PostPosted: Thu Aug 16, 2012 5:25 pm 
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Location: Kailua 96734
NOHUHU wrote:
As far as other non-structural dimples, dents and such, I think Hobie has suggested using hot/cold water for these cosmetic repairs. Heat guns are not the best tools for heating large areas (or mixing with water). :shock:
Here's a great repair video done by Jacques B and Brendan at Hobie. Also, it's a great ad for Hobie sunglasses...

[youtube]http://www.youtube.com/watch?v=OpuIJzMotDg&list=UUYPKHYQ_nH2dk79kwaTTLiQ&feature=player_detailpage[/youtube]


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 Post subject: Re: Mast Support Fail
PostPosted: Thu Aug 16, 2012 10:21 pm 
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Joined: Wed Jun 20, 2012 10:16 pm
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Location: Lexington, NC
I have a 2007 AI. It seems to me that stressing the hull to much by expanding or contracting the V frame is a bad idea because you can't move the bottom attachment point up or down without stressing the 2 fixed attachment points below the cross brace. The fixed welded triangle must expand or contract equally in all 3 directions. Therefore if too much tension is needed to raise or lower the receiver, it will begin stressing the 2 upward studs one way or another along with some strain on the V itself.

I installed black diamond plate rubber mat about 1/8" thick in the whole area around the receiver with the receiver resting on top of it so it was shimmed up about an eighth, reinstalled the V frame as I described earlier, and now it furrows very smoothly.


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 Post subject: Re: Mast Support Fail
PostPosted: Fri Aug 17, 2012 12:35 am 
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Location: Kailua 96734
Drew, I don't understand the logic of this repair.

If you did not change the setting of the turnbuckle, you did not change the height of the mast cup relative to the Aka crossbar.

Shimming the top lip of the mast cup will not change its height at all. It will only deflect the top hull downward slightly. The mast cup is still the same length.

You must have made the proper tuning adjustments to the turnbuckles when you reinstalled the V-frame. You could have easily and safely made a 1/8" adjustment without the shim.


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 Post subject: Re: Mast Support Fail
PostPosted: Fri Aug 17, 2012 3:17 pm 
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Location: Central Coast NSW Australia
Still no official advice from Hobie? :?


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 Post subject: Re: Mast Support Fail
PostPosted: Fri Aug 17, 2012 6:14 pm 
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Location: Lexington, NC
Perhaps it pulled the top hull down slightly and bottom hull up slightly to meet in the middle. My spool now has a little bit of clearance above the bearing plate. I did notice the base of the receiver was not quiet touching the inner bottom hull when I placed it back before tightening every thing down. Snugging by hand the V frame did not make it touch down. When I ran the nut down on the bottom stud did it find it's home. I did not notice any upper deflection but could be too little to see by just looking.

My guess is with the slight added thickness of the upper deck, the V , when hand snugged a few threads shorter. The base plate of the v frame resting in the receiver tab, (Still slight gap from receiver base to bottom of hull). Upper V points snug on the upper studs, With the V is now a tad smaller, every thing pulls together when the 3 nuts were run down.

I think it deflects the bottom much more then the top because there is more stiffness where the top of the V attaches and 2 points at that vs 1 at the bottom. Therefore the bottom hull is brought up to meet the receiver that is slightly raised.


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 Post subject: Re: Mast Support Fail
PostPosted: Fri Aug 17, 2012 9:41 pm 
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Location: Kailua 96734
The gap you saw introduced at the bottom makes sense, after the shim was added. So there is now a little negative pull on that anchor point, which is what was needed anyway, to raise the mast. With or without the shim, it's nothing to be concerned about I would think.

On both the AI and TI, I was able to deflect up or down 1/2" with no problems and not much turning of the V-frame. On the AI, it shows up very quickly. You can use a ruler as you tweak.

You are correct about the hull bottom flexing easily. The top 2 anchor points of the V do not really deflect at all though. What happens is the mast cup moves up and down and flexes the upper hull around the mast hole. Less so on the TI.

Our TI hull was severely overstretched by a positive factory turnbuckle setting. The bottom had an ugly bulge and the mast was spinning on the bearing plate. You could see the puckering of the plastic deck around the mast cup too. It has always been hard to furl.

That's all gone now...


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 Post subject: Re: Mast Support Fail
PostPosted: Sat Aug 18, 2012 2:36 am 
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Location: Lexington, NC
Yea, the only concern would be the slight increase of leverage the whole mast above the bearing will have on the receiver, as the higher and closer to the the receiver is to the bearing, the more leverage the sail will have on it's base. I think in my case, too minuscule to worry about.

In any case, after reading about breakage in this area, I have thought about coming up with some type of base plate that surrounds the receiver base with a snug fit and epoxying that to the hull only for extra support.


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 Post subject: Re: Mast Support Fail
PostPosted: Sat Aug 18, 2012 5:37 am 
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Joined: Sat Nov 05, 2011 1:58 am
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Location: Forster, NSW, Australia
I reckon the strap round the miragedrive is an easier alternative. Epoxy is not particularly grippy on these hulls.

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2012 Tandem Island "SIC EM"
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 Post subject: Re: Mast Support Fail
PostPosted: Sat Aug 18, 2012 7:57 am 
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Location: Lexington, NC
Using straps is a good idea, but the receiver gets forces on it from different directions, so if a base plate will stick, I may try that. I so far have had success with an epoxy called G flex that was made for kayaks.


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 Post subject: Re: Mast Support Fail
PostPosted: Sat Aug 18, 2012 12:19 pm 
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Off topic, but just a bit, how do you drain your mast cup after sailing/washing?
(I keep a 3' length of irrigation/polypipe tubing on board to siphon it out.)
Scott


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