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PostPosted: Wed Apr 02, 2008 10:09 pm 
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Joined: Mon Jul 25, 2005 8:20 pm
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Location: Campbell, CA
Last year I noticed excessive up/down oscillation of my hulls in relation to each other. This I believed was due to significant slop where the front cross-bar end seats in the hull. I pulled things apart and discovered highly elongated holes in the fiberglass where the casting pins, pictured below, engage the hull.

Image

So, I hired a structural fiberglass repair expert to fabricate and install a new receiver-hole area made of a composite material similar to fiberglass, only harder (called G10, if I recall) in that spot. He did a fantastic job. But I took the boat out sailing and, well, not a big difference, it's still sloppy (I'm comparing to a H16). (note: my trampoline is very tight)

When I ponder the role of the casting, and the gap between the casting and cross bar (see popsicle stick) it looks to me like it is not intended to snugly fit the cross bar, rather it serves to capture the cross bar between the bottom of itself and the bed of the crossbar pocket in the hull. Making vertical positioning of the casting very important; if the casting were adversely raised a small amount (as in elongated holes), it would open the gap and allow the hull to rotate axially about the screw anchor point at the hull rim, causing slop that could not be reduced tightening the screws.

My questions: Am I correct about the function of the casting? Can an improperly positioned casting cause slop? And how stiff should a 17 be?

Thanks,

Dan
Campbell, CA
03 H17 SE


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PostPosted: Thu Apr 03, 2008 6:55 am 
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I was watching a thread either here or on Catsailor.com regarding the 17 and how flexieeeee they are.

It sounded like that was the nature of the beast.

Sam

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PostPosted: Thu Apr 03, 2008 7:49 am 
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Yes, it may very well be the case. However, don't you think there would be a lot of chatter on this in the 18 forum too? Those are larger heavier hulls and I think they have the same materials and geometry? In addition, I can not imagine the engineers at Hobie Cat being satisfied with the design if it were as floppy as my boat is.


Peace

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Dan Peake
2003 H17SE
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PostPosted: Thu Apr 03, 2008 10:01 am 
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The Hobie 18 crossbar to hull connection is completely different.

The 17 is tight when new. Certainly the elongation of the glass holes is the cause of this slop. The critical contact point for the casting in the crossbar is the lower surface. Reposition the casting as low as possible.

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PostPosted: Thu Apr 03, 2008 3:11 pm 
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Thanks for the reply Matt. That supports my thought exactly.

I just spoke to Jeremy at Surf City Catamarans, who suggested I first achieve an optimal casting position, and then pour an epoxy bed under the cross bar to achieve a net/form fit. Sounds like my boat is going back to Elkhorn.

Peace,

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2003 H17SE
2005 FX1


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PostPosted: Fri Apr 04, 2008 5:42 am 
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I have an older h17 with wear like that also. After twenty years of ocean and harbor chop, I thought that was normal. Sailing with a tight rig may help keep the boat 'as one'


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PostPosted: Fri Apr 04, 2008 5:52 am 
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Here's the catsailor thread regarding H17 hull flextion and solving it.

http://www.catsailor.com/forums/showflat.php?Cat=0&Number=138802&an=0&page=7#Post138802

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