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Cross-bar slop tech-pics for discussion
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Author:  Dan P. [ Mon Mar 09, 2009 11:38 pm ]
Post subject:  Cross-bar slop tech-pics for discussion
My 03 H17 was very loose a few years ago, so I had a local glass expert route out a pocket and install a block of a hard glass substance I believe was called G10 in order to firm up the connection between the cross-bar end casting and the hull. It was an okay solution. The epoxying of the cross-bar beds would have made it better, but if you study the geometry of the situation, you will see that even that is not going to last in areas where there is heavy chop.

I wanted a permanent solution, so I got a guy (?Lentz? of NC, from this forum) to cut-out and send me hull sections from a 17 cadaver so I could study the problem and come up with a fix that was both DIY and tightenable over time. I came up with a fix (the general idea is represented below) , but never tried it on my boat.

Here are some pics with some quick and dirty annotations and a funky representation of the fix I mentioned.

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Other ideas include adding structural brackets to the top-side. Or, a cable/bolt affair which would attach the same way the shroud chain-plate anchors do (under the lip), come up through a hole through the hull lip, and anchor via a cable over the end-cap "hump" onto the top of the cross bar. All of these are major projects with too much sailing down time for me to even think about.

Enjoy the pics!

Peace,

Dan Peake
Campbell, CA
2003 H17
2005 FX1
Author:  fastcat [ Tue Mar 10, 2009 12:34 pm ]
Post subject: 
Looks like a good solution, though I might substitute saturated fiberglass wool for the epoxy to anchor the bolts (the wool adds a huge amount of strength to the situation and a fiberglass to fiberglass interface would seem optimal). I sail my 2000 in pretty heavy chop, but haven't had that problem yet. Each spring I do disassemble my boat and tighten where needed. I will take an extra close look this year to make sure I not heading for the same problem. 8)
Author:  mmiller [ Tue Mar 10, 2009 2:02 pm ]
Post subject: 
Typical solution is to add resin / epoxy and chopped fiber to the holes and re-seat the castings. Never heard of more than that being needed. The loads are all transmitted into the glass that makes up the structure the casting is bonded to. The loads are primarily vertical (upwards).
Author:  Dan P. [ Tue Mar 10, 2009 8:28 pm ]
Post subject: 
Thanks for the comments guys. Having sliced the structures for a better view, there are two things that jump out at me and seem important from a materials strength and maintenance stand point.

(i) the stuff above the ".280" layer is not load bearing, it is a soft foam covered by the decorative half dome shell. If the .280 layer has been breached by the casting pins, a butt joint of new reinforcing glass/ and resin may eventually give way into the soft stuff above. While the new reinforcement may be as strong as new, the problem has simply been moved from directly above the pins to an edge outside and above the span of the two pins - My opinion is not settled on whether or not this is an improvement over new, but please bear in mind, I have never done it or seen it done.

(ii) the hull's shear plate (flat, oval, vertical surface against the casting) gets sawed by the motion of the loose cross bar end over time. If you look closely at the section pics you can see that this saw slit leaves the casting retained vertically by the relatively thin shell of the half dome. See in the pics above how the dome has fractured above the shear plate. I am guessing that there is no effective way to restore strength in a confined "saw" slit like this.

I believe that the various resin/glass fixes, and my bolt fix, will eventually creep into a loose state. Where I believe that I have an improvement is in the ability to periodically tighten things back down. I bet it works well for the 18 and the many other boats that use bolts.

Peace,

Dan Peake
Campbell, CA
2003 H17
2005 FX1
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