CS30 Structural Grid Repair In Bilge - SailNet Community

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Old 04-17-2012
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CS30 Structural Grid Repair In Bilge

Greetings,
Does anyone know what the internal composition of the stringers in the bilge of a CS30 consist of? I'm wondering if the grid structure is hollow, or has coring?
Has anyone repaired/replaced sections that were cracked due to grounding the boat?
Many Thanks.
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Old 04-17-2012
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Re: CS30 Structural Grid Repair In Bilge

GREETINGS EARTHLINGS; Have you tried and cut for a sample or drill to see the swarff ? as always GO SAFE
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Re: CS30 Structural Grid Repair In Bilge

It's a boat I'm considering buying and fixing myself as a project. I'm going to see the boat this weekend and will have a better idea then. I was just hoping to get some insight into the construction to mentally prepare what would be required for repairs.
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Old 04-17-2012
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Re: CS30 Structural Grid Repair In Bilge

Quote:
Originally Posted by krazykoozak View Post
Greetings,
Has anyone repaired/replaced sections that were cracked due to grounding the boat?
I know sailnetters are annoyingly conservative and I hate to have to play that cliche but...

Fin keel boats, especially more modern designs, often distribute the keel loads with a some form of lattice in the bilges of the boat. This is because the loads on the keel are significant, more than enough to cause failure where the forces concentrate - especially where the keel meets the hull aft.

A hard grounding at speed stopping a 4 ton boat all focused on that point and hard enough to rip apart the structure designed to support that load? Scary. I would be nervous that as the load transferred to parts of the structure not designed to support it (i.e. the hull laminate, then the bulkhead tabbing, even the chainplates and rigging) there would be damage that's invisible to non-destructive examination.

Do you know exactly what happened to the boat?

Have any photos you can share?
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Old 04-17-2012
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Re: CS30 Structural Grid Repair In Bilge

I am pretty sure the grid is fiberglass without any wood core. My CS27 is and it pre-dates the CS30 by a few years. The grid is hollow.

Depending on how hard the hit was the damage could be extensive. To repair it properly access is needed which could mean removal of cabinetry.

I was on a 33' Beneteau recently that hit a rock. The damage was repaired professionally - for 26k.
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Re: CS30 Structural Grid Repair In Bilge

Thanks for the reply Mitiempo and Zedboy.

The boat is said to have been grounded on a shoal under power.
The subsequent survey for the insurance claim indicated no damage to the exterior hull, but a deformation of the aft upper end of the keel, and substantial damage to the stringer grid in the aft section of the bilge.
hopefully the attacements of photos i have will load...

Thanks again for your input.
Attached Thumbnails
CS30 Structural Grid Repair In Bilge-dsc07156.jpg   CS30 Structural Grid Repair In Bilge-dsc07157.jpg   CS30 Structural Grid Repair In Bilge-dsc07159.jpg   CS30 Structural Grid Repair In Bilge-dsc07160.jpg   CS30 Structural Grid Repair In Bilge-dsc07162.jpg  

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Re: CS30 Structural Grid Repair In Bilge

Yeah right no damage to exterior hull. That puppy flexed real nice to deform the keel like that and crack those stringers. Hard to tell what the glass underneath looks like without chipping/peeling off that cracked gelcoat.

My little bit of experience with this tells me the glass can still be flexible even on an older boat - lots of stories of improperly stood (standed?) boats' hulls "popping back out" once put back in the water, presumably with no ill effects.

Whether you could make a claim that everything is still ok just because the stringers look healthy under that gelcoat, and assume things just flexed and took the impact ... I'll let bigger experts than me weigh in. And if the glass looks bad, all bets are off.

My boat is wood
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Old 04-17-2012
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Re: CS30 Structural Grid Repair In Bilge

Hopefully rugosa will notice this, you might want to PM him.. he worked with CS for a time.

This looks like a pretty serious grounding, and though undoubtedly repairable it's not a small job. A big part of it is determining the actual extent of the damage. The hull skin (apparently intact could have internal damage not visible from outside. I really don't think this is a DIY repair for most of us.. Kinda scary - the boat would have to be nearly free to take this on.
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Old 04-17-2012
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Re: CS30 Structural Grid Repair In Bilge

That's some serious impact to compress the bend into the keel. CS 27 through 36T were solid glass grids. Expect same on other models. When I worked at CS '78 to '83 we took in a 36T that had grounded in Bahamas and disected it. Lots of fun to tear one apart. The damage extended beyond the visible, including delamination (downward tearing) at forward end of bilge, (upward tearing) in way of engine bearers, etc. CS furniture fit was highly consistent so look for uneven cabinet mountings, cabinet and cabin doors that bind or have uneven joints, screw plug pops, tabbing delamination, tanks shifted or off mounts. Split the shaft coupling to get an idea if the engine moved too. Also check steering thoroughly - impact at forward edge of rudder, binding turns (bent stock). The cheapest thing to fix will likely be the impact ding in the keel. Hopefully it is free to a good home.
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Old 04-17-2012
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Re: CS30 Structural Grid Repair In Bilge

When a fiberglass boat is damaged the cracks are easy. They're obvious and not difficult to estimate. The real, and expensive, part of the problem is delamination. At the top of the trailing edge of that keel, there was enough force to bend the keel and shed whatever coatings (gel coat, paint, epoxy sealer) were in place. When the glass is deflected that far you can bet it's delaminated. my guess is that the delam is probably on the order of 12 inches across and 10 inches fore and aft. Basically, the same goes for the grid. Cracks are cheap, delams, not so much. Forget the surveyor, get a qualified glassman and don't stop grinding until you've reached the perimeter of the delams. Otherwise, it's like building a house on sand.
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