J/30 Class Association Forums J/30 Forum The Boat, Sails and Equipment Dewatering Aft Bilge - Need Advice

I have an older J-30 with the same moisture issue you describe on the starboard side of the hull.

Postings other places on this site indicate that the primary source of this moisture is from the engine exhaust.

I have had the area around the exhaust tube rebuilt and also have had the worst area of my hull where delaimation had begun (starboard stern quarter) re-cored.

Two questions:

1) What areas of mosture intrusion into the core did you identify, if any, other than the vermiculite/bilge line ?

2) Since I am not re-coring the entire starboard side of the hull would barrier coating be of any value? Since there is moisture in the core, isn't it almost certain to get into the laminate even if I barrier coat?

Great work Rich. Hope you're taking pictures as you go along.

Are you removing interior furniture, or simply (nothing simple about it I'm sure) the floor?

I have only removed the floor and tanks, I plan on leaving the molded interior in place for the most part. In places where the core is wet and under an immoveable component, I will recore from the outside - for instance under the bulkhead and floor in the head/closet area. I've cut away some tabbing to allow for parts of the repair, but again, I'm leaving plenty of margin to scarf together old and new laminates. My tools of choice are a circular saw for cutting laminate and a sawsall for cutting tabbing and details. I also use a rotary trimmer for tight spots. A pneumatic chisel is key for attacking vermiculite and stripping away layers of laminate.

I had a bit of an ugly discovery yesterday (tearing things down really undermines one's ability to engage in selective denial). The aft-most keel bolt (aft of the last stringer) is badly rotten (1/2 of diameter is gone). On my boat, this bolt was tucked into a combination of resin and polyester fillter, which let the bilge water stagnate around and down into this bolt. Stainless is only rust resistant in the presence of oxygen (either air or moving water), since it relies on a coating of nickel oxide to remain 'stainless'. In stagnant water, stainless is very prone to corrosion and in my boat this has led to a badly deteriorated bolt. There is also evidence of spider cracking with rusty oxidation on the keel where this bolt is placed. If you see rust here, you've got at least some corrosion.

In general, it is best to keep your keel bolts bone dry. This means no cracks on the keel joint and no water penetration from the bilge. Generally speaking, the best approach to sealing the keel bolts is to 'cap' the bolt with a blob of thickened epoxy (thickened with lightweight and brittle agent like microballons). This cap keeps the bolts dry, yet can be chipped away for inspection. Don't encapsulate the bolt unless its completely dry.

I'm going to sister this bolt using a method similar to this one:
http://www.sailnet.com/collections/articles/index.cfm?articleid=caseyd0040

Using Aquamet 22 (which is more corrosion resistant - though not absolutely): http://www.machinist-materials.com/stainless_table.htm

This bolt was largely, but not completely covered by resin, which I strongly suspect is the reason it failed. On other J/30s, if this bolt is encapsulated, you may be fine. I'm not sure if this was a manufacturing defect or design defect. Also, I have yet to inspect the other bolts - I'm hopeful that their exposure to air kept them more intact. If they are shot, I may opt to drop the keel, or add a couple of extra sister bolts. Ugh.

This bilge area seems to be a major Achilles heel on this boat...

Unless your bilge is full of standing water, I'd say the overwhelming likelihood is that your core is wet from the outsite. This can be from blisters, damage to the outer laminate or a crappy thru-hull fitting. My engine's water intake (starboard) is bad and wet in the immediate vicinity. The rest of the core in that area is OK since there's no blistering.

The vermiculite is a great destination for water, but doesn't seem to impact the core it is next to. The inner laminate is several times thicker than the outer laminate, so its less susceptible to osmosis that penetrates the core. Not impossible that your water is coming from the inside, but it seems to me less likely.

The standing water aft of the bilge seems to collect on the center seam, which is solid glass, so, again I think the core is less likely to be impacted from the inside than the outside.

Finally, to reiterate: if you don't have a nice thick barrier coat, you're taking an unreasonable risk in *all circumstances*. A barrier coat slows or halts existing problems from worsening and keeps new problems from cropping up. Blistering gets more likely under three conditions:
- Warmer water
- Lower salinity
- Freezing weather in winter

So if you've got a boat up in Maine, you're likelyhood of blistering is mitigated (but still a substantial risk) since the penetration is slower. If you've got it in a freshwater lake in Texas, you're in prime osmosis territory. The other factors is the presence of freezing air while the boat is being stored. If you've got osmosis in your hull, but it never freezes when you're boat is on jack stands, your water may evaporate out without actually busting the surface (though it will still weaken the gel and laminate). If your soggy hull goes through a series of freezes in the winter, you've got a perfect set of conditions for expanding water to crack your gelcoat and develop classic blisters. Over time blisters always get worse if they are not fixed. If you have a substantially wet core, a barrier coat will slow the problem, but its not a fix by any stretch of the imagination.

Finally, one interesting thing to note. Since fresh water makes blisters *more* likely, special attention should be paid to 'Fresh water boats' on the market. This is great for some corrosion issues, but can actually be a check in the negative column as far as wet core issues go.

Brief qualification (after several long rants in this thread - I type very quickly):

I tend to write with an 'authoritative' tone about all this (bad habit). Don't be fooled into trusting my judgement, or anyone else's for that matter, over your own investigation and experience.

Check with the class measurer before doing anything. I'm less concerned about one design considerations since my boat really is in rough shape and I don't have reasonable alternatives to my approach that will result in a safe vessel. I'm going to build this repair right - I'll document and share it with a measurer if we decide to race one design, but I'm not going to rebuild it with the same design weaknesses that it came from the factory with. The boat won't be lighter (If anything heavier) or manifest any changes to hull shape or handling, so I'll take my chances after the fact.

If you're a serious class racer, you should tread carefully and get class measurer approval prior to any modifications - especially that 12ft carbon bowsprit and bulb keel any of you might be planning on tacking on!

I took some pictures this weekend that should answer a few questions for the curious.

Enjoy!
http://www.6degrees.com/j30/underthefloor

Rich

Rich,

What you have shared is very valuable for many of us. I'm within 1 week of having Rhapsody in the water, and to quote one of the comments you have with the pictures "... it's not wise to go looking for trouble". I will stick my head in the sand until the end of this season, then do some more investigating. I don't have the skills to do a major repair like this without professional help (that may mean the shrink too!).

Good luck on the balance of your repairs. I'd love to see your finished work.

Bill

Thanks!

I'm sure I'll document and post info as I go along. Until then, its going to be an epic task to get done.

Rich,
Bill just turned me on to this discussion. I'm in the middle of epoxy sealing my entire bilge on Nemesis (#435), and adding an electric bilge pump system. I started by taking a large diameter drill bit and rattled around the bilge knocking off anything that even thought about being loose before any epoxy hit it. I must also say that the bilge was totally dry for the whole winter, and only saw water when I washed it down a few days before the drill hit it. I've brushed the straight West System epoxy resin onto all verticle areas of the bilge, and pourd it in to the bottom. However, it is not so thick as to cover the keel bolts. All are bolts and washers are exposed on top. My concern is the drain from the "Other Bilge". I have no opening for it. Where should we expect to see that? Between the bilge pump and cooler drain hoses? To the side of one? Should I drill a new one back from next to either hose? I need a clue as I'm ready to paint and now's my last best chance to have a nice job done.

Thanks for all your time and effort in sharing this with us.
Mark R.

Sealing the bilge is a good idea. Sealing the keelbolts is also a good idea, if they are completely dry. I'll be inspecting all of my bolts before I seal them to be sure I don't trap moisture in there, which is would be worse than having them alternating between wet and dry. You'll also want to be sure your keel joint is completely dry before you seal anything. Its an all or nothing proposition - totally dry and sealed, or unsealed and as ventilated as possible.

As far as sealing them with solid resin, this doesn't seem like a good idea to me. Resin is super hard stuff and removing it will be nightmare when you want to inspect you bolts. If you use a lightweight filler like microballoons, it will be relatively brittle (still extremely tough), so you can chisel it off without too much pain and suffering. I also wouldn't bury the entire bolt in resin, just cover it with a blob. I'm pretty heavily referencing this article:
http://www.sailnet.com/collections/articles/index.cfm?articleid=caseyd0040

As for the 'Other Bilge', there is no drain other than whatever water can weep around the drain hose that is buried in the vermiculite under the floor. Because of its position, it doesn't drain and is therefore a prime spot for nasty moisture to accumulate, especially if your 20+ year old bilge hose leaks. So I don't have an easy answer to your question - its lower than the lip of the bilge, so it can't drain. I've floated the idea in a previous post in this thread of adding an additional hatch in the floor over this spot so it can be sponged out periodically. This would entail cutting out the hatch, digging out the vermiculite and old cruddy hose and fabricating some sort of latch to keep this new part of the floor from falling out every time it gets stepped on. Here's a rough image of what I'm thinking of:
http://www.6degrees.com/j30/underthefloor/bilge.jpg