Keel crack and osmosis

[Phillip]

I agree with Rod, but careful thought is required before you get carried away cutting holes in the keel even though I suggested an extra drill hole.

Relooking at the photos that water is coming out of EITHER the water tank [do you use it?] or the ballast. Its very close to both.

[Ianb]

Looking at the photo and the drawing of where the lead is, I think your hole is aft of the lead. The description of this spot is illegible on the drawing, but might just be plain old bilge, or it could have been a diesel fuel tank. The flow shape in the photo indicates that the void is open to atmosphere on the top. Water, then goo would match oily gunk floating on the surface of water. Can you get access to the bilge under the stairs? Do you now, or did she ever, have a diesel engine?

[Troppo]

Rod: That's a neat idea with the wire. Today it should have stopped dripping so I will poke around and try to develop some idea of the void. No, she never had a diesel motor so I assume the leak is not from some keel fuel tank.

One of the old guys at the club who wandered past said he had some kind of similar problem in his large powerboat, the engineer he hired to fix it (Brisbane) drilled a hole from one side to the other and let it drain before repairing. So, in theory, the suggestions of another hole and doing some kind of flushing then filling with epoxy has some merit. However, as much as I love busting things up to fix 'em, I am not keen to do any extra drilling at the moment.

Phil/Ian: Water tank or ballast or bilge? Ballast, I think. My model Top Hat has the original water tank running above the ballast so it is well out the way. I use it regularly. The ballast takes up the forward half (approx) of the keel with water tank on top. The aft half the keel is bilge, open right to the bottom of the keel. Two years ago when I discovered the other crack in the bottom of the keel, it was in the aft section and I could get to it from the bilge on the inside. After repairing that crack I then coated the inside walls of the bilge with dynel and epoxy and made a new water tank in the bottom part. So when I first saw the tiny drip, I thought it was the old crack leaking water from that new tank but it is not.

This new crack [which would have been there for years so not 'new' but so small hard to find] is very close to the boundary between the ballast and the rear section which was open bilge until I made the new tank at the bottom. However I have carefully checked on the inside. Also, it if was under my new tank, the drill hole I made would have gone into the tank and fresh water would have come out since I use water from that tank all the time.

Ian made the observation about the flow of water. I would have to agree, the way it gushed out, given the drilled hole was small, indicates the void is open to atmosphere at the top. Or it's a huge void. There was no 'glugging' like you get when pouring fuel out of a container with a nozzle, it just gushed right out.

The other thing Ian said was about oily gunk floating on water. Now this is a real puzzle. The first fluid that came out was only slightly contaminated and it was later that the black stuff came out and seems a bit thicker and a bit like oil. Even in the bottle it seemed to be a bit of water on the bottom and the black stuff floating on top. Like oil. But the black stuff is not oil. It dries out leaving dark brown/blackish stains and with enough water it washes away. A few people have sniffed my bottle of the black muck and said "smells like fiberglass chemicals" so I don't think it is fuel.

Actually, when I punctured the osmosis blisters with a screwdriver and hammer, the fluid that drained out of them left the same kind of dark brown/blackish streaks down the hull as that fluid from inside the keel left on the ground. I think it even smelt the same not that I was sticking my nose into the osmosis-blister fluid.

Just thinking about the fluid. Some was almost water, some was strong chemical soup. Maybe a void open at the top somewhere. Perhaps over time, a bit of rain is getting in up the top somehow and some has been in there long enough to make chemical soup. Maybe the original water tank is leaking down into the ballast underneath it. I have no inspection hatch so can't check it out. The other possibility is that the tiny crack under the keel was enough to let water in seeing as the boat sits in water 24/7 and being over a metre down would have a bit of pressure. Hmmm.

Thank you folks for your thoughts and suggestions.

Off to the boat shortly, will see if any new developments.

[bearmcnally]

hi Troppo
This is Bear's guess ? That crack ,split ,delamination or fibreglass rot I've been told it's called these days .Looking at the photo's 1st and 2nd and the bottom bubble my guess is the leak is under the lead. The lead when it is placed in the hull ,is just placed in and a mixture of resin poured in around the lead to help hold it in place.My guess is the liquid coming out is 30 years of salt water ,lead and what ever else has been mixing under lead.The slit could just be a dry area or it could also be that the resin has broken down over the years and has started a leak and that muck is finding it's way out through the laminate .

Like I've said ' These Mk 2/3 are now hitting 30 years of age plus and are now needing some loving (not having a shot at you Troopo you're on top of it ,and are teaching many as you go along)

Cheers Bear

PS Re,surveys most aren't worth the paper their written on .Just getting my late fathers Swanson 38 insured .$25 a foot to tell me what I already know as my Father and I built her. Oh ! by the way surveyors aren't interested in osmosis as such because it is not a insurance companies interest ???

[Ianb]

The worry is if the hole is connected to the atmosphere, it can sink the boat if not sealed.

It would be interesting to measure outside and inside and locate eactly where your hole is. It certainly looks pretty close to the bulkhead between lead and your new water tank. Maybe it is bilge water that seeped into the gaps between lead and the hull, and a bit of internal osmosis been going on.

You could flush without drilling another hole, seing as there looks like an opening above. Get some small diameter hdpe garden drip watering hose and stuff it up the hole and connect to the tap. (your local garden shop will stock the stuff, complete with hose and connectors.) Back flushing will reveal where it is coming from. Then let it drain out and you can pressure fill with slow set epoxy. (you would have to do in small quantities to stop it going off too quickly.)

[Troppo]

Osmosis and antifoul has been completed!

Sanded back the filler which went over the fibreglass and epoxy. Just have to be careful where the keel curves up and out not to sand too much out.

Sand back the fill.

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Painted over with a one pack primer, two coats, to help seal the repairs.

Priming the repairs

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Two coats of antifoul rolled on and almost ready to go back in the water. Used Altex No 5 for a change. one 4 litre tin is enough but the second coat was very light on to get it around. Previously used Awlcraft with good results.

Finished antifoul

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[Troppo]

Keel problem: I didn't drill any more holes but I worked out a way to do minor flushes. Simple by pushing the garden hose minus end fitting against the hole, water pressure was enough to force water in. I put in about two litres at at time, let drain, repeated it. I even squirted in some detergent several times then fresh-water flushed. Squirted some metho in and let drain. With all the flushing, the drips coming out would be much cleaner but after several hours, the liquid dripping out was back to the black resin-smelling muck.

I put a cloth plug in one evening and when I pulled it out next morning, it came out with a strong puff of air blowing drops of liquid around. I was happy about that as I now don't think the keel void is open to the atmosphere somewhere inside. I think the void is large enough that the initial fluid ran out quickly giving the impression that the void was open to atmosphere but it is not.

My exploratory holes, only one goes all the way through. Who would think those hairline cracks would let water in the keel and seep goo out.

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Yesterday morning, with the keel hole having been oozing fluid for well over a week, I plugged the hole with a dowel. Since the oozing seemed almost stopped, I cleaned the area, drilled half-way through with a bigger drill bit and pushed in a piece of dowel soaked in epoxy. Even if the epoxy did not work, water pressure can't push the dowel up into the keel void as the bigger hole it fits in does not go all the way up. I hoped with the cleaning and cutting fresh fibreglass that the epoxy would set properly.

In the afternoon I discovered the epoxy had not set, a little of the ooze had come through. I scrubbed the area with detergent, wiped over with metho, ran a hair dryer on it for a quarter hour then gave a light sand and whacked on a big patch. I hoped that since the plug was in, that there would be less ooze. However when I was using the dryer, I noticed it was still weeping ever so slightly from the main drilled hole and a hairline crack. It amazed me how it could get through such a fine crack. The ongoing ooze was not making me confident of my repair.

To do the patch, I cut about a dozen pieces of fibreglass cloth to shape, small to big to fit the crater I had ground out. Using the lid off a take-away dish, I lay a piece of peel ply across it. This is the stuff that will not stick to epoxy and I was using it to hold the fibreglass cloth in place while the epoxy set. I stacked the pieces of fibreglass cloth on the peel ply on the lid and wetted them out with epoxy as I went. Then holding the patch up to the bottom of the keel, I pushed it in place and using masking tape got it to firmly stay there.

patch under keel, epoxy setting, peel ply holding in place

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So far so good. I made the patch thicker than the original surface because it can always be ground back, but also I wanted the extra thickness because I was not sure a thin patch would handle any possible seepage of the sludge. The seepage seemed so minuscule that I thought it may not be a problem.

This morning, I pulled off the peel ply, gotta luv that stuff. Tidied up the rough edges using my grinder. Didn't bother grinding back to make perfectly level.

The patch was excellent. Pity about the seepage!

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I was very happy with the way the patch worked. Except for one detail Seepage of the problem fluid could be seen through the repair. However, it felt dry to my touch so I primed it. Later to my astonishment, I saw fluid was starting to seep through the primer. Oh, cuttlefish!!!

Tomorrow Windchaser goes back into the water. The problem is no worse now, maybe a little better with the patch, than when Windchaser came out of the water. Unfortunately, water will again seep very slowly into the voids inside the ballast area of the keel. If that little bit can seep out, being under the water, pressure will most certainly push some in over time.

A proper repair, which are the ones I prefer to do, would require Windchaser sitting on the hard for a month or two I reckon. It would involve drilling more holes, doing lots of flushing and giving a long long time to drain and dry. Then it would be ready for infilling with resin to strengthen it. As it is, the port wall of the keel is showing some signs of bulging out, the sidewall has been weakened. If I do nothing, I may still get many years of use before needing to do more repair. Certainly not a problem I envisaged when before I bought Windchaser since I read in the survey (which was a year old at that time) that the hull was sound. I guess little cracks like this are easy to overlook even if they have been there a long time.

troppo