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Rot in Bilge twin skin Kauri

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just looking for some advice as I am out of my depth. I am renovating a lotus 9.2, twin skin Kauri. Long story short but I have had a lot of issues with leaking windows and now I appear to have a problem in the bilge with rot. The top Kauri appears to be ‘fluffy’ which I assume is Rot? The bilge has been wet for a long time and the Kauri is really wet and I am able to peel back the wood in places.


just seeing if there are any options for repairing the Kauri/bilge from the inside. I don’t think the rot has got through into the outer skin but very difficult to get to as it is under stringers in places.

Hoping for some good news……… but feel like it might be a major.





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Fluffy could be over zincing with cathodic protection. It strips something out of the wood (Lignund?) leaving just the cellulose wood fibres - note, my terms might not be right, but the effect is the same. Excessive cathodic protection on wood is a thing.

We have a double diagonal kauri boat of similar vintage and had a spot of this. We've dealt with rot as well, including replacement of large parts of the ply deck, after we removed the teak overlay.

Either way, you need to take it out. On how to take it out, that is really up to you. Ours was in the keelson, so we could get at it to physically remove it. Chisel. Make sure it is very sharp, and go across / along the hull, not down, so you don't juncture it. You can possibly use a small reciprocating saw, or a dremel (very small hand held spinning tool, like a dentist drill, but for DIY / wood working).

All you need to do is get back to sound wood. It is a bit like unravelling a sweater, you don't know how far you need to go back until just after you have done it. You can work this out by tapping though, refer below comments. Once you have sound wood, then you need to scarf in new wood. This is just a case of trimming / cutting wood to size and using sufficient epoxy resin for a solid bond. 

It is a good idea to use Everdure on your wood, esp if you think it is rot. You apply maybe 3 coats, the first thinned alot, the next not so thinned etc. The everdure penetrates the wood, displaces moisture then cures like epoxy. It is the best (and only) way to remove / prevent / treat rot in boats like this. Future proofs for future leaky windows. Using everdure helps with regular epoxy bonding as well. 

The bits we have dealt with have been small / discrete spots, and easy to access for removal by cutting and scarfing. If you have planks in the double diagonal gone, that is beyond my experience too. First step would be to clean it out with chisels and what-not to determine the extent of the issue. If it is a major, then you'll have to work out what to do then. Possible strip the exterior hull and re-plank and then re-glass and paint. That would be a major ball ache. If it is that far gone, you may need professional help, or ditch the project - but don't jump the gun, you need to establish the extent of the problem before talk like that.

If you have soft spots, with experience you can work out where they are by tapping, either inside or outside the hull. You need to listen to the sound. Dull is bad. "in tune" - loud is good. My father does this and uses the handle end of a big old screw driver. Surveyors do this religiously. I think they use a special round-ended hammer. Any tool that isn't going to scratch the surface but is solid is ideal. You can just use your knuckles, but they get a bit sore if you do very much of it.

If you are getting worried the whole thing may be terminal, it would pay to ask a surveyor to tap over the hull and get a feel for the extent of the issue, and if it is fixable he would probably also find all the other soft spots for you.

Hope that helps. 

PS, hope you aren't in the water when you start poking around in soft wood with a chisel. If you are, be gentle ;-)

PPS fresh water in the bilge is bad. Salt water is much better. A dry bilge is best of course. I can't actually remember why, I think it is that the salt acts as a bit of a preservative, while fresh water doesn't, and strips away natural oils etc in the kauri.

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Thanks. Very insightful. Not in the water fortunately, but stuck in my driveway (and has been for some time). Yip need to take a breather and figure out actually damage and then go from there. Been a long project all ready so hoping for some good news as to far into the project to give up now. Thanks again for the response.

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I would get a small hammer and do a tap check on the outer hull skin around the keel, rotten wood or voids will sound quite different to areas of sound skin. (watch a you tube video on how its done there are bound to be a few) . With the external skin ruled out and feeling better already :-) get an old screwdriver, sharpen the end to a point (we used to call it a podger, don't know why)  and poke it gently into any suspect areas from the inside, any rotten or dozy wood, will be immediately apparent compared to sound timber as the point will sink in relatively easily.  Furry timber that are still firm is likely to be fundamentally sound and small areas of genuine rot can be locally chiselled or ground out then filled with epoxy. A grizzled old sea dog once told me that sea water is a dilute disinfectant and helps preserves wood but fresh water is the enemy where  it collects. 

You will need to dry out the wood before any application of epoxy glue or preservative  etc and this will be underway already but it can be accelerated with a dehumidifier just keep any eye on it as you go so things don't get too dry. Post some pics after the investigation is complete, plenty of experienced folks  on this site that can offer advice.

Don't despair as its all fixable !


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Really appreciate the response. Yip probably the advice I need but have been burying me head in the sand for a while but now at a cross road. Don’t have the money to rebuild or skill. I will engage an old head for a survey and good look. If anyone knows anyone in the Auckland area that would suit having a look, any recommendations are welcome. Thanks again

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