Strange-Looking Patch on Keel

[OffSeason]

Hello again!

Well, thanks to you all for your help with my questions thus far. I was looking at the pics of my Contessa 26' while I had her on the hard.

Here are some pics of a strange looking patch/repair job on the aft end of keel. Any comments on what it might be, and what urgency I might be faced with to repair it if it is a problem.

She is back in the water now after my rudder rebuild (as discussed elsewhere on this forum) and it appears I now have to re-attach the prop shaft to the gearbox. My plan is to haul her at the end of the season and bring her home where I can give her a winter of TLC.

Any comments on what you see in these pics would be appreciated! Thanks!

All the best,

Mike

[captain58sailin]

Mike,
When you haul her out take a phenolic hammer and tap briskly over the whole keel and if you hear a dull spot, that can be indicative of water incursion into your keel. You need to use even strokes flexing at the wrist and strike with the same force each time. Place your other hand's finger tips lightly on the area just adjacent of the hammer and if you get into a dead spot move the non hammer hand around the area while continuing to strike the spot and you can feel the difference in the vibration in the glass from solid to soft, the soft is more active. Take some sidewalk chalk and mark the area, be generous, go wider rather than closer. Then either consult with a surveyor or if you feel pretty certain you have a bad spot; drill a small hole and see if the saw dust comes out wet or water comes out, doesn't hurt to put a bucket under it over night to see what seeps out. I just tried googling the hammers and no luck, they are getting harder to find, used to be, you could get them at a gunsmith supply place. They also make a hard plastic hammer that will do basically the same thing, they are not as good, but for a quick and dirty idea if you have a problem the hard plastic hammer will suffice. For my bona fides, I am a marine surveyor and a member of the ABYC, among other things.

[GordMay]

I think the photos clearly show a compromised ballast/keel skin (the Contessa 26 has encapsulated iron or lead ballast).

After testing for unseen damage, remove and repair the affected areas.

The various non-destructive tests for hull soundness, such as percussion sounding*, I/R temperature** & U/S moisture readings, can be very difficult for the layman (or inexperienced/unqualified expert) to interpret.
However, even the novice/amateur should be able to discover suspicious “differences”, worthy of further examination.

* If a Phenolic or Nylon or Urethane plastic hammer is unavailable, a white rubber mallet can be substituted. Most hardware & big box stores carry some sort of suitable “soft” hammers. As the Captain notes, the combination of hammer sound (pitch, resonance, & feel (report & vibration) should reveal differences between compromised & un-compromised laminate areas.

** If a hull has hydraulic de-lamination or wet patches, infra-red imaging (or even a non-contact thermometer) will accurately show areas having a higher moisture content, as “colder“.