Thermographic survey
I have mentioned a few time the benefits of thermographic survey.

Having 5 minutes spare, I thought people might like to see some images from the survey of Tiderace II, when we had our keel/hull problems.

It works with ambient temperatures, is very quick and doesn't cost much. This was some 5-7 years ago and from memory and cost less than £500 to have undertaken.

Changes in colour show a change in the makeup of the structure. You are therefore after a uniform colour and uniform colour changes; as per the first image. Whilst it wont tell you what is wrong, e.g. osmosis/delamination etc, it very clearly tells you where you need to look.

Good shot of the STBD side, Clearly showing the frames and longitudinals.

Shot from aft looking fwd, clealry showing the extent of the damaged area.

An internal shot, identifying an area of discontinuity in the GRP, ontop of the egg box structure. Unlikley that this are would have been examined in a tap test; however damage is clearly evident in this image.

interesting! What are your next steps based on this? And as I assume the measurement is related to misture in the laminaten, I think it is not applicatie to check for corrosion under mastfittings?

It picks up changes in density of material; so if there is moisture in the GRP it will show this; equally it will show if there is delamination, ie air, in the GRP. Not sure how well it will work on metal; worth researching.

The work that was done following the survey was roughly, removal of keel, grinding back the grp externally around the hull and keel sump, and internally around the keel sump/egg box/hull, washing with fresh water to remove as much of the salt crystals as possible, re-laminating and then reinstating the keel. Whilst the yard came up with the repair plan, I paid and independent surveyor to agree it and oversee the work.

Wasn't a particularly pleasant experience and could have been avoided if I had hired a competent surveyor on purchase. Lesson learnt! And lost of great sailing since!

Cheers
Adrian