Hi, sorry for all of the controversy surrounding this potential boat (buy). And if this info is a repeat of what's been bludgeoned to death, previously, my apoligies. I kind of avoided the other thread, as it got out of control before I even saw it as having been started.
That said, pics, or no, you're never really going to know about the integrity of the steel, until you hire a metallurgist/forensic engineer, to come out and:
- Take a close look at things where they stand, defects & all.
- Take some metal samples to his shop; from the sections of the keel where things both: seem awry, & where they "appear to be fine". So that he can determine on the molecular level, what's going on, & it's likely causes. Plus how significant or not it is. That, as well as how prevalent & widespread it is or isn't.
The suggestion about tapping with the butt of a screwdriver’s a good one. Especially in order to look for more voids, as well as areas of thick fairing compound. As both are areas which would bear closer investigation.
For either can hide patched over rust/rusting spots (or nothing).
More specifically, either;
- Areas which have rusted in the past, were ground down, & then were patched with fairing compound.
- Or were rusting, & thus were cut out. And then patched with small pieces of new plate, welded on, post pour. Ones which possibly rusted away from the inside, which would be a symptom of a trend that’s truly "Bad Juju", as Tarzan would say.
For if there’s water in there, in various, unknown locations & amounts, then things will (probably) rust from the inside out. As to whether or not that’s the case, such is where NDT comes in (below).
Also, completely filling in the void that's left when patching a keel, post pour, is nigh on impossible, as I understand it. And thus it leaves an area vulnerable to future rusting from the inside. Kind of unpreventably so.
Regardless, I’d say that you don’t, under any circumstances, want there to be, or have been, water in between the lead & the steel. And to eliminate uncertainty regarding that, you need the services of a professional in order to determine as much. And if so, to what degree. Ditto on judging the quality of the plating material & whether it's thickness is appropriate.
That, plus the owner/builder should have a copy of the boat's blueprints & specs, which will state what type & thicknesses of metal should have been used where. Use them as a guide to have a pro check out the boat's construction.
It would probably help you: In order to learn more about the boat. And when interviewing professionals prior to hiring them to come inspect things. To do some studying on (NDT) Non-destructive Testing. And there are even forums
which are dedicated (mostly) solely to such.
MyNDT Forum of Nondestructive Testing (NDT) Discussions in Ultrasonic, Eddy Current, Radiography ...
Olympus - Non Destructive Ultrasonic Test Equipment, Ultrasonic, Phased Array, Microscopes, Thickness Gages, Flaw Detectors, Innov-X, NDT, Remote Visual Inspection, Eddy Current, X-ray Fluorescence, X-ray Diffraction
Also, & this may have been mentioned before, but it’d likely be worth getting to know your way around the Metal Boat Society https://metalboatsociety.wildapricot.org/
& also Boat Design Forums
And this bit is just an opinion from a; tool guy, with a lot of formal engineering, & plenty of the hands on sort as well.
But if the keel plating is tearing already, & is as thin in real life as it appears to be in the pictures, then barring a Lot of assurances from a few different metal, & metal boat experts, then I, personally, would be leary of trusting it. Even if then.
As it sounds like you already if you are too.
So from a guy who's been burned, the couple of times he didn't trust his gut about boats. Trust yours!
As at the end of the day, it's your heiney, & those of your loved ones onboard that are on the line. Not to mention your wallet.
As a partingl thought, in an article about yacht refitting, & or buying
boats, Nigel Calder has said “If there’s anything structural wrong, just walk away”. A Refit Reality Check | Cruising World
For fiscally, & labor wise, such things just get too big too easily, breaking your wallet & heart along the way.
BTDT, & it Hurts