Steel keel, encapsulated lead, ultrasound testing?

jerrytug

jerrytug

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If any experts would be kind enough to tell me, can you test the thickness of a steel keel if it is full of lead? (on the hard standing, from the outside)
And can you test the thickness of the hull, from the outside, if the inside is sprayfoamed?

Is internal hull sprayfoam a bad idea for maintenance on a steel hull (which is apparently rust-free? )

Many thanks Jerry. (might have found the 'dream boat' and I want reasons not to buy it)
 
I am not an inspection expert but I have used many of the techniques and worked alongside people who could justifiably call themselves experts. I suspect that the answer to the question is 'yes'. Ultrasonic thickness measurements depend upon reflection of the signal from an interface, in this case the inner surface of the steel I doubt that the signal cares what is on the other side of the interface. It is normal to measure remaining thickness of vessels and pipework in a whole variety of chemical and petroleum applications, in which the fluid has no effect on the reading.

I am not up to date but I suspect that there are now techniques that could tell you something about the lead also!

The same definitely applies to sprayed PU foam.

I understood that internally sprayed foam on steel hulls was the preferred treatment.
 
jerrytug said:
If any experts would be kind enough to tell me, can you test the thickness of a steel keel if it is full of lead? (on the hard standing, from the outside)
And can you test the thickness of the hull, from the outside, if the inside is sprayfoamed?

Is internal hull sprayfoam a bad idea for maintenance on a steel hull (which is apparently rust-free? )

Many thanks Jerry. (might have found the 'dream boat' and I want reasons not to buy it)
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I have an ultrasound tester ordered for delivery soon, when I get back off ship I will test it on my own boat which sounds similar construction and let you know, as for the spray foam , if its kept dry it seems ok , if you have a deck leak for instance the water pools in the foam and eats the boat from the inside out, i spent 9 months under a tarp cutting and welding as soon as i bought my boat , but i paid peanuts and knew the problems, also knew id do it my self
 
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ribrage said:
I have an ultrasound tester ordered for delivery soon, when I get back off ship I will test it on my own boat which sounds similar construction and let you know, as for the spray foam , if its kept dry it seems ok , if you have a deck leak for instance the water pools in the foam and eats the boat from the inside out, i spent 9 months under a tarp cutting and welding as soon as i bought my boat , but i paid peanuts and knew the problems, also knew id do it my self
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I believe that this is a potential problem on Etaps. If water gets into the foam between the two mouldings it can waterlog it and greatly increase the weight.
 
vyv_cox said:
I am not an inspection expert but I have used many of the techniques and worked alongside people who could justifiably call themselves experts. I suspect that the answer to the question is 'yes'. Ultrasonic thickness measurements depend upon reflection of the signal from an interface, in this case the inner surface of the steel I doubt that the signal cares what is on the other side of the interface.
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It can probably only see the interface if there is a change in the speed of sound there: either a different material or a thin air gap. The speed of sound in steel is 6100 ms-1 and in lead (high density, low Young's modulus) it's a miserable 1150 ms-1 - slower than water, in which it's 1400 ms-1. I'd expect a lead/steel interface to be easily detectable.
 
jerrytug said:
If any experts would be kind enough to tell me, can you test the thickness of a steel keel if it is full of lead? (on the hard standing, from the outside)
And can you test the thickness of the hull, from the outside, if the inside is sprayfoamed?

Is internal hull sprayfoam a bad idea for maintenance on a steel hull (which is apparently rust-free? )

Many thanks Jerry. (might have found the 'dream boat' and I want reasons not to buy it)
Click to expand...

FWIW I was once told by a boat builder and yard owner ( he was a keen wooden boat man and we were chatting about the alternative materials) that the most serious problems he had had with steel yachts were all rust from the inside, often hidden by foam
 
We had a steel boat with an encapsulated keel with lead in it and the hull had insulation, the ultrasound test had no problems. One thing to be careful about is our boat was once given an ultrasound test and the steel was 2mm thicker than it is, the test kit couldn't identify paint.
 
KellysEye said:
We had a steel boat with an encapsulated keel with lead in it and the hull had insulation, the ultrasound test had no problems. One thing to be careful about is our boat was once given an ultrasound test and the steel was 2mm thicker than it is, the test kit couldn't identify paint.
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Aha thanks, so a survey would involve scraping expensive paint back to the metal in lots of places, thats good to know.
 
When I had my steel long keeler (Encapsulated lead) ultrasounded the surveyor read at 18 inch interval IIRC so yes a lot of scrapings. Not a problem with mine as it was due to be shotblasted. One very vulnerable place for rot is the keel step if keel mounted mast, a good marker for how the boat has been looked after. The rot here can also go up the mast.
 
jerrytug said:
Aha thanks, so a survey would involve scraping expensive paint back to the metal in lots of places, thats good to know.
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not if you stump up for a more expensive tester, the one I have waiting will detect paint etc as my old tub is faired steel with no chines or welds visible I had no intentions of re epoxying the hull and long boarding all that bl00dy lot again - once was enough thank you

link here : http://stores.ebay.co.uk/omnitronshop/Ultrasonic Thickness Tester-/_i.html?_fsub=4636345011

we shall see if its a good as they say, getting lifted in three weeks time, lifting the engine , cutting out a plate in the bottom of the keel to let out all the unreachable ****, IE spanners , screwdrivers and squeeky dogs toy before chipping , epoxying and repainting, then going exploring with the ultra sound to see what the internal unreachable bits are like 15 years after I replaced them !
 
Thanks for the linky ribrage, not too pricey for such a useful bit of kit, I hope it works for you Jerry

That's a specially useful link for me, I have my eye on a steel yacht for sale, and the guy is just giving the hull a nice paint job...now my mind is at ease that it's technically possible to do it through a few coats of paint!
 
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