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Old 01-08-2011, 08:42   #16
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Re: Testing a Steel Hull for Defects . . .

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Originally Posted by rustypirate View Post
The first thing you will need to do is perform an internal inspection.
Most steel sailboats will rust from the inside out. the rust will occur wherever the water can pool along stringers and ribs inside the hull with plenty of oxygen available.
Make sure that you can get eyeballs on as much of the internal surface of the hull and deck as possible. If any paint appears loose or flaking, then a hammer test is a good verification. I recommend a rubber mallet for this as it will not chip the paint unless it was flaking off anyway, and you can apply a firm enough hit to shake loose any flaking rust if it is there.

Make sure that you check areas that will get extra wet like anchor lockers and deck accessed storage.

Check the zinc annodes to ensure that no stray current may be causing corrosion.

If the boat cannot be hauled out, dive on it to examine the undersides. DO NOT use a chipping hammer for this as the potiential for punching a hole through a thin sopt can make a leak which if untreated will sink the boat.

Some things I have seen are bulges in the paing on the topsides caused by rust swelling underneath. Fiberglass patches over rusted out steel to stop pin-hole leaks.
Thanks Rusty. Good tips. Looked at a boat today with STAINLESS STEEL lockers - nice!

Regards,

G2L
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Old 01-08-2011, 09:01   #17
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Re: Testing a Steel Hull for Defects . . .

There is some good advice but Boracay's is the best. Do not go around banging or stabbing the hull while it is in the water. The is a reasonable possibility you will "hole" the boat and then have automatically purchased a sunken wreck. It is too risky. I have seen steel hulls in boatyards that you can easily push a screwdriver through. I have also seen floating steel boats that it seems only the paint is holding things together. If you tried to take them out of the water with a travelift the straps would cut through the rotten plates.
- - Instead follow the advice to visually check zincs, and the inside bilge and other areas very carefully for evidence of rust or stingers that are separated from the hull plates. It is all visual and you can use toy periscope or a plastic borascope to see in area not easily accessible. A strong powerful flashlight is essential to getting sufficient light into areas.
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Old 01-08-2011, 09:12   #18
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Re: Testing a Steel Hull for Defects . . .

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Originally Posted by osirissail View Post
There is some good advice but Boracay's is the best. Do not go around banging or stabbing the hull while it is in the water. The is a reasonable possibility you will "hole" the boat and then have automatically purchased a sunken wreck. It is too risky. I have seen steel hulls in boatyards that you can easily push a screwdriver through. I have also seen floating steel boats that it seems only the paint is holding things together. If you tried to take them out of the water with a travelift the straps would cut through the rotten plates.
- - Instead follow the advice to visually check zincs, and the inside bilge and other areas very carefully for evidence of rust or stingers that are separated from the hull plates. It is all visual and you can use toy periscope or a plastic borascope to see in area not easily accessible. A strong powerful flashlight is essential to getting sufficient light into areas.
Got it. Thanks - G2L
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Old 03-08-2011, 19:18   #19
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Re: Testing a Steel Hull for Defects . . .

On hammer testing:
* In the water is doubtful. Generally you are listening, not making dents.
* Not a chipping hammer or rubber hammer; must be a moderate ball peen hammer or equivalent (weight depending on thickness of steel). You need the hard surface. You are listening to the ring, not making holes.
* You can hammer test without damaging paint, but it requires patience and a lighter touch. A very hard plastic face hammer can work.

On UT testing:
* Yes, good gauges can read through good paint. However, bottom paint is not generally "good paint." It is too soft and too poorly adhered, at least on old boats. You may get a good signal, you may not. If the gauge shows the A-scan blip this will be clear, so it will not be a guess. UT on the topsides through paint should be no problem.

On visual:
* Yup, that is always the best bet. Eyes top tech for judging localized corrosion.

On thick coating and fiberglass patches:
* You've GOT to look underneath. Sprayed-on foam insulation has been the death of many tanks and boats.

_______

You got a look of good advise in these posts.
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