Testing a Steel Hull for Defects . . .

[Gone2long]

Threadmates,

I am considering buying a steel hulled boat and am wondering how I can get a sense of the worthiness of the hull. The boat was constructed in 1980 and is sitting at anchor.

The owner is selling at a discount, so I am sure that he will not want to take it out of the water unless I am willing to pay to haul her out, and there may not be a crane able to lift her where she is now located.

Is there any reliable way to test for defects while she is in the water? Any old sailor's tricks that might be useful?

Lastly, I'll probably have to make a judgement on the hull myself since the boat is in a relatively remote area.

Any help that anyone could provide would be greatly appreciated.

Regards to all,

G2L

[boasun]

1. By striking the hull with a chipping hammer... If the hammer goes through the skin or puts a deep dent in the skin. It is not for you.
2. Electronic thickness gauge. Using the stated thickness of the metal as a guide, you can determine if the skin has be reduced in thickness due to either rust chasing or pitting out where you can't get to the interior of the hull. Or reduced by electrolysis.
But the boat needs to be hauled out for testing of the hull below the water line. And that is the buyers problem.

[thinwater]

Originally Posted by boasun

1. By striking the hull with a chipping hammer... If the hammer goes through the skin or puts a deep dent in the skin. It is not for you.
2. Electronic thickness gauge. Using the stated thickness of the metal as a guide, you can determine if the skin has be reduced in thickness due to either rust chasing or pitting out where you can't get to the interior of the hull. Or reduced by electrolysis.
But the boat needs to be hauled out for testing of the hull below the water line. And that is the buyers problem.

UT testing can be done in the water, but access is less; you are limited to what you can reach. Hauled is much better.

If the paint is not very tight, it is required to blast off everything that is loose. The more layers, the more trouble getting go numbers can be.

However, UT testing will miss pitting smaller that than the transducer head (anything smaller than ~ 3/16-inch is often missed). There is no substitue for a good visual internals and external exam. UT is for measuring general thickness, not detailed condition.

Hammer testing is very valuable, but it looks brutal and scares owners. It's really quite safe.

[Boracay]

If you can look at the plans or contact the designer then you can check what the scantlings for the hull and deck should be. If there is a builder's certificate it may list the plate and frame thickness for the hull and deck. Looking at the boat sitting in the water check that it sits level and on its marks. A few people standing on the toerail may be of interest.

The owner may have records showing how frequently the anodes have been replaced and when this was last done.

There may be photographs that show the hull below the waterline with some detail together with the condition of the rudder and the propeller.

Much can be gained from a visual inspection. Rust spots on the outside of the hull above the waterline and the external surface of the deck may only be cosmetic but would need to be checked carefully. An internal inspection, particularly along frames, stringers and bulkheads and all visible welds can also be very informative. Attention may need to be paid to the internal wiring, particularly the state of any automatic bilge pump and switch. The presence of any pools of internal water should also be noted. The type and condition of all through hulls, seacocks hoses and clamps should be checked and assessed as to their suitability.

These are the items that come to mind for a steel boat. There are a multitude of items on all boats that need to be checked as part of the "due diligence" of boat buying.

Based on the above it is wise to draw up an operating budget for the boat.

If, after assessing the above items the boat is still attractive then engaging the services of a surveyor experienced with steel boats is essential.

[Gone2long]

Originally Posted by Boracay

If you can look at the plans or contact the designer then you can check what the scantlings for the hull and deck should be. If there is a builder's certificate it may list the plate and frame thickness for the hull and deck. Looking at the boat sitting in the water check that it sits level and on its marks. A few people standing on the toerail may be of interest.

The owner may have records showing how frequently the anodes have been replaced and when this was last done.

There may be photographs that show the hull below the waterline with some detail together with the condition of the rudder and the propeller.

Much can be gained from a visual inspection. Rust spots on the outside of the hull above the waterline and the external surface of the deck may only be cosmetic but would need to be checked carefully. An internal inspection, particularly along frames, stringers and bulkheads and all visible welds can also be very informative. Attention may need to be paid to the internal wiring, particularly the state of any automatic bilge pump and switch. The presence of any pools of internal water should also be noted. The type and condition of all through hulls, seacocks hoses and clamps should be checked and assessed as to their suitability.

These are the items that come to mind for a steel boat. There are a multitude of items on all boats that need to be checked as part of the "due diligence" of boat buying.

Based on the above it is wise to draw up an operating budget for the boat.

If, after assessing the above items the boat is still attractive then engaging the services of a surveyor experienced with steel boats is essential.

Helpful suggestions from all of you. Will start with a visual and a hammer, then go from there if conditions warrant it. Was thinking that the hammer idea can also work underwater as a rough indicator, used with a pair of fins, snorkle and mask, given that the underwater growh is not too obtrusive.

Thanks again to all,

G2L

[Artif]

Originally Posted by Gone2long

Was thinking that the hammer idea can also work underwater as a rough indicator, used with a pair of fins, snorkle and mask, given that the underwater growh is not too obtrusive.

Thanks again to all,

G2L

Be very careful using a hammer underwater, hitting a thin spot could be expensive, if you put it through the hull.

[Gone2long]

Originally Posted by Artif

Be very careful using a hammer underwater, hitting a thin spot could be expensive, if you put it through the hull.

A couple of taps top side should clue me as to how hard I might want to to knock on the bottom (if ya know what I mean. : )

Thanks for the advice,

G2L

[Gnwceleste42]

Some higher end ultrasound gauges will read steel from epoxy for exact reading and not stripping. Definitely haul unless you understand the full potential costs of blasting to white steel and epoxy as well as some spot welding etc.as part of your investment

[Boracay]

I strongly advise against using a hammer or screwdriver to check a steel hull, particularly below the waterline.

If you believe this to be necessary then the boat may not be a good candidate for purchase.

[Jacko]

Gone2long A very simple starting point !! If you can dive on the boat and check the Anodes if they are gone ( eaten away to nothing left ) I suggest that you be gone !!! There is every chance that you will have major repairs to do also if there is rust around the water line this is an area that will show that there is no anode protection so head for home and find another boat to look at Cheers Jacko

[thinwater]

Originally Posted by Boracay

I strongly advise against using a hammer or screwdriver to check a steel hull, particularly below the waterline.

If you believe this to be necessary then the boat may not be a good candidate for purchase.

In truth, this is mostly true. You will need to re-paint. Mostly it is a method for use where there is more corrosion than most boat purchasers would accept.

Where it is useful is in areas where UT testing gives inconclusive results; sometimes there are areas where it is very difficult to get clean echos and the reverse side is not easily accessible.

(I've done UT inspections on thousands of oil tanks, many tankers, and a few smaller boats.)

[lorenzo b]

Are we talking about a sailboat with compound curves or a work boat with hard chimes and flat steel?
Do you like to weld?

Bad news; you need a new bottom
Good news; you get a new bottom

[Gone2long]

... More good tips. Appreciate them.

I am looking at two steel boats and one cement one. More on the cement in another thread.

As per the question by one of our thread mates above, the boats are single chine steel sailboats, not unlike Boracay's Roberts 44.

Don't know how to weld, but learning may be in my future. : )

Regards to all,

G2L

[lorenzo b]

If they are sailboats, I would not worry too much, they do not get the abuse and neglect of a workboat.

[rustypirate]

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.