Non destructive testing for potential delamination

[Alaris]

There’s a 2’x5’ area on my new boat that sounds significantly different from the rest of the hull when sounded with a hammer. It is a symmetrical area behind the prop and in front of the area, running athwartships on the bottom.

The surveyor complained about it in the survey so now the insurance company wants it fixed. There is no cracking, deflection, or any sign whatsoever of damage from inside the hull or outside.

The hull is apparently airex core but with solid glass along the centerline, around the through hulls, and around the rudder post. It is conceivable that there is solid glass in this area where there are several through hulls just ahead of the rudder.

There are no other surveyors within easy driving distance of the boat to get a second opinion.

If it’s delaminated I will fix it, not a big problem. But how can I determine if that’s the case without drilling a hole for a core sample? The seller got very emotional when the surveyor suggested drilling the core and basically begged me not to drill into the boat in his presence. The boat will be stored in his marina for another month so I want to keep him happy.

 

[slug zitski]

There’s a 2’x5’ area on my new boat that sounds significantly different from the rest of the hull when sounded with a hammer. It is a symmetrical area behind the prop and in front of the area, running athwartships on the bottom.

The surveyor complained about it in the survey so now the insurance company wants it fixed. There is no cracking, deflection, or any sign whatsoever of damage from inside the hull or outside.

The hull is apparently airex core but with solid glass along the centerline, around the through hulls, and around the rudder post. It is conceivable that there is solid glass in this area where there are several through hulls just ahead of the rudder.

There are no other surveyors within easy driving distance of the boat to get a second opinion.

If it’s delaminated I will fix it, not a big problem. But how can I determine if that’s the case without drilling a hole for a core sample? The seller got very emotional when the surveyor suggested drilling the core and basically begged me not to drill into the boat in his presence. The boat will be stored in his marina for another month so I want to keep him happy.

Don’t know your boat ..many times in the area of the shaft log , rudder bearing …thier is no core and a bunch of secondary structure on the inside that confuse a tap tap tap inspection

examine the construction ..look for fastener penetrations that might have allows water in

take a core sample with a hole saw if things don’t look right

 

[Max Rockatansky]

So drill when he isn’t around.

You could try a moisture meter, but the hammer has told the story and the only real confirmation will be sampling.

 

[DDW]

If the core has been rebated around the thru hulls, you can easily see that step from the inside contours. If you don't see that, either it is solid or hasn't been rebated.

Drilling a small shallow hole from the inside would tell you very quickly if there is core or not - don't have to go all the way through. Inner skin is probably going to be 1/8" or less if cored, if solid more than 1/2". You'll know when you hit core.

A strategy sometimes used for absurd insurance requirements is to certify that the issue has been corrected "according to industry standards" etc. There are cases where this can be done by signing your name with no other effort.

 

[longy]

^^I'd do this. Identify the center of the worst sounding area. Carefully remove some inner skin. Examine core. Re- glass over inspection area.

 

[DDW]

You can start small, with like an 1/8" hole sunk <1/4". That may tell you a lot. If is it cored and if the core is wet. I'd not remove any more laminate than that until I saw a problem. If everything is perfect, but cored and suspected delam'ed, then you need a small hole saw on the inside skin. A moisture meter might tell you something, just be warned that on an old cored boat it is highly likely to show wet. When I walk through the boatyard with mine, at least 8/10 cored boats >=10 years old are wet. Doesn't seem to hurt them that much, as long as it isn't wet balsa.

 

[mckenzie.keith]

I had a Freya 39 some time ago. The ballast was fully encapsulated. That is, the keel was part of the mold. The ballast was dumped in in little pieces, I guess, and then they poured resin in. However, the ballast did not extend all the way aft to where the rudder was attached. There was a hollow section between the end of the ballast and where the rudder attached. It sounded very different when tapping. This also created a deep bilge area where the bilge pump inlet hose was located.

The Freya hull was solid fiberglass, so we didn't have to worry about wet core in the hull.

 

[Grrr...]

So drill when he isn’t around.

You could try a moisture meter, but the hammer has told the story and the only real confirmation will be sampling.

You can't trust moisture meters either. I've high quality moisture meters tell me to fix areas that were absolutely bone dry when I cut into them. I created entirely new swear words for that situation. At least it was in the non-skid where grind the whole area and make it disappear. The bottom? Hell, no one will even see it.

Drill a hole, rip some of the core out with a screwdriver and check it for moisture, then just refill it with thickened resin.

 

[DDW]

Moisture meters require a LOT of education and care in use and interpretation. Unfortunately many surveyors do not understand that. But they can give you information, correctly used and interpreted. There could be delamination, there could be moisture, there could be both, there could be neither, there could be core, there could be none. Drilling a hole and checking the dust for core and moisture may answer some of those questions. All of those questions may not be answered until you completely destroy that piece of hull, but you can start slowly - that's my point. Even if it is cored, badly delaminated, and wet, the boat will probably survive another decade if you do nothing at all.

 

[Alaris]

Great news. Got a second opinion. Said the first thought of potential delam is totally wrong. Bought the boat.

 

[Monkey]

Great news. Got a second opinion. Said the first thought of potential delam is totally wrong. Bought the boat.

Don’t be so sure your problem’s gone. I had a survey done last year and a whole lot of moisture was found in the exact same area. The boat was rock solid, but the core was soaking wet after cutting her open.

 

[DDW]

I think the problem was insurance. If insurance accepts the second opinion, then the problem is gone. Even if the boat sinks because of it.

 

[phill_nz]

as always a pic is very useful
it may not look like anything to you .. but may tell volumes to others

 

[Alaris]

as always a pic is very useful
it may not look like anything to you .. but may tell volumes to others

This is what I got from the surveyor.

Keep in mind the boat is solid glass on the centerline, around through hulls, and at the rudder. So obviously it’s going to sound different in the areas bounded by those.

The area noted is exactly symmetrical. Almost like it was built that way…

 

[phill_nz]

did you tap it yourself .. if so how much difference was there in the sound

Moisture Meters: Can You Trust Them? We Test Five Models - Practical Sailor

Since 1974, Practical Sailor’s independent testing has taken the guesswork out of boat and gear buying.

www.practical-sailor.com

 

[Alaris]

did you tap it yourself .. if so how much difference was there in the sound

Moisture Meters: Can You Trust Them? We Test Five Models - Practical Sailor

Since 1974, Practical Sailor’s independent testing has taken the guesswork out of boat and gear buying.

www.practical-sailor.com

I did tap it myself, and used a moisture meter. The meter showed consistent readings throughout. It sounded different from the solid areas but the same as other cored areas.

 

[Will1073]

What make of boat?

 

[Alaris]

What make of boat?

Little Harbor 44

 

[Crash]

He says in his best Yoda voice, "Always a puzzle this is..."

Short of drilling into the subject area, you don't know what you don't know. It might be solid, it might not be. It might be delam'd, or it might not be. It might be wet, or it might not be.

I once bought and S2 9.1 that I knew had wet decks. It wasn't a question of if, it was a question of how much and how badly. The first winter the boat spent in Norfolk, we had a good hard cold snap and the deck cracked in front of the mast partners. OK, gonna do the repairs sooner rather than later. Had a surveyor come and survey the deck to get an idea of what was wet and what was delam'd and what was both.

As you can see, some area tested wet or delam'd, yet were discovered to have a previous solid (no core) repair that had been done. They sounded different, tested wet, yet the skins were well adhered, and there was no moisture. Drilling was the only way to figure it out. In fact, I drilled all the suspect spots first to ensure I knew the extent of the damage.

I would recommend you drill a couple spots throughout the area in question just to confirm the second survey. Easily filled with thickened epoxy if nothing strange found.

 

[Rain Man]

Last boat I bought I said to the owner I wouldn't buy it unless she let me take some core samples. I brought epoxy with me to do the repair if I didn't like what I saw. She let me take the samples, everything was fine, though we did later find one small wet spot that needed a repair.

Without core samples I wouldn't touch a balsa-core boat.