Need Some Advice on Hull Inspection

[CKDK08]

I am considering moving up to a larger boat. Currently have a 22' Hunter that just is not big enough. It has been a great boat to get back into sailing since I was away for 25 years doing other things.

I am looking at 30-36' and have found a few I want to take a closer look at. I am mechanically inclined so I am not afraid to tackle those kind of things. Even an engingine rebuild is possible.
The thing that I am least comfortable with is hull condition. The big topic on all the forums seems to be blisters. Here is my main question. If a boat has been on the hard here in Michigan for 6 months of winter storage will any blisters still be apparent or will they have dried out and shrunk up????

Feel free to chime in with opinions, I want to hear all sides.
Thanks,
Craig

[S/V Illusion]

There is definitely a lot of paranoia regarding the presence of blisters - in reality, they can be minor and of little consequence and easily fixed or, in extreme cases, can be indicative of a bigger issue requiring a more extensive (read - expensive) repair. In most cases, it is a watch and wait issue after fixing the first few. There are far more indidious problems than blisters such as rotted deck core, rusted or weakened chainplates, etc. which bear more trepidation in boat buying.
Once blisters are evident, they don't disappear upon extended storage so you need not worry about that as a latent issue.

[David M]

Originally Posted by CKDK08

If a boat has been on the hard here in Michigan for 6 months of winter storage will any blisters still be apparent or will they have dried out and shrunk up????

Feel free to chime in with opinions, I want to hear all sides.
Thanks,
Craig

That of course depends on the original moisture content, time out of the water, air temperature and humidity. Thats an impossible question to answer without some professional help.

You need to hire a marine surveyor to make a positive determination of hull condition. The surveyor will make a visual inspection, tap on the hull with a hammer listening for voids and delamination and will also check the moisture content of the hull with a moisture meter...although there is some controversy about moisture meters.

If the hull is at unacceptable moisture levels he will probably recommend that it sit out of the water, possibly for months, and then recommend that a few layers of an epoxy moisture barrier such as Interlux 3000 be applied to the hull after it is nice and dry. Unfortunately, this is not something that you can do for yourself. Expect to spend anywhere from $200 to $500. I would not necessarily go with the cheapest surveyor. They have their own accreditation society(AMS)(SAMS). Make sure he is a member. Anyone can call themselves a marine surveyor. Not everyone can get accredited.

[Charlie]

I agree with David M about getting a marine surveyor but before spending the money on that take a look at the boat for yourself. Don Casey's book, "inspecting the aging sailboat" will teach you how to look at a boat with a surveyor's eye. Sounding the hull with a hard rubber ball peen hammer will give you a good idea whether there are soft spots or not. Looking down the length of the boat and checking to see the hull is fair will give you a good idea of whether the ull is deformed. From there there are many other things to look at. Read the book its worth it.

After your inspection hire the best marine surveyor ahnd have him take a look.

[GordMay]

Hammer-Sounding a Hull (Tap-Test):

The methodical process of Tap-Testing or Hammer-Sounding a hull leaves a lot of room for interpretation, which only comes with experience.

While the layman may not to be able to interpret the exact tonal qualities returned, you should be listening for any sudden change in sound.

Lightly tap the hull with a clean*, lightweight (4 oz?) plastic (or rubber) hammer, hitting the hull squarely (to avoid leaving marks). Generally, begin your tapping in a visually “good” location, higher on the hull. This should give you a baseline reference.

* I wrap the hammer head in a clean cotton scrap of rag (secure /w elastic hair band)

As the hammer strikes the fiberglass hull, a clear, crisp report should be heard.
Good, dry, solid laminates give a clear, crisp, higher pitched return (ring), and the hammer will be lively, springing back with each tap.

If the report is dull or dead, and sounds like a watermelon, there may cored material that is wet.

Cored hulls return less ring, and wet laminates gives an even lower dead tone (thud).
Bulkheads, stringers, and grid liners also return lower dead tones, somewhat like a slight echo or drum sound.

Place your fingertips near the strike location, feeling for a sharp crisp vibration (tingling).
Your eyes should also be focused on this area, looking for blemishes, disturbances, discolorations, etc.

[dcstrng]

Although I’ve ground, filled and faired a few blisters over the years, I’ve never been real clear how to actually detect them other than poking around and just becoming one with the hull for a few hours -- until I was just scanning Gord’s hammer-technique… I’ll have to try that. In any case, finding a few blisters wouldn’t put me off a boat – but when it starts getting more than a do-it-yourselfer could manage to repair in a day or so, I’d start being concerned with the overall state of the hull…

Any blisters I’ve discovered were after I owned the boat, and inevitably a few pop up every few years -- or so it seems -- so it wasn’t a matter of deciding to buy, but rather deciding what to do… I’ve never actually gone to a full barrier coat like many professional yards do, but, thankfully, many of the older over-glassed hulls seem to be the least vulnerable in my experience and at least in non-cored hulls (all I’ve ever owned) not remotely close to rocket science to fix – ten minutes perusing the West-System booklet (or whatever plastic potion one is inclined to use) will tell ya all you need to know on the subject, if one is inclined to tackle the repair themselves… nothing here to be feared, indeed I procrastinate far more over standing on my head doing oil-changes, busting my knuckles cleaning outboard plugs and sweating through the chore of doing topside bright work than fixing hull blisters -- which instead of baking in the sun on deck, is usually spent on a pleasant Sunday afternoon puttering away in the shade of the hull…

[ssullivan]

There is a better way to test the hull for voids and delamination yourself. The hammer test Gord mentions is great, but it takes some skill to understand the sounds you are hearing, as mentioned.

One way to do a preliminary check of hulls, before you have to hire anyone, is to use a large medallion, coin or even a padlock.

Go along the hull and deck and tap (don't whack, but tap firmly as as not to leave marks).

When you hit solid fiberglass structure, you'll hear a very distinctive "click" sound. The click is like hitting your fingernail on a formica counter, or a hard wood desk.

When you hit junk, you'll hear a hollow or "clack" type of sound. The hollow sound is like hitting your fingernail on say... a softcover book.

The two different sounds the dense metal object make are much more easily interpreted by someone who has never done it before.

I just used this technique a couple weeks ago to eliminate the *majority* of cats I looked at. More than 50% on the market were delaminating or had serious structural issues. Maybe that's why they were still on the market...?

When you find a "clack" spot you can usually push hard on it and see it give in some way or another.

On one cat, I had them all over the coachroof, so I walked up on it. I nearly fell THROUGH the deck when bouncing up and down on it. It gave way by a measure of *inches* when tread upon. Others, just a small amount of an inch, but you'll be able to feel the softness on the decks once you find the center of it with the above method.

[Alan Wheeler]

Looking for damage in Hulls by "tapping" can be very misleading and I seriuosly suggest that anyone that has not had a great deal of experiance in both building and repair of boats, don't do it. There will always be "noises" that don't sound right, but are infact quite OK and it is quite possible for area's to sound OK and yet be an issue. A tremendouse amount of experiance is required to be able to interpret what you hear and where you hear it, what to tap where and what to expect to hear in return. Each material, be it GRP, Timber, GOP, FC, steel etc etc, will all have very different responses and most importantly, reasons why they sound the way they do in the various area's around the hull.
Sean, even having a coach roof move under foot, may not be a delaminating issue(not saying yours wasn't) but could be just the construction. It would aslo mean that maybe that vessel is not suited to blue water cruising, but it may not be a structural fault that has caused the problem.

[Charlie]

I have to disagree with the statements above about hull tapping test. I read Casey's book and found some spots that were obviously mushy using a rock as my tapping tool. I pointed them out to the surveyor when he came thru and he confirmed that most of them were soft spots both with his hammer and with a moisture meter. Some of them wereen't soft spots though. All I am suggesting is that there is alot of preminiary work that can be done before going to the expense of hiring a surveyor. BUT DO HIRE A SURVEYOR.

[ssullivan]

Originally Posted by Alan Wheeler

Looking for damage in Hulls by "tapping" can be very misleading and I seriuosly suggest that anyone that has not had a great deal of experiance in both building and repair of boats, don't do it. There will always be "noises" that don't sound right, but are infact quite OK and it is quite possible for area's to sound OK and yet be an issue. A tremendouse amount of experiance is required to be able to interpret what you hear and where you hear it, what to tap where and what to expect to hear in return. Each material, be it GRP, Timber, GOP, FC, steel etc etc, will all have very different responses and most importantly, reasons why they sound the way they do in the various area's around the hull.
Sean, even having a coach roof move under foot, may not be a delaminating issue(not saying yours wasn't) but could be just the construction. It would aslo mean that maybe that vessel is not suited to blue water cruising, but it may not be a structural fault that has caused the problem.

Yes, the test should only be performed on GRP. Of course it doesn't work on wood, metal, ferro or "other."

Most surveyors worth their salt use tapping as well before using a moisture meter. Its very easy to do correctly. On some of the cats, water would come up when I compressed the laminate, and on others, the coachroof just deflected in (not in a normal fashion, but in a very bad way). The test is valid for proving structural soudness, no mater if you are talking about moisture or just a defect.

[Pblais]

The big topic on all the forums seems to be blisters. Here is my main question. If a boat has been on the hard here in Michigan for 6 months of winter storage will any blisters still be apparent or will they have dried out and shrunk up?

Hull thumping aside I never heard about a boat sinking from blisters. It isn't usually related to other problems but it could happen where the hull bottom had blisters and the deck was delaminating and / or had bad coring. Blisters look like hell but they won't make the boat leak. If the boats has them then they don't go away no matter how long it's been hauled out. They only grow in water or perhaps stay the same size and appear in more places. The process to repair them is very simple but the process also requires a great deal of hand labor hence the high cost of repairing the blisters and making the hull smooth again. It is done all the time.

At 30 to 36 ft you'll be talking about a lot of systems and a marine surveyor is required else you won't be getting an insurance policy. So assume you will get the boat surveyed. The hull inspection is one of the many things to be examined. It's a good way to make the list of things a mechanically inclined member of the Cruisers Forum could pursue. Being mechanically inclined is a good thing but the survey lets you know if your efforts are better placed on another boat. Not all boats are worth the expense to fix them even when you do all the labor yourself. There are materials costs and other expenses to consider so the survey is money well spent.

[Alan Wheeler]

Yes you can Knock on wood. And you can tap away on GOP and even steel. Not a lot of sense tapping on FC. That requries a different aproach.
Charlie, I am njot sure what you are disagreeing on, because you have then turned around and stated what I said in a different way. You read a book and and then you also state you shoudl still hire an expert. Is that not what I said in a more expanded explination?

[Charlie]

Sorry Wheels it isn't very clear is it. What I am disagreeing about is that only an expert can hear the difference in sound when there are soft spots on the hull. I think that the sound is pretty obvious.


I looked at the hull of an Islander 36 tapped it and found a fair bit of soft fiberglass. I should have just walked away before spending any money on a surveyor. I wasted more money by having the surveyor come out and confirm my suspicions.

[Sailormann]

After the boat has been sitting on the hard for the winter, you may find that it has develop a little "acne" rather than a real case of blisters. This happens when water gets underneath the surface finish and pools, then expands as it turns to ice in the winter. It can be a bit unsettling in the spring to find it has happened to the boat, but it's easily repaired.

There are thousands of opinions on this, but I would personally avoid a boat that had a serious blister (one that has damaged anything more than the gelcoat). To me, they are indicators of an overall poor maintenance schedule. These blisters take time to develop and I would not purchase a boat from someone who allowed it to happen. It is a virtual certainty that there will be other issues with the boat.

[w42]

If you go tapping to detect delam, you also need to consider the construction underneath. Specifically, bulkheads. Tapping on the deck above a bulkhead may sound more "solid" than to the sides of the bulkhead. Does that mean those sides are delaminating? No. If the sounds varies over an area of the deck, clear of a bulkhead, does that mean there is delamination? Maybe.

The only way to know for sure is to drill two small holes to fill with epoxy (if you are doing a repair). For a prospective purchase, get an opinion from a surveyor.