Sounding out around thru-hulls

Bob L · Post by **Bob L** » Tue Feb 14, 2006 12:56 pm

So I joined my surveyor for the survey. He did the woodpecker routine with a nylon hammer, and around most of the thru-hulls the sound went "thud" instead of "ping". He suggested pulling them, letting them dry, coating the edges of the hole with epoxy, and then reinstall and rebed.

As the survey went on, doubts arose over his intuition. He said the rudder had intrusion and I should drill it to let it drain, then epoxy the seams and freshly drilled holes. After drilling nothing came out.

So when sounding out a hull, do thru-hulls sound dead from the backing blocks? My intuition told me that the seacock backing block was the cause of the "thuds", not saturation (it's a solid laminate hull, no core).

Jason K · Post by **Jason K** » Tue Feb 14, 2006 2:17 pm

That's a good question and, in truth, I'm not totally sure of the answer. However, I'd say your intuition makes sense, given that the hull is not cored. Certainly different densities and thicknesses will create different acoustics, so its logical to think a backing plate and a metal through hull would sound different than regular laminate.

Are there any other indications of moisture in the laminate?

Bob L · Post by **Bob L** » Tue Feb 14, 2006 2:23 pm

He had his mosture meter out, which indicated moisture, but I'm not sure I trust that thing. He did the rudder and it indicated moisture, then we came back (after I drilled it!!), and it indicated nothing.

Post by **Tim** » Tue Feb 14, 2006 3:08 pm

If the backing blocks are wood, or wood encapsulated in fiberglass, might they have water in them? This could account for the moisture readings around the through hulls. Or if the through hulls have a particularly large metal flange, perhaps the moisture meter was reading the metal.

In the rudder, the meter was likely registering an internal metal web, which are common in most modern rudders.

Note also that it takes only slight amounts of moisture to peg most moisture meters. These are all reasons why so many surveyors now discount the moisture meter results in a survey.

The lack of core is very telling around your through hulls It does sound to me as if the sounding was registering the backing blocks behind the laminate, as even laminate containing some moisture does not report a dull thud when sounded the way a cored (and wet) laminate might.

The moisture meter is not the miracle tool that the general public and (still) many surveyors hope it is. The capacity for error is large.

Summersdawn · Post by **Summersdawn** » Tue Feb 14, 2006 3:44 pm

You have to trust your gut instinct a certain amount. When I had my boat surveyed (a San Juan 24), the surveyor told me my stock 29' mast was 9' too long, and that I had cut 9' off of the end of it. I had to show him the original sales brochures and give him a letter from my sailmaker, or he would have written that up as a necessity, which would have meant I couldn't insure my boat unless I either had my boat resurveyed (by a different surveyor), or cut 9' off the end.

Post by **Tim** » Tue Feb 14, 2006 4:04 pm

Grr...

What in the world was a surveyor doing making such judgements in the first place? That irritates me so much, the way some of these guys are like that.

And besides, what was he thinking: a 20' mast on a 24' boat? Even sailiing dinghies have masts that are longer than the boat, for heaven's sake.

A bozo will always be a bozo regardless of the title they give themselves.

Summersdawn · Post by **Summersdawn** » Tue Feb 14, 2006 5:04 pm

Grr...

What in the world was a surveyor doing making such judgements in the first place? That irritates me so much, the way some of these guys are like that.

And besides, what was he thinking: a 20' mast on a 24' boat? Even sailiing dinghies have masts that are longer than the boat, for heaven's sake.

A bozo will always be a bozo regardless of the title they give themselves.

Ahmen to that Tim. Joe Nobody from Nanaimo second guessing Bruce Kirby. I was so ticked off at the guy, but what can you do? I'm glad he eventually listened to reason.

JonnyBoats · Post by **JonnyBoats** » Wed Feb 15, 2006 1:47 am

What in the world was a surveyor doing making such judgements in the first place? That irritates me so much, the way some of these guys are like that.

Well remember half of all marine surveyors are below average, just like with brain surgeons, accountants or any other profession. Only in Lake Woebegon does this not hold true; where "all the children are above average". ;-)