Yep, yesterday and the day before we made 11 holes below the waterline in the boat. Ok, you caught me again, we actually removed 11 old through hulls and ball valves, so technically we opened up 11 existing holes. There is only one through hull that remains, and it is an obviously much newer one than the rest, so we decided it still should have plenty of life left in it.
|The two removed from two days ago|
Why did we remove them? Well, some of them didn't look in the best of condition, and I had heard several reports of people having problems with electrolysis weakening the original valves or through hulls in much shorter time frames than one would expect of quality valves under normal conditions. There were also reports that some boats had through-hull holes that were not properly sealed and would allow water penetration into the balsa core. The final straw was that I managed to break the handle off one of the old valves trying to open it on our trip north, rendering it permanently closed. Since I didn't want a valve coming off in my hand (as the handle already did) and I don't want any delamination problems with the hull, we decided to pull and replace all the old through hulls.
Now, to the uninitiated or those unfamiliar with boat maintenance, replacing one of these things might not sound all that difficult. Remove the attached hose, unscrew the valve, remove the through hull nut, and remove the through hull itself with assembly being exactly the opposite, adding in a little sealant along the way. But, in reality, one thing will almost always prevent this easy sounding process: corrosion.. Since 1999, or whenever some of these parts were previously replaced, corrosion has been doing its best to convert these collection of parts into one giant, seized together piece. The chances of me getting one to come apart...well...I'm probably far better off expecting that lottery ticket I bought will hit the jackpot.
The only real way to remove these things is to cut off the head of the through hull (this is the part that is clamping it to the hull from the outside) and then coax the remaining bit out of the hole. I find a lot of swearing helps coax it out...preferably in multiple languages if you know them.
|The head of a through hull before we started work on it|
Cutting the head off can be done using a hole saw and a wooden bung. You pound the bung into the through hull from the outside, carefully center your hole saw guide bit in the middle of the bung, and drill a hole the size of the through hull until the head pops off. Or that is the hole saw process I've been told. I don't have hole saws nor enough bungs to sacrifice 11 of them to the cause, so I took an alternate approach. I grind the heads off with an angle grinder that I do have.
This sounds difficult and potentially dangerous to a fiberglass boat hull, but if you go slowly and keep control of the grinder, it isn't that bad. Using the curve of the grinding wheel, you simply grind away a cup or tapered shape at the center of the through hull.
|Ground down through hull head about ready to come off.|
You will reach a point where you will begin to see the head separate. Underneath that separation line is actually sealant (the through hulls are designed with a taper to hold a bead of sealant...it help keeps them water tight and all of that).so you aren't grinding into your hull. Once you get that line to appear (at least in regular intervals) around the through hull, you can stop grinding and use a screwdriver to break any remaining thin layers of metal and then pop the head off. I use a utility knife to score the bottom paint around the through hull in an attempt to prevent the head of the through hull from taking off too much of the adjacent bottom paint.
|Carefully popping the head off without damaging the hull.|
At this point, providing the previous installer didn't use something as
Looking at the cut through hulls, I'm not sure if I had a problem with zinc being leached out of the bronze (I think the theory was that the "bad" through hulls had a high zinc content and electrolysis was leaching the zinc out of the bronze). There were certainly some surface areas that were more copper colored than bronze, but internally they seemed properly colored to me. I did notice a couple different colors of bronze (in the picture below), but neither were decidedly copper looking to my untrained eye, so I'm guessing those are just different bronze formulations. If you happen to have any knowledge on this, please leave me a comment below.
|Different colors of bronze or a zinc problem, what do you think?|
One problem I did find was that the two through hulls for the air conditioners did not have the core properly sealed, and only the sealant was preventing water from entering the balsa core. So, before I re-install them, I will need to cut out a bit of the balsa and seal it with epoxy to guarantee no future water penetration. I haven't inspected all the holes yet, but thus far the other ones on the starboard hull all seem to be in solid fiberglass with no exposed core.
|All except the two largest valves. 4 different manufacturers.|
So, here you have it....a picture of most of yesterday's work. Wonder if I can find a metal recycling company nearby and recoup a little bit of the money involved in this project.