Saturday, July 11, 2015

She Won't Float Now

Nope, if you drop Rover in the water right now, she would probably sink rather quickly. Ok, so being a cored composite construction catamaran, she probably won't become submerged (since I don't have a big lead weight in my keels, she would only sink to the point that the natural buoyancy of the plastic, balsa, and wood she is made of) but she would take on some water pretty quickly. After all, I don't think the painters tape that is currently covering the 11 holes in the boat are likely to stop sea water.

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 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 stupid strong as 3M 5200, you can probably twist the valve assembly and work it free.  If it was stuck with 5200...well..I'm not exactly sure what you would do besides curse a lot more.  You might need to go invest in those hole saws at this point because my understanding is that 5200 is very in fiberglass and gel coat will come off with it.

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.


  1. Hi Mike,
    Judging from the amount of thread between the nut and what would have been the outer hull, I assume the yellow handled valves are from the A/C. If there is working space, try and feather out the balsa away from the opening, and layup some glass over the feathered area to seal the balsa.

    1. The thickness of the hull in all valve locations are roughly similar...but that may not be obvious from the picture. You do happen to be correct, the Apollo (yellow handle) valves are from the air conditioner supplies...and were apparently an after-market addition given all the other holes are through solid fiberglass.

      The hole for the 3/4" through hull is about 1 1/8" diameter. I'm digging out the balsa around the interior of the hole now (I actually just came back in to find out how much I should dig out) and then will insert a poly plastic wrapped PVC pipe into the hole as a form (3/4" ID PVC is about 1 1/8" OD...convenient) and inject thickened epoxy into the gap left by the dug out balsa.

      This should result in an epoxy "sleeve" for the hole that will not only seal the core from moisture, but also provide a more compression resistant mounting surface for the through hull. Less likely to leak and the balsa is protected even if it does. Seemed like the best solution to me.