groco through hulls

BALANCE · Post by **BALANCE** » Mon Apr 13, 2009 11:38 am

I have not uploaded the pictures onto my computer yet but wanted to throw this out there. I have the old grocos. In my sanding around them I have found a round hole above and below them. After sanding I was able to stick my nail in there and pop it out. A very large bronze flat head is now visible. Should I refill this with fresh epoxy or reuse what I have pulled out. It seems that these discs had some white bedding....

Rachel · Post by **Rachel** » Mon Apr 13, 2009 12:02 pm

I'm going to guess you are on the outside of the hull and are describing the filler covering the heads of the machine screws that go through the hull to attach the seacocks (nuts would be inside on the seacock flange).

Now I have to say that identifying them was my main contribution; I don't have a definite opinion on what to refill them with, although I would use new material. Thoughts that come to mind are thickened epoxy, or polyurethane or polysulfide caulk.

Rachel

okawbow · Post by **okawbow** » Mon Apr 13, 2009 12:23 pm

I filled mine with thickened epoxy, because I never wanted them to come out. If I ever have to remove them, it will be more work. A softer fairing compound might be better if you think you may remove them, but there is always the slim chance they could break, some how work out, and leave a hole in your hull.

Hirilondë · Post by **Hirilondë** » Mon Apr 13, 2009 12:32 pm

If you removed the filler with your finger nail I would find it hard to believe it was epoxy. Or that the epoxy was put over a really dusty countersink. If it was epoxy, I don't see how you can reuse it. I will never ever cover a fastener I might want to remove with epoxy, or anything held in place by epoxy. I don't see any point in it, and it sure makes removal a pain. The fasteners are holding your hardware in, nothing over the fastener will add any strength at all. Any good bedding filler like polysulfide or polyurethane will work just fine. I would go with polysulfide (3M 101 or Lifecaulk) if I was painting over it.

BALANCE · Post by **BALANCE** » Mon Apr 13, 2009 4:00 pm

I did not remove the filler with my nail, I removed what appears to be fiberglass discs, there is some residual white bedding around it. These bolts were countersunk from the outside above and below the through hull itself.

Rachel · Post by **Rachel** » Mon Apr 13, 2009 4:51 pm

okawbow wrote:I filled mine with thickened epoxy, because I never wanted them to come out. If I ever have to remove them, it will be more work. A softer fairing compound might be better if you think you may remove them, but there is always the slim chance they could break, some how work out, and leave a hole in your hull.

I agree that you don't want them to come out; that said, I don't think that if one of the bolts failed and "wanted" to come out, that a plug of thickened epoxy alone would hold it in.

If I were worried about the bolts, I would take them out and inspect or replace them. Knowing they were in good shape, I wouldn't worry about the "bungs" needing to hold them in place. There should be four (or however many holes there are in the seacock) good bolts there, with nuts inside, plus the outer rim of the through hull, plus the sealant. Also, the seacock backing plate should be thickening the hull in that location (helping the bolts to not want to "pull through" the hull).

I don't meant to sound negative; that situation and reason for covering them with epoxy just doesn't ring true to me (not that I wouldn't fill with thickened epoxy, maybe, but just the thought of needing to hold the fasteners in with it.

Rachel

bcooke · Post by **bcooke** » Mon Apr 13, 2009 5:06 pm

but there is always the slim chance they could break, some how work out, and leave a hole in your hull.

A slim, slim, SLIM chance. I would say you have a much greater chance of being swallowed whole by Moby Dick's nephew. It would take a tremendous impact to break the bolt. It would take an act of God for the bolt to fall out (it still has a nut and washer on the inside right?) Water pressure is pushing the bolt in. The bolt most likely has sealant in the bolt hole adding some adhesion.

My car has a thousand bolts and any one of them, if they were to fall out, could be catastrophic. And yet millions of people every day drive cars without a bolt falling out and causing a mishap.

I think you are pretty safe.

A little sealant like Dave suggests would be okay if it helps you to sleep at night. I think I have a skim coat of epoxy/fairing filler over mine that is easily brushed off with DA.

BALANCE · Post by **BALANCE** » Mon Apr 13, 2009 8:48 pm

I think I'd be inclined to go the epoxy route, just for peace of mind. What would the best filler be, the colloidial?

okawbow · Post by **okawbow** » Mon Apr 13, 2009 8:55 pm

In 25 years of industrial maintenance, I've seen hundreds of broken fasteners. Many broke just under the head, and some had disastrous results. A loose object slamming against a through hull a few times could easily break a weakened bolt.

The best fix might be to install through hulls like Mainesail posted on another website, by threading studs into the backing plate from the inside, thereby not putting holes in the hull in the first place.

bcooke · Post by **bcooke** » Mon Apr 13, 2009 9:14 pm

In 25 years of industrial maintenance, I've seen hundreds of broken fasteners. Many broke just under the head, and some had disastrous results.

A torque wrench is your friend. In 25 years of aircraft/marine/automotive maintenance I have rarely seen a properly installed properly engineered, bolt fail. Corrosion being the only real exception.

Corrosion is really the only thing that is going to weaken a properly installed seacock mounting bolt and a silicon bronze bolt is not going to corrode that quickly. There really isn't any cyclic stress on a seacock bolt. There really isn't any stress at all on a seacock bolt. Other than a direct impact of course but that isn't going to cause just the bolt to break and fall out. Its going to tear the whole seacock out and leave a big hole in your boat.

If it were really a concern I think there would be evidence of that. Personally, I have never heard of a seacock failing due to the mounting hardware weakening and failing. Heck, half the time people never even use bolts to hold the seacock in and there is rarely a problem with that either. I don't recommend the practice but it happens.

There is probably no way we are ever going to see eye to eye on this one.

Oscar · Post by **Oscar** » Mon Apr 13, 2009 9:32 pm

A torque wrench is your friend.

Definitely. I tend to overtighten things by hand....so I now own three torque wrenches and, especially in automotive work, use them to keep myself under control. That, and it helps getting things tightened up evenly. Oil pans come to mind.....

BALANCE · Post by **BALANCE** » Mon Apr 13, 2009 9:55 pm

Here's what it looks like.

I left the discs with the boat but it appears to me that what was cut out when countersinking the bolt was put back with bedding.

Oscar · Post by **Oscar** » Mon Apr 13, 2009 10:46 pm

You could cut a plug out of polyethylene (the stuff that starboard is made of) and stick that in there with bedding compound and then paint over.....

Hirilondë · Post by **Hirilondë** » Mon Apr 13, 2009 11:01 pm

Oscar wrote:You could cut a plug out of polyethylene (the stuff that starboard is made of) and stick that in there with bedding compound and then paint over.....

Nothing, absolutely nothing sticks to King Starboard. The paint will fall off of it, but you probably won't notice, because it will have fallen out of the hole first.

okawbow · Post by **okawbow** » Mon Apr 13, 2009 11:54 pm

bcooke wrote:

Corrosion being the only real exception.

Corrosion is really the only thing that is going to weaken a properly installed seacock mounting bolt and a silicon bronze bolt is not going to corrode that quickly. There really isn't any cyclic stress on a seacock bolt. There really isn't any stress at all on a seacock bolt. Other than a direct impact of course but that isn't going to cause just the bolt to break and fall out. Its going to tear the whole seacock out and leave a big hole in your boat.

If it were really a concern I think there would be evidence of that. Personally, I have never heard of a seacock failing due to the mounting hardware weakening and failing. Heck, half the time people never even use bolts to hold the seacock in and there is rarely a problem with that either. I don't recommend the practice but it happens.

.

My Bristol spent 30 years in the Annapolis area. When I got it home, I decided to remove the through hulls, including the one for the ice box drain. It was so weakened by corrosion, that it twisted in half. The bolts crumbled into pieces. The other through hulls were so good, I re-installed them. maybe they were newer.

I agree that the odds of one of the bolts breaking is almost zero.. under normal conditions. The through hull I removed looked ok from the outside, but the metal was reddish and soft. It pays to check all the through hulls every year for electrolisis. I'm not so picky about most things, but those that potentially sink the boat make me over cautious.

The bolts are only there to keep the through hull from turning, and to possibly keep it in place in case the outer mushroom falls off. Studs screwed into the backing plate would do that job just as well, and not penetrate the hull.

Rachel · Post by **Rachel** » Tue Apr 14, 2009 12:42 am

okawbow wrote:The bolts are only there to keep the through hull from turning, and to possibly keep it in place in case the outer mushroom falls off. Studs screwed into the backing plate would do that job just as well, and not penetrate the hull.

This is actually how I installed mine; with bronze bolts tapped into fiberglass backing blocks (although if I were to do it again, I might still use bolts through the hull - just because I like the thought of them there).

I think in the case of your really corroded units, a dab of thickened epoxy over the bolt head wouldn't have made much difference; but like Britton says, it's not always possible to agree. That is the beauty of boats and the sea - you can still pretty much do as you see fit and then live with it. I love that :)

Rachel

Post by **Tim** » Tue Apr 14, 2009 6:02 am

I think any useful information that was going to show up in response to the original question has been posted.

Let's leave this one alone now. I won't lock it...yet.

BALANCE · Post by **BALANCE** » Wed Apr 15, 2009 2:54 pm

(whisper)...which filler? Collodial?

Rachel · Post by **Rachel** » Wed Apr 15, 2009 4:35 pm

Colloidial Silica would work fine as a filler.

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