Through hull and back

The foil was there to act as a shield for grinding and welding hot bits flying into a mysterious part of the boat I call "the smuggling locker".

Behold the starboard exhaust pipe nipple. It's more or less right at the unloaded waterline of Alchemy and is the passage for the combined diesel exhaust and cooling water. As the attentive may recall, I had a flooding episode last August when the threads on the port 29-year-old Schedule 40 galvanized steel pipe nipple that drained the galley sink failed and water came in. Unfortunately, because I'd spilled some transmission fluid while doing an oil change in the bilges, I had left the bilge pump off. Won't make that mistake again.

When taking off the starboard side ball valve, the starboard side pipe nipple (the drain for the head sink), crumbled. This occasioned a rapid revision of the winter to-do list. New, non-metallic ball valves were ordered, and welder-fabricator extraordinare Andrew Barlow was located and offered boat bucks to replicate the four engine-bay pipe nipples, two which were the problematic below the waterline drains and one of which was the starboard side, waterline-depth exhaust and the second of which was the port side bilge pump exit.

The pipe nipples were all 1 1/2" outside diameter and were upsized with these rough fittings to take 2-inch I.D. exhaust hose.

The waterline pipe nipples, perhaps because they've spent less time submerged, were in markedly better condition than the "drain" nipples which were always submerged in water. I can't draw any conclusions about this in terms of any galvanic/electrolytic component to the failure of one and the clearly imminent failure of the other, save to note all these nipples presumably date to the boat's construction in 1988 and maybe 30 years is all you get. Maybe 20 is a better plan. Less nerve-wracking, certainly.

Mrs. Alchemy, who fits this space better than I, put up some tinfoil to keep grinder sparks from flying into the aft cabin and other places I did not care to have ablaze while I was doing hot yoga below decks.

I do know that, as with every "reset" on this boat, I have an opportunity to change the old ways for the new. Schedule 40 galvanized steel pipe was replaced with Schedule 80 316 grade stainless steel  pipe, welded in three passes with stainless steel stick welding to the hull. As can be seen from the linked chart, Schedule 80 pipe is over a quarter greater in wall thickness than Schedule 40. I'm going to paint these inside and out with two-part epoxy, as well, for insurance against corrosion.

Wanted on the voyage: the drain nipples, left, with NPS threads, and the exhaust nipples, right, which are grooved to take hose clamped exhaust hose directly.

A fly in the proverbial ointment in the fabrication of these pipe nipples was the typical NPS "straight pipe thread" customary in the marine industry. Most home plumbing fittings have NPT threads cut on them, the "self-sealing" type that does not require pipe dope. NPS require pipe dope, or the pressurized water external to the boat will creep up the threads...not good. For the puzzled, Rod Collins explains why this is important here. Note I do not have the load-spreading flanges seacocks on fibreglass and wooden boat require as a steel hull plate is essentially its own flange. But I still needed NPS threads: the Forespar 93 Marelon ball valves and they are quite clear on why NPT won't work.

The outside of the exhaust pipe nipple, minus the nipple. Further grinding down to "flush" followed.

Andrew, who has a machine shop where he works, expressed frustration that not only could he not locate makers of the very typical pipe nipple sizes I needed with NPS threads, he could not even locate an NPS die I could purchase so that a lathe operator could cut these threads. Trusting in my own powers of Google-fu, and already knowing that a fair bit of plumbing uses these threadforms, I tried my hand at sourcing the needful.

No...luck. I found places in the States that had what I needed, but not locally. Every gruff-voiced plumbing supply guy knew exactly what I was talking about, but couldn't help me. Luckily, Andrew found a fellow who had the right dies and could do the work quickly. And cheaply. Huzzah.

Lights, action, camera. Good thing I haven't put in the water tanks yet.

Having removed the existing nipples (grunt work a specialty), Andrew moved in to prep the area to be welded (a few passes with a sanding disk of ferocious efficiency on a DeWalt angle grinder of surpassing sincerity). His Miller welding unit is beautiful, compact and can work on 120 or 240 VAC, but to get the right penetration, 240 VAC is better. Andrew therefore brought some 10 ga. lead and a willingness to get into the yard's power stand to good effect.

I was prepared to sacrifice a 30 amp shore power cable. I didn't have to.

I'm just glad we seemed to be the only boat plugged in.

Zap factor enhanced, the prep proceeded. Bare metal (which I will paint over in a day or two when it warms up a bit) was revealed where once were nipples. Sailing is dirty fun, isn't it?

Well, at least I can gauge the thickness of the paint lay-up.

Andrew had me holding the pipe nipples on the inside while he did a couple of tack welds on the outside. It looked thusly from his viewpoint:

This job on a non-steel boat would have been half as loud and twice as long. I know because I've done it.

And like this from mine:

Before...

...during...

...and after.

Once the external tack welds were done, Andrew proceeded to make several passes of the SS stick both externally and on the engine bay interior. We agreed that doublers were unnecessary, such was the strength of the welding in making the pipe and the plate as one.

The whole bay needs a clean-out now and the engine a wash, but nothing caught fire.

Brought to you by Hydraulic Hatch, improving your blog since 2017.

The work was completed in three and a half hours and I am well-pleased. I have an insurance survey happening on March 30 and it will be nice, if not essential, that I get the boat back to "able to float securely" condition for that date with the new ball valves in place.

No nipples like new nipples.

Oh, and while I alluded to this earlier, I did not quite explain why the redo of the both the port and starboard waterline pipe nipples was necessary. It's because I'm finally going for "transverse exhaust" idea I mentioned four seasons ago. I have all the parts aboard I need, save for a couple of reducer barbs, and it's pretty straightforward to do.

The "skin fitting" with appropriate flap for the bilge pump exit.

As for the bilge pump (which will remain forever on "auto" going forward, naturally), its new exit will be near the exhaust, but not so near as to ever get warm. I can fit that myself.