Old dump outlet opening?

[reelfishin]

I have an older aluminum cuddy cabin which has a dump to sea type head installed. I don't need it at all and don't care to replace it. The problem is that its got two 2" plastic through hull fittings which for the time being are simply bridged together with a length of rubber hose.

I'd like to either make valid use of the fittings, while replacing them with new or simply fill in the holes.

I have a salvaged sink and water tank from another boat I stripped, I think that would come in handy as a use for the holes. Having the ability to rinse off your hands while fishing in clean water would be nice, but in reality, I'd rather have the space for seating or storage in the cabin. It's only an 18' boat so there's not a lot of space. I pretty much want to figure the easy way out here. I don't want to deal with welding in the holes, I've been that route on these and the chance of warpage is too great as is the chance of future cracks around the welded area.

The original head is no longer legal and to be honest, I don't care to have to deal with the maintenance factor.

The way I see it is that the sink will take up about the same space as the head did, if I make it's holding tank a seawater tank, then I can make use of both holes. The dump hole is just above or at the water line, the lower hole is about a foot from the keel about midship. I tossed the head day one when I got the boat, (never even brought it home), I put a car radiator hose on it and ran it that way for a season. A hose of through hull failure would be catastrophic as it would mean a minimum of a 2" diameter water leak below the water line. I'd rest better knowing there were no below the water line openings but the holes are there and the through hull fittings don't leak and I have two new fittings to install.

I'm sort of leaning towards the sink idea but to do it the way I'd like it, it would be a freshwater sink not seawater, which only makes use of the upper hole. as a drain. The boat has a freshwater tank, which is filled via a hose fitting on the port side. The sink when in the other boat was seawater filled and is all stainless and bronze.

Any ideas?

 

[drewpster]

Re: Old dump outlet opening?

I would use the top hole above the water line as a drain like you suggested. It is my understanding that most waterways do not restrict gray water (sink) like they do sewage.

To fill and seal the lower hole I would use a garboard drain fitting.

To install it I would back the flange part of the fitting with a plate and sandwich the hull between the flange and the backing plate. Through bolt the flange and the backing plate and seal them with 5200. Install the plug and your hole is filled.

If you are concerned about galvanic corrosion due to dissimilar metals, aluminum flanges just like these can be found at plumbing supply houses. It is most likely a special order piece as they are mainly used in special plumbing applications, but they are available.

If you do not want to order a special piece like that you can simply use two pieces of thick aluminum plate to sandwich either side of the opening in the hull. Drill the plates to accept through bolts and seal them with 5200. Walla! sealed hole and no welding. If you do not trust a liquid sealer like 5200, you can make gaskets to seal your plates. You can get gasket material from an auto parts store. Just make sure your plates are thick enough that they will not distort under the clamping pressure of your through bolts. Also make sure the area of the hull to be sealed is flat enough so that your plates will seal.

 

[reelfishin]

Re: Old dump outlet opening?

I would use the top hole above the water line as a drain like you suggested. It is my understanding that most waterways do not restrict gray water (sink) like they do sewage.

Water from the sink would not be a problem, besides, it would be no worse than rinsing your hands off over the side of the boat.

..........make sure the area of the hull to be sealed is flat enough so that your plates will seal.

The area the lower port is in isn't flat at all, to top it off its on a lapstrake type hull. The existing through hull fitting is carved or shaped to fit the curve of the hull and to overlap one of the strakes slightly.

 

[pole position]

Re: Old dump outlet opening?

When I removed my overboard toilet, I installed a new shut off ball valve and also put a cap on the threads to make sure that it didn't leak in case the valve got opened accidentally.

 

[drewpster]

Re: Old dump outlet opening?

The area the lower port is in isn't flat at all, to top it off its on a lapstrake type hull. The existing through hull fitting is carved or shaped to fit the curve of the hull and to overlap one of the strakes slightly.

This complicates things.
If you are not concerned about the looks of the work, it is possible with careful measuring and fitting, to make a patch. To guarantee a good permanent seal it will take rolling and bending the patch and backing plate to conform to the curve and strake of the hull.
Personally I would get a pro to patch it. A good body man with a TIG welder can weld aluminum foil. (TIG- tungsten-inert-gas) The TIG welding process is ideal for thin materials. It is a very clean and precise type of welding using highly controlled and localized heat. With an experienced welder the patch would be stronger than the surrounding metal and fatigue would be non-existent. Do some looking locally. I bet you can find a auto body man that would come out and do the work for a negligible cost. It would be even cheaper if you can trailer the boat to them. The advantage is that once it is done, its done. There would be no concern about leaks down the road. Also with a little grinding, filling, fairing and paint you would never know the hole was ever there.

I am surprised to hear that the through-hull under the water line is made of plastic. Normally any fittings under the water line are made of more robust material. If it were made of metal it would be possible to weld the fitting up.

BTW- Welding aluminum foil is possible. It was done by my father at the Redstone Arsenal in the 1960's using a large bank of incandesent light bulbs screwed in and out to control the current. Sounds like allot of bored engineers with too much time and money on their hands.

 

[reelfishin]

Re: Old dump outlet opening?

Most autobody repair on aluminum panels these days is done with adhesives.
I worked in the automotive business for 20+ years and have many buddies in the autobody trade, none weld aluminum.
I have my own tig machine and could weld it if needed but its been my experience that even tig welding such a repair on older, possibly oxidized older aluminum could lead to cracking or at the very least warping.
If I were to seal the hole flush, I'd be most likely to try a sandwich type repair with a permanent adhesive.

I've seen several boats like this, all use white PVC through hull fittings.
If I leave the hole for future use, I'd have to seriously consider finding a bronze fitting, but then again, what's there has lasted over 40 years.

I do wish that the outlet port was higher, it's almost dead at the water line. I would venture to say that a full load of passengers and gear would put that below the waterline. It would only be about the water at cruise then.

What's there now don't leak, I just don't trust it. I doubt the plastic through hull will fail, it's pretty stout looking and certainly not UV damaged being under the boat. What I worry most about is the rubber hose and hose clamps that's bridging the two ports right now. If I could find a way to leave the ports and more securely block them, that would be fine for now too. I just don't want any surprises at sea.

 

[drewpster]

Re: Old dump outlet opening?

I assumed an auto body man would be experienced in welding thin metals. I forgot they mostly change parts these days.

In my trade aluminum is welded using a mig.....routinely. But the majority of it is done on thicker materials. Our fab shop just completed several aluminum platforms to be used by our training department. All the work was done with a mig using wire made for aluminum. The tubing they used to make the platforms had about 1/16 to 3/32 walls. Frankly we thought TJ (welder) would have problems with it, but it worked out fine. I can see your point about welding anything much thinner than that. I have often heard debate about how safe it is to weld aluminum. I leave that to the experts. However I do know it can be done.