Thru Hulls on a Steel Boat

[SPARK]

Use galvanized pipe then you only have to protect the weld area.

[SabreKai]

Originally Posted by At sea

Have you considered straight sections of mild steel pipe from the cockpit to the hull, simply welded each end. No need for seacocks. That's the setup on my steely. It's been that way, untouched, for 30 years and still appears sound. Just a suggestion.

I've considered it, my first steel boat had a similar set up. My problem is that a straight pipe down through the hull would still be just ahead of the prop disk. Reverse, gun it and take a shower. Working with solid pipe to move the drain points forward would be really difficult and would tend to cause access problems under the cockpit floor if I need to get under there to work on the transmission, coupler, and stuffing box. I am considering the straight through design with the exits further back on either side of the rudder. This would require a dog leg and a cross over but could be done with 2, 2.5 or 3 inch pipe. I'm not sure how difficult it is to bend steel pipe with a hydraulic jack set up but that may be another option instead of multiple welded sections. Fill the pipe with sand, weld caps on and bend away. I have a 20 ton jack handy.

[chala]

Originally Posted by SPARK

Use galvanized pipe then you only have to protect the weld area.

Would the zinc on the pipe work like a zinc anode and disappear quickly?

[SPARK]

Only if the zinc is exposed. You need to paint it.
That is why you don't paint an anode, it would not work.

[hpeer]

Originally Posted by chala

How can you successfully clean and apply protective coatings inside a pipe? I found it to be a problem even with short length.

My Murray 33 has straight steel drain pipes and I worried over this for quite a while. This year I attacked it by welding a round 2" brush to the end of a piece of all thread. I worked the all thread up and down until I got all the loose stuff off.

Then I taped some sponge to the end of a broom stick, stuck the sponge down into the drain, all the way, and poured in my two part epoxy paint. I worked that up and down until it was well coated.

Ditto with the two part top coat.

Messy but seemingly effective.

[SabreKai]

I did the same thing with the rudder tube on my old H.O.28. wire brush welded to a 1/4 inch rod and it cleaned out the tube just fine. I used a sponge rubber ball on a pull cord to apply the epoxy coating. its a very effective method for painting the tube insides.

Further to the subject of straight through pipes, I was just down looking at Sabre Dance and it occured to me that my cockpit is one seriously huge bath tube. The foot well alone is 36 cubic feet of space, while the area above the seats to the coaming is probably another 55-60. The first place it would drain to is into the cabin through the companion way. I'm now debating adding 4 more drain ports at seat level.

You can see the size in this photo. And the companion way.

[SabreKai]

I was a tad off on my estimates of the volume of the cockpit. I measured the cockpit yesterday preparatory to cutting a new access panel in the floor, and it turns out to be 61 cubic feet, give or take a tad. That works out to 3910lbs of water if she is pooped and the companion way doesn't give way.

Any guesses as to the results of 2 tons added to the stern? Not pretty no matter what you guess.

Now I'm thinking a couple of good sized scuppers from seat level out the sides or transom, in addition to a couple of 2 inch drains.

[S/V Alchemy]

SabreKai, when you come over next week, I'll show you my cockpit scuppers. I just have a little footwell good for maybe a quarter ton of water, but even if completely filled it would drain in seconds.

Retrofitting them would involve some labour on an existing steel boat, but if you have the stern transom height, it's doable.

[SabreKai]

One of the many things I'll be looking at for sure. sorry I couldn't make it this weekend. Sometimes life has other plans for ya.

[bobsadler]

Has anyone got any long-ish term experience with TruDesign ball valves as sea-cocks?

Ball Valve | Tru Design Plastics

[Boracay]

I fitted three of them to Boracay (with matching thru hulls) a few months ago.

I was getting "high" voltmeter readings (0.02V?), there was corrosion under one SS thru hull, the holding tank outlet was too small and I needed an accessible sink drain seacock.

SFSG - So far, so good...