Replaing Seacock Backing Plates

[tjr818]

Adam,
I have been contemplating adding backing plates, but I have never done this - yet. I think that I would put #2 before #1 (just incase the seacock is stuck) and #6 before #5. I think that if you spin the though hull you will need to rebed it, although that might be a good idea too.

[hilbert]

As Tim suggested, I would also unscrew the seacock first.
I used a steel bar that I picked up at Home Depot to grip it and then turned with a wrench. A length of pipe slipped over the handle can be used to add leverage.



If it is difficult to unscrew, then I would carefully heat it with an electric heat gun. I held this board over the mushroom, with a hole centered on the mushroom to protect the surrounding fiberglass from the heat.



I would also suggest applying some penetrating oil to the nuts on the thru bolts and let it sit overnight.

[John Stone]

That's exactly how I did it too. Worked just fine.

[jbenagh]

So the present score is seacocks 1, Jeff 6. The head intake seacock just does not want to come out.

Some background: all my seacocks are the original Spartans (except the galley one I replaced last year that I plan to revert to the Spartan). I could not find a wrench to fit the Spartans despite the loan of an awesome wrench from Bob Dugan (that wrench fit the galley Groco thru-hull perfectly). So I made two using 1/4 in steel bar stock from Lowes. Unfortunately, they did not match the stock sizes of 1.5in and 0.75 in so I ground down the stock to 1.430in and 0.630. These worked great for everything except the head intake (a 3/4in seacock). Every try on that one bent the tool. I made another tool, double-ended, and carefully cooled the metal while grinding, in case I ruined the temper. When I tried it again, I heated the thru hull with an electric heat gun until hot to the touch. I bent both ends of my tool. I will have to grind this one out. It must have been attached with epoxy or 3M 5200. The galley one I did last year with Sikaflex and it came out nicely.

A couple things were kind of revealing. The lavatory cabinet has always been kind of damp, to the point where we keep toilet paper in zip locs. Also, there has always been a small trickle of water when I use the holding tank discharge. While removing the lav backing plate, I noticed the bottom half was not really attached to anything; once I sawed it the bottom half pretty much fell off without any work:


The discharge seacock has two screws into the valve body; I believe these are drains. Access to these was blocked by the two mounting bolts. It was difficult to access one of them because the drain was backet out but could not be retightened since the the mounting bolt was in the way. Once I removed it I could see the path the water followed from there. I think I found the second mystery leak.

I removed the backing plates so I can replace them with G10 per MainSail's instructions. The discharge one is a pain in the neck since it is let into the space between the liner and the hull:


If you do make the fiberglass backing plates, you need more than a bench top drill press. The one I borrowed (5A; no HP rating) will not turn the 6in hole saw other than to make a mark I can follow on the bandsaw. The bandsaw works pretty well but two plates dulled the 1/4in blade pretty badly. There's five more to go so I'm buying another couple blades.

It's getting warmer and brighter now so I should resume a lot of work in the next few weeks.

Jeff

[jbenagh]

Actually the bandsaw worked really well for cutting the backing plates out of G10. It didn't appear to dull the blade abnormally once I remembered to turn on the dust collector, doh! Here's the completed backing plates and the Coosa material for the cockpit sole all cut up for installation:


I followed mainesail's method for backing plates: http://www.pbase.com/mainecruising/replacing_thruhulls
I cut three 6in backing plates (cockpit scuppers and galley), two 5 1/4 (lavatory and overboard discharge), one 4 1/2 (engine) and one 4 (head intake). I initially thought I would make all of them 6in but that would require pretty serious cutting of the liner. Oh, and for the cockpit sole, I cut one piece of 3/4 in thick to 11 3/4 in square, one 1/2 in thick to 11 3/4 x 24 to go under the pedestal and the tiller access and several 6 x 24 pieces to fit in on the sides of the cockpit.

Now I just need it to warm up enough so epoxy can cure.

Jeff

[hilbert]

If you do make the fiberglass backing plates, you need more than a bench top drill press. The one I borrowed (5A; no HP rating) will not turn the 6in hole saw other than to make a mark I can follow on the bandsaw.

There is more than one way of achieving an aim. I used a Rockwell Bladerunner with a Bosch Bi-Metal 21 TPI blade to cut 5/8" backing plates.
Are you planning to through bolt the flange or use Maine Sail's alternative of drilling and taping the G10 for threaded studs?

[jbenagh]

I think I'm going to thru bolt them.

[hilbert]

Maine Sail also used thru hull bolts on his own boat, "a personal preference".

I tried both methods last year. The thing to check for is that you have good access for drilling the holes at the proper angle thru the hull.
Sometimes the cabinetry or other obstacles gets in the way, then it really makes sense to use the alternate method of threaded studs in G10.

[jbenagh]

I am pretty traditional, so bolting seems like a good idea.

I got two more backing plates out today. The two cockpit scupper plates had pretty much completely failed. The adhesive still was stuck to the hull and plywood but the plywood just came apart along its glue lines! Glad I'm doing this project. Only two left to take out.

Jeff

[Keith]

I have a simple question on what material to use to fill the countersunk holes to cover the screw heads on the hull?

Keith

[hilbert]

I have a simple question on what material to use to fill the countersunk holes to cover the screw heads on the hull?

Maine Sail used 3M Marine Premium Filler http://www.pbase.com/mainecruising/repl ... lls&page=2, but did not explain his selection.

I'm a bit like the guy that only has a hammer and everything looks like a nail, except that my hammer is epoxy. Needless to say that I covered the holes with thickened epoxy and then a few coats of barrier epoxy paint. This is by no means a recommendation to use epoxy and I am interested in the answer to your question.

[Jim Walsh]

Those Groco strainers are a nice thing to have. Just remember to put a light coat of antifouling on the inside, not just on the outside.

[Ron M.]

The engine intake seacock is the one I didn't make a backing plate for. Noting the engine bed liner is 3/8" - 1/2" thick and well bonded to the hull it seems like overkill to add one at this location.

[jbenagh]

All my backing plates are epoxied in now. Next up will be drilling holes and installing all the hardware and new hoses. I forgot pictures of the cockpit drains. Here are all the rest. Even though the engine, lavatory and head intake all go through the liner and the hull, I think the backing plate might be a good idea. At least in the lavatory, it looks like there was some filler material between the liner and the hull and an area with no liner, just filler. After 5-6 of them doing all 7 wasn't much extra work.
Head:

The overboard discharge is kind of set in to the liner:

Lavatory:

Engine:

Galley:

[jbenagh]

Here's how I clamped them in place while the epoxy cured. A 3in #10 screw with a wing nut through a scrap of 1/4in ply covered with packing tape. I had to cut off 2 of 3 in the 3/4 seacocks since epoxy got on the threads.