Sealing shaft-log options

[ricksoth]

My Cal 27 was converted to outboard power in 2004 when the inboard diesel died. I removed the iron hunk last year, and now that I'm on the hard for bottom paint it's time to seal the shaft log. I cut the SS shaft and pulled it and the stuffing box off the inside. I cut off the bronze strut basically flush so that it can be painted over.

My original thought was to use a new stuffing box rubber hose with a bronze barbed fitting and clamps plus a bronze cap sealed with 4200 and clamped to the log inside. A non-leaking stuffing-box alternative. This seems like it might be all that is needed, since the old shaft and stuffing box have kept water out of the boat since 2004.

The boat yard suggested 8-hours ($130 per plus supplies) to epoxy and glass over the openings at both ends of the shaft log. How long can grinding a bit of gelcoat and bottom paint off the 1.25" ID tube and then placing some glass and epoxy really take. Seems overkill for a $6,000 boat.

While at the marine hardware store (Fisheries Seattle) I spotted the tapered hole plugs and an idea was born that maybe two of these and some 4200 are really all it needs. Clean up both tube openings a bit, and slather up the plug with 4200 and tap it into the holes. When cured trim off the inside, and that is done, on the outside trim to the gelcoat line and then either simply bottom paint over it or maybe apply a bit of epoxy to the exposed wood with or without some glass also. If these plugs keep out water in holes in wood boats, having two is really overkill maybe, and the inside is just backup.

What do others think about this water sealing project.

Thanks, Rick

 

[justsomeguy]

Seems overkill for a $6,000 boat.

Do it yourself.

 

[Captain Larry-DH]

Do it yourself.

Maybe use 5200 rather than 4200. I’m not a fan of 5200 for removable fittings, but in this case you’re planning a permanent solution. While you’re at it, consider replacing the ballast you lost when you pulled the engine. (Maybe just an equivalent weight of secured poured cement.) Your boat was designed for it.

 

[dlochner]

8 hours doesn't sound excessive for the job. It is more than just removing gelcoat and putting some fiberglass over it.

The hull needs to be sanded down to form a 12:1 bevel, so that is a circle of about 15 inch radius diameter. Then multiple layers of glass need to be applied to build up the thickness to match the hull thickness, then lots of fairing and sanding before spraying gelcoat on followed by sanding and polishing. Thinking about it 8 hours seems like an underestimate.

The plug option would work for a while. The problem would be exposure to water causing the wood to rot. The repair would be in an easy to forget about place with catastrophic consequences if it failed. This option would not be my choice.

A better option than a wooden plug would be a fiberglass rod epoxied into place on both sides. Thoroughly clean and sand the inside of the tube and glue it is with thickened epoxy. It wouldn't be necessary to do a full 12:1 scarf to cover the plug, maybe a 6" diameter area with several layers of 1708 of fiberglass covering both the inside and outside of the plug.

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[Scott T-Bird]

What's your vision for the future of this boat? To make a repair that a second party would stand behind, the yard price seems pretty cheap to me. The angled exit path on the underside of that skeg would be a little more complicated to fiberglass and fair than the usual hole to fill. It's a different story when you are giving your boat to a second party to repair and be responsible for performance. You may not care if the boat sinks while passengers are on board but a second party would certainly care if there is liability involved! They don't do this stuff to suit your pocketbook.

But your repair may be just fine if you only have a 5 or 10-year plan for the boat. True, just about any expense is not justifiable on a 50-year-old boat worth $6 K. I would do it like Dave says with a fiberglass rod that can't rot. 5200 would be a better choice than 4200 to conform to the outside portion of the hole. Disclose the repair to the next owner.

 

[Ward H]

A better option than a wooden plug would be a fiberglass rod epoxied into place on both sides. Thoroughly clean and sand the inside of the tube and glue it is with thickened epoxy. It wouldn't be necessary to do a full 12:1 scarf to cover the plug, maybe a 6" diameter area with several layers of 1708 of fiberglass covering both the inside and outside of the plug.

Dave, would this option be suitable for filling a thru hull hole of 1" to 1 1/8" in size? While I have never needed to do the 12-1 grinding and layering of fiberglass, I always wondered if it was overkill for a 1" hole.
I may be eliminating two 1" thru hulls next year and your suggestion sounds a like a bit less work than the normal 12-1 layup.
While I can do fiberglass work, I just hate it.

 

[dlochner]

5200 would be a better choice than 4200 to conform to the outside portion of the hole.

There is no need for a flexible adhesive in this application. The plug needs to become one with the hull. Epoxy will do that, 5200 will not.

Dave, would this option be suitable for filling a thru hull hole of 1" to 1 1/8" in size? While I have never needed to do the 12-1 grinding and layering of fiberglass, I always wondered if it was overkill for a 1" hole.
I may be eliminating two 1" thru hulls next year and your suggestion sounds a like a bit less work than the normal 12-1 layup.
While I can do fiberglass work, I just hate it.

I don't think so. The shaft log repair is an awkward shape and very deep. Trying to grind away enough glass to get a good 12:1 bond on the OP's boat would be a challenge because the of the shape of the hull. If the flat area around the hull was larger, then getting a good scarf joint would be much easier and the plug wouldn't be necessary, although it might make serve as a backing to the glass.

How thick is the hull at where the thru hulls were installed? Probably on the order of a ½", so you would need a 6 inch diameter circle. Or if you worked from both sides, a 3" diameter circle. Because you would only be filling half the hull thickness on each side. The two sided approach will be stronger and you have less fairing to do on the outside of the hull because you won't fair the inside.


Note: In an earlier post I may have over estimated the scarf area on the OP's project. Nonetheless the challenge for that area on the keel is the shape and knowing the thickness of the hull. And, in my haste I overlooked an obvious error, it would be 15" in diameter, not radius. It was early in the morning (for us retired guys) and coffee hadn't fully kicked in. I used the diameter of the hole not the thickness of the laminate to determine the scarf area. That's my story and I'm sticking to it.

 

[ricksoth]

Thanks to all that have shared their wisdom and thoughts!

Since the outside (bottom) of the shaft log opening has been fine for 40+ years (1977 build date) maybe leaving that out of the fix is a better option, and focus on the inside point only.

By using a small portion of the tapered wood plug trimmed to "just barely" slide down the tube from the inside and held in place - effectively creating a "dam" - and then an epoxy putty could be mixed up and poured into the tube, curing in place making the primary waterproof barrier.

Then using my new rubber tube stuffing box hose, the 1.5" OD barbed threaded fitting and threaded cap affixed to the shaft log using the two SS hose clamps for both the barbed fitting and shaft log (same as what was on the stuffing box) provide the secondary backup.

This seems like a KISS approach and something I can do myself while the boat is getting the bottom paint done, etc.

This change would be communicated to the new owner when I sell it in 5-10 years.

Thoughts?

 

[dlochner]

By using a small portion of the tapered wood plug trimmed to "just barely" slide down the tube from the inside and held in place - effectively creating a "dam" - and then an epoxy putty could be mixed up and poured into the tube, curing in place making the primary waterproof barrier.

Hydrostatic pressure is working against you in this solution. I wouldn't go this way at all.

 

[ricksoth]

Dave, how is creating an epoxy plug inside the tube just past (behind) the stuffing box cap replacement ? When a motor is installed, the only leak prevention is a flax stuffing box compression nut, which seems much less secure.

As you can tell from my OP, I'm fairly unknowledgeable about all of this, but if a stuffing box worked since 1977 shouldn't a stuffing box alternative along with a epoxy plug be even more secure?

 

[ricksoth]

Here is the stuffing box alternative - plastic parts just for conceptualization. Bronze version behind is to large so will find a 1.5" OD to replace white plastic and bronze cap for the black plastic cap.

 

[dlochner]

Dave, how is creating an epoxy plug inside the tube just past (behind) the stuffing box cap replacement ? When a motor is installed, the only leak prevention is a flax stuffing box compression nut, which seems much less secure.

As you can tell from my OP, I'm fairly unknowledgeable about all of this, but if a stuffing box worked since 1977 shouldn't a stuffing box alternative along with a epoxy plug be even more secure?

Rick,
Essentially, what I suggested was an FRP plug that is the length of the shaft log. I didn't do a deep dive in to shopping for solid FPR rod, just took the first one that showed up on McMaster-Carr which a G-10 product. Personally I would feel more comfortable with a G-10 rod epoxied into the tube than something I might create as it will be built to known stringent standards.

The traditional stuffing box is vulnerable to leaking and it is designed to leak. The one big difference between your plug and the stuffing box is a human one. Inspecting the stuffing box and hose is part of regular maintenance of the drive train. We are more likely to check it will doing our normal maintenance and it will signal to us when it needs greater attention by leaking more than usual. Eliminating the engine and takes the shaft log out of the normal maintenance schedule, it is out of sight and out of mind.

Sealing the outside with a few layers of glass is a belt and suspenders approach and a bit cosmetic. With the hole sealed water can not access find its way into any gap that maybe between the rod and the shaft log.

To prep the interior surface of the shaft log, get a hole saw one size smaller than the shaft log. Glue 80 grit sand paper to the outside of the saw and sand away. You can use some sticky back paper or 3m 777 spray adhesive. The paper will peel off later.

Smear the rod with a good thick layer of thickened epoxy and slide the tube into the shaft log.

Finish up with a couple of layers of glass on the outside to fully seal the hole.