J/30 Class Association Forums J/30 Forum The Boat, Sails and Equipment New season, new projects

Well the sun was out and temps climbed above 40 degrees so spring must truly be on its way up here in the frozen north. To celebrate, I removed her winter coverings and let her deck see the sunshine once again.



On the agenda to be completed before our May 1st launch is some engine surgery (I found this which makes me feel confident), rebedding stanchions and various deck hardware, cabin heater install, new kiwigrip, sheave box maintenance, mast lighting replacement, waste hose replacement, cutlass bearing replacement along with the usual bottom paint and bright work maintenance so it's looking like I've got a busy month ahead of me.

Two questions that I have;
1) I plan on caulking the exposed deck seams and chain plates with 3M 4200 as I noticed some water migration. If water has penetrated the exposed deck seams it will follow the inside of the hull to the bilge and the core shouldn't be exposed right?
2) The only part of my engine instrument panel that is actually still working is my tachometer and towards the end of last season even that seemed to get a little twitchy (tach guage would fall from 17 to 14 for short periods even though I could hear the engine chugging away reliably at 17), what would cause such fluxuation?

Hope spring is treating everyone well!

-Josh

Hi Josh,

I would answer question #1 with both a yes and no. The seam is an inward flange hull deck joint, bonded and sealed with 5200 adhesive or similar. This would seem to be just one lap joint, but it is more like three. The deck was created in two major layups, the second of which added the balsa core. Same for the hull. Even a slight compromise in that area will cause water to wick to the core. The water source could be the portions of the hull deck joint that are not covered by a well caulked toe rail or portions of the joint without toe rail, but only if the 5200 was compromised. The bigger issue are the fasteners that penetrate all of these layers. If the FRP to FRP joint near these fasteners has a slight compromise, this would provide a path to the core, whether the water source was the 5200 sealed lap joint, or more likely, the bolt hole itself. The bolt holes are the source for my boat as well as others I have seen.

Bottom line is that caulking the joint can't hurt, but further investigation might be in order. As far as caulking the other items, butyl tape might be a better choice. However, I may try an experiment by blue tapeing off a very thin fillet area on a test piece, then applying a very thin fillet of 5200 and see how that performs over time and how much effort will be required to remove it a year later.

GL,

-Chris

By bolts you mean the stanchion, toe-rail and pulpit bolts that run through the seam? I am going to unbolt the stanchions and re-bed but I didn't think there would be core all the way to the deck seam, just assumed that it would be all glass at that point like the centerline of the hull.

Thanks!

josh

I agree with Chris except for using 5200 as the sealant externally on the seam. You want something that will flex with any movement and temperature variations. If the deck was removed and rebedded, then use 5200.

5200 dries like cement, and is for permanent adhesive bonding, not as a filler applied to an external joint.

Josh - you want to properly epoxy isolate all the stanchion holes. Oversize drill, fill with thickened epoxy, redrill the holes, then countersink the top surface of eack hole to provide and area that will form a sealing ring around the fastener. This will significantly reduce leaks.

Thanks Bill, that's my plan. I will bed the bolts with butyl tape and use what on the exposed deck joints?

Yes, and your assumption is correct - core does not extend to the stanchion bolt holes. However, if water gets into these holes and they haven't been epoxy isolated, there is a real chance that there is a weakness which water will use to wick to the core.

-Chris

So I've taken the plunge and will be pulling my yanmar apart down to the cylinder head, grinding and reseating the valves and cleaning the scale out of the exhaust manifold and cylinder head cooling passages. I have the exhaust manifold off and can see plenty of it along with some carbon buildup. What would you use to clean out the passages, get what I can with a wire brush and flush with water or do something more drastic like muriatic acid?

and deeper we go



until we finally have the cylinder head off.


Plenty of carbon on the valve heads and some fairly pitted metal on the forward cylinder portion of the cylinder head. Once I have the valve itself out I can see just how much steel has corroded away to the point where there is a crack across the valve seat!


Great, I'm definitely way over budget for this spring's projects already without buying a whole new cylinder head. And after browsing around the interweb for a few minutes I discover that I can't find one anywhere anyway, price notwithstanding. What to do? It was a long shot but I grabbed the mig from the garage and a dremel tool...


Shaping the weld bead by hand was some delicate business. Eventually the tolerances seemed close and I could finish by grinding the valve seat with the valve itself using lapping compound and this is what I ended up with.


Will it work? I'm not sure but I certainly hope so.

Josh - you're doing what I did on Rhapsody engine rebuild 2007 but I pulled the engine to do it in my basement over the winter. I had no cracks in the head. Nice weld job. The only concern I'd have with it is the surface of the weld isn't heat treated (lower Rockwell hardness than the rest of the head) and that spot may wear.

I used hammer, chisel and Dremel tool to get hardened carbon out of the water passages, then soaked the passeges with acid, once the head was reassembled to the block followed by thorough fresh water flush.