Chain plates Hunter 49

[Screen Saver]

Anyone seen this before ?
Found this today on starboard side chainplate: It looks very much like a crack but it doesn’t make sense to me to be a stress crack vertically like its trying to pull the chain plate horizontally apart. It looks like its trying to pull the outside half away from the inside half. If it was a stress crack I would have thought the crack itself would have been horizontal and the tension up would try to pull it in half. The bolts on these chainplates are not visible on the outside and Im wondering if the chainplate is made in two halves and laminated together somehow, over the top of the bolts and its delaminating. Is that even possible ? I did see someone asking a similar question with a similar observation, but no one answered. Does anyone know how Hunter makes there chainplates

 

[justsomeguy]

Just replace it.

 

[jssailem]

Looks like Stainless Steel corrosion has occurred. Water has entered the metal and is corroding on the inside.
I would remove and replace the piece before I went sailing again.

You could remove the chain plate and have the piece inspected.

The type of pitting is recognized on the basis of metallography testing of a pitted cross section. The pattern is identified on the basis of penetration depth, shape and size (Figure 1). A standard guide for identifying and rating pitting is provided in the ASTM G46 – 94 (2018) standards.

 

[Georgedoyle]

I'll check mine today.

 

[Screen Saver]

Looks like Stainless Steel corrosion has occurred. Water has entered the metal and is corroding on the inside.

You seem to have some Knowledge in this area, but I have trouble get my head around SS absorbing moisture and corroding from the inside out, or penetrating an area that is not fractured. If the chainplate was perhaps made of two bits and welded together then yep your answer would make perfect sense to me. its probably found its way through a crevis in the weld and yep, working hard to dissmast me. However, if its a sold piece as a lay person in the detail of metals I have to say I'm Skeptical. For the moment I will try to find out how they are made. If its in two halfves and welded ( the question would be why they did that) and I would be inclined to just re grind and weld. If its one peice and with no other theory than yours, yep I guess I need to replace it. if Im doing one, I guess I need to do the other..... Where is Glen Henderson when you need him to tell me how these were made

 

[jssailem]

Fair enough.
Remove it and begin grinding on it.
I am not a professional metallurgist nor blacksmith. There are some here who will likely share their expertise.

I was not there when the chainplate was created, and I have not heard from you about the experience to which the boat has been exposed.

I have dealt with stainless steel chainplates on several medium and large sailboats.

All of the ones I have encountered were solid cast or blocks of stainless steel, milled to size and shape. Non were welded.

Pit corrosion develops when the piece's surface is damaged, and oxygen is deprived. The corrosion is not based on a weld issue but a flaw or contaminant that occurred in the original build.

You should certainly remove the piece and begin to grind away the damage. If you are lucky, the damage is on the surface and will disappear at the touch of the wheel. If you are unlucky, you will be surprised at the depth to which pit corrosion can compromise stainless steel.

 

[Screen Saver]

Thanks John. The boat is 2008 and it has sailed many more miles than others (130,000nm). it would very seldom sea salt water or even spray up that high, and it is to some extent protected on top by the U section beginning of turnbuckle. The stainless is high polished I think they call it mirror finish and while in the last couple of years it hasn't been polished as often it would normally be polished every year at least. I did notice it about 1 year ago and at that point I just assumed it was some light tea staining and while mentally telling myself I should have polished this more often. Now that I have started rigging replacement and a much closer lock at everything I can see this is not the case as I can infact feel it with my finger nail and a polish does not remove it. What has got me as explained is that it is if someone/something was trying to cut it in half down the forward and aft axes of the boat and pull that half to starboard. I found another blog of someone else whom clearly had the same thing, some 8 years ago based on his description and he never got an answer to his question and was also wondering if it was done in two halves. One of the Riggers & SS welders here tell me that some manufactures were welding a second layer on the top of the half of the chainplate running it out to nothing about halfway down. This was done "they say" to spread the load area across the pin, not so much to strengthen the chain plate. So I guess its possible Hunter did the same thing only ran it all the way down because perhaps 6mm stainless twice is cheaper than 12mm. Who knows. I have posed the question to Hunter Marlow, whether they know or will answer we will see, I have also asked the spare parts guys if they have couple. (none are listed) Back to the mast in the yard for today and perhaps tomorrow I need to pull off the chaiin plate.... not looking forward to that either.

 

[jssailem]

2017, I removed the mast on my 1973 boat, a Cal35 Cruiser, for refurbishing. I had multiple chain plates, all with some small amounts of pit corrosion. I carefully began to grind the metal's rust pits. The pits were superficial. Once removed, I polished the chainplate to a bright shine. I then took the chainplates to a shop to have them cleaned and dunked in an acid bath (passivation treatment). The process is reported to provide a thin oxide layer on the stainless steel. It is done to maximize the natural corrosion resistance of the metal.

Good luck with your project. Let me know how it goes. Hopefully, you'll get an answer back from Hunter Marlow.

 

[Screen Saver]

Update: Sailboat Owners: "The chainplate are supposed to be made out of one solid piece of stainless and have never seen this with what appears to be be 2 pieces of stainless welded together. We may have a set in stock and will check and get back to you but if not we can have a set made. "

This is now a bigger concern as it would appear to be a single piece.
Yesterday I went to take it off and then realized I would need to pull the entire rubrail off in order to the chainplate off. Either that or cut a section out of the rubrail which is not exactly a great.
Im trying to see what portable Xray possibilities are so i can be sure what's going on.

 

[Terry Cox]

Either that or cut a section out of the rubrail which is not exactly a great.

Before you start cutting, check to see how the chainplate is secured to the hull from the inside. Can you tell whether it is through bolted, in which case, removing the bolts would allow you to lift the SS plate out of the slot rather than cutting the rub rail.

 

[jssailem]

What @Terry Cox says. Just like the solid chainplate, it is not in the interest of a builder to make a boat owner replace the whole rub rail to get at the chain plate.

They should be through bolted with access inside the boat. Be sure to run a line from the mast to the deck and make it taut so you support the mast while restoring the chain plate.

 

[Screen Saver]

Terry John,
Mast is out, that's, I'm doing rigging replacement and solving or investigating this was one of my todo tasks.
H49 has NO through bolts, ie the outside of the chainplate is very nicely polished like a mirror.
So there are 4 studs on the inside. I believe they are welded to the chainplate and pass through a plate set in the hull Fibre glass then appear on the inside where there is another plate and 4 x 28mm nuts, which are now lose. However, to get the chain plate out you must pull it away from the boat which you cannot do, due to the rubrail as you can see from the picture which pass across the chainplate.
There is no way this is coming out without removing the rub rail and someone has actually just removed there's on a 49 and said its a nightmare.... or I cut a section of the rubrail just a bit wider than the chainplate. Not a very professional or aesthetically good solution but certainly much easier.

 

[isaksp00]

Would it be feasible to cut the old chainplate just below the rub rail, then slide the top half up and pull the bottom half outward? You could try to replace it with a piece made without welded studs, rather use stainless bolts through holes following the same layout as the holes on the inner support piece. Or, warm the rubber insert and pry it out around that area, and if you can access enough of the keeper screws, pry some of it out enough to slide the new one with studs up from the bottom? That all assumes you have a plastic keeper with rubber insert.

 

[jssailem]

Sounds like a bad design. Cutting the rub rail would be my last and final choice.
Does your rub rail terminate at the stern. If so these usually slide on a track. Remove the fastener and try to slide the rub rail out to where you can access the chainplate.
Taco Marine is a major manufacturer of rub rail. TACO Marine | Rub Rail TACO Marine
You may find your unit here. It may give you clues to a non cutting solution.

 

[jssailem]

In my experience rub rails are attached to the hull. Where you see the chain plate behind the rub rail there should also be the hull deck joint. To cut means also cutting this joint. Bad idea.

 

[jssailem]

As @isaksp00 suggests, once the internal nuts are released, can the plate be lifted at the stud area away from the hull, and slipped down from under the rub rail.

 

[JamesG161]

My quick review of the issue...

The Cracks and minor pitting is normal for the years of service.

Take off that piece and take it to a Certified Welder to fix it for another 10 years.

Jim...

 

[Screen Saver]

In Answer to some of the thoughts:

Yea I could probably cut the old/existing chainplate and get it out. Wouldn’t be Easy cutting through 12mm stainless. It would need to be cut with grinder still not sure that would get the old one out because I would need to cut under the rub rail which would be below the bolts. Hence the top half with studs would still be behind the rubrail.. It is a possibility maybe, then I would need to make up a new chainplate with through bolts, not the smooth finished ones.

Yes not a great design. Rubrail is in two halves, from front to about 2/3 down the boat. The stainless strip on top terminates about half way down. According to others the rubrail is glued about every 4 to 6 inches and screwed between each glue point.

Yes the rub rail basically goes over the deck joint. I saw these being made in the factory. The top and bottom half of the boat sit ontop of each other with glue and screws, the rub rail pushes over the lip of this joint. So yea cutting the rub rain and not the joint I think will be ok with a small Dremel

The rub rail pushes on the outside of the chainplate. There is no room to the chainplate horizontally more than about 1/8”, given I have all the nuts off, that’s it.

The cracks I can see are not so much of a concern, its what’s below inside I cant see, that’s my worry. The stainless welding guys here and a few others I have spoken too, are saying if its one piece as Hunter suggest, it must come out and be replaced, because its clearly below the surface. And got into the metal. If its two pieces and this corrosion is simply in the V of the weld, then no drama we grind it out the weld and reweld. I looked at portable X-ray as well seems that’s about $1800.00. Every one has put me off trying to take off the rubrail, so if it comes out I will likely cut just the rub rail with a Dremel in one place and see if I can free up about 1 foot pas the cut enough to get the chainplate horizontally about 4” out. If those that have had the rubrail off are correct with there glue and screw placement it should mean 2 or 3 screws and 2 or 3 breaking the glue spots free. That’s my current plan, but I will wait another day or so while hunter try to check with the manufacture that the chainplates were all one piece and whether that have any.

 

[Screen Saver]

Well in the end I decided not to attempt to remove the whole rubrail. I elected to cut a section and remove the chainplate. depending on how this is actually constructed it doesn't look good to me. It looks like they have just stuck 4 studs on the plate, so all the shearing load is sitting on the welds. I hope Im wrong and I certainly wont be doing the same if it is as it appears. Hopefully the studs go all way through (or nearly) and the weld on the studs is really just holding the studs in place and not really takeing much load.

 

[jssailem]

Wow.
Thanks for the images. One never knows till the hidden is exposed.

Your rub rail will need a termination where cut. If not fixed in place it will move due to heat/cooling expansion and contraction.