Repair blog: chainplate & tie rod replacement Bavaria 47 cruiser 2001 (FINISHED)

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Hello,

For the benefit of other Bavaria owners, I am staring a forum repair blog on my 2001 Bavaria 47 Cruiser port side chainplate tie-rod replacement-overhaul. I see this is a topic that has risen in this forum too, however I did not see it answered with finality. I'm not planning on losing my rigging due to this

To start, please see attached images of my vessels portside chainplate rod fastening corrosion. The rusty connection is directly beneath the galley top, behind the sink. Obviously, there is corrosion pitting present. I am going to replace the fittings and overhaul the otherwise good looking starboard fitting too. Just for good measure.

My first step has been emailing Bavaria to request specifications for the pieces (torque specs) and availability of parts. Also, has anyone had similar jobs done on a similar Bavaria? On inspection, I find it disturbing that the original fastenings of the deck chainplate are of A2 grade steel. I'm upping this to A4.

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First update of this repair:
1) SVB24.com does not stock anything for the Bav47 cruiser 2001 chainplates and tie rods;
2) Bavaria official customer support, to whom I called, said it is a very old boat from an old era of the Bavaria company and they likely have nothing available to support the repair - drawings, manufacturer, nothing.

So that means I'll have to manufacture the part myself - which is not a problem. I'll take the rusted stuff off the boat, try to measure some torque specs, create drawings and send them off to a shop.

My main question presently is the amount of pre-tensioning of the tie rod that links the chainplate to the bulkhead. There must be some, however I'm unsure how much and how to measure it really. It must be equal or more when compared to rig tension. Bolt removal-torques will not be an adequate number as they are rusted and there is more friction when compared to a new part.

Any input on the tie rod tension is greatly appreciated, thanks!

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Update #2

I got the chainplate off yesterday - in fact it was not under much pressure. I held the deck bolts with a hex wrench and undid the nuts of the backing plate to which the tie rod connects. I was fully expecting the bottom plate to "snap down" when loosened, however this did not happen. The tie-rod is still stuck to the hull. It is a rather elaborate system. Once I get it all off I'll upload a picture. I need to go buy a 45 mm wrench..

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Update #3

Today I got the whole chainplate assembly off the boat. I had to remove the galley sink to get proper torque applying access to the 45 mm large nut holding the tie-rod to the bulkhead bracket. It took some large wrenches and a plenty supply of penetrating oil to get the last nut off. Now the galley is a mess, however on the upside the hardware does not look even half as bad as it did when it was still mounted to the boat.

To be honest, the parts look OK to me. However there is still two dark corners to explore - namely the stainless tie rod itself is a "free floating" piece. On the deck side it is sitting in a ball joint and on the bulkhead side it is somehow stopped in the cylinder from which the massive 45 mm threaded rod sticks out of. I'm going to look at the floating points and see if there is anything up there.

I'm having second thoughts on having anything replaced in this assembly. However, as said, I'll open up the tie rod joints, clean all the parts up, inspect them and see if I can find anything. I'll maybe swap out the tie rod, as it is the thinnest part in the whole assembly. Everything else is massive compared to it.

Again, any ideas-suggestions are welcome.

[Yngmar]

Nice work. Can you show the ball head of the tie rod as well? That's likely the critical part.

On ours, one of the through-deck bolts had a crack in the head, so I replaced them all. The rest was fine, although ours hadn't been leaking for as long as this one. Polish it all up and check for cracks (can use dye if you want to be fancy). Unlikely there'll be any problems with the lower bracket, it's massive.

[Ailatan]

Well done, I had similar problems but I only needed to remove the top part.
After cleaning everything with a rust remover I found out that everything was in perfect condition so I put them back in place with new sealant so no leaks since then.
There is a post in this forum somewhere with pictures similar to yours.
In any case I understand that if you didn't feel 100% safe with the situation of the tie rods you did well cleaning and ordering new parts

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Update #4

I got a new reply from Bavaria with the actual technical drawing of the tie rod (as shared below)! Also, the company that made these chainplates and rods is not active anymore. Many thanks to Bavaria for digging up this old information for a essentially not very attractive customer. Big plus to their customer support for this.

It is good that I got this drawing, as it lists all the materials used and how the device is assembled. Most importantly, the cylindrical housing into which the large M30 threaded rod screws into is mechanically pressed to effectively lock the threads. Good luck to me trying to disassemble this That will not happen unless I use destructive methods, which defeat the purpose here as the parts look OK.

Also, the tie rod is made of DIN 1.4462 steel (duplex stainless), which has a stronger yield strength than your typical AISI316L  steel (450 MPa to 700 MPa vs. 170 MPa to 310 MPa). Rigging wire is likely AISI316L if not AISI304. So yeah... out of the box, rigging should be at least 2x weaker than the tie rod, though there are two wires attached to the chainplate.

/.../
Nach montage des Gewindstanges, wird 2 Schlüsselflächen gedrückt, womit der gewindstang wird festgehalt
/.../

Which translate with Google to:
/.../
After assembling the threaded rod, 2 wrench surfaces are pressed, which holds the threaded rod in place
/.../

In any case ... I'm not planning on destructive opening of the tie rod because that would defeat the purpose. I'll open up the top half and inspect it, as that is a simple task of cutting 4x small spot welds with a Dremel type cutter and then weling it shut again.

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Update #5

I opened up the ball-socket of the chainplate facing tie rod end today, cleaned it up and concluded that I could not see any wear. There was some burned plastic in there and I think I know what it is: namely when removing the tie rod I could see burning marks and mushed plastic on the fiberglass around the chainplate backing plate (on images attached).

It is likely that during production the backing plate was heated up to near red hot and pressed against the inner face of the deck of the boat. This would have melted created a smooth faced joint between the chainplate and backing plate. Fiberglass on the inner hull is very uneven on average.

I welded the socket back shut and cleaned all the rest of the parts with an angle grinder (steel brush) and used an ultrasonic bath for cleaning the small stuff: washers, nuts etc. I put some lithium grease in there for good measure.

Only pitting I could see is on the M30 threaded rod. This is AISI304 and the pitting is likely between the interface of the large nuts. The interface likely held moisture locked and enabled the reduction reaction to take place. Next stop is putting it all back again.

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Update #6 - FINAL

Yesterday I finished my 2001 Bavaria 47 port side chainplate and tie rod install (99% of it). I've attached images of what the end product looks like.

I decided to install the deck mount with butyl tape, as an experiment, as it is a somewhat dynamic fixture and butyl tape can stay sealed under shear loads while Sikaflex cannot (once a threshold is passed). I understand that it is a matter of decision and preference somewhat.

Also, I was faced with the issue of how tight should the tie rod be? I had no tensiometers at hand and I ended up by tuning the tension by ear - yes, I tapped on the starboard rod, listened for the pitch and tightened the port rod until a similar pitch was heard. I confirmed the results with a smartphone tuning app, which surprisingly worked well. The starboard rod was resonating around 80 Hz at the E2 pitch.

The 0.1 % still left to do is tightening the two large M30 nuts to properly form an anchor-lock for the rod. I cannot fit two wrenches in the bulkhead bracket and I'll have to find a way to jam the upper nut so I can torque the lower one.

To conclude this topic, here is what I learned in short:

• The chainplate-tie rod is well engineered and it is not an easy task to reproduce, as the steel used is not off-the shelf 304 or 316L type;
• The rust I saw was superficial and the only pitting I saw was on the 304 steel M30 bolt: eg. rust seen on this setup is most likely not a red alert;
• The plans I received from Bavaria do not include a torque or tension rating for the tie rod. What I concluded acoustically is that the factory installed starboard tie rod resonated around 80 Hz or the E2 pitch.
• I would like to thank Bavaria customer support for digging up old plans (as shared in this thread) for a retail market customer, they could have very well said NO and I would have accepted this.

Thanks!