Navtec tie rod block material

[mbowser]

Originally Posted by dlj

I would stick to 7075 for the blocks. You have a contact interface with the rod rigging which is nitronic 50, a high grade austenitic stainless steel. That interface with 316 will give you other problems that you don't want. 7075 is an amazing aluminum alloy well suited for the purpose at hand.

As you have said, given the boat is 40 years old, and the problem has been water ingres, fix the water ingres problem and stick to the 7075.

I've just seen this thread and did not see if in fact you had the original aluminum block tested or not, but that block would most likely be 7075 for what you have there in terms of use.

dj

That's good to know, I knew that the actual tie rod was nitronic 50, but hadn't considered any nobility issues. I haven't had the blocks tested, but I did get in touch with the former rigging forman for Hinterhoeller yachts (he may have actually rigged my boat when it was built). He was pretty sure that the blocks were hard anodized 7075. 2 of the blocks look like they day they were installed, 3 could probably be cleaned up, and 1 is pretty corroded and needs to be replaced. Each of the corroded blocks corresponds to the compressed deck issues and improper sealant used.

I'm pretty confident I can fix the deck issues (and ensuing water leaks) with the design I'm implementing and the new aluminum blocks I'm having machined (7075 with hard anodization) will outlast me.

[mbowser]

Aluminum blocks are ordered, looks like they should be finished and delivered sometime in mid-April. Screenshot below is for the 4 lowers, the 2 uppers are the same material, but larger rod size (not pictured).



In the meantime, I'm heading over to the boat today to bore out at least one of the areas to measure the depth of the deck. I 3d printed a few templates for the holesaw cuts and marked the area for removal, but didn't have time to actually make the cut when I stopped by yesterday.

[mbowser]

Finished up the g10 inserts, I ended up epoxying 2 pieces together (the top I routed with the jig and for the bottom, I used some 1/2" g10 plate that I had from a previous project).

I traced the cutout template onto the deck at each chainplate opening and cut off the top skin and core with a hole saw and oscillating saw.


The core on each of the port side chainplates was crushed but no signs of water ingress. The starboard side had minor crushing, but also no water issues.
All the inserts fit well, so the next step is to epoxy them in place. I'm going to laminate a layer of 1708 biaxial glass onto the bottom skin and then epoxy the g10 inserts on top of that using thickened epoxy, taking care to keep the mess to a minimum.

[Bowdrie]

Most excellent work I must say.

[mbowser]

Thanks Bowdrie, this is one of the first projects I've done where I really leaned into CAD and 3D printing to prototype and refine before implementation. The level of precision is quite a bit better than my usual 'just go for it' mode. Of course it could all go to ***** when I epoxy the inserts in, but as long as I plan out my steps, I don't usually have any issues.

The last piece of this puzzle is to source through bolts that are .25" longer than what is currently used. Normally, I would just source them through McMaster Carr, but it has an odd head on it that was clearly custom fabricated. They appear to have been plated at one time, but I'm pretty sure they are bronze. I have a feeling that they aren't original, but I've never seen another Navtec setup like this in person.

It almost looks like the heads were formed and ground down to fit in the chainplate slot, but I'm not sure. The heads are definitely 'beefier' than something I could purchase stock. I'll probably take them to a machine shop and see what they recommend, but I'm interested in opinions.

[dlj]

Is the diameter coming up to the threads smaller than the OD of the threads? Is there then a "shoulder" coming up to the head?

Can you take a file and clean of a small area on the head, then take a photo so I can see the color of the base material without the oxidation?

dj

[mbowser]

Originally Posted by dlj

Is the diameter coming up to the threads smaller than the OD of the threads?

Yes, the diameter is slightly smaller than the OD of the threads. I assumed that it was elongated, but maybe that is by design?

Is there then a "shoulder" coming up to the head?

There seems to be a very small shoulder between the narrower section and the head.

Can you take a file and clean of a small area on the head, then take a photo so I can see the color of the base material without the oxidation?

I scored the top with a file and it certainly has a bronze color and seems to be soft like bronze. I don't think I could have scored stainless steel that easily. Sounds like you might be familiar with this type of bolt?

[Bowdrie]

It appears that that bolt is a "headed" bolt with rolled threads.
The bolt was put in a die and the head was either cold-headed with a trip-hammer, or heat was used to first soften the head, my guess is that it was "cold headed".
Actually, if a big bronze bolt can be obtained with the right thread size a good blacksmith can cut the existing head off and form a new head.
Or, a big bolt with a normal "hex-head" could have its head reformed.
It defiantly looks like something that was a custom run.
The head has a remarkable resemblance to the head of a wheel stud, the kind that were pressed-in thru brake drums from the rear.
But the rolled threads and bronze material say otherwise.

[mbowser]

Originally Posted by Bowdrie

It appears that that bolt is a "headed" bolt with rolled threads.
The bolt was put in a die and the head was either cold-headed with a trip-hammer, or heat was used to first soften the head, my guess is that it was "cold headed".
Actually, if a big bronze bolt can be obtained with the right thread size a good blacksmith can cut the existing head off and form a new head.
Or, a big bolt with a normal "hex-head" could have its head reformed.
It defiantly looks like something that was a custom run.
The head has a remarkable resemblance to the head of a wheel stud, the kind that were pressed-in thru brake drums from the rear.
But the rolled threads and bronze material say otherwise.

Yikes, I know less than nothing about this sort of thing. I guess I'll be making a trip to a machinist who knows about this sort of thing to reproduce. I'm guessing using off the shelf bolts won't suffice here?

[dlj]

Originally Posted by mbowser

Yes, the diameter is slightly smaller than the OD of the threads. I assumed that it was elongated, but maybe that is by design?

There seems to be a very small shoulder between the narrower section and the head.

Attachment 288623


I scored the top with a file and it certainly has a bronze color and seems to be soft like bronze. I don't think I could have scored stainless steel that easily. Sounds like you might be familiar with this type of bolt?

Attachment 288624

This looks like an engineered fastener. Your image of the head is out of focus so it's pretty hard to see the color. Definitely a copper based alloy. Likely one of the bronze alloys. But there are literally hundreds that it could be.

The reduced shaft below the threads could be for several reasons. The shoulder near the head is likely a fitting for the fixture it is mounted in.

I would need a lot more information about this entire mounting structure to give you much more.

This is not something that can be assessed properly over this kind of forum.

dj

[mbowser]

Originally Posted by dlj

This is not something that can be assessed properly over this kind of forum.

dj

Agreed, my rig literally depends on these fasteners and I'm not going to rely on guesses. I'm going to take a trip down to Rigging Only in Fairhaven in the next week or so, I've had them do work on previous projects and they should be able to at least identify a path forward.

[dlj]

Originally Posted by mbowser

Agreed, my rig literally depends on these fasteners and I'm not going to rely on guesses. I'm going to take a trip down to Rigging Only in Fairhaven in the next week or so, I've had them do work on previous projects and they should be able to at least identify a path forward.

I've used rigging only.pretty good folk there. If you need help with figuring out what that bolt is, drop me a PM.

dj

[s/v Jedi]

What exactly are the concerns with these bolts? Don’t standard bolts fit? From all rigging components I have seen they are either stainless steel or they are chromed bronze so I guess this is chromed bronze, which should be easy to identify. The chrome is just for good looks. I would guess the nuts are stainless steel to prevent galling.

[mbowser]

Originally Posted by s/v Jedi

What exactly are the concerns with these bolts? Don’t standard bolts fit? From all rigging components I have seen they are either stainless steel or they are chromed bronze so I guess this is chromed bronze, which should be easy to identify. The chrome is just for good looks. I would guess the nuts are stainless steel to prevent galling.

Standard bolts would fit with some minor modifications, but I'm concerned that stock bolt heads won't provide enough strength since 2 bolts are responsible for the load on each shroud. The existing bolts are clearly custom formed for the application and have a head that is .17" thicker than a stock bolt (stock = .313", existing = .500").
I suspect that you are right that they are chromed bronze though, but I want to make sure I get this right.

[Bowdrie]

You might contact Fair Wind Fasteners.
They don't show such a bolt in their catalog, but they might be able to point you in a good direction.
https://fairwindfasteners.com/?devic...nd%20Fasteners
Edit, check these guys out, they do far more than what thier website would suggest.
https://www.porttownsendfoundry.com/