Navtec tie rod block material

[Bowdrie]

Originally Posted by mbowser

I'm a bit limited on available area because of adjacent stanchion fittings so I can't go much larger that the footprint of the tie rod block underneath (2"x3.32").

That's ok, go as big as you can with the flange and as small as you need with the insert.
The flange could be rectangular with an oval insert.
You'll have to see what works best within the constraints of area/space, it's one of those da**nable aspects of boats we're all faced with,

[boatpoker]

Don't forget to Tef-Gel any contact point between your ss Sta-lock rigging and your new aluminum block. This will prevent future corrosion.

[mbowser]

I redesigned and 'ovalized' the G10 insert this morning and was able to come up with an arrangement that for the deck cut uses 2 cuts with a 2" hole saw centered 0.7" from either side of the chainplate center. The tangent cut between the 2 holesaw cuts can be done with an oscillating saw and shouldn't be too difficult to pull off. Even if it's a bit wonky, the 'island' flange will hide any sins and it will be epoxied in place so it won't matter.



I enlarged the corresponding 'island' to have a .5 inch overlap on the deck. I'm pretty sure I'll have room for it, but I'm 3d printing the model now to test on each chainplate location on the deck



I updated the overall assembly with the ovalized G10 insert



Once I'm sure that this slightly bigger ovalized assembly will fit, I'll be sending the files off to a CNC shop to get both the underdeck aluminum tie rod block (I need 4) and the G10 inserts machined. I'm guessing that the cost will be in the $500 neighborhood. Seems pricey, but once it's done I will never have to worry about the core turning to wet cardboard again.

[mbowser]

Thankfully, I have a 3d printer and I'm able to create full size plastic models to see if parts fit before I send it off to a machine shop and actually spend real money. I only had red PLA on hand so the models are pretty flashy .
Unfortunately, I made a mistake in the distance between the 2 bolts that go through the whole assembly, because when I printed it out, it just didn't fit. The spacing was off by .075" and it was enough to bind everything up so it didn't fit properly. I found the mistake, corrected it and reprinted. This time everything fit as it should. Catching that mistake made the 3d printer purchase last year well worth it. I ran over to the boat to see if the new ovalized design wouldn't interfere with any adjacent fittings on the deck

Everything fit great and I was able to insert the bolts through chainplate and 'island' through the existing bolt holes in the deck and everything fit flat. I fit it to all 6 chainplate with good results so I think I'm going to take the plunge and send it off to the machine shop. Unfortunately, there is a 36 business day lead time on Xometry.com, but I'm going to have to do some shopping (I'll try sendcutsend.com and others).



Next it's time to actually open up the deck and cut out the oval section. I printed a template to find the center of each circle. Hopefully, I'll get to that in the next few days and do a trial run on one of the deck locations.

[s/v Jedi]

Originally Posted by mbowser

Thankfully, I have a 3d printer and I'm able to create full size plastic models to see if parts fit before I send it off to a machine shop and actually spend real money. I only had red PLA on hand so the models are pretty flashy .
Unfortunately, I made a mistake in the distance between the 2 bolts that go through the whole assembly, because when I printed it out, it just didn't fit. The spacing was off by .075" and it was enough to bind everything up so it didn't fit properly. I found the mistake, corrected it and reprinted. This time everything fit as it should. Catching that mistake made the 3d printer purchase last year well worth it. I ran over to the boat to see if the new ovalized design wouldn't interfere with any adjacent fittings on the deck

Everything fit great and I was able to insert the bolts through chainplate and 'island' through the existing bolt holes in the deck and everything fit flat. I fit it to all 6 chainplate with good results so I think I'm going to take the plunge and send it off to the machine shop. Unfortunately, there is a 36 business day lead time on Xometry.com, but I'm going to have to do some shopping (I'll try sendcutsend.com and others).

Attachment 287752

Next it's time to actually open up the deck and cut out the oval section. I printed a template to find the center of each circle. Hopefully, I'll get to that in the next few days and do a trial run on one of the deck locations.

Attachment 287753

Have you considered making them yourself out of carbon fiber? You can use the 3D print to create the mold, then use the YouTube videos to see how they create the parts (chopped carbon fiber and epoxy pressed into the mold by weight, clamp or vacuum)

[mbowser]

I did that with my Alberg, but didn't have the 3d printer at the time so my shapes were simple rectangles. Depending on machining costs (and lead time), I may go that route, but I want to have all the costs and time constraints in front of me before I make a decision. It's certainly a viable option though.

[Coltrek]

I don't want to get in trouble with any of the posters and their good ideas, but My own opinion would be to not use Aluminum or Carbon Fiber with SS. They don't like each other. If anything, I would make it out of 316L SS. Or Bronze, which would give you a green deck. Using SS would be little difference from Aluminum, the material cost will be the least of your concerns.

[mbowser]

Originally Posted by Coltrek

I don't want to get in trouble with any of the posters and their good ideas, but My own opinion would be to not use Aluminum or Carbon Fiber with SS. They don't like each other. If anything, I would make it out of 316L SS. Or Bronze, which would give you a green deck. Using SS would be little difference from Aluminum, the material cost will be the least of your concerns.

I think you are right that SS would be the best option for the blocks, but they are about twice the price of aluminum and since they are underdeck, they shouldn't get wet (which I think, is what causes galvanic corrosion in the presence of dissimilar metals). In reality, several of these block clearly had some water leak on them and caused some corrosion over the years, but it is a 40 year old boat and it's minor considering the age. Another consideration is that a previous owner caused this water ingress problem by over-tightening the underdeck tie rods on the port side. Plus, I've ordered the aluminum block designs already (~$250 for 4).

As far as carbon fiber goes, I don't plan on using it. I don't believe G10 has any properties that could lead to galvanic corrosion when in proximity to dissimilar metals.

Speaking of G10, I decided to try a slightly different course for replacing the compressed core. I designed and had a few shops quote me on the price of machining 6 of them and it was fairly ridiculous. More expensive than aluminum and the design really isn't that complicated. So I designed a few 3d printed jigs that will allow me to do this with the tools I have on hand (jigsaw, router, drill press). I'll post some pictures once I have a few completed. If it works out I will have spent only about $100 on G10 plate instead of ~$4-500 to have them machined. We'll see.

[s/v Jedi]

Originally Posted by mbowser

I think you are right that SS would be the best option for the blocks, but they are about twice the price of aluminum and since they are underdeck, they shouldn't get wet (which I think, is what causes galvanic corrosion in the presence of dissimilar metals). In reality, several of these block clearly had some water leak on them and caused some corrosion over the years, but it is a 40 year old boat and it's minor considering the age. Another consideration is that a previous owner caused this water ingress problem by over-tightening the underdeck tie rods on the port side. Plus, I've ordered the aluminum block designs already (~$250 for 4).

As far as carbon fiber goes, I don't plan on using it. I don't believe G10 has any properties that could lead to galvanic corrosion when in proximity to dissimilar metals.

Speaking of G10, I decided to try a slightly different course for replacing the compressed core. I designed and had a few shops quote me on the price of machining 6 of them and it was fairly ridiculous. More expensive than aluminum and the design really isn't that complicated. So I designed a few 3d printed jigs that will allow me to do this with the tools I have on hand (jigsaw, router, drill press). I'll post some pictures once I have a few completed. If it works out I will have spent only about $100 on G10 plate instead of ~$4-500 to have them machined. We'll see.

How did I never think of 3D printing patterns for the router…

[mbowser]

Originally Posted by s/v Jedi

How did I never think of 3D printing patterns for the router…

Exactly! I was laying in bed the other night and realized that I was WAY overthinking it and could do the G10 inserts in 2 pieces epoxied together. The first jig I made was for the top part of the assembly. I bought a piece of 12x12x.25" G10 to see if I could do a reasonable job with the top part (labeled 1 in photo). It showed up last night and I cut out the rough parts and tapped the holes. The hole locations are really the only important part of all the pieces and allow to locate the assembly together so I made sure those were good to 1/100"


I printed a 2 part 'sandwich' jig so the top and bottom bearings on the carbide bit would ride on it and screwed it down to a piece of plywood. Next time I'd do it with ABS, but PLA certainly works for small scale production like this. I made a PLA/G10 sandwich and screwed it all together and fired up the router. It took about 30 minutes to route out all 6 tops. Next I can use the bottom of the existing jig to run the roundover bit, but will have to do that this evening.

Here's what I have so far:

[mbowser]

I couldn't find a newish roundover bit in my pile of router bits, so I ran over to the hardware store and bought the cheapest .25" carbide roundover bit I could find. Part 2 of my jig allowed me to stabilize the piece while cutting off the edges.




I'm pretty happy with the result and only out about $50 instead of ~$4-500 if I had a machinist make it. The left/red is the PLA, the yellow is the finished piece.

Now I need to do part 2, but have to accurately determine the depth of the deck (minus bottom skin) so I can order another piece of G10. I think it will be in the 3/8-1/2" range.

[Mike Burch]

Originally Posted by Coltrek

I don't want to get in trouble with any of the posters and their good ideas, but My own opinion would be to not use Aluminum or Carbon Fiber with SS. They don't like each other. If anything, I would make it out of 316L SS. Or Bronze, which would give you a green deck. Using SS would be little difference from Aluminum, the material cost will be the least of your concerns.

I second this. 316 is expensive, but as Coltrek points out, the material cost is the least of your worries, and the weight difference is unimportant. Forget bronze, and don't even think of carbon fibre. Even the smallest machine shop will be able to mill you a bit of 316, and it will take them little longer than doing it in 6061 or whatever.

The fact is that aluminium has let you down. Why give it a second chance?

[Ken Goodings]

[QUOTE=mbowser;3879993]I'm in the process of rebuilding a 1986 Niagara 35 and I'm replacing all the above deck rod rigging (probably original) with wire and Sta-Lok fittings, but plan on keeping the underdeck tie rod assembly intact. They are in good condition except for the aluminum tie rod blocks that tie the underdeck cold headed rod to the deck mounted chainplate.

I'm surprised. Our 1979 Niagara 35 Classic had the NAVTEK rod turnbuckles pinned above deck to heavy aluminum chain plates which were bolted to glassed in plywood knees under the deck.
We resigned completely in 2005 with 5/16" wire and StaLoc fittings turnbuckles which are compatible with metric 8mm StayLoc wire and inserts.

[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

[mbowser]

[QUOTE=Ken Goodings;3883084]

Originally Posted by mbowser

I'm in the process of rebuilding a 1986 Niagara 35 and I'm replacing all the above deck rod rigging (probably original) with wire and Sta-Lok fittings, but plan on keeping the underdeck tie rod assembly intact. They are in good condition except for the aluminum tie rod blocks that tie the underdeck cold headed rod to the deck mounted chainplate.

I'm surprised. Our 1979 Niagara 35 Classic had the NAVTEK rod turnbuckles pinned above deck to heavy aluminum chain plates which were bolted to glassed in plywood knees under the deck.
We resigned completely in 2005 with 5/16" wire and StaLoc fittings turnbuckles which are compatible with metric 8mm StayLoc wire and inserts.

Hi Ken, I wonder if the interior structures in the Classic model allow for 'normal' chainplates to be directly bolted to bulkheads. I've never been aboard a Classic version, but I was aboard another Encore version and it had the same tie rod assemblies that mine has. The back stay does have a standard chainplate (aluminum) bolted to a frame on the transom behind the propane locker.