35-3 New Strut [Master Thread]

trickdhat

Sustaining Member
Blogs Author
The haul out was going too well... The keel joint hasn't shown a drop of seepage, the blisters are better than I thought they were going to be, the rudder seems solid, and the engine removal went well. Even the shaft looks good and we're going to shorten it to clean up the gap between the strut and the prop. Then we found this:
20221003_180339.jpg

40 years of sitting without a galvanic isolator has finally caught up to the boat beyond replacing zincs every 6 months. I've since added one, but obviously the damage has already been done.

On the optimistic side, this gives me an excuse to completely clear out the engine compartment all the way back to the rudder post and I won't have to decide on an arbitrary point where to stop the cleanup as the yard will need assess to the top of the strut.

I've started to call around for advise on a replacement. Here's what I've found so far:

Marine Hardware - $1,200 (Down from $1,600 just for me this one time according to Ron). They claim to have the original specs they will cast it from. It will take 10-12 weeks. There's a chance the will have one off the shelf, but it's a slim shot. their foundry is in Michigan and they finish the part in Redmond.

Monel Foundry Arlington - apx. $1,200, but they were non committal on an estimate until they see the original part. They plan on using the original strut as a mold by adding filler to the par to account for shrinkage (insert pool joke here). about 4 weeks. I'm in Everett so this would be the most accessible

Port Townsend Foundry - $1,200. They plan on using the original to measure and using an existing mold that's right on or close. They said they do not have any on hand.

Has any other 35-3 owners had to replace their strut?

@Prairie Schooner has a great post on rebedding his https://ericsonyachts.org/ie/thread...inside-and-a-zinc-question.19649/#post-153865,
@NW26 has a good post as well https://ericsonyachts.org/ie/threads/26’-3-prop-shaft-strut.20031/#post-157973,
and @bigd14 has a fantastic blog about replacing one on his 30+ https://ericsonyachts.org/ie/ubs/blog/bigd14s-blog.3493/
 

Prairie Schooner

Jeff & Donna, new owners 7/21
. . . .
40 years of sitting without a galvanic isolator has finally caught up to the boat beyond replacing zincs every 6 months. I've since added one, but obviously the damage has already been done.
. . . . .
Can O Worms  2 sm2.gif I feel your pain, Nick. Good news, *goofy metaphor alert* there is light at the end of the stern tube.
I have a bunch of photos if you think any of those will be of help. I always wonder what's inside when I start a project.
Good luck,
Jeff
 

bigd14

Contributing Partner
Blogs Author
Bummer! The good news is you have the engine out and are already deep into the aft end. Getting to that point is half the battle. Good luck with the rest of it.
 

Pete the Cat

Member III
I went through this same thing 25 years ago with my Tartan. The boat was only 10 years old but had in a bad electrical environment and the strut was pink. Here is a great plus for replacement now:: When you get the strut back and have the engine in place, you can position the strut in some wet, thickened epoxy and get the alignment perfectly down the center of the strut and down tube. I believe this is the way the factory set the strut. Takes a lot of fiddling out of the process. There is another thread on this process here somewhere.
 

trickdhat

Sustaining Member
Blogs Author
(originaly posted to the wrong thread)

The yard got the strut out today. They used a hole saw to hog out most of the material. It looks like it went well. I was a little late to catch them before they went home so I'll have to follow up tomorrow to see the actual strut.
 

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bigd14

Contributing Partner
Blogs Author
A hole saw! Brilliant! Why didn't I think of that? I used a grinder and I'm still finding sediment layers in out of the way places.
 

Pete the Cat

Member III
(originaly posted to the wrong thread)

The yard got the strut out today. They used a hole saw to hog out most of the material. It looks like it went well. I was a little late to catch them before they went home so I'll have to follow up tomorrow to see the actual strut.
Looks like they used a hole saw to get in and then a Sawzall to do most of the work. How thick is the hull at that point? And is it lays of laminate? or just splooge and filler?
 

trickdhat

Sustaining Member
Blogs Author
Update:

I picked up the strut yesterday and had a good conversation with the yard. I thought the strut was initially installed with the bots used to level and align before glassing over from the top. However, each bold hole was filled with bedding compound indicating none of the bolts ever protruded past the base of the flange. The yard thinks the bolts functioned more like rebar in a concrete structure.

20221007_123917.jpg
I quickly turned around to make the ferry to Kingston so I could make it to the Port Townsend Foundry before they closed. The owners, Pete and Kathy Langley, were extremely friendly and helpful. We spent some time looking for a suitable replacement molds and ended up with this one:
20221007_142108.jpg

The angles are a bit off, but Pete noticed the line indicating where the strut exited the hull was not parallel with the flange. He said it's common in this kind of application and indicated the strut was not a great fit to begin with. That's the advantage of bedding the strut from the top. It allows for more variance that can be fixed with the bedding compound. The mold we chose should line up better with the lines of the hull. It will require more grinding to level the bed and I'll have to have that conversation with the yard next week.

When I asked about replicating the existing strut, he said it was possible but it would be about $1,000 more in labor to create a new mold. He didn't see the advantage and advised against it. The new strut should be more hydrodynamic, has a larger flange for a more secure installation, and has more material around the cutlass.

A few other things he mentioned was that the strut would be sufficient for a much larger HP engine. We found a few other molds with a smaller web and shorter bearing surface. I wanted to keep it as close as possible so we steered away from those. He also mentioned that the length of the bearing housing was longer than standard and would require using two cutlass bearings cut down to fit. I hadn't heard this anywhere, so I was a bit surprised.

They should be doing the pour late next week or early the following week depending on how many other projects come in over the next few days. When I asked Kathy when the pour would be, she smiled and asked if I was asking to see the pour. Both her and Pete were exited to hear I was interested and said they would give me a few days notice. I'm not sure if it's going to work with my schedule, but if I can make it work I will!

Pete spent the next 1/2 hr showing me around the shop. I could have spend days looking through everything and picking the brains of everyone there. Here's some pics:

Raw material:
20221007_142836.jpg

Mold storage:
20221007_143052.jpg

Parts waiting for final machining:
20221007_143305.jpg

The winning 6M boat of the 1936 Olympic Games:
20221007_143410.jpg

A masthead fitting for an 89' mast. The boat is currently in route to Port Townsend under a jury rig to save on shipping expense of the large spar. The Piece in the foreground is a bow roller assembly for an Ingred 38.20221007_143613.jpg
 

Christian Williams

E381 - Los Angeles
Senior Moderator
Blogs Author
Port Townsend Foundry in action:

 

Prairie Schooner

Jeff & Donna, new owners 7/21
I picked up the strut yesterday and had a good conversation with the yard. I thought the strut was initially installed with the bots used to level and align before glassing over from the top. However, each bold hole was filled with bedding compound indicating none of the bolts ever protruded past the base of the flange. The yard thinks the bolts functioned more like rebar in a concrete structure. *1
. . .
When I asked about replicating the existing strut, he said it was possible but it would be about $1,000 more in labor to create a new mold. *2 He didn't see the advantage and advised against it. The new strut should be more hydrodynamic, has a larger flange for a more secure installation, and has more material around the cutlass.
. . . .
Pete spent the next 1/2 hr showing me around the shop. I could have spend days looking through everything and picking the brains of everyone there. Here's some pics: *3
. . . .
*1- This is in line with what I discovered during our strut project.
*2- In my experience I'd call this the pattern, or model. I'd say the mold is the negative cavity created from the pattern to be cast into. For bronze, the mold would typically be sand or ceramic shell.
*3- I love looking around workshops. Thanks for sharing the tour!! Move heaven and hell to be there for a bronze pour. Very dramatic!
 

trickdhat

Sustaining Member
Blogs Author
*1- This is in line with what I discovered during our strut project.
*2- In my experience I'd call this the pattern, or model. I'd say the mold is the negative cavity created from the pattern to be cast into. For bronze, the mold would typically be sand or ceramic shell.
*3- I love looking around workshops. Thanks for sharing the tour!! Move heaven and hell to be there for a bronze pour. Very dramatic!
I think it's a mold pattern or plug, but they called them molds so I went with it.

It's a very cool process and I'm going to try to make it work. There's a good possibility the pour will fall on one day where my wife is out of town and my work isn't too flexible. The number one priority is getting the strut back in the boat so we can get the boat back in the water. I can always visit another time to see another pour or, like Christian posted, there's a few YouTube videos out there of the foundry doing their thing.

On my way back from the foundry I started thinking about other possibilities including purchasing an off-the-shelf strut from Catalina Direct or Buck Algonquin. I'll measure the strut today and post what I find so others have the option of going that route. For me, the excuse to make a trip to Port Townsend and work with the foundry is too cool to pass up.
 

trickdhat

Sustaining Member
Blogs Author
Here's the measurements from the old strut:
 

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Prairie Schooner

Jeff & Donna, new owners 7/21
I think it's a mold pattern or plug, but they called them molds so I went with it.

It's a very cool process and I'm going to try to make it work. There's a good possibility the pour will fall on one day where my wife is out of town and my work isn't too flexible. The number one priority is getting the strut back in the boat so we can get the boat back in the water. I can always visit another time to see another pour or, like Christian posted, there's a few YouTube videos out there of the foundry doing their thing.

On my way back from the foundry I started thinking about other possibilities including purchasing an off-the-shelf strut from Catalina Direct or Buck Algonquin. I'll measure the strut today and post what I find so others have the option of going that route. For me, the excuse to make a trip to Port Townsend and work with the foundry is too cool to pass up.
Yeah, I'm just being a pedantic twit. Though after being a product designer and model maker for forty years I've developed some strong opinions. As we find in sailing, people use terminology differently. Hard to argue with folks running their own foundry. Though, I'd probably try to engage them in a friendly discussion about it. Did I mention that I can be a pedantic twit?

If the prices for the new casting and off-the-shelf are close enough, I might go with the foundry, just because I like to see those places stay in business, which has nothing to do with what's best for your boat or wallet. By the way, $1000 for a new pattern/mold isn't bad. But, in your situation, I'd likely go with the pattern they already have. You're going to be rebuilding that section of the hull anyway and can tailor it to the new strut.

Thanks for posting in such detail, Nick. I'm learning and enjoying it.
Jeff
 

trickdhat

Sustaining Member
Blogs Author
Sounds like we're of similar minds Jeff. Marine Hardware in Redmon have the original design, but they are the same price and quoted a 10-12 week lead time which made the decision easy. Even if port Townsend was more expensive and had lengthy lead time, I still would have gone with them for all the reasons you mentioned above... I'll try to keep up the the progress as much as I can.
 

trickdhat

Sustaining Member
Blogs Author
Out of pure curiosity I took the grinder to the old strut to see how deep the dezincification had gone. I have no idea how much is too much, but out of self preservation I'm going to tell myself this isn't good. particularly the gauges left from extracting the strut have pink at the bottom and the entire cutlass shaft is pink.

20221016_122318.jpg
20221016_122328.jpg

If I didn't have any skin in the game (ie, didn't just place an order for a $1,200 replacement and an unknown cost of install) I might be more inclined to think this was just sacrificial damage.
 

Christian Williams

E381 - Los Angeles
Senior Moderator
Blogs Author
Despite paying attention more or less over the years I still know less than enough about this stuff.

Bronze has no zinc in it (it has tin) , so how can dezincification occur? Brass, yes

Yet we put sacrificial zinc anodes on the strut and prop shaft?.

We have metallurgists here, or at least informed persons. Eh? Or shall I just keep doing this out of faith.
 

trickdhat

Sustaining Member
Blogs Author
Despite paying attention more or less over the years I still know less than enough about this stuff.

Bronze has no zinc in it (it has tin) , so how can dezincification occur? Brass, yes

Yet we put sacrificial zinc anodes on the strut and prop shaft?.

We have metallurgists here, or at least informed persons. Eh? Or shall I just keep doing this out of faith.
This is really interesting. I've always heard bolts, props, and struts turning pink referred to as dezincification. I had no idea that bronze didn't contain zinc. A quick google search reveals I have no excuse for this misunderstanding. Sounds like a good question to ask the foundry.
 

Prairie Schooner

Jeff & Donna, new owners 7/21
Maybe we are lead astray by using 'dezincification' too broadly. Would a more useful general term be 'galvanic corrosion'?
There are many alloys of bronze, with copper as a base. The copper/tin is around 88/12, I think. Tin is more noble than copper.
I think of a silicon bronze as being more common in marine environments. Nick, it would be interesting to know what alloy the foundry uses for yours.


Speaking of copper -
two cents 03.jpg
 

bigd14

Contributing Partner
Blogs Author
I might be more inclined to think this was just sacrificial damage.
And you might be correct- right up to the point when it fails! I think its the right call. And by doing so you are able to address all the other problems hidden in the stern area and won't have to worry about it for many years.
 

trickdhat

Sustaining Member
Blogs Author
I remember Pete saying they make the strut and propellers out of a more workable bronze so the strut can be straightened if bent and the prop can be repitched. It looks like most propellers and struts are made out of Manganese Aluminum Bronze which actually isn't bronze because it contains a large amount of zinc. I wonder if this is the material our struts are made of and why they are susceptible to dezincification. I'll specifically ask the foundry about this next time we talk
 
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