F&C 44': 30yr STERN TUBE replacement: Advice?

[PUDDLE JUMPER II]

Originally Posted by Jim Cate

^^^^

An excellent summary of the facts. Skip, I think you should pay attention to this one!

Jim

Understood, agreed...

[Rumrace]

DuPont plastics dealer would know tubes in stock. To melt the polyester bond would ignite the fibreglass. Burns real good too.
Lining up a new tube is going to be challenging. I’d do a shout out for sure. The difference between adding nylon vs fibreglass is massive. The nylon from DuPont is not actually nylon. It’s a product which didn’t compromise nylons patent and it’s a way better product. It has carbon fibre content with connected strands. For fun I priced out the PC to make your tube and it’s $23.00 so 3X the cost of polyester.

[pcmm]

I replaced my stern tube a few years ago when the old one stopped being adhered to the stern post. The original one was fiberglass I suspect made by Morgan as it was just made with cloth and had many dry spots in it. I replaced it with a tube of filament wound glass and epoxy from a company on the west coast called "Litek composites". Its a bit of a job as I had to cut out the forwad bulkhead that supported the stern tube (mine was 22 inches long with a cutless on one end and stuffing box on the other). replace that bulkhead and all the foam that filled a cavity behind.

Getting the tube aligned was actually pretty easy. I partially installed the old cutless about half way ( after having a friend skim it on a lathe to make it slightly less of a friction fit in the tube) and on the end where the stuffing box goes, I inserted dowels all around the prop shaft. I was lucky in my case. Prop was 1-1/4" and the ID of the tube was 2" so I was able to use sections of 3/8" dowel all around the prop shaft to get it centered in the tube. Once the Tube was epoxied & glassed in place I removed everything, installed a new cutless bearing, the stuffing box and slid the prop shaft back in place. filled the cavity, faired and glassed over all of it and it was better than factory!!!

all in all it was a month of weekends to demo and replace. All of this was done in the bowels of a full keel!!! I hope to never again have to do that job!!

[ItDepends]

Originally Posted by Rumrace

DuPont plastics dealer would know tubes in stock. To melt the polyester bond would ignite the fibreglass. Burns real good too.
Lining up a new tube is going to be challenging. I’d do a shout out for sure. The difference between adding nylon vs fibreglass is massive. The nylon from DuPont is not actually nylon. It’s a product which didn’t compromise nylons patent and it’s a way better product. It has carbon fibre content with connected strands. For fun I priced out the PC to make your tube and it’s $23.00 so 3X the cost of polyester.

I am highly confused why Dupont would worry about compromising the nylon patent for a couple reasons. Nylon was invented in the 1930's and is LONG out of patent. Second, DuPont actually INVENTED nylon and owned the original patent. So what ARE you talking about here???

If you are talking about nylon that "is not nylon" what product ARE you talking about??? A link maybe?

And if this is a carbon fiber product, you are aware that carbon is the MOST noble material you could possibly use and you would be putting every other piece of metal in the drive train at risk of accelerated corrosion when immersed in saltwater? This is exactly the reason that graphite packing is never recommended for saltwater propshaft use.

[Rumrace]

Great stuff pcmm. Good info thanks

[pcmm]

Originally Posted by Rumrace

Great stuff pcmm. Good info thanks

I documented the process here:

https://www.nevermonday.ca/2020/03/i...rip-stern.html

[Rumrace]

Sure sorry. Nylon 6/6 Tubing, Zytel 42 Dupont, Straight Tubing

It’s just a dealer list of tubes in PA-6

[Rumrace]

As to the ugly history of nylon and it’s imitators it’s a good read. DuPont butters it up nice. Read DuPonts article on PA6 evolving to PA-66, 12 and now 11. 11 is very new super strong $120.00 a kilo

[boatpoker]

Originally Posted by Rumrace

As to the ugly history of nylon and it’s imitators it’s a good read. DuPont butters it up nice. Read DuPonts article on PA6 evolving to PA-66, 12 and now 11. 11 is very new super strong $120.00 a kilo

So its saturation point is more than three times higher than polyester in salt water but shows testing only in fresh water. What effect is that saturation on strength and susceptibility to hydrolysis. When will they test in salt water or is that a scenario they don't envisage.

[ItDepends]

Originally Posted by Rumrace

Sure sorry. Nylon 6/6 Tubing, Zytel 42 Dupont, Straight Tubing

It’s just a dealer list of tubes in PA-6

You seem to know nothing about what you write. Those tubes have no carbon in them whatsoever, and are totally inappropriate as stern tubes. They are not sold as such, and should NEVER be used as stern tubes. They can not be glassed in and the dimensions are inappropriate.

Please, only give advice on topics you know and understand.

[PUDDLE JUMPER II]

Originally Posted by pcmm

I documented the process here:



https://www.nevermonday.ca/2020/03/i...rip-stern.html

Great project post!! Bravo... As you can see we are doing the same BS on my boat, digging out the SS shaft log is a lot of digging.

Side note-- are you familiar with the variations of G10 material out there? I am starting to research this before I buy the pipe. I wondered if you knew anything that might be helpful since you completed your project over 6 years ago....

[Rumrace]

Actually its the fact checkers that confuse themselves. PA-11 has Carbon Fibre content. PA12- Poly Carbon. They are hybrid nylons acquisitions of DuPont
It’s not plumbing pipe from Home Depot so it’s got ya stumped.
All plastic can absorb moisture before it’s cured cast or printed. We run the plastic in dryers before use.

[Rumrace]

Google harder lads

[boatpoker]

Originally Posted by Rumrace

Actually its the fact checkers that confuse themselves. PA-11 has Carbon Fibre content. PA12- Poly Carbon. They are hybrid nylons acquisitions of DuPont
It’s not plumbing pipe from Home Depot so it’s got ya stumped.
All plastic can absorb moisture before it’s cured cast or printed. We run the plastic in dryers before use.

I know its' your practice to leave questions unanswered but I'd really like an answer to post #24

[skipperpete]

Vetus also supplies stern tubes in a variety of sizes and either GRP or the more traditional and replaceable bronze ( with threaded end caps)