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Old 18-12-2016, 09:14   #16
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Re: Non-standard stern tube and cutlass bearing

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I just had a crazy Idea.. OK I have many I know.

1-1/4" CPVC tube, available everywhere has a 1.125 ID (exactly what I need) and 1.375 OD. If I add 0.02 ss shim stock (available from granger) around a 6" long section of cpvc tube it works out to a 1.415 od again just about perfect.

I could even get a slightly thinner shim stock and epoxy it to the CPVC (maybe not sure how well it would stick). So for about $30 in parts I could make about 5-6 cutlass bearings. I would need to hacksaw cut some short water grooves in the tube.

CPVC is 7500 psi tensile strength compared to nylons 10,000 psi. CPVC has same compression strength to nylon. Pretty sure the old bearing was Nylon.

I could roll my own plastic cutlass bearing for not too much money.

Please tell me why this would not work???
This sounds like something I would think of. I love crazy ideas!

My concern with cpvc would be primarily it's abrasion resistance and then it's brittleness.

I can't figure out how to copy links on my phone but if you google taberabrasion tester you'll see that cpvc wears about 4 times faster than nylon (in that test) and would probably significantly reduce the amount of time between needing to replace the bearing.

That may or may not be an issue depending on how often you can or wish to change the bearing. Obviously you've made sourcing and cost of the part meaningless. The labor and expense to replace the part becomes more of an issue though.
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Old 18-12-2016, 09:32   #17
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Re: Non-standard stern tube and cutlass bearing

+1 for visconite. they will make whatever you need, and cheap enough to get some spares at the same time. since im a new build i was able to size stern and rudder tubes (G10) the same with identical shafts so ordered-up 6 bearings all the same for $350 total. so ive got custom bearings of proven material and a set of spares. sweet deal i thought.
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Old 18-12-2016, 10:11   #18
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Re: Non-standard stern tube and cutlass bearing

I'm wondering if it's possible to turn down the shaft diameter to 1" over the portions of it's length where it meets the bearings & such, but leave it as is where the prop is attached, & at the transmission, etc. That way you can go with more off the shelf bearings, but still retain your current prop. Although if you switch to a 1" shaft, you shouldn't have any issues finding props ranging in price anywhere from cheap to free.
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Old 18-12-2016, 16:10   #19
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Re: Non-standard stern tube and cutlass bearing

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I'm wondering if it's possible to turn down the shaft diameter to 1" over the portions of it's length where it meets the bearings & such, but leave it as is where the prop is attached, & at the transmission, etc. That way you can go with more off the shelf bearings, but still retain your current prop. Although if you switch to a 1" shaft, you shouldn't have any issues finding props ranging in price anywhere from cheap to free.
Unciv, maybe I'm misunderstanding, but how would she slide either end of t he shaft through the smaller bearing ?

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Old 18-12-2016, 17:36   #20
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Re: Non-standard stern tube and cutlass bearing

sc, that is a pain. The folks had all the nominal bearing sizes around when they built the boat. Strange they would go for something oddball.
Trying to wrap my head around the dimension.. you have a s.s tube 1.5" x .043" wall. This goes right thru to the inside? to a traditional packing gland? pretty skinny wall. If thats not the case then;
(I'm sure you looked close but) My first thought is that tube is remnants of an old bearing. Sure would be nice to get that hole to accept a Johnson/duramax beam bearing.
ce
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Old 18-12-2016, 18:18   #21
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Re: Non-standard stern tube and cutlass bearing

It might work, which, given the effort that replacing the bearing entails, is actually a strike against it. CPVC is very brittle and will melt readily under friction. Given the relatively close tolerances dictated by a .125 wall thickness (even less if you allow for clearance in the bore), the water grooves are likely to weaken the plastic enough to induce cracks very quickly.

Due to nylons notorious absorption of water, it's not very likely that it was used for a cutlass bearing.

There are many sources for small quantities of proper engineering plastics., in this case delrin comes to mind. A one foot piece of 1.375" OD rod can be had from these people for 7.00.

1.375" dia. Black Acetal Rod

That would leave you to find someone to drill it to the proper dimension, and the problem of securing the rather slippery delrin in the stern tube...

Best of all would be to find a piece of Vesconite, surely someone has some somewhere near you. For instance I have a 2 foot piece here, but it is unfortunately 65 x35mm (2 5/8"x 1 5/16")...
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Old 18-12-2016, 18:23   #22
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Re: Non-standard stern tube and cutlass bearing

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sc, that is a pain. The folks had all the nominal bearing sizes around when they built the boat. Strange they would go for something oddball.
Trying to wrap my head around the dimension.. you have a s.s tube 1.5" x .043" wall. This goes right thru to the inside? to a traditional packing gland? pretty skinny wall. If thats not the case then;
(I'm sure you looked close but) My first thought is that tube is remnants of an old bearing. Sure would be nice to get that hole to accept a Johnson/duramax beam bearing.
ce
From what I remember the actual wall thickness was not that skinny. It could be 1-5/8" tube. Count no measure outside dia as it's flush with hull glass.

The SS tube goes straight through, I shined a light up it. It's only 24" ish long. Plus I had Cree the manager at Berkeley Marine center look at it too. The tube is not light weight and appeared to be glassed in the hull. My guess is somebody shipped the wrong tube to wayfairer way back when.
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Old 18-12-2016, 18:29   #23
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Re: Non-standard stern tube and cutlass bearing

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+1 for visconite. they will make whatever you need, and cheap enough to get some spares at the same time. since im a new build i was able to size stern and rudder tubes (G10) the same with identical shafts so ordered-up 6 bearings all the same for $350 total. so ive got custom bearings of proven material and a set of spares. sweet deal i thought.
I will give a call to visconite later this year. I emailed them back in 2009 but they could not get it too me in time and then I found the 1-1/2" bearing that I had turned down.

I was hoping that someone would say that "Bubba's cutlass bearing supply" has that size in stock. I can dream.

I suspect CPVC is a bit soft but with an average velocity of 4.4 fps for the prop shaft, it's might not be so bad. I suspect CPVC would be similar to the rubber bearing surface wear wise.
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Old 18-12-2016, 18:36   #24
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Re: Non-standard stern tube and cutlass bearing

sc, that makes more sense, probably 1 1/2" sch 40, that was nice of them...
Have you given Duramax a call/email, they have been excellent over the years. May have a good / inexpensive solution.
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Old 18-12-2016, 18:40   #25
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Re: Non-standard stern tube and cutlass bearing

vesconite has a calculator on their page you can use to request a quote - easy as can be. its harder to get someone on the phone as there in so africa...
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Old 19-12-2016, 04:13   #26
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Wink Re: Non-standard stern tube and cutlass bearing

Can't help with your main problem but maybe your problem why it wears out so quickly is that there is air trapped in the bearing. I used to have to replace my cutless bearing every six months, I had all kind of reasons from engieers why but no solutions. I changes my seal on the propeller shaft and bought Duramax Cutless bearings, problem solved. I now bleed the seal once a week to ensure no air
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