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

[PUDDLE JUMPER II]

So my 30+ year old stern tube is rusted at the bilge end...and Lord only knows what is inside marring the shaft. Since I am getting a new shaft, cutless, and prop-- I thought it would behoove us to go the extra 'optional mile'-- and cut her out.

Two points of reference:

1) I am beginning to research stern tubes-- should they have a bearing inside them like the cutlass? My stern stube is 13"

2) My Stern tube is fiberglassed into the hull-- i am dying digging this out of the hull and the damage I am doing 'necessarily' / 'proactively'?? Am i nutso?

All this said-- what type of long term Stern Tube should i considering using for this next 30 years?

3) What are some best practices in considering this endeavor? I found this article helpful but only scratched the surface of the subject...
https://citimarinestore.com/citiguid...omplete-guide/


Appreciate any articles or insight you might have to offer as I embark on a new level of refit onboard...

Cheers,

Skipper T

[skipperpete]

A 13 inch long sterntube is heartening, that short length allows all sorts of mechanical intervention, you could make a few long stemmed burrs or flap wheels to grind the tube inner diameter to a point where it’s thin enough to collapse it and break the resin bond.....It certainly needed replacing. If you damage the Grp around the tube while trying to extract it, consider using “Chockfast orange” pourable epoxy compound to fill the void around the stern tube and lock the tube in place at re assembly... permanently.
I’m not fond of having a bearing on the inboard end of the stern tube, especially if the distance from the stern gland to the gearbox flange is short. There should be one at the outboard end of the tube and one in the P bracket.
Finally, chockfast needs a bit of pre planning before you get to actually pouring it, the mix can go off remarkably quickly and the manufacturer “Epirez” can help with cure speed control suggestions.

[Fore and Aft]

Puddle Jumper I have a fiberglass tube with a cutlass bearing in one end and PSS seal at the other end. Cutlass bearings can be machined to any external diameter and PSS seals come in a variety of stern tube sizes. An easy job and a good improvement in my opinion.
I wonder if you could heat that stern tube up with a heat gun then rotate it with a pipe wrench. All you have to do is break the resin bond on the tube then you can drive it out with a hammer.
Cheers

[PUDDLE JUMPER II]

Originally Posted by Fore and Aft

Puddle Jumper I have a fiberglass tube with a cutlass bearing in one end and PSS seal at the other end. Cutlass bearings can be machined to any external diameter and PSS seals come in a variety of stern tube sizes. An easy job and a good improvement in my opinion.
I wonder if you could heat that stern tube up with a heat gun then rotate it with a pipe wrench. All you have to do is break the resin bond on the tube then you can drive it out with a hammer.
Cheers

I am not aware that heating the old SS Stern tube will break the bond-- is this a statement or a question?

I certainly LOVE the idea and beats digging any more precious FRG away from my original hull...

[PUDDLE JUMPER II]

Originally Posted by Fore and Aft

I have a fiberglass tube".

FRG tube or g10 tube? Where did you purchase?

[fourlyons]

Originally Posted by PUDDLE JUMPER II

FRG tube or g10 tube? Where did you purchase?

Any decent marine retailer will sell fiberglass tube designed for this, I bought from Fisheries Supply in Seattle. Here is a link,
https://www.fisheriessupply.com/cent...r-post-housing

[Fore and Aft]

Puddle Jumper 2, I sometimes clean my spatulas with a heat gun and it's amazing how quickly a bit of heat causes the epoxy filler to peel of the spatula. I was thinking the same thing with your stern tube. With a bit of heat and some leverage from a pipe wrench you might just break the bond of the resin. Then it's just a matter of driving it out with a hammer........Those electric heat guns work surprisingly well. I am trying to rack my brain if I have ever done something similar in my boat building career.
Fourlyons is right, a quick google shows plenty of glass tube suppliers around. I made mine using a piece of PVC pipe as a mold. I did this as I had plenty of old glasss and resin to use up.
Cheers

[PUDDLE JUMPER II]

I guess the question is why German Frers decided to use Stainless Steel for the Stern Tube... why metal? I am not a navel architect or navel engineer--- I am curious about what the long term effect would be going with G10? Why is this important? if this ever needs to come out of the boat--- it will have to be drilled out--as once this is epoxied in place, it becomes an extension of the HULL... Not so unlike the Stainless Steel tube I am dealing with now... lol... But at least there MIGHT be a chance to break the bond between the materials. With an FRG or G10 Pipe i am looking at online everywhere--- this effort would be futile.

Real question---- How much clearance should there be between shaft and Stern-Tube wall?

[PUDDLE JUMPER II]

Real question---- How much clearance should there be between shaft and stern-tube wall?

I'll need to figure this out if and when I get my stern tube out-- and old shaft back from the shop that is making me a new one...

As for stern tube material-- what are your thoughts regarding Vesconite material vs G10 piping material?

Non Metallic Rudder, Stern Tube & Pump Bushings | Products | M.S. Marine & Offshore | Obliged to Tradition, Committed to Innovation

[Rumrace]

I suggest you don’t touch the glass rather grind it out from the interior. My choice would have been a nylon like PA6 or PA12. Both stronger rust proof self lubricanting, deaden vibrations, chemical, salt, fuel proof. Two piece
There is a grinding auger you can rent which you can expand the diameter. If you could clamp a drill either end you can clear out the decayed metal which likely ruined the previous shaft.

[PUDDLE JUMPER II]

@Rumrace... I am googling this type of Nylon now and trying to understanding how it would behave submersed for 20 years... Thanks for the tip!

What do you think of Vesconite? Non Metallic Rudder, Stern Tube & Pump Bushings | Products | M.S. Marine & Offshore | Obliged to Tradition, Committed to Innovation

[boatpoker]

Is this where you want to be a guinea pig ?
FRP stern tubes have been around for 50yrs and after thousands of surveys I've never seen one fail.

[ItDepends]

Originally Posted by PUDDLE JUMPER II

So my 30+ year old stern tube is rusted at the bilge end...and Lord only knows what is inside marring the shaft. Since I am getting a new shaft, cutless, and prop-- I thought it would behoove us to go the extra 'optional mile'-- and cut her out.

Two points of reference:

1) I am beginning to research stern tubes-- should they have a bearing inside them like the cutlass? My stern stube is 13"

2) My Stern tube is fiberglassed into the hull-- i am dying digging this out of the hull and the damage I am doing 'necessarily' / 'proactively'?? Am i nutso?

All this said-- what type of long term Stern Tube should i considering using for this next 30 years?

3) What are some best practices in considering this endeavor? I found this article helpful but only scratched the surface of the subject...
https://citimarinestore.com/citiguid...omplete-guide/


Appreciate any articles or insight you might have to offer as I embark on a new level of refit onboard...

Cheers,

Skipper T
Attachment 266318Attachment 266319

K, Let's start with, "Does this need to be fixed?" YES!!!!!!! YES!!!!! YES!!!!!! This is a boat-sinking problem. Seriously

Now, does the stern tube need a cutlass bearing? Maybe... Depends on the design of your boat. I believe your boat has an external strut supporting the propshaft. In this case normally, no. the only cutlass bearing would be in the strut. But... if the shaft unsupported lengths are long, that might change. No way to know without measurements, shaft sizes, materials, etc, etc. If there IS going to be a cutlass bearing in the stern tube, that makes the alignment of the stern tube with the strut critical.

What to make the stern tube out of? FRP. Period. Stern tube material in the exact sizes for you shaft, packing gland, and (if needed) cutlass bearing are available from any decent marine supply. There is no other proper choice for this case. Nylon can not be glassed to reliably, and does not have the required mechanical strength, and changes size when it is in water. Who CARES about it being "self lubricating"? The shaft should NEVER touch it!!!! Just NO.

If your shaft is scored from rubbing against the existing stern tube, that would indicate a SERIOUS alignment issue that needs to be fixed.

This is a difficult job for a beginner to be 100% sure the engine, sterntube and strut are all in perfect alignment. There are a lot of details to this. I would strongly encourage you to, at the very least, hire somebody who is experienced with this to give you eyes-on advice.

If you get this wrong, it will lead to no end of problems. Everything from failing transmission bearings and seals, to packing gland leaks, to catastrophic flooding.

[Jim Cate]

^^^^

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

Jim

[PUDDLE JUMPER II]

Originally Posted by ItDepends

K, Let's start with, "Does this need to be fixed?" YES!!!!!!! YES!!!!! YES!!!!!! This is a boat-sinking problem. Seriously



Now, does the stern tube need a cutlass bearing? Maybe... Depends on the design of your boat. I believe your boat has an external strut supporting the propshaft. In this case normally, no. the only cutlass bearing would be in the strut. But... if the shaft unsupported lengths are long, that might change. No way to know without measurements, shaft sizes, materials, etc, etc. If there IS going to be a cutlass bearing in the stern tube, that makes the alignment of the stern tube with the strut critical.



What to make the stern tube out of? FRP. Period. Stern tube material in the exact sizes for you shaft, packing gland, and (if needed) cutlass bearing are available from any decent marine supply. There is no other proper choice for this case. Nylon can not be glassed to reliably, and does not have the required mechanical strength, and changes size when it is in water. Who CARES about it being "self lubricating"? The shaft should NEVER touch it!!!! Just NO.



If your shaft is scored from rubbing against the existing stern tube, that would indicate a SERIOUS alignment issue that needs to be fixed.



This is a difficult job for a beginner to be 100% sure the engine, sterntube and strut are all in perfect alignment. There are a lot of details to this. I would strongly encourage you to, at the very least, hire somebody who is experienced with this to give you eyes-on advice.



If you get this wrong, it will lead to no end of problems. Everything from failing transmission bearings and seals, to packing gland leaks, to catastrophic flooding.

Thank you for your thoughtfulness-- and your time on helping a newbie couple figure this out... Grateful...

1) the shaft is 1 3/8" by 68 1/2" long

2) New shaft will be Aquamet 22HS

3) The plan is: once we understand the OD of what the stern tube should be with a 1 3/8" shaft-- we will order the 13-14" Stern Tube in G10 FRG fashion based off of personal experience with this nasty material and resilience to moisture

4) Shaft / Marine professional-- geeessshh... If I had a dollar for every number I've called in my GEO requesting service-- I could buy a two week vaca in St Thomas USVI... Short answer-- YES AND absolutely!! Need someone that can slum the Green Cove Springs, Florida ghetto area-- where my boat found ONE of the last DIY yards in Florida that soon will be extinct... If you know of a chap that fits said, above criteria you pointed out-- please do share his/ her information with me? The worst they could say to me is no thank you- or your crazy?

5) Alignment issues: nope, not so much, I am a Hydraulic driven boat (transmission)-- my Perky 4-108 creates the flow that my industrial Parker Hydraulic Remote Drive spins the shaft... Engine & shaft are happily married in separate bedrooms; pump is fixed to a beast of a bracket fiberglassed into the hull--4' away from said partner engine... Hence why the shaft is so long and pricey...

6) Cutlass Bearing in my stern tube...hhhmm...God I wish I were a navel engineer that could calculate both resistance from my 5" Cutlass bearing (in strut) and the possible resistance from my 13" Stern tube cutlass bearing-- then factor in the resistance of my MAX-PROP 4-Bladed prop which has yet to get her toes wet... With all of this data-- ascertain if I would be overloading the Perkins & my Hydraulic drive by adding this additional item to the system? My Perk is only a little 50hp...

7) Cutlass bearing in my virgin stern tube-- if i did this --I woukd be adding an additional expense in my maintenance cruising kitty that was not previously required by German Frers navel architecture for this boat... The stainless Steel Stern Tube has lasted 40 years-- would a cutlass bearing (inside my stern tube) last as long? If not-- what would I hope to gain by adding this feature to the mix?

These are things that I ponder while I sit by a roaring fire pit...

Cheers...

Skipper T