Reply
 
Thread Tools Display Modes
 
Old 11-01-2015, 07:39 AM   #1
Senior Member
 
ddalme's Avatar
 
City: LAFAYETTE,LA
Country: USA
Vessel Name: Relenti
Vessel Model: Atlantic 30, 1983
Join Date: Mar 2015
Posts: 406
Extending shaft log tube

I'm getting ready to do a haul out and have the bottom cleaned and checked and change out a frozen sea cock, weld a broken dive platform brace, clean and polycoat, etc. Was also thinking about extending the shaft log inside the boat about 6" to facilitate easier access to the packing gland. The generator sits over it, making it very hard to work with. See any problem in doing so? Boat is a 1983 Atlantic 30 with a Volvo tamd40b engine. I have about 24" of shaft between the gland and the engine coupler.
__________________
Advertisement

ddalme is offline   Reply With Quote
Old 11-01-2015, 07:51 AM   #2
Guru
 
O C Diver's Avatar
 
City: Fort Myers, FL... Summers in Crisfield, MD
Country: USA
Vessel Name: Slow Hand
Vessel Model: Cherubini Independence 45
Join Date: Dec 2010
Posts: 4,803
How do you plan to extend it and keep the extension rigid? I replaced the tube in my charter boat when increasing the shaft size and in the process made it longer. But that's very different from adding to an existing shaft log.

Ted
__________________

__________________
Blog: mvslowhand.com
I'm tired of fast moves, I've got a slow groove, on my mind.....
I want to spend some time, Not come and go in a heated rush.....
"Slow Hand" by The Pointer Sisters
O C Diver is offline   Reply With Quote
Old 11-01-2015, 07:58 AM   #3
Senior Member
 
ddalme's Avatar
 
City: LAFAYETTE,LA
Country: USA
Vessel Name: Relenti
Vessel Model: Atlantic 30, 1983
Join Date: Mar 2015
Posts: 406
I would glass another tube to the original and make a former that attaches at the joint and to both stingers. Heck, I could section the fiberglass tube and install without removing the shaft, but I want to change the hose on the gland also. So that's out.
ddalme is offline   Reply With Quote
Old 11-01-2015, 08:16 AM   #4
Guru
 
Capt.Bill11's Avatar
 
City: Sarasota/Ft. Lauderdale
Country: USA
Join Date: Apr 2014
Posts: 5,422
Just you the correct hose and extend it. I see no need to extend the log. The box floats on the shaft so extending the hose 6" is no big deal.
Capt.Bill11 is offline   Reply With Quote
Old 11-01-2015, 08:23 AM   #5
Senior Member
 
ddalme's Avatar
 
City: LAFAYETTE,LA
Country: USA
Vessel Name: Relenti
Vessel Model: Atlantic 30, 1983
Join Date: Mar 2015
Posts: 406
Quote:
Originally Posted by Capt.Bill11 View Post
Just you the correct hose and extend it. I see no need to extend the log. The box floats on the shaft so extending the hose 6" is no big deal.
That would give me about 19" of hose. That's not to much? Am I over thinking this? Would be a lot easier fix.
ddalme is offline   Reply With Quote
Old 11-01-2015, 08:35 AM   #6
Guru
 
Capt.Bill11's Avatar
 
City: Sarasota/Ft. Lauderdale
Country: USA
Join Date: Apr 2014
Posts: 5,422
Quote:
Originally Posted by ddalme View Post
That would give me about 19" of hose. That's not to much? Am I over thinking this? Would be a lot easier fix.
I've extended them several inches before to get the packing to ride on a smoother portion of the shaft with no issues. As I said the box floats on the shaft and there should be little twisting force on it. So with the correct stiff hose I see no problem.

But ask a shop or two that deals with prop shafts and see if they have an opinion.
Capt.Bill11 is offline   Reply With Quote
Old 11-01-2015, 08:44 AM   #7
Senior Member
 
ddalme's Avatar
 
City: LAFAYETTE,LA
Country: USA
Vessel Name: Relenti
Vessel Model: Atlantic 30, 1983
Join Date: Mar 2015
Posts: 406
Quote:
Originally Posted by Capt.Bill11 View Post
I've extended them several inches before to get the packing to ride on a smoother portion of the shaft with no issues. As I said the box floats on the shaft and there should be little twisting force on it. So with the correct stiff hose I see no problem.

But ask a shop or two that deals with prop shafts and see if they have an opinion.
Thanks Capt.-will do-this forum is awesome!
ddalme is offline   Reply With Quote
Old 11-01-2015, 09:24 AM   #8
Guru
 
HopCar's Avatar


 
City: Miami Florida
Vessel Name: Possum
Vessel Model: Ellis 28
Join Date: Aug 2011
Posts: 3,489
I don't see a problem with a long hose either but I'd call Buck Algonquin and talk to them first.
You'll need to use very heavy wall hose not just regular exhaust hose. Buck sells it but only in short lengths. While you're talking to them, ask if they can cut you a longer piece.
__________________
Parks Masterson
www.hopkins-carter.com
HopCar is offline   Reply With Quote
Old 11-01-2015, 09:40 AM   #9
Guru
 
City: gulf coast
Country: pinellas
Join Date: Jun 2014
Posts: 2,196
the shaft is positioned by the strut and transmission flange. The rubber hose mounting the packing system just stops the assembly from spinning and allows it to flex with the shaft if necessary. So like Bill I see no reason it cant be longer provide the hose is fairly stiff as they usually are. Can it be 2' long? My guess is that would be OK.
bayview is offline   Reply With Quote
Old 11-02-2015, 07:02 AM   #10
FF
Guru
 
FF's Avatar
 
Join Date: Oct 2007
Posts: 16,512
BEWARE !!

The hose used for shaft logs is a very special thicker heavy duty item


.It is NOT water hose or exhaust or toilet hose , but is a totally different product , and must be ordered as such.
FF is offline   Reply With Quote
Old 11-02-2015, 08:01 AM   #11
Senior Member
 
ddalme's Avatar
 
City: LAFAYETTE,LA
Country: USA
Vessel Name: Relenti
Vessel Model: Atlantic 30, 1983
Join Date: Mar 2015
Posts: 406
Quote:
Originally Posted by FF View Post
BEWARE !!

The hose used for shaft logs is a very special thicker heavy duty item


.It is NOT water hose or exhaust or toilet hose , but is a totally different product , and must be ordered as such.
Roger
wouldn't do anything less
ddalme is offline   Reply With Quote
Old 11-02-2015, 08:09 AM   #12
Guru
 
Northern Spy's Avatar
 
City: Powell River, BC
Country: Canada
Vessel Name: Northern Spy
Vessel Model: Nordic Tug 26
Join Date: Feb 2012
Posts: 2,665
The hose on my boat approximately 2' long. This is on a 1.25" shaft. Not sure of the ID, but I'm guessing it's 3" or better OD.

The risk is torsional load on the hose due to packing drag.
Northern Spy is offline   Reply With Quote
Old 11-02-2015, 10:36 AM   #13
Senior Member
 
Liberty2015's Avatar
 
City: Pittwater
Country: Australia
Vessel Name: Liberty
Vessel Model: 57 foot Halvorsen
Join Date: Aug 2015
Posts: 178
If it was me ......I Would extend it with the extension of the F/G tube and re enforce as you suggested. It is done once and done properly. I would pre seal the ends of the cut tube before glassing.

Cheers Chris D Liberty Australia
Liberty2015 is offline   Reply With Quote
Old 11-02-2015, 11:27 AM   #14
Guru
 
Nomad Willy's Avatar
 
City: Concrete Washington State
Country: USA
Vessel Name: Willy
Vessel Model: Willard Nomad 30'
Join Date: Oct 2007
Posts: 13,701
I would extend the stern tube.

I think most stern tubes have a machined fwd end to accept the hose. If that's so on your boat get a FG stern tube piece that has the ID of the OD of the end of the stern tube that accepts the hose. If need be you could but a short piece of stern tube on the fwd end to mate w you're stuffing box ID. 5200, Marine Tex or some other epoxy could be used to "glue" these parts together.

Without the machined fwd end of the stern tube good alignment would be very difficult I would think.

Using a very long hose will transfer the bearing load that the hose and stuffing box provides (some to considerable depending on the hose and the boat) to the stern bearing and leave the shaft largely unsupported where some support previously was. If an intermediate bearing is close to where you want to terminate the stuffing box this wouldn't be a consideration but if it was a long way to the transmission flange (or the next intermediate bearing) shaft support may be lacking.
__________________
Eric

North Western Washington State USA
Nomad Willy is offline   Reply With Quote
Old 11-02-2015, 11:48 AM   #15
Senior Member
 
ddalme's Avatar
 
City: LAFAYETTE,LA
Country: USA
Vessel Name: Relenti
Vessel Model: Atlantic 30, 1983
Join Date: Mar 2015
Posts: 406
I'm going back to do some measurements and just from memory, I think I'll fiberglass an extension on the existing tube with support braces. That way I can get the proper hose and not be worried about a too long hose twisting, etc. on my shaft.
ddalme is offline   Reply With Quote
Old 11-02-2015, 12:14 PM   #16
Guru
 
Ski in NC's Avatar
 
City: Wilmington, NC
Country: USA
Vessel Name: Louisa
Vessel Model: Custom Built 38
Join Date: Jan 2014
Posts: 3,879
Can you get to it well enough to do a good glass job, or are you going to pull the gennie?

Another option would be to use a hose sleeve under the gennie to couple a FG tube to existing tube, then a second sleeve to couple the gland.
Ski in NC is offline   Reply With Quote
Old 11-02-2015, 12:21 PM   #17
Guru
 
Capt.Bill11's Avatar
 
City: Sarasota/Ft. Lauderdale
Country: USA
Join Date: Apr 2014
Posts: 5,422
Quote:
Originally Posted by manyboats View Post
I would extend the stern tube.

I think most stern tubes have a machined fwd end to accept the hose. If that's so on your boat get a FG stern tube piece that has the ID of the OD of the end of the stern tube that accepts the hose. If need be you could but a short piece of stern tube on the fwd end to mate w you're stuffing box ID. 5200, Marine Tex or some other epoxy could be used to "glue" these parts together.

Without the machined fwd end of the stern tube good alignment would be very difficult I would think.

Using a very long hose will transfer the bearing load that the hose and stuffing box provides (some to considerable depending on the hose and the boat) to the stern bearing and leave the shaft largely unsupported where some support previously was. If an intermediate bearing is close to where you want to terminate the stuffing box this wouldn't be a consideration but if it was a long way to the transmission flange (or the next intermediate bearing) shaft support may be lacking.

You might be right. But I find it hard to believe a stuffing box on a flexibly hose add any significant support to a shaft. Especially when you consider how close the distance is between the coupler and the first bearing supporting the shaft in most cases.

The whole point of having the box on a hose would seem to be that it floats on the shaft and can move with it.

I would think if the box is going to add support it would have to be of the type that is hard mounted to a cross member and not free floating.
Capt.Bill11 is offline   Reply With Quote
Old 11-02-2015, 01:02 PM   #18
Guru
 
Nomad Willy's Avatar
 
City: Concrete Washington State
Country: USA
Vessel Name: Willy
Vessel Model: Willard Nomad 30'
Join Date: Oct 2007
Posts: 13,701
Support ...

Yes .. What I proposed would probably leave the tube unsupported and it could act like a tuning fork w it's own set of vibrations and possibly cause structural fatigue and perhaps failure.

By the way I suspect I have my terminology screwed up. Shaft log, stuffing box? What is the hole in the keel of a wood boat called? And there is the tapered bronze casting through which the shaft passes .. shaft log? Packing gland is the barrel shaped bronze tube like thing that we put packing in. But I think it's often or usually called the "stuffing box". The old wood boats of the 40's ect actually had a box like wood structure that I think the packing gland was lag screwed to via a flat plate that was part of the packing gland.

Many here know all this stuff. Would someone who does present the real propper terminology?
__________________
Eric

North Western Washington State USA
Nomad Willy is offline   Reply With Quote
Old 11-02-2015, 01:53 PM   #19
Guru
 
Capt.Bill11's Avatar
 
City: Sarasota/Ft. Lauderdale
Country: USA
Join Date: Apr 2014
Posts: 5,422
OK, what I'm talking about is the stuffing box. Not a strut tube with a bearing in it.

And since a stuffing box on a hose can't add much if any support to the shaft, that's why I've never been to concerned about extending the hose.
Capt.Bill11 is offline   Reply With Quote
Old 11-02-2015, 02:36 PM   #20
Guru
 
Northern Spy's Avatar
 
City: Powell River, BC
Country: Canada
Vessel Name: Northern Spy
Vessel Model: Nordic Tug 26
Join Date: Feb 2012
Posts: 2,665
Quote:
Originally Posted by Capt.Bill11 View Post
OK, what I'm talking about is the stuffing box. Not a strut tube with a bearing in it.

And since a stuffing box on a hose can't add much if any support to the shaft, that's why I've never been to concerned about extending the hose.
Exactly, if anything it adds overhung load.
__________________

Northern Spy is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off





All times are GMT -5. The time now is 04:42 AM.


Powered by vBulletin® Version 3.8.8 Beta 4
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2006 - 2012