jfkal
Active member
Any good ideas on how best to change a stern tube on a GRP production boat?
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Changing a stern tube
- Thread starter jfkal
- Start date
maxi
Member
Hi, you know how to choose the easy jobs, or not.
The method I used (suggested by a very experienced boatyard manager) was to obtain an industrial hacksaw blade which is approx 1" wide, and then to make a single fore & aft cut through the wall of the sterntube throughout it's length.
Then make a long cold chisel, I used an old piece of reinforcing bar, and use this to carefully fold the walls of the stern tube in, onto itself. This will eventually reduce the diameter of the tube sufficiently to pull the whole thing out.
Use a broom stick or similar, well wrapped in cloth that is soaked in acetone, to clean the void before attemping to install the new tube.
Hopefully your new tube is the same diameter as the old, if not, you are in for an interesting but achieveable task. Either way you will feel like a mad proctocologist before you finish. Good luck.
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The method I used (suggested by a very experienced boatyard manager) was to obtain an industrial hacksaw blade which is approx 1" wide, and then to make a single fore & aft cut through the wall of the sterntube throughout it's length.
Then make a long cold chisel, I used an old piece of reinforcing bar, and use this to carefully fold the walls of the stern tube in, onto itself. This will eventually reduce the diameter of the tube sufficiently to pull the whole thing out.
Use a broom stick or similar, well wrapped in cloth that is soaked in acetone, to clean the void before attemping to install the new tube.
Hopefully your new tube is the same diameter as the old, if not, you are in for an interesting but achieveable task. Either way you will feel like a mad proctocologist before you finish. Good luck.
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vyv_cox
Well-known member
I agree with you that this is the ideal way but cutting the tube on many boat designs would be a nearly impossible job. The tube on my Sadler is close to 3 ft long, with very limited access from inside, and I can't think of a way to make a cut so long without specialised equipment. Before doing that I think I would try a more brutal method, see if it can be rotated with a pair of Stillsons. Try heating inside the tube with a blowlamp to break down the resin close by. Make up a puller with a long length of studding of as large a section as possible. Reserve big hammers until you are really desperate!
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colvic
New member
Does the tube screw into the fittings at either end? If so wouldn't the easiest way be to remove the prop and the stern gland and then unscrew it. That way you can fit a new one very easily. Did it a couple of months ago.
Phil
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Phil
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vyv_cox
Well-known member
Really? Changing a stern tube?
It seems we need some clarification from jfkal that he really means the stern tube. In a GRP boat in my experience the stern tube is a fixture, glassed into the hull during manufacture. I can't think of many reasons why this would need to be replaced.
However, in your experience it is something else. So I think we need to know before he starts doing something destructive for no reason.
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It seems we need some clarification from jfkal that he really means the stern tube. In a GRP boat in my experience the stern tube is a fixture, glassed into the hull during manufacture. I can't think of many reasons why this would need to be replaced.
However, in your experience it is something else. So I think we need to know before he starts doing something destructive for no reason.
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maxi
Member
Re: Really desperate
I appreciate your concerns but my stern tube (which had to come out due to approx 1sq inch being missing, thanks to a previous owner running the shaft off centre, and 1 sq inch doesn't half let in a lot of water very quickly) was also approx 3' in length and very securely installed. I mounted the large hacksaw blade in a slot cut in a piece of 20mm conduit and did all the cutting from outboard - took approx 1 hour of blood sweat & toil. The folding process was relatively quick, easy and effective, having wasted loads of time with stillsons, hammers etc.
This method was certainly a good one, once I had cleared my mind of all the objections and ineffective short cuts. By the way, grp is highly heat resistant- up to a certain point where things get exciting, be careful with your heat experiment.
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I appreciate your concerns but my stern tube (which had to come out due to approx 1sq inch being missing, thanks to a previous owner running the shaft off centre, and 1 sq inch doesn't half let in a lot of water very quickly) was also approx 3' in length and very securely installed. I mounted the large hacksaw blade in a slot cut in a piece of 20mm conduit and did all the cutting from outboard - took approx 1 hour of blood sweat & toil. The folding process was relatively quick, easy and effective, having wasted loads of time with stillsons, hammers etc.
This method was certainly a good one, once I had cleared my mind of all the objections and ineffective short cuts. By the way, grp is highly heat resistant- up to a certain point where things get exciting, be careful with your heat experiment.
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jfkal
Active member
The new tube is indeed having a thread but the old would not budge at all and is apparently glassed in 
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jfkal
Active member
The new tube is indeed having a thread but the old would not budge at all and is apparently glassed in ((
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