Stern tube replacement in a GRP Hull

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hallberg36

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The sterntube in my HR36 needs replacing after the cutlass bearing holder came adrift causing the shaft to be bent and the outboard end of the bronze alloy sterntube (male thread) to be damaged beyond repair. Hallberg have offered little practical advice or information to assist so I am interested if anybody has suffered a similar problem, and any useful info with regard to removal and replacement.

The cutlass bearing housing is secured in place by a single bolt and it appears this came loose and allowed the bearing housing to "unwind". It appears that this bolt is not screwed into any metal insert fixed in the hull, but merely threaded into the GRP hull and held by sikaflex...not an arrangement I am particularly impressed with. I am hoping to avoid removing the engine and also avoid damaging the adjacent areas of hull by accessing the sterntube by cutting through the filler surrounding the tube in the propshaft valley accessed in the aft cabin....only the inboard bronze alloy bearing, and the aforementioned cutlass housing are fixed in place, mainly by sikaflex, and the outer bearing with the single bolt mentioned above....the rest (intermediate section)of the tube is surrounded by filler/resin, which will have to be removed to gain access.

I have a sketch of the setup but so far have not managed to paste it here as it appears I do not have permission, so any comments or suggestions will be greatly received.
 
Some builders would grease the tube before encapsulating in resin so it would not stick, here's hoping. Try taking off the inside stuffing box and see will the tube come out the back end. Otherwise you may have fun demolishing GRP in a limited space. An SDS drill with a sharp chisel in it used as a jackhammer, no rotation, may help, being long and thin. There really should be a metal plate with threaded hole inside the hull for the bearing holder bolt, and why are there not two of those? If HR are less than helpful it won't help their reputation.......If it is as you describe I would be wanting to keep it quiet.
 
You may well find the tube is not actually glassed in but relies on being clamped by the two housings at either end. It is quite common to just set the locking screws straight into GRP as they do not take any load - it is only to stop the bearing housings from unscrewing. Normally, however they have two screws rather than one. There are various different manufacturers of stern tube assemblies such as Vetus or www.lakesterngear.co.uk that you might wish to explore for replacement.

When replacing the screws you might consider boring the holes oversize then filling with epoxy with a screw coated in grease set in it. Once it is cured you will have made a thread for the screw which is more secure than just screwing into GRP.
 
We removed the cutlass bearing housing two weeks ago to make it easier to replace the cutlass bearing. I was surprised to find the housing on ours has no locking screw. It took a giant wrench to undo it though.
 
Talulah said:
We removed the cutlass bearing housing two weeks ago to make it easier to replace the cutlass bearing. I was surprised to find the housing on ours has no locking screw. It took a giant wrench to undo it though.
Click to expand...

Yes, the screws are belt and braces. If the tube is the right length and the mounting faces at both ends are robust it should never come undone.
 
Have done a couple of these this year though both on Colvic hulls.
Pretty much depends on access on which method to use.
If you can get access inside then stitch drilling and or the use of a multi tool cutter like this will do it.
mutogop108vli.jpg


If there is little access internally then cut in from the outside like I did on the colvic watson recently, see
http://www.ybw.com/forums/showthread.php?426083-What-lessons-for-this-week/page18

Need to see it really to give you a more detailed plan of attack.
 
First of all thanks to all who have taken the time to reply and off their comments and advice. Access from within the hull is pretty limited and can only improve by removing the engine and gearbox...quite a big job as it has to be lifted up through the cockpit sole in the centre cockpit. Unfortunately I am still unable to post the sketch that HR have provided but I can advise that there is no inner stuffing box as such or any flange or fastenings visible. The sterntube is just glassed in through a small partial bulkhead and penetrates the engine space sufficiently to attach a Volvo Penta rubber stern gland held in place by a clamp on the outside of the sterntube. There doesn't appear to be any inner fitting at all....just the tube glassed in and a fillet of silicone or epoxy run round the penetration. For some reason all HR36 hulls have only one bolt on the cutlass bearing fitting....I am aware that usually there are 2 bolts on an oval flange bolted to the hull. Perhaps if there had been 2 the "failure" would not have occurred? I do have a multi-cutter as shown above and am familiar with the "stitch drilling" method. The outer end of the tube (threaded but damaged and "belled out" due to the bent shaft is obviously accessible but the intermediate section is not visible having been "glassed in" or surrounded by filler, and I'm wondering if all this will have to removed if the tube was not greased when fitted? As mentioned earlier, Hallberg have not been forthcoming and have offered little help or advice....something I'm not particularly pleased about as I've been the proud owner of 2 of these boats for more than 20 years and fellow sailors have struggled to "shut me up" singing their merits....not sure I'll continue to be their biggest fan? As these boats are now very popular I was hoping that somebody would have experienced this and have specific information on the installation, and removal/replacement?
 
Were there any signs of debris around the shaft? a rope wrapped round is the only way I would think you could get enough force to do that sort of damage. As far as bolts to hold something that has to unscrew GRP is very strong if the force is not just trying to pull the bolt straight out, so to stop a carrier rotating one bolt would be enough. We just use epoxy in a thin layer for locating and holding bearings, they don't need a grub screw although some yards put this in as added security.
 
Gladys said:
As the OP has an HR, I would have thought a conversation with HR (who I understand from a friend who is an owner are very helpful) would be a good idea?
Click to expand...

But the OP said "Hallberg have offered little practical advice or information to assist ...".

I think HR take the view that this sort of job is boatyard work, and that boatyards will be able to tackle it. I owned an HR for 19 years, and found HR helpful with requests for spare parts, etc.
 
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I haven't persisted with HR as thought their initial response demonstrated how unwilling they are to get involved...I may well go back to them depending on how things develop but thought that as a supposed valued customer over the years they would have been more helpful. As per the above post, they basically said that the job should be handed over to a boatyard, but I live in a marina and familiar with the local engineers and they are not much wiser than me as to how best to proceed. As an old fashion type I always think you're better off attaining as much info on how the installation was designed/installed before grabbing the wrecking bars and drills/saws...only for somebody with better knowledge to advise later that it wasn't necessary to tear things apart to such a degree?
 
Well it needs to be replaced and if its glassed in you need to remove the glass or at least some of it.
I'd drill a series of 10mm holes through the glass and fill these with penetrating oil and then get a BIG set of stillsons and a short length of scaffold tube and wind it off from the outside.
If it doesn't move drill more holes until it does.
You could use a puller, we have a nice hydraulic one that would do nicely but often winding it out works just as well.
If it still doesn't budge and you don't want to lift the engine then cut in through the hull from one side.
The hull will be around 20mm thick or so.
Cut it all out and then glass it all back together again.
All a bit agricultural but it works.
 
I can remember doing one on a Cobra 850 20 years ago. The tube was glassed in and I had to chop it out of the side of the Skeg with a 4 1/2" angle grinder and the glass a new one in. As far as i remember I managed to get one from T. Norris.
 
This question came up some time ago. One solution is to buy a bi-metal hole saw a bit bigger than the outside of the stern tube. Cut off the back bit, leaving a tube with teeth on one end and weld this to a length of tube of the same size. What you now have is a hole cutter long enough to cut the surrounding glass/filler away.
 
I had a look at the hull on BoatData and there is some room between the tube and the skeg/rudder. Dropping the rudder looks to give a clear shot. But if difficult, then a series of short bits of tube added by welding as the cutter moves in.
Hilti do 'diamond' long hole saws for masonry, might be a bit pricey for a one shot deal.
 
for clarification - here is the Stern Tube / Cutlass Bearing arrangement on a HR36

the Cutlass Bearing housing unscrews from the Stern Tube and in my case ( despite HR saying there is a M10 bolt ) that apart from the sealant / epoxy fairing it in, then was nothing to stop the bearing housing unscrewing. Fitting a Rope Cutter made this even worse at it's attached to the Cutlass housing

Consequently, when I replaced the Cutlass Bearing I tapped a 10mm * 30mm deep thread hole into the hull so there was something to prevent rotation

Kevin
 

Attachments

Once again thanks to all for their replies and suggestions...I especially like the suggestions from Downwest about the specially modified hole cutter, and thanks to Kevin for the Cutlass Bearing Removal pdf file...I had already got this from HR...but very little else by the way of assistance or information. I have replaced the cutlass bearing myself, as necessary over the years as have an engineering background....unfortunately the current situation is rather more complex hence the invitation to members of this forum for the benefit of their wisdom and advise. Also I can confirm that the method shown in the the file provide (hook the bearing out with a bent piece of wire) bears little resemblance to my experience of shifting the damn thing after removing the grub screw etc... but that is the least of my worries at the moment as the shaft etc...have all been removed.

I have emailed HR again as the more I thought about it I think their response has been pretty shoddy in view of their supposed reputation, and I have bought and collected 2 boats from their yard over the years so do know that they have some very good people at the yard...unfortunately as it was over 20 years ago I don't have any names to go back to so appear to be stuck with an office "wallah" behaving like a "customer service technician" in an overseas call centre! I'll post any more developments as and when they become available.
 
hallberg36 said:
Once again thanks to all for their replies and suggestions...I especially like the suggestions from Downwest about the specially modified hole cutter, and thanks to Kevin for the Cutlass Bearing Removal pdf file...I had already got this from HR...but very little else by the way of assistance or information. I have replaced the cutlass bearing myself, as necessary over the years as have an engineering background....unfortunately the current situation is rather more complex hence the invitation to members of this forum for the benefit of their wisdom and advise. Also I can confirm that the method shown in the the file provide (hook the bearing out with a bent piece of wire) bears little resemblance to my experience of shifting the damn thing after removing the grub screw etc... but that is the least of my worries at the moment as the shaft etc...have all been removed.

I have emailed HR again as the more I thought about it I think their response has been pretty shoddy in view of their supposed reputation, and I have bought and collected 2 boats from their yard over the years so do know that they have some very good people at the yard...unfortunately as it was over 20 years ago I don't have any names to go back to so appear to be stuck with an office "wallah" behaving like a "customer service technician" in an overseas call centre! I'll post any more developments as and when they become available.
Click to expand...

Yep - the piece of wire trick is a joke, I used a double bladed hacksaw through the tube to remove the old cutlass bearing. Putting the new one in was a oven for the housing, freezer for the bearing trick and do it quick.

Have you tried talking to Transworld in Hamble = the guys there are very knowledgeable and have many years of experience with HRs - you probably will not get much sense out of Ellos now as the Swedes are all on holiday ( today being midsummer )
Kevin
 
hallberg36 said:
The sterntube in my HR36 needs replacing after the cutlass bearing holder came adrift causing the shaft to be bent and the outboard end of the bronze alloy sterntube (male thread) to be damaged beyond repair. Hallberg have offered little practical advice or information to assist so I am interested if anybody has suffered a similar problem, and any useful info with regard to removal and replacement.

The cutlass bearing housing is secured in place by a single bolt and it appears this came loose and allowed the bearing housing to "unwind". It appears that this bolt is not screwed into any metal insert fixed in the hull, but merely threaded into the GRP hull and held by sikaflex...not an arrangement I am particularly impressed with. I am hoping to avoid removing the engine and also avoid damaging the adjacent areas of hull by accessing the sterntube by cutting through the filler surrounding the tube in the propshaft valley accessed in the aft cabin....only the inboard bronze alloy bearing, and the aforementioned cutlass housing are fixed in place, mainly by sikaflex, and the outer bearing with the single bolt mentioned above....the rest (intermediate section)of the tube is surrounded by filler/resin, which will have to be removed to gain access.

I have a sketch of the setup but so far have not managed to paste it here as it appears I do not have permission, so any comments or suggestions will be greatly received.
Click to expand...
Its been some years since you ran into your stern tube issue. I am now having the same issue. HR offered a few suggestions. I am curious to know how you went about repairing yours.
 
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