stern tube glassed in at almost max angle

30boat said:
FWIW the Aquadrive coupling will cope with a lot more than 2º.More like 8º.
Click to expand...

You are right, I should have checked the Halyard website, which confirms your 8 degrees. My comment was based on memory from when I fitted mine nearly 10 years ago. However, I think it's better to have it as aligned as possible, so mine is pretty much exactly on line.
 
I'm sure this has been checked, but looking at the coupling diameter and the distance it is behind the engine feet, about 12" by the picture, are you sure there is room for the coupling in the keel? Just looks a bit tight.

Very difficult to get that tube out now, you'll never get at the glass at the far end. In extremis you could cut it off both ends, make good outside and grind off all you can reach inside, then mount a new tube exiting above the existing one, and at a better angle. Would there be room to swing the prop?

I'm used to bigger engines than this, and prefer vertical fore and aft ply beds, 2 or 3 or 4 x 18mm, glassed overall with the engine between them mounted on full length angle brackets. Angle iron would be easy but it is not 90 deg on the inside.
 
I would cut it out and start again. FWIW, all the stern tubes that I have installed (many) have been put in using a procedure that is, by and large, similar to what Blueboatman has suggested. I honestly believe that it is the quickest and most effective method, both cost-wise and time-wise. The pre-assembly method is especially useful when the outer end of the shaft is in a P-bracket.
 
Mechanical Devices Operating At The Edge of Their Specification May Be Unreliable

vyv_cox said:
You are right, I should have checked the Halyard website, which confirms your 8 degrees. My comment was based on memory from when I fitted mine nearly 10 years ago. However, I think it's better to have it as aligned as possible, so mine is pretty much exactly on line.
Click to expand...

Last year I had an Aquadrive installed. The company that fitted it stated that they would install it with a slight misalignment. They stated that the CV joints wear more rapidly if in perfect alignment.

I don't know how misaligned mine is, nor if what they say is technically correct. I thought it was worth mentioning here so at least if you are contemplating the Aquadrive installation you can have this clarified with Aquadrive.

Personally I would chop out your stern tube and realign with the engine installed before glassing in. The reason I fitted an Aquadrive is due to a sheared coupling because of misalignment. The prop shaft bent, wrecked the stern tube and cost a lot of cash to correct. It also nearly resulted in my vessel being wrecked on a lee shore in a F7.

You are in a good position to fix it and fibre glass is probably the best material to cut out and re work without any loss of form or strength.

My experience of anything mechanical that is being asked to work at the limits of its envelope, is reduced reliability.
 
Having done this job on my Corribee, with the same engine, I have absolutely no hesitation in agreeing with all those that say chop it out and do it again.
I would cut out as much as you can with a Fein Multimaster (or the Bosch equivalent), which will do the job with very little mess (compared to an angle grinder!). I like the long drill idea as well - sounds feasible.
My installation is at http://corribee.org/technical/engines/inboard-engine/ in case you're interested - shows the stern tube and skeg modifications as well.
(I also fitted an aquadrive, but it's not compulsory! I just happened to be in a position to get hold of one for the right price).
 
BlowingOldBoots said:
They stated that the CV joints wear more rapidly if in perfect alignment.
Click to expand...

I have heard this too. I can only state that mine has been in use for about ten years, something like 1800 engine hours. It is pretty much exactly aligned, although I haven't checked it for a long time. There is no discernable wear in the joint.

I can understand the reason for the statement and have come across similar situations in ball bearings in other equipment. If there is no movement between the balls and the raceways, apart from a very small imposed vibration, then a condition of fretting can develop. If there is some misalignment then grease is drawn into the nip between balls and raceway. However, in a CV joint there is never any rolling motion, so fretting might produce significant fretting wear but the result would only be some increased clearance and not the harmful vibrations that occur in a rolling bearing when the machine starts up.
 
Will try very hard to cut the stern tube out on saturday, when the chap who glassed it in will cut it out so he says ,I hope to be able to save the tube otherwise i shall have to import from the usa it is not easy getting special boat stuff here.I must say I am finding all of you very helpful, all ideas are most welcome.
 
OK, moving on: :D

Bajansailor said:
...{snip}...David has a Volvo shaft seal which he plans to install - however I am wondering if the cutless bearings inside the stern tube (especially the forward bearing) might not get too hot, as there will not be a steady supply of cooling water flowing over them - only water that seeps in slowly from outside.

We were discussing the possibility of fitting a Halyard Marine Aquadrive unit instead of the Bullflex coupling. The mounts on the engine are fairly flexible, and I am wondering if the shaft (held rigidly in the cutless bearings) will cope with the vibration from a single cylinder engine, even with the Bullflex coupling in between (?).
There is enough room to fit an Aquadrive unit - but they are around GBP 450, hence a significant extra expense.
Click to expand...

I share your concern about the amount of movement that the engine mounts will allow vs the rigidly mounted shaft, but I've got no basis for this, other than gut feel.

I note in the information from the Vetus site referenced above that the centering part of the Bullflex coupling can be removed to allow it to accomodate lateral missalignment, but have no idea how much it will tolerate. Again my gut feel (and please feel free to shoot me down anyone) would be to do away with the cutless bearing at the inner end of the tube, fit the volvo seal here, and connect the shaft to the engine with the Bullflex coupling with it's centering part intact. Our 2GM20 moves around a lot at idle, and I would expect the 1GM10 to be as bad, or worse.

Davis has also purchased a Vetus muffler and a gooseneck for the exhaust, and is thinking that he should also install an anti-syphon valve. The slope from the standard exhaust elbow to the muffler box is rather shallow (the box will sit in the 'vee' of the hull, above the GRP stern tube), hence I am thinking it might also be prudent to have a S/S 'high rise' exhaust elbow fabricated (?)
Click to expand...

Do you mean an anti-syphon valve in the cooling water feed to the exhaust elbow? If so, I would say he should, but the Vetus fittings are outrageously expensive for what they are - especially the ones without valves that pee a constant stream over the side which are just a hollow plastic moulding. Maybe he could get something similar fabricated ?

I *think* there are recommendations from Yanmar about the fall needed in the exhaust, but I can't find anything in the manuals I've got (Operators & Workshop). I would be guided by them as to whether a high-rise elbow was needed.

I do think it's worth the time to get it all right at this stage.

Andy
 
Had a chat with David this evening.
Latest plan is to leave the stern tube as it is for now, remove the cutless bearing at the inboard end of the stern tube, perhaps modify the Bullflex coupling by removing the centering part (as suggested on the Vetus site), and have another go at re-installing the engine on the beds and aligning it to see how high the mounts will have to be raised to allow for the slightly steeper shaft angle.

If the above is not feasible, then David has a friend who also wants a Bullflex coupling of the same size, so he would have no problems in selling it on.
And he would then look at buying an Aquadrive unit from Halyard Marine - although this will then involve glassing in a substantial transverse frame to take the thrust loadings.

If anybody is planning on an early winter holiday in Barbados and travelling light, then I am sure that David would be keen on introducing you to Mount Gay if you acted as an Aquadrive courier.... :)

Re the anti-syphon valve,yes, that would be the one in the cooling water feed to the exhaust elbow. The elbow is probably going to be about or slightly below the static waterline.

I think that he will still probably need to arrange some sort of a cooling water feed to the stern tube for the cutless bearing, as there are no intake ducts as per what one might find on a 'conventional' bronze stern tube.
 
Bajansailor said:
...Latest plan is to leave the stern tube as it is for now, remove the cutless bearing at the inboard end of the stern tube, perhaps modify the Bullflex coupling by removing the centering part...
Click to expand...

Not an expert, but I would either remove the inner cutless bearing OR the centring part of the coupling, but not both - something needs to steady the inner end of the shaft.

Surely it's quicker, cheaper and easier to chop the tube out and re-set it than go through the exercise of fitting an Aquadrive ??

Another 0.02p :D

Andy
 
Ooops, sorry, yes, I got that wrong! Just read the bumpf about the Bullflex again re how one would have to leave the centre part of the coupling if the inner cutless bearing is taken out.

Although Vetus say the Bullflex will cope happily with a rigidly mounted shaft, I am wondering if it will be happy with a single cylinder engine at slow speeds?

It would be a not very pleasant job to chop out that GRP stern tube now, so I think David will install the engine and try it 'as it is', with the Bullflex, and see if it works.
If not, then take the boat out again (she is on a trailer on the beach, and it is relatively simple to take her out of the water) and either cut out the stern tube & re-align it, or sell the Bullflex and buy an Aquadrive.
 
Bajansailor said:
so I think David will install the engine and try it 'as it is', with the Bullflex, and see if it works.
If not,
Click to expand...

He needs to be aware that one of the main reasons for the maximum engine angle is that the oil pickup is at risk with excessive aft rake. In choppy conditions the pump could run dry, with serious consequences for the bearings. Another reason is that with large engine angles the depth of oil at the aft end is such that the crankshaft may strike the oil surface as it turns, leading to massive aeration of the oil and, again, poor lubrication. In view of the fact that the angle is very close to the recommended maximum it needs very careful monitoring of the dipstick to ensure the level is neither too high nor too low.
 
The way these engines move about at tickover I don't think restricting the shaft ability to move is a good idea.I installed a 1GM10 on my previous boat and in the end fitted a Aquadrive.The engine jumped so mucht the shaft was touching the stern tube.
The small bulkhead needed for the Aquadrive doesn't have to all be that substantial.It can be made of 10 or 12mm plywood glassed over with a few layers of roving and epoxy.I've done it three times and it's not a big deal.Just make sure the laminate is well abraded before you do the job
 
Thank you Vyv, that is a very good point - yes, it would require very careful monitoring of oil level. (And how many folk do this consistently?).

They say the Bullflex can cope with 2 degrees of miss-alignment, but it would still be prudent I think to try and line it up properly in the first place, without having to rely on this 2 degrees to achieve an acceptable angle of inclination.

Re 30Boat - I think David is getting rather keen on the idea of an Aquadrive, especially as he can easily flog on his Bullflex, and he probably will go down this route if careful trials indicate that the current proposed arrangement will not work. Certainly installing a wee bulkhead for an Aquadrive will be a damn sight easier than chopping out the stern tube!
 
Last edited:
Bajansailor said:
Certainly installing a wee bulkhead for an Aquadrive will be a damn sight easier than chopping out the stern tube!
Click to expand...

Maybe 30boat is a lot more capable than I am! I didn't find the job as straightforward as he seems to have done. It's the measuring up and jig making that takes the time. I started with a cardboard mockup, although the weight of the Aquadrive makes this rather tricky. I then made a second mockup in plywood, getting all the holes and cutouts in the right position and being able to bolt up the Aquadrive to more or less ensure that everything fitted. I then took the pattern to a fabricator who profile cut the final item from 5 mm steel. Even after all this it didn't fit at first and needed some grinding before I was happy with it.

The plate was epoxied in place but I still had to do some work later, as the drain hole at the bottom was too small and regularly blocked with muck carried forward from the stern locker. Here it is as completed. I sprayed it with car paint to match the bilge colour.
DSC00630.jpg
 
just been checking the area where an aquadrive would have to be positioned in relation to where the engine bed is and there is not enough lateral room due to the narrow ''V''.,myself and bajansailor are going tomorrow to see the possibility in extending the beds much farther forward to try and be able to install an aquadrive.
Does anyone know the actual over all width of the aquadrive section that fits into the bulkhead bracket?
 
You must log in or register to reply here.

Share this page

Top