Stern gear options - Beta50

[TandC]

Afternoon all,

 

On our new boat - 45 x 10ft shell - we're having a Beta50S installed. This is the Beta50 with an acoustic box that the engine and the PRM150 gearbox sit in, with the drive flange outside connected up to the prop shaft/drive etc.

 

But while we've fixed on that engine arrangement - we haven't fixed what stern gear we should go with....   I have asked Beta for recommendations and I wasn't entirely reassured with the "that's for you to decide" answer, although when I spoke to someone else there they said "well i think a lot of people use the Aquadrive because it makes alignment so easy".

 

Can I ask for any advice on this?   

 

We don't do huge amounts of cruising - liveaboards but tied by work to our residential mooring - so hardly chugging up and down the length of the system - should that have any bearing on things.

 

The other consideration is that as we are limited on our boat build length, and want to maximise the cabin space, therefore options for stern gear that take up less "length" - if that would allow the engine to be sat further toward the prop, therefore the bulkhead further, and therefore increasing the internal cabin size (although i guess we're talking about negligible differences). 

 

I am at a loss on what the options are and where to start.

Edited October 27, 2022 by TandC

[GUMPY]

Just because you have a flexible coupling doesn't mean you shouldn't bother about alignment. They run better if the alignment is good. Propshafts with Hardy Spicer joints excepted.

[Alan de Enfield]

9 minutes ago, TandC said:

I am at a loss on what the options are and where to start.

 

If you are not going to be moving, why not just leave a 'space' and decide in a few years time ?

or

You could even not bother with the engine and gearbox (saving you £000's) and you'd gain another 6 foot of cabin space, and, when you are not tied to one spot change the 'houseboat' for a cruising boat when you stop work.

 

Win - Win.

Edited October 27, 2022 by Alan de Enfield

[TandC]

Thanks - my comment re. easier alignment was really just explaining the extent of the advice from Beta - which wasn't that  helpful.  Obviously i'm interested in the right system beyond just alignment (which will be an issue for the engine installer anyway).

 

And we do move - just another one of the considerations in my mind. So do still need an engine. 

 

Also - where do you even get any advice on Aquadrives from - they seem to have a network of distributors rather than a UK presence... hmm... 

 

[Tracy D'arth]

Aquadrive was GKN.  Ask Furnace Vale Marina.

Also Python Drive, similar but cheaper.

Its not just the initial alignment that is vital but the continued alignment when the boat is used, mountings do settle over time.

[TandC]

Thanks - looks like Aqua is now with Halyard - https://halyard.eu.com/aquadrive-antivibration-systems/ .

 

Python Drive - looks like that is another option and from previous posts comment that they're cheaper and take up less length, although those are older posts so things may have moved on.

 

Thanks - grateful for anyone else's experiences. 

[GUMPY]

Loddon has a Python drive, 30 years old and still functional 🤔

[Tony Brooks]

That is a larger engine and you may have trouble getting a two element flexible coupling in whilst still allowing access to repack the stern gland. The common two element flexible couplings are one modem by Centaflex and the two that use constant velocity joints mentioned above.  Two element flexible couplings can handle both radial and angular misalignment such as when a flexibly mounted engine jumps about on its rubber mounts or the mounts collapse under load (which they will do over time).  Single element flexibles can only cope with angular misalignment so you tend to get more vibration and possibly noise when underway.

 

Some flexibles are far from flexible so in my view should not be sold as such so check the specks.

 

An alternative is a rigidly mounted engine, properly aligned, and no flexible coupling but that is very old school and I doubt Beta supply an engine that does not use flexible mounts.

 

The two element flexibles also contain a thrust bearing to take prop thrust so the engine is not being pushed forwards and backwards as you go into ahead and astern. This helps the life of the rubber engine mounts.  The fact the shaft can not wave bout helps the life of any gland packing and the shaft bearings.

 

I note that you say you will not be moving much but the extra cost of Aquadrive is peanuts compared with the cost of the boat and it may well be a selling point in the future. I consider such couplings very well worth the money.

 

The topic title says stern gear and that includes the shaft, bearings and gland. Personally I would always go with a conventional packed gland plus an Aquadrive but some seem to like the Vetus stern gear with a packless gland and a rubber shaft bearing.  I don't think rubber bearings running in mud soup are a good idea (fine on clean rivers). If you are persuaded to go down the Vetus route make absolutely sure what you are getting into, both technology, ongoing cost, maintenance and design wise (they use a non-standard shaft taper for the prop). Such a setup handles the engine jumping about better than a conventional gland and bearings but not as well as the Aquadrive.

[TandC]

Thank you Tony.  My thinking was along the same lines that the cost of Aquadrive at this stage is minimal in amongst everything else. 

 

When you say may struggle to "get it in" - what would be a minimum distance between the stuffing tube and the coupling to allow repacking? 

 

Because of course you're right -  it is all these component parts which dictate the position of the engine - how far forward it sits from the V point where the swim joins/ends (does that point have a technical term?!).    And then at that point, only then can you decide on the placement of the bulkhead in front of the engine...     I guess in my head I am thinking - what is the MINIMUM distance, because that allows the engine to sit further back and the bulkhead to come back too. 

 

So, is there a bit of wisdom on how much room you need to allow for easy re-packing?

 

 

Oh, the other thought I had with relevance perhaps to the bulkhead:  The size of the keel cooling tank:  It needs to be 12.5 ft2 in surface area.    Is it bad practice to have any of the skin tank within the cabin area, the bulkhead mounted over it so that some still extends along the swim but into the cabin...

 

So many variables my head hurts.

 

I should also say that Nick at TW Marine has been incredibly helpful so thanks for that tip.   

 

Loddon - thanks for the Python recommendation.  I did  discuss Python with T W Marine and Nick said it now retails more expensive that Aquadrive... 

[Tony Brooks]

22 minutes ago, TandC said:

When you say may struggle to "get it in" - what would be a minimum distance between the stuffing tube and the coupling to allow repacking? 

 

To a degree that depends upon the type of gland. Let us assume it is a conventional two stud affair, with a pusher that pushes the packing into an oversize bore in the gland casting and keeps the packing all but water tight. I would say the length of the pusher plus an inch. If the gap with the pusher pulled ack is much less it makes it more difficult to remove the old packing and fit the new.

 

22 minutes ago, TandC said:

I did  discuss Python with T W Marine and Nick said it now retails more expensive that Aquadrive... 

 

He also claims it is more noisy, but remember he is an Aquadrive agent. However, he gives first class customer service so that would be enough for me. Very nice chap, as his dad was.

[IanD]

24 minutes ago, TandC said:

Thank you Tony.  My thinking was along the same lines that the cost of Aquadrive at this stage is minimal in amongst everything else. 

 

When you say may struggle to "get it in" - what would be a minimum distance between the stuffing tube and the coupling to allow repacking? 

 

Because of course you're right -  it is all these component parts which dictate the position of the engine - how far forward it sits from the V point where the swim joins/ends (does that point have a technical term?!).    And then at that point, only then can you decide on the placement of the bulkhead in front of the engine...     I guess in my head I am thinking - what is the MINIMUM distance, because that allows the engine to sit further back and the bulkhead to come back too. 

 

So, is there a bit of wisdom on how much room you need to allow for easy re-packing?

 

 

Oh, the other thought I had with relevance perhaps to the bulkhead:  The size of the keel cooling tank:  It needs to be 12.5 ft2 in surface area.    Is it bad practice to have any of the skin tank within the cabin area, the bulkhead mounted over it so that some still extends along the swim but into the cabin...

 

So many variables my head hurts.

 

I should also say that Nick at TW Marine has been incredibly helpful so thanks for that tip.   

 

Loddon - thanks for the Python recommendation.  I did  discuss Python with T W Marine and Nick said it now retails more expensive that Aquadrive... 

 

If you want to avoid re-packing (and greasing) you could also consider a PSS shaft seal, these are generally reckoned to be the best/most reliable -- but like Aquadrive, are also expensive...

[GUMPY]

Mine is on a Beta 50 the original owner struggled with cooling in a NB so converted the engine to Heat exchanger cooling which I am very happy about as it works well. Couple of 30 year old pictures of the install. At this point the engine is keel cooled but the exhaust and oil cooler is raw water cooled.

My Beta is so old it predates their colour system

 

There is plenty of room to access everything even though now its all boxed in (pictures were taken pre fit out)

[ditchcrawler]

4 hours ago, TandC said:

Thanks - my comment re. easier alignment was really just explaining the extent of the advice from Beta - which wasn't that  helpful.  Obviously i'm interested in the right system beyond just alignment (which will be an issue for the engine installer anyway).

 

And we do move - just another one of the considerations in my mind. So do still need an engine. 

 

Also - where do you even get any advice on Aquadrives from - they seem to have a network of distributors rather than a UK presence... hmm... 

 

Its something normally installed by the boat builder, I am not surprised Beta wouldn't advise, the marinise engines not fit boats. The aquadrive is just a coupling to go between the shaft and the gearbox. With a flexibly mounted engine I would say its a good idea.

[IanD]

21 minutes ago, ditchcrawler said:

Its something normally installed by the boat builder, I am not surprised Beta wouldn't advise, the marinise engines not fit boats. The aquadrive is just a coupling to go between the shaft and the gearbox. With a flexibly mounted engine I would say its a good idea.

There are also some drives which allow misalignment (and transfer thrust to the hull) but are shorter than the Aquadrive/Python (and have better noise isolation) such as the Centaflex-AGM-16-1 (OK for Beta 50 with standard 2:1 gearbox), but they're not easy to find in the UK -- might also be cheaper than Aquadrive/Python...

 

Edited October 27, 2022 by IanD

[J R ALSOP]

37 minutes ago, Tony Brooks said:

 

To a degree that depends upon the type of gland. Let us assume it is a conventional two stud affair, with a pusher that pushes the packing into an oversize bore in the gland casting and keeps the packing all but water tight. I would say the length of the pusher plus an inch. If the gap with the pusher pulled ack is much less it makes it more difficult to remove the old packing and fit the new.

 

 

He also claims it is more noisy, but remember he is an Aquadrive agent. However, he gives first class customer service so that would be enough for me. Very nice chap, as his dad was.

Just like to say as Nicks dad I am still well alive and kicking.

[Tony Brooks]

1 hour ago, J R ALSOP said:

Just like to say as Nicks dad I am still well alive and kicking.

 

Thanks, As I had not seen him at Crick or the Marina for years I feared the worst.

[Bee]

In my opinion the arrangement pictured by Loddon is about as good as it gets. Conventional stern gland, hefty python drive thrust bearing and two CV joints. The only thing I would take issue with is the colour - yellow and brown!!?  That's never right and will lead to sea sickness.

[Alan de Enfield]

5 minutes ago, Bee said:

I would take issue with is the colour - yellow and brown!!? 

 

Vomit and Diarrhea

[GUMPY]

54 minutes ago, Bee said:

In my opinion the arrangement pictured by Loddon is about as good as it gets. Conventional stern gland, hefty python drive thrust bearing and two CV joints. The only thing I would take issue with is the colour - yellow and brown!!?  That's never right and will lead to sea sickness.

Its not yellow and brown that's due to colour saturation in the picture, its more cream and a maroon/red.

2012 picture

 

 

 

[blackrose]

18 hours ago, TandC said:

But while we've fixed on that engine arrangement - we haven't fixed what stern gear we should go with....   I have asked Beta for recommendations and I wasn't entirely reassured with the "that's for you to decide" answer, although when I spoke to someone else there they said "well i think a lot of people use the Aquadrive because it makes alignment so easy".

 

I'm confused by this thread because I thought "stern gear" included all propulsion equipment behind the gearbox including prop shaft, propeller and possibly stern gland. But the discussion only seems to be about a flexible coupling? Isn't the choice of prop quite important?

[Tony Brooks]

11 minutes ago, blackrose said:

 

I'm confused by this thread because I thought "stern gear" included all propulsion equipment behind the gearbox including prop shaft, propeller and possibly stern gland. But the discussion only seems to be about a flexible coupling? Isn't the choice of prop quite important?

 

That is why I added the last paragraph to my first post in this topic. The first post did not make clear how much the OP knew about "the stern gear" so I felt the rest of the gear needed raising.

[blackrose]

39 minutes ago, Tony Brooks said:

 

That is why I added the last paragraph to my first post in this topic. The first post did not make clear how much the OP knew about "the stern gear" so I felt the rest of the gear needed raising.

 

Yes, I saw you'd mentioned it, but the main topic of discussion still seems to be the coupling, which to my mind isn't as important as matching the engine and gearbox with the right prop.

[J R ALSOP]

14 hours ago, Tony Brooks said:

 

Thanks, As I had not seen him at Crick or the Marina for years I feared the worst.

Tony, it was Steve's dad Willy Web who passed away a few years ago.

[ditchcrawler]

1 hour ago, blackrose said:

 

Yes, I saw you'd mentioned it, but the main topic of discussion still seems to be the coupling, which to my mind isn't as important as matching the engine and gearbox with the right prop.

Maybe they have sorted that bit.

[IanD]

13 hours ago, Bee said:

In my opinion the arrangement pictured by Loddon is about as good as it gets. Conventional stern gland, hefty python drive thrust bearing and two CV joints. The only thing I would take issue with is the colour - yellow and brown!!?  That's never right and will lead to sea sickness.

 

A conventional stern gland can be difficult to access with the "Super Silent" Beta 50 that the OP is proposing, the box gets in the way. And on a super-quiet boat the Aquadrive also transmits some noise through to the prop/bearing (especially if a bronze stern tube bearing is used) because it's torsionally rigid (all metal-to-metal contacts), compared to other like the Centaflex which has rubber isolation elements.

 

I know some people (including Bee) think a conventional stern gland is best because it's cheap and simple and can be restuffed relatively easily, but a good-quality greaseless stern gland like PSS is also very reliable and long-life and needs no maintenance at all, it uses a carbon/stainless face seal -- unlike the Vetus and others which rely on o-ring seals which are less reliable and need lubrication with silicone (every 250h IIRC).

 

Both have advantages... 😉