Radice seal question

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Restoration man

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Hi I’ve just bought a pair of genuine rmta Radice seals to replace traditional stuffing boxes on my storebro biscay 31 , most people seem to have nothing but praise for these , and there a 1/4 price of P.S.S. seals and in my opinion less moving parts to go wrong, while I was waiting for them to arrive I was looking on the net and accidentally found the instructions for the Volvo version ( apparently made by the same company as Radice seals or so I’ve read on this forum ) in the Volvo manual it states that a maximum of 150mm between the center of the p bracket cutlas bearing to the gearbox flange see photos below mine is 160mm ,it states that if it’s longer than the 150mm it will require a support bearing being installed, I’m assuming a new stern tube with cutles bearing in it ???my Radice seals have now come and nothing is mentioned in there instructions regarding this ? I don’t want to have to get new stern tubes made with cutless bearings as this is going to add to the cost Significantly , just wondering what your thoughts are on this matter C2CEF5F4-FEF9-4186-8816-BE92851C98E9.jpeg3FF5E2A4-81BF-4DBD-B4A1-68363BE8D80F.jpegC42EEC85-F646-4F87-B31F-7ED9F194B8B1.jpeg24069CEB-F436-4A94-9F4E-771ED25F4E97.jpeg2EF6AF3E-F16D-4F0D-8C20-754BC70D44F5.jpeg
 
Speak to Lake Engineering who are the distributors. You don't say what the inboard end of the stern tube is like and whether it is possible to fit a bearing, although I would think the small excess length is unlikely to be a problem. Funnily enough I was dealing with exactly the same issue on my own boat today discussing the new engine and stern gear. The shaft is not as long as yours, but we are still going to put a bearing in the forward end of the tube because I want to use a Bullflex coupling and these work best if the shaft has 2 bearings.
 
vyv_cox said:
Your highlighted text says 1.5 metres, not 150 mm.
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Sorry my mistake missed a zero off , so my unsupported length is 100mm longer than the recommended 1500mm , I have solid gearbox Coupler don’t know if that helps ? But as I said nothing is mentioned in the Radice instructions
 
Restoration man said:
Sorry my mistake missed a zero off , so my unsupported length is 100mm longer than the recommended 1500mm , I have solid gearbox Coupler don’t know if that helps ? But as I said nothing is mentioned in the Radice instructions
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The first critical of a 25 mm shaft as long as 1600 mm is going to occur at quite low rpm so there is a very good chance that it will bang on the stern tube at certain revs. There could also be quite high displacements at the seal, which will probably not be good for it.

I would do as Tranona suggests and fit a bearing or bush at the inboard end of the stern tube.
 
vyv_cox said:
The first critical of a 25 mm shaft as long as 1600 mm is going to occur at quite low rpm so there is a very good chance that it will bang on the stern tube at certain revs. There could also be quite high displacements at the seal, which will probably not be good for it.

I would do as Tranona suggests and fit a bearing or bush at the inboard end of the stern tube.
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I have got 40mm shafts on this ,not sure if there less prone to whipping around at this diameter ?
Ive not noticed any witness marks on the shafts or the tubes ,even though it was badly aligned and the shaft was nearly touching the tube at the bottom , the old engine mounts must have gone soft ,
Also one of the shafts was also bent, I can only assume this happened by hitting something as the p bracket had been messed with by previous owner, I can’t comment much other than the above , as I’ve never actually been out on the boat I bought it as fixer upper
 
Restoration man said:
I have got 40mm shafts on this ,not sure if there less prone to whipping around at this diameter ?
Ive not noticed any witness marks on the shafts or the tubes ,even though it was badly aligned and the shaft was nearly touching the tube at the bottom , the old engine mounts must have gone soft ,
Also one of the shafts was also bent, I can only assume this happened by hitting something as the p bracket had been messed with by previous owner, I can’t comment much other than the above , as I’ve never actually been out on the boat I bought it as fixer upper
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A rule of thumb is nsupported length between two bearings should not be more than 40x the diameter of the prop shaft. That would be 1.6 meters for a 40mm shaft. However, as you have a solid coupling between gearbox and shaft that will significantly reduce the tendency to whip so I believe you are ok and no need to add an intermediate bearing. Obviously, radial and angular alignment at the coupling is critical and a Volvo/Radice seal will work well, it certainly does on my similar installation!

Www.solocoastalsailing.co.uk
 
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I would think with your 40mm shafts the P bracket cutless will be at least 125mm long. How much of the shaft is aft of the stern gland? The Radice is a pretty good support bearing with effectively about 60mm of cutless type support aft of the lip seals.
 
Tranona said:
I would think with your 40mm shafts the P bracket cutless will be at least 125mm long. How much of the shaft is aft of the stern gland? The Radice is a pretty good support bearing with effectively about 60mm of cutless type support aft of the lip seals.
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Hi my p bracket cutless bearings are 160mm in length I’ve included a picture of the current set up , Do you know if the Volvo version has the cutless type support like the Radice version C5CB9AC9-5094-4176-9F53-782DC21E8060.jpeg8C594437-B333-4313-A453-EAE45B8EDC40.jpeg
 
The Volvo is near enough identical to the Radice - as you know made by the same firm in Italy. I would think you are pretty safe using the seal, but worth speaking to Lake Engineering first - they are very knowledgeable. Not clear what the current hose is attached to (have you checked it is the right diameter to take the seal?). It may be just a GRP stub, but there might be enough clearance to insert a composite bush as a bearing, although that would allow no movement of the engine so you would need a flexible coupling. As I said earlier the set up I have used and am fitting in my current boat is a bearing in the tube and a Vetus Bullflex coupling. this allows the engine to move independent of the shaft and even allows a small amount of misalignment. BTW assume you are going to feed water to the seals from the engine.
 
Plum said:
A rule of thumb is nsupported length between two bearings should not be more than 40x the diameter of the prop shaft. That would be 1.6 meters for a 40mm shaft. However, as you have a solid coupling between gearbox and shaft that will significantly reduce the tendency to whip so I believe you are ok and no need to add an intermediate bearing. Obviously, radial and angular alignment at the coupling is critical and a Volvo/Radice seal will work well, it certainly does on my similar installation!

Www.solocoastalsailing.co.uk
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Thanks that’s good to know , also the measurements I took were to the middle of the cutless bearing ,if I were to measure to the front of the bearing it’s only 1525mm , I don’t think it’s been moving much in the past as I can’t see any marks on either shaft or tube so ? it should be ok
 
Tranona said:
The Volvo is near enough identical to the Radice - as you know made by the same firm in Italy. I would think you are pretty safe using the seal, but worth speaking to Lake Engineering first - they are very knowledgeable. Not clear what the current hose is attached to (have you checked it is the right diameter to take the seal?). It may be just a GRP stub, but there might be enough clearance to insert a composite bush as a bearing, although that would allow no movement of the engine so you would need a flexible coupling. As I said earlier the set up I have used and am fitting in my current boat is a bearing in the tube and a Vetus Bullflex coupling. this allows the engine to move independent of the shaft and even allows a small amount of misalignment. BTW assume you are going to feed water to the seals from the engine.
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I’ve got bronze stern tubes, the id is to big to take a 40mm cutless , the od is 70mm instead of the 60mm needed by the Radice seal I plan on using a silicone 70mm to 60mm reducer to reduce the size or have a 60mm pipe welded to accept the Radice
C93F6006-B6DF-4B58-AF52-1B4D8AD484C4.jpeg6DC594AF-D03F-43CD-9958-BCD8C7C4D6EC.jpg
 
Look at having that sleeved and turned down on the outside to 60mm. That is what we did when we replaced a white metal bearing in a Stuart Turner stern tube using a standard 1" cutless. Expect to do something like it on my current project but have not dismantled it yet. Really suggest you talk to Lake Engineering as this is just the sort of thing they are good at. See what they suggest. No connection other than a satisfied customer over the years. However that will still mean you have a solid connection and you need then to have a flexible coupling. Don't know the reducer in your link but my concern would be whether the 60mm stub would be robust enough to get a clamp seal for the Radice.
 
Tranona said:
Look at having that sleeved and turned down on the outside to 60mm. That is what we did when we replaced a white metal bearing in a Stuart Turner stern tube using a standard 1" cutless. Expect to do something like it on my current project but have not dismantled it yet. Really suggest you talk to Lake Engineering as this is just the sort of thing they are good at. See what they suggest. No connection other than a satisfied customer over the years. However that will still mean you have a solid connection and you need then to have a flexible coupling. Don't know the reducer in your link but my concern would be whether the 60mm stub would be robust enough to get a clamp seal for the Radice.
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I don’t think I could get it turned down as small as 60mm without modification because the ID is to big and the wall thickness might become to thin, I could have bronze reducer turned up I’ve got a chap who does stuff like that for me and he’s cheap and get it welded or epoxy in ??? Or just epoxy a sleeve in and turn it down to 60mm ?? , not sure if you understood my other idea ? But have look at the picture I was planning on putting a 60mm stainless joiner tube between the silicone tube and the Radice seal see by crude drawing 5469C4AC-5F1D-4C86-81EA-6A819ADD0FB9.jpeg
 
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