Bonding metal to grp

parsifal said:
What was the original arrangement installed by the builder and what's wrong with repairing/restoring that? I'm sure he would have gone for the simplest solution.
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Unfortunately the original setup had been bodged and replaced at some point in the past so I am starting again.
Fortunately another owner of the same model has provided details of his arrangement and copper is what is used there, possibly a thicker walled tube than I can obtain hence my desire to reinforce it.
For those not convinced about the metal choice, it is connected to a piece of bronze so I wish to avoid stainless as that could cause deterioration of the bronze.

If anybody has a 2m long bronze pipe/tube lying around then that would also be a suitable alternative!!
 
Kelpie said:
Unfortunately the original setup had been bodged and replaced at some point in the past so I am starting again.
Fortunately another owner of the same model has provided details of his arrangement and copper is what is used there, possibly a thicker walled tube than I can obtain hence my desire to reinforce it.
For those not convinced about the metal choice, it is connected to a piece of bronze so I wish to avoid stainless as that could cause deterioration of the bronze.

If anybody has a 2m long bronze pipe/tube lying around then that would also be a suitable alternative!!
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25mm X 15mm bronze tube is available, but it is about £50 per metre.
 
Hmmm. So I can get 26mm diameter bronze for a reasonable cost (c. £80) *but* the 3/4" BSP thread should be 26.6mm. So I could cut in a thread but it won't fully engage, and this seal is what stands between the sea and the inside of my boat.
The size that has the diameter and wall thickness I need will actually cost about £270.
Smiths can supply a somewhat better match at £220.
These prices are for SAE660, not Phosphor Bronze...
 
The major diameter of 3/4 BSP is 1.041" which I make out to be 26.4414. I would say that, in practice, this is not a real problem if you don't cut to full depth but slightly less. A fitting for a boat is not to a tool room or laboratory standard. IMHO. Feel free to disagree; it is your boat after all, not mine.
 
I would think it will be very difficult to achieve a consistent glue line over such a length. My business is with FRP materials and we use pultruded FRP profiles to make various things such as posts. These are often made by inserting one tube inside the other to achieve higher stiffness etc. But the problem has always been to ensure good bonding between the inner and outer tubes.

Just a thought, but would an alternative approach to wet-laminate over the metal tube be an option? You would achieve an ideal and consistent bond to the metal over the whole length. If you were to use boat tape with epoxy, this could be a reasonably neat solution. Granted the external finish will not be smooth (unless you fork and fill it!) but is this needed?
 
Yep a match would be pretty much impossible, but there are fillers that I would have thought would work for this application.

I don't claim to be a marine engineer (far from it) but I would be looking at a copper nickel alloy
 
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prof pat pending said:
Yep a match would be pretty much impossible, but there are fillers that I would have thought would work for this application.

I don't claim to be a marine engineer (far from it) but I would be looking at a copper nickel alloy
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The brazing rods I use are copper nickel. I suspect that it it would be cathodic to the bronze, dependent upon the precise composition, and clearly a lot smaller than the tube. We are not certain of the composition of the plate but its longevity suggests it to also be a bronze. So galvanically it may be OK but there is still some risk that would be better avoided.
 
Copper/Nickel is usually OK with Bronze iirc, but somewhat dependant on the Nickel content

Always tricky when working with unknowns.
We have a portable analyser at work which tells you the make-up of the metal after striking an arc on it. Great bit of kit, if I was closer I'd bring it along. Perhaps look for a company prepared to give a demo :)
 
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Well, thanks to everyone (especially Vyv) who has offered advice on this matter. Tomorrow I shall be ordering up a nice shiny length of bronze tubing, and have even worked out a way to get it up here. I'll post a pic of the finished article in position as it is quite hard to explain in words.

And, in the end, I'm not going to be bonding any grp to metal after all, so my thread was rather poorly titled...
 
I am seeking advice on how to bond a bronze shaft-strut (AKA a stern bracket, or P bracket) to a GRP hull. The boat is a Kingfisher 22+ and when it was built it was fitted with a 5 HP Brit Imp petrol inboard as recommended by the builders. The original owner had a great deal of trouble with the Brit Imp probably because the location of it being underneath the cockpit floor, was too hot. He removed the engine and binned-it. Presumably he did not own a gear-puller or propeller puller as the prop-shaft has been crudely hack-sawed through where it exits the hull. The P bracket was also disposed off "in order to reduce drag" and there is no propeller. Unfortunately the stern tube is for a 3/4" shaft which is a little non-standard. Power-wise 3/4" is not a problem as an old colleague the late "Captain Bligh" assured me that a 3/4" shaft would be OK for up to 20 HP without even upgrading to Duplex.

Anyhow I'm rambling on a bit (it comes with old age!) I've managed to buy a 3/4" P bracket that looks about the right size and I've bought spare Cutlass Bearings from Lake Engineering. The odd thing about the bracket is that there are no bolt holes for mounting it! Instead there is a black coating on its mounting foot. Some kind of adhesive must have been used but what would it be?

As to a power source, the space where the Brit Imp used to be is tiny. I did buy a used marine diesel that had a stainless-steel hydraulic motor but the hydraulic motor was stolen from my shed. The local Heroin addict who likes collecting what he calls scrap metal is the prime suspect as he often goes burgling to feed his habit. He is particularly partial to bronze-propellers.

Yanmar YSE, YSB or YSM engines are a possibility as they might fit underneath the sink. (With the Kingfisher 20 range the sink is part of the hull and is used as a step when entering the cabin!) The BMW D7 (Hatz industrial engine) is another possibility because of its low height but job number 1 is the adhesive.

Thank you for reading this rather lengthy letter and Best Regards from Davey.
 
I would stay away from BMW D7s and the Hatz related Renault diesels. Apart from their age, they seem to have few advocats and those that like them, also seem to love other old and tricky machinery.

With the cost of new replacement diesels, a friend with a 1GM10 has been talking about 'what if'? As a natural tinkerer, I have been looking at the marinization of one of the little engines used in the toy cars that one can drive without a licence here. They often turn up in scrap yards and I expect one of the two cylinder donks would be a good swop. Gearbox adapter and heat exchanger, along with an injector elbow... A day in the workshop?
DW
 
Agree with bolting on - never heard of a P bracket glued on. You may well have to reinforce the inside of the hull. Take great care in lining it up with the stern tube and shaft.

Don't waste your money on those old Yanmars. Not only are they big heavy things but will shake all the fillings out of your teeth and fittings on your boat!. The Hatz is only marginally better because it is smaller and lighter. The only sensible engine to fit is a 1GM or 1GM10. You should be able to get one secondhand reasonable, but try and buy with as many of the ancillaries as possible as you could easily find the cost being more than the value of the boat - and make an outboard seem like a better choice.
 
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