epoxy and stainless

[Talmine]

I have a stainless steel stern tube exiting through the fibreglass on my long keel yacht, Biscay 36. A leak has developed around the stainless/fibreglass join. It is apparent that this tube was installed during construction with the seal being acheived through a lot of internal fibre glass. This is now impossible, for me, to reach.
I propose to cut a significant groove into the the fibreglass around the external part of the tube and fill this with epoxy. My questions are; does epoxy adhere well to stainless, I have some West system left over from a previous job, or is there a better alternative.

Jim

 

[nimbusgb]

provided the stainless is roughed up epoxy should bond well to it.

Is there a better way. Well there are a few other options but I think I'd go about it the same way. A lot depends on how big your 'big groove' is. I think I would be tempted to cut back quite a large area to ensure the seal and integrity of the construction. Big job.

 

[tobble]

Should bond well as long as you prep the surfaces properly, i.e. thoroughly degrease with meths or similar. would suggest you go over with more glass too as your groove will compromise the strength - you're talking about a lot of force on it as the engine bounces around

My stern tube came out in my hand when I was trying to get the cutlass holder off last year! I used Sikaflex to make a waterproof joint, and epoxy/fibreglass for rigidity. probably an odd way to do but that's what made sense to me at the time...

 

[castaway]

Is the stern tube fixed with the 2 bolts in the usual way ? If that is the case it may be better to use Sikaflex ( or similar) as a seal rather than using the epoxy/original GRP to hold it in place.

Has the shaft been damaged or running out of alignment?.

I guess if you plan on using epoxy a call to SP systems or West might be best bet to get reliable info ?


Regards Nick

 

[oldsaltoz]

G'day Jim.

The west system resin will be perfect.

Use a chisel to open the area up, look for any brownish discoloration, indicating a problem area, this should be removed, as should any very white abd dry looking glass (lacking enough resin when applied).

Also very important that the material is very dry, or you will be sealing moisture in and causing a bigger problem later.

Remove any discolouration on the stainless tube with a non ferrous tool and clean the area with Acetone about 15 minutes before you start mixing resin.

You could slip an '0' ring over the tube prior to glassing. (We invented this and have been doing it for many years on rudder stocks with no problems). Just make sure it's a good fit and get a dab of Vaseline under it making sure the tube has none left on it.

You could use Micro-fibres and finish with a layer or two of roving's to give a smooth finish. Do not CSM as the voids will result in more resin being used and less strength.

I hope this helps.

Avagoodweekend......

 

[VicS]

I think I would prefer something with a degree of flexibility such as Sikaflex or a similar polyurethane adhesive sealant.

Whatever you use the key to success will lie with the preparation of the surfaces.

There are primers for Sikaflex

Sikaflex Users Guide

Sikaflex Marine Handbook

 

[savageseadog]

To fix a leak Sikaflex would be more useful.

I don't know what access problems you have or the exact configuration of what your dealing with but I have an idea that might work. It is possible to obtain long diamond drills which are basically a metal tube with a cutting edge at the end. You would get a drill that would fit over the shaft with a collar (sticky tape) or turned wooden dowel with step. This would create a concentric void.

 

[Talmine]

Thanks for the advice. I have spoken to Wessex Resins (West) who made similar comments about preparation and suggested I use their 404 high density filler as it is structural. The tube doesn't have the normal 2 studs to bolt a collar onto but I'm considering epoxying studs in and making a collar to hold a sikaflex joint as a back up. Thanks for the O ring suggestion I'll definately try to incorporate that. A belt and two pairs of braces is my favourite approach. Looks like I'm going to be busy.

Jim

 

[matelot]

never been wildly keen on bonding dissimilar materials in this way. Added to that I have had nasty experiences with stainless in situations where a joint between stainless and grp has leaked but insufficient air was available and the stainless corroded at a rate / in a way you wouldnt believe. Are you sure that the tube is still sound? In one piece even? Have you tried moving it?

Might not be practicable in your case but I would think of removing the stainless altogether and replacing with an epoxy bonded GRP tube