Metal to metal adhesive, reliability / performance

[Malish]

Hi
I have a '78 Rival 34 with a stainless 70L fuel tank suspended from the cockpit floor and held in place by four tangs close to the corners of the tank, the tangs attach the top of the tank to the underside of cockpit floor via threaded studs from the cockpit floor. Whilst inspecting the shaft seal at the weekend I noticed one of the tangs had failed at the welded point of contact with the tank (with subsequent slight movement of the tank) something that I didn't like to see. Whilst the perfect solution would likely be take the tank out and repair or replace, that would also involve removal of the engine and a large amount of faff. I wondered if an alternative approach would be to use a metal-metal adhesive, such as one of the 3M Scotch Weld series, to glue a new L shaped tang onto the side of the tank in order to resolve the issue. Does anyone have experience of these adhesives (I don't) - would this approach work? Take surface preparation and de-greasing with acetone as a given.

 

[vyv_cox]

I would only use an adhesive in conjunction with a mechanical solution. Is it possible to make a larger L shaped bracket and pop rivet it to the tank? With adhesive between to close any leaks.

 

[Clancy Moped]

For a quick fix I've used this stuff with success.

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[Fr J Hackett]

Can you not get someone to weld a new tang on insitu

 

[ean_p]

Without any doubt I would install a strap that picks up both studs and wraps down and around and up again to attach to the stud at the opposite side so that the tank is 'hung' in the strap. While at it I would fit one to the other two studs also. You might want to check for a perforation in the area of the torn weld too? If yo go ahead and fit a couple of straps as suggested then some insertion rubber between tank and strap will make for a snug fit.

 

[Arcady]

I‘m currently in Holland watching the fit out of a new aluminium boat. I’m amazed how many fixings are glued to metal. Sometimes metal to metal, sometimes wood to metal. I asked one of the managers how long a glued joint was good for. He shrugged his shoulders and told me “more than fifty years” He went on to explain that he used to work for Fokker aircraft and that much of each aircraft was glued together.

I was intrigued to see that all of the interior joinery on our boat is fastened to hundreds (thousands?) of wooden blocks all glued to the metal frames. Not a mechanical fastening in sight.

All the above has caused me to reconsider my past predjudices against glued-only joints. I think if you design a new tang with enough surface area, and take good advice regarding glue, I suspect it will be fine.

 

[vyv_cox]

I‘m currently in Holland watching the fit out of a new aluminium boat. I’m amazed how many fixings are glued to metal. Sometimes metal to metal, sometimes wood to metal. I asked one of the managers how long a glued joint was good for. He shrugged his shoulders and told me “more than fifty years” He went on to explain that he used to work for Fokker aircraft and that much of each aircraft was glued together.

I was intrigued to see that all of the interior joinery on our boat is fastened to hundreds (thousands?) of wooden blocks all glued to the metal frames. Not a mechanical fastening in sight.

All the above has caused me to reconsider my past predjudices against glued-only joints. I think if you design a new tang with enough surface area, and take good advice regarding glue, I suspect it will be fine.

I agree with all you say but there is a world of difference between a factory fitted, designed joint and a bodged repair using a DIY adhesive. ( No disrespect to the OP).

I like the straps idea but they will need some stiff angle in the corners to keep them tight .

 

[Malish]

Thanks for the responses, they cover most of the permutations I have reflected upon
Space to do anything close to the tank is at a premium, I'll have a chat with the local stainless welder to see if he is interested; I didn't want to make holes in the tank unless as a last resort.; the tang attachments are in front of the tank so any straps would have to be in an X arrangement (but I was giving that some serious thought as a second line of defence). Arcady's comments align closely with mine in terms of past prejudices and current thoughts, hence the original question... I also have vague recollections of Lotus car metal-work now being glued together; 3M Scotch Weld is not a low grade product although granted I will not be in a factory environment. I would just like to know if others have experience of using it in anger so I can either minimise the the 'DIY bodge' tag or take a different route.

 

[Daverw]

Can you fix brackets above and use ratchet strap to hold tight?