A bit of help with epoxy and glass specifications please

Timbow

Timbow

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I am repairing an old mahog grab rail off the coach roof. I have removed it and it isn't broken in two but cracked and weakened. I am going to get some glue into the crack and cramp it but it needs to be a strong repair - you can't have a grab rail that breaks when you grab it, so I was going to wrap glass mat around the wood and impregnate with epoxy several times to encapsulate the weak section. I have seen it done on spars so the fine mat is invisible and it looks just like thick varnish. I don't think it will give me any difficulty, but...

When I order the mat what exactly am I wanting to ask for? Is it a particular weave or fineness? Is there any complication with matching the mat and resin or applying the two?

Thanks.
 
The surface tissue will be fine, however rovings of the weight would provide more strength in this application.

Also note, epoxy resin is not UV stable and will break down on deck unless you cover it with a highly UV rated varnish.

Sand off and high spots first, don't try to close the crack, better to fill with glue for a stronger finish.

After sanding and cleaning, mix a small batch of epoxy and hardener then add 30% by volume or weight it doesn't matter, of Methylated Spirits, this helps the epoxy penetrate the surface.

Let this cure and lightly sand and clean, mix another smaller batch of resin and hardener and add some micro fibres or tiny bits of fibreglass and add some of the dust from the sanding to colour the mix, apply this only in the open crack/s and overfill just a bit; now apply the roving with the overlap on the underside of the rail.

Let this cure and sand as needed then clean, you can now apply the UV blocking varnish.

Hope this helps.

Avagoodweekend......:)
 
oldsaltoz said:
After sanding and cleaning, mix a small batch of epoxy and hardener then add 30% by volume or weight it doesn't matter, of Methylated Spirits, this helps the epoxy penetrate the surface.
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I have it on good authority that you shouldn't use more than 10% methanol (or meths) to thin epoxy resin because it weakens it. 10% does make a big difference to the viscosity. Remainder as per oldsaltoz's post, especially the varnishing bit - many (6 or more) coats of a good UV protective varnish is required...

Hth,

Boo2
 
Thanks all. I had heard that epoxy would discolour in sunlight but i wasn't aware that it was so very vulnerable to UV. What happens if it is left unprotected? By the time I have done my glue repair, epoxy/glass sheathing several times and then a minimum six coats of varnish I could have made a new rail from teak and left it in the white.
 
Timbow said:
Thanks all. I had heard that epoxy would discolour in sunlight but i wasn't aware that it was so very vulnerable to UV. What happens if it is left unprotected?
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Eventually it cracks and crumbles away from the substrate.

Timbow said:
By the time I have done my glue repair, epoxy/glass sheathing several times and then a minimum six coats of varnish I could have made a new rail from teak and left it in the white.
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I'd do that, tbh. Thin glass cloth won't add that much strength anyway, and while it might seem sound you really need the grab rail to be strong enough to stop a falling man as the last ditch between them and the sea.


Boo2
 
Boo2 said:
I have it on good authority that you shouldn't use more than 10% methanol (or meths) to thin epoxy resin because it weakens it. 10% does make a big difference to the viscosity. Remainder as per oldsaltoz's post, especially the varnishing bit - many (6 or more) coats of a good UV protective varnish is required...

Hth,

Boo2
Click to expand...


Listen to Oldsaltoz, he is the man on these matters.
 
repair

Timbow said:
I am repairing an old mahog grab rail off the coach roof. I have removed it and it isn't broken in two but cracked and weakened. I am going to get some glue into the crack and cramp it but it needs to be a strong repair - you can't have a grab rail that breaks when you grab it, so I was going to wrap glass mat around the wood and impregnate with epoxy several times to encapsulate the weak section. I have seen it done on spars so the fine mat is invisible and it looks just like thick varnish. I don't think it will give me any difficulty, but...

When I order the mat what exactly am I wanting to ask for? Is it a particular weave or fineness? Is there any complication with matching the mat and resin or applying the two?

Thanks.
Click to expand...
Life long boat builder Here !
Use Balcotan 100 fast its stronger than epoxy and will fill gaps up to 3 mm. Just spray the area with a fine water mist and apply the glue wait till totaly set sand and varnish no need for tape. All the best Pete
 
theguerns said:
Life long boat builder Here !
Use Balcotan 100 fast its stronger than epoxy and will fill gaps up to 3 mm. Just spray the area with a fine water mist and apply the glue wait till totaly set sand and varnish no need for tape. All the best Pete
Click to expand...

Hmm. Not really. It certainly isn't strong when bridging gaps. But yes I may well use PU Glue to do the initial mend.

Thanks
 
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