Thread repair epoxy?

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chrisbitz

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Bromley, Kent - Sail in Medway
www.freyacat.co.uk
my boat has a lot of fixings screwed straight into the hull with machine screws, which initially, I thought was a bit strange?

However I looked on the inside yesterday, and noticed that there is some hard white stuff that they're actually screwed into, maybe embedded into the GRP?

Some of these screws are no longer gripping.. How best can I repair them? is it possible to get some sort of liquid I can drip into the holes, and then screw up tight again, or something along those lines? It's not an easy job to get to the inside and put a nut and washer on, as I initially thought...
 
nigelmercier said:
More likely they are screwed into nuts that have been epoxied in.
Click to expand...

Is that the normal way that they do that sort of thing..? I don't think it is on this boat, there is no bulge on the inside where a nut could go. just about 1/4" GRP?

Also, I've just remembered, I have seen self tapping screws used too.. But these machine screws are on the winches on top of the coachroof..?
 
Thanks very much, that sounds spot on. Fortunately, I got it all back on OK again, as I wanted to seal it with butyl tape. I can only guess that the threads in some of the plate holes have gone.. I'll put a longer screw and a nut on them

I've also got a wobbly pulpit too, and I'm pretty sure that has self tapping screws.. Do you know of an epoxy that I can repair those threads with?
 
Although they grip well in grp, a self-tapper isn't the strongest of fittings for something like a pulpit. It should really be through-bolted if that is practicable, with a backing plate (or at the very least, substantial 'penny' washers). If the hole itself needs repair, you should bore oversize, bevel the edges (inside edge in particular), fill with epoxy + microfibres, then re-drill the hole. Better still, also slap another layer or two of rovings on the inside. I'm assuming the decks aren't cored, in which case a slightly more elaborate approach would be needed.
 
chrisbitz said:
my boat has a lot of fixings screwed straight into the hull with machine screws, which initially, I thought was a bit strange?

However I looked on the inside yesterday, and noticed that there is some hard white stuff that they're actually screwed into, maybe embedded into the GRP?

Some of these screws are no longer gripping.. How best can I repair them? is it possible to get some sort of liquid I can drip into the holes, and then screw up tight again, or something along those lines? It's not an easy job to get to the inside and put a nut and washer on, as I initially thought...
Click to expand...
Try putting them in with some filled epoxy. If you have some liquid epoxy use a little high density filler with it rather than an easy-to-sand low density type.

Otherwise look out for a filled epoxy such as JB Weld http://www.jb-weld.co.uk/j-b-weld-guides-and-repairs/how-to-use-j-b-weld-original


Clean the screw threads but if then coated with the thinnest possible film of oil or grease they will not be glued in and it will be possible unscrew them at a later date if necessary


I usually use some epoxy with self tappers in GRp but I'd not use self tappers for anything that takes much critical load. I'd through bolt a pulpit with good backing pads and plates or penny washers
 
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Have seen pullpits/pushpits attached with just a machine screw, with no backing or nut. The idea presumably is that in the event of an accident, the screw pulls out before too much damage to the hull.
 
Pye_End said:
Have seen pullpits/pushpits attached with just a machine screw, with no backing or nut. The idea presumably is that in the event of an accident, the screw pulls out before too much damage to the hull.
Click to expand...

Yes I've seen that and I think it's criminal, because sooner or later a heavy bloke is going to grab hold and haul himself out of a dinghy, wearing a heavy rucksack, with an outboard motor in his other hand. Through bolts with backing are vital in my view!
 
jerrytug said:
Yes I've seen that and I think it's criminal, because sooner or later a heavy bloke is going to grab hold and haul himself out of a dinghy, wearing a heavy rucksack, with an outboard motor in his other hand. Through bolts with backing are vital in my view!
Click to expand...

The installation I have in mind would need considerably higher forces than that to pull them out and does not carry this sort of risk.
 
My boat was built with a lot of Helicoil thread inserts in the grp; eg for the rudder strap screws, genoa track screws, etc.

She's 46 years old so it must be a technique that's reliable.
 
The use of helicoils set in GRP for deck fittings is a new one on me. How do they fair corrosion wise? I am assuming they are made from steel.

Any way back to Q posed by the OP.

JB Weld would be the stuff I would use. It can be tapped and would be as strong if not stronger than the original thread in GRP.
 
jerrytug said:
Yes I've seen that and I think it's criminal, because sooner or later a heavy bloke is going to grab hold and haul himself out of a dinghy, wearing a heavy rucksack, with an outboard motor in his other hand. Through bolts with backing are vital in my view!
Click to expand...

Blimey! If he tried that on my boat, the whole pulpit would have crumpled, regardless of the fixings!! It's only 1" tubular stainless!
 
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