Grinding fibreglass

[bumblefish]

A prior owner of my dinghy undertook a real bodge job of slapping some GRP mat on the sole, it is now lifting and needs to be taken off, ground down and covered/coated. I intend to grind it back, see if I need to build it up again and then flowcoat or anti-slip paint it. But, what sort of grinder disc should I use, metal, stone? Any further advice would also be useful.

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[snowleopard]

after a lot of experimenting and building 6 grp hulls from scratch, i am convinced there is only one good way to do it:

a 4.5" (115mm) angle grinder with 24 grit sanding disc. cuts fast, doesn't clog, lasts for ages.

you can get the grinders for as little as £12 from screwfix.

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[AndrewB]

Just a coarse sandpaper disk on a power drill or better, angle grinder attachment, will do the job fine.

But beware, the dust is nasty stuff. Cover up well and use a decent face-mask and goggles.

 

[StephenSails]

On small areas I use flap sander or for larger areas random orbital sander.

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[Ivy]

Stick with the angle grinder and 24grit paper, stone and metal disks work if you want to cut a hole in the boat though diamond is better for this.
If the nmat is allready de-laminating get a sharp chissel or a lever of some kind under it and see if it will lift off, it will save on all that dust.

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[oldsaltoz]

G'day Andrew,

As it's only a very small area you can use a standard steel grinding disk, a new one will reduce the chances of introducing any contamination.

If you plan a lot of grinding, a 4.5 inch grinder fitted with a concrete grinding disk will save you a lot of time; it looks a bit a starfish they has been turned on the centre, all the arms at an angle rather at 90 degrees.

Just one disk will remove all the gelcoat from several 30 foot yachts and still be in good condition. I know this because mine is, and it's done hours and hours of glass grinding, never clogs.

Hope this helps. . . . .



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