How much grinding is enough

Hi guys,
As most of you probably know I am restoring my boat. Ive made it as far as sanding down the old fiberglass with a flap disc but i wasnt sure how much i should sand off. Ive got it sanded down so the darker glass is gone and it is nice and smooth so i was wondering if this would be enough or not. Im hoping so because ive spent probably close to 10 or more hours grinding and its starting to get a little sickening.

Re: How much grinding is enough

You only need to sand where you are laying more glass, and then only enough to make it smooth enough to prevent air pockets when you lay down the new glass. If there is delamination anywhere, you want to sand that completely off, as well as remove any pieces of wood which may be rotten, yet are glassed in. Every single piece of wood in my 1990 hull was rotten, even the pieces which seemed all glassed in.

Re: How much grinding is enough

lowkee said:

You only need to sand where you are laying more glass, and then only enough to make it smooth enough to prevent air pockets when you lay down the new glass. If there is delamination anywhere, you want to sand that completely off, as well as remove any pieces of wood which may be rotten, yet are glassed in. Every single piece of wood in my 1990 hull was rotten, even the pieces which seemed all glassed in.

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K thanks lowkee. I have all the old wood removed and there is no delamination left so now ill just be waiting until i get the engine removed so i can tackle the transom. I was also wondering if there is anything other than epoxy putty to use for fillets around the transom and the sharp sides of the hull?

Re: How much grinding is enough

There sure is. PL poly construction adhesive. I used a whipped cream consistency poly/3m-bubbles/cabosil mixture for filleting, as the PL only works for tight fillets and not big rounded ones, which I needed for the thick mat I used.

Re: How much grinding is enough

If, when grinding, you hit air, you've probably gone too far.


A more useful rule is probably "grind until you hit clean, solid FRP".. for the most part grinding is to remove old surface material to give any new glass/adhesives a good surface to attach to. It's possible to do a good epoxy joint with solid technique, the right materials, and proper temps for hardening and still end up with something that pulls right off, because the surface it adhered to was loose or inadequately stuck to the glass under it.

Personally I grind away all delaminated glass or bubbles, any loose glue or resin, wood debris, cloth fibers, basically anything between me and the hard solid glass, then clean the dust off and wipe down with xylene or another solvent. Then I start attaching new material.

Erik

Re: How much grinding is enough

I grind until I get so pissed off and itchy that I cant stand it anymore. When my goggles fog up so bad i trip over myself and the grinder is the temp of the sun. THAT is when you are done.......for the day.

Re: How much grinding is enough

thrillhouse700 said:

I grind until I get so pissed off and itchy that I cant stand it anymore. When my goggles fog up so bad i trip over myself and the grinder is the temp of the sun. THAT is when you are done.......for the day.

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Lol ive been doing that for the past week so i think im done.