grinding

Discussion in 'Fiberglass and Composite Boat Building' started by pasty63, Aug 28, 2012.

  1. pasty63
    Joined: Oct 2007
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    pasty63 Junior Member

    I've been grinding on my transom for awhile and I'm about 1/3 done. I have a Makita 4.5 in. grinder and am using 36 grit pads. Where the wood was soft, the little grinder does pretty well, but there are still large sections where there is solid 1/2 inch plywood. It seems a 7 inch grinder with 24 grit would make my life easier on these sections - does anyone have any recommendations for the larger units?

    Thanks -.bryan
    Bayliner 3270
     
  2. SamSam
    Joined: Feb 2005
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    SamSam Senior Member

    Pawn shops are jam packed with those type of tools these days. Offer them a third or half what they ask.
     
  3. gonzo
    Joined: Aug 2002
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    gonzo Senior Member

    Craftstman and Makita make good grinders. Milwaukee are really powerful but heavy too.
     
  4. wooky30014
    Joined: Jun 2012
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    wooky30014 Junior Member

    Pasty63, I don't know if this would work for you but my idea (yet untried) is hooking a random orbit sander with rough discs to a small shop vac to hold down most of the dust and I used a sawzall to do the cutting I needed done, again just a little dust was made and vac picked it up easily.
     
  5. tazmann
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    tazmann Senior Member

    I have been grinding off fiberglass mat layer and found the 4-1/2" with 36 grit works best, tried 24 grit and it was slower and took more pressure. I thought my 9" grinder would be faster so I picked up a 7" 36 grit disk and tried it out , nope it was slower at removing material and after about 10 minutes I thought my arms were going to fall off "overhead"
    On the plywood try a chisel
    Tom
     
  6. groper
    Joined: Jun 2011
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    groper Senior Member

    i use the flapper discs... you know the ones with many little peices of sandpaper overlapping each other radially? These work much better and last heaps longer than standard discs...
    [​IMG]
     
  7. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    Buy a cheap power plane and some replacement blades. You'll be done in a half hour and you can toss the dicked up blades when you're through.
     
  8. whitepointer23

    whitepointer23 Previous Member

    good idea,
     
  9. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    This is my preferred tool on transom core removal. I just change blades frequently. I can plow through 1.5" of plywood in minutes and yep the stables ding up the blades, but hat's what a sharpening stone is for.
     
  10. pasty63
    Joined: Oct 2007
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    pasty63 Junior Member

    Grinders

    I'll try a better planer
    - that's what I started with but It was getting jumpy
     
  11. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    Staples are commonly used to hold fabric, mat and the layers of plywood together as the goo cures. A planer's blades will get beaten up pretty quickly. The logical choice is a cheap one from Harbor Freight, because tossing a $20 tool in the can doesn't feel too bad. Yes, it will jump around as you make a mess of the surface. A power chisel with a sharp blade can do a fine job too. You'll sharpen the blade a few times, but this isn't very hard.
     
  12. Frosty

    Frosty Previous Member

    I use 16 grit, this usually does not clog as it is so course, it will rip out what you want in minutes.
     
  13. ondarvr
    Joined: Dec 2005
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    ondarvr Senior Member


    I've always found flapper discs to be much slower when used on F/G, the grit wears down and gets dull before the new grit is exposed, so you are always using a worn out pad. Brand and construction methods may affect how quickly fresh grit it exposed, but I've never found one I liked.
     
  14. ondarvr
    Joined: Dec 2005
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    ondarvr Senior Member

    Grinders can be very slow on good plywood and the correct grit for the job can change with the exact conditions you’re faced with, so it can be a trial and error experience.

    Another frequently used method is a pry bar and a big hammer. Since polyester doesn’t bond to plywood as well as other products you can sometimes use this to your advantage. If you can get under a corner of the plywood see if you can pry it loose, be careful, if the outside skin is thin, or the bond is too good, you can flex and fracture the gel coat or laminate. You can also jam the pry bar between the layers in the plywood and peel it off leaving only the surface veneer attached to the transom, this makes the grinding or scraping much easier.
     

  15. pasty63
    Joined: Oct 2007
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    pasty63 Junior Member

    Grinders

    I'm using every tool imaginable on this project - chisels, pry bars, hammer, grinder, sander, skil saw, reciprocating saw, vice grips, tears, derisive language and even a little patience.

    I really appreciate all the advice. I'm looking forward to getting to the epoxy phase of this repair.

    -.b
     
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