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The proper way to wet sand a Gel coat hull

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  • The proper way to wet sand a Gel coat hull

    Hey all, im the guy with the 30 scarab over hull project. I thought I would set this little thread up and get everyone’s opinion on how to correctly wet sand a gel coat hull that is 20 some years old.


    My hull is chalky, kind fo shinny in places, and rough in other places. I have a red stripe along the hull that has scuff marks, scratches, and gouges that have not gone all the way through the paint, but need to be sanded out. I was planning on wet sanding my hull and bringing that old gel coat back to life. I have read that you can really restore Gel coat.
    Now, I have read not to use anything over 800 GRIT wet, and I have read that Mr. Oop’s used 600 grit DRY, and now I am confused…..I was planning on doing 600 wet, then 800 wet then up to a 1000. However I don’t know if im going to mess it all up. I THINK Gel coat is pretty forgiving, however this is my assumption, some reassurance from an experienced person would help!! Like I said I was going to do the entire thing (30 ft) and I really need to hear from someone who has done this and knows tips tricks and can build my confidence. Items such as pre cleaning? Do you NEED to apply acetone first? Or other questions in regards to what to look for and what to expect when sanding. Your expertise needed:
    Its all done with mirrors.....


  • #2
    Re: The proper way to wet sand a Gel coat hull

    jserb,

    Not new to your project, just a lurker. I am in SCS, MI not too far away...

    Use 400 wet with a little dishoap in the water. It will prevent the paper from clogging up. After that, wash down with 50/50 mix of white vinegar and water. Dry it off. Then 600 wet then vinegar water wash, then 800 which should be plenty. Use 3M imperial paper, it is the best, doesn't load up real easy and lasts a long time. You will need a lot. Change pieces often. After the 800 grit, go to an aggressive rubbing compound, like 3M Imperial Compound and apply with a variable speed orbital buffer. Spin it as fast as you can without building too much heat on the hull. Use a good thick wool bonnet on the buffer. Once you finish that, go to a finishing compound, like 3M Finesse it II. Same rules apply, but don't use the same bonnet. After that is wax time. Collinite is the best, but a high quality automotive wax like Mothers Carnauba Cleaner wax will do, just may not last as long and/or require more coats.

    ***And no I do not work for 3M. I have just used their stuff with success.

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    • #3
      Re: The proper way to wet sand a Gel coat hull

      I plan on doing a gelcoat revival on my dad's boat once mine is finished (payment for all the years he let me and my friends use it).

      One question though - What's the point of the vinegar wash?

      -Ryan
      My Project:
      Hull and Interior
      Outdrive and Engine

      Comment



      • #4
        Re: The proper way to wet sand a Gel coat hull

        check this out,this is how Mark did his '65 MFG
        great article with before and after pictures..........

        http://www.shareaproject.com/pages/p...t,p,27,00.html

        woosterken
        woosterken
        '74 MFG gypsy
        '95 F150 4X4

        Comment



        • #5
          Re: The proper way to wet sand a Gel coat hull

          Vinegar is an excellent mild solvent. It will not damage the gelcoat and it will remove any of the sanding dust particles on the boat. Acetone could be used I guess, but not recommended because it can deteriorate the gelcoat and effect the resins in the hull. When you move to a finer grit, you don't want to have any large particles hanging around that can cause swirl marks if trapped under the finer paper. After each grit it is necessary to wash it down. White vinegar just because it is an excellent all around solvent and it is cheap, like a buck or two for a gallon. It is also good to use to wash it down after it waxed and being used for everyday maintenance. Many household soaps and detergents will strip the wax on the hull. White vinegar or marine cleaners will not.

          Vinegar is also good to gargle with at night to rid your mouth of germs. A small bit, about 1-2 oz mixed with a about 8 oz of OJ will help with regularity. It soothes burns, sun or otherwise and helps heal cuts. It is also good to use as a hair wash.

          The smell goes away in about 5 to ten minutes, so wait a minute or two after you wash your hair and gargle with it to pick up your date.

          Comment



          • #6
            Re: The proper way to wet sand a Gel coat hull

            I've brought back 2 gel coats with course buffing compound, light compound then a good wax. If you do want to wet sand it, 1200 grit will get you to where light compound does. Start with 600, 400 is too course, 800 might not take you down quick enough. use a sanding sponge and lots of slightly soapy water, rinsing your paper out often. 3M is about the best you can get at a reasonable cost, they make great products. I've never used the Gel Coat restore but If someone has, I'd like to see before and after pics!
            1997 Larson 226LXi
            5.7EFI
            Bravo III 26p Props

            Comment



            • #7
              Re: The proper way to wet sand a Gel coat hull

              Originally posted by AZSenza View Post
              Start with 600, 400 is too course
              I assure you its not. Your arm will fall off before you even think about making a dent in it. It obviously depends on the level of oxidation. I think jserb has some pretty heavy oxidation, it is a good idea to try a small spot and see what is required grit wise.

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              • #8
                Re: The proper way to wet sand a Gel coat hull

                well doing it by hand is out of the question, and i dont have an air compressor, so i am planning on buy one of these tonight, look at e m tell me which one would be better? for this type of sanding do you want high RMP or slow???
                http://www.harborfreight.com/cpi/cta...emnumber=90820

                http://www.harborfreight.com/cpi/cta...emnumber=92623

                thanks
                Its all done with mirrors.....

                Comment



                • #9
                  Re: The proper way to wet sand a Gel coat hull

                  http://www.harborfreight.com/cpi/cta...emnumber=90820

                  Is the same one I use. Get a couple of wool bonnets, they help cut the finish, I usually run mine around 2 on the speed dial. the foam helps put a shiny finish, use it with the last coat of polish prior to waxing. You'll need a few good rags to get where the buffer wont. I use the yellow polishing cloths from Costco.

                  and yes 400 might be a good place to start but always start with the finest you can get away with in the worst spot, then work back if its not comming out.
                  1997 Larson 226LXi
                  5.7EFI
                  Bravo III 26p Props

                  Comment



                  • #10
                    Re: The proper way to wet sand a Gel coat hull

                    Originally posted by jserb View Post
                    well doing it by hand is out of the question, and i dont have an air compressor, so i am planning on buy one of these tonight, look at e m tell me which one would be better? for this type of sanding do you want high RMP or slow???
                    http://www.harborfreight.com/cpi/cta...emnumber=90820

                    http://www.harborfreight.com/cpi/cta...emnumber=92623

                    thanks

                    Hay John

                    I have the second one , It Works petty good just the trigger sticks !!!! Love the variable Speed the thing has , and I had 320 on mine and it really eat the gelcoat, Dust was just a flying off , wet sanding will be better !!! Also why dont you start with some of the higher grit and work it down to the ruffer stuff !!!When you find one the works well stick with that !! Just when you start out on a spot try to hit it flat !!!!! you come in on a angle and it will leave a divt !!! lol Had to fix a few of mine !! LOL

                    Ok Come join the fun buddie !!! hahahaha John
                    http://s274.photobucket.com/albums/jj258/jcsercsa/

                    STANLEY CUP CHAMPS 35-36 36-37 42-43 49-50 51-52 53-54
                    54-55 96-97 97-98 01-02 07-08

                    Comment



                    • #11
                      Re: The proper way to wet sand a Gel coat hull

                      hey guys, well i can purchase either sander but i need to know where both of you found your 7'' fine 600,800, 1000 grit sanding paper for this machine. the place by me dosent have that fine. Where did you get your sanding paper for that machine? Can you e mail me a link? thanks guys!!
                      Its all done with mirrors.....

                      Comment

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