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Gelcoat Info and Info for epoxy vs. polyester

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  • Gelcoat Info and Info for epoxy vs. polyester

    http://www.westsystem.com/ewmag/22/polyester.html

    http://www.westsystem.com/ewmag/22/fiberglass.html

    http://www.westsystem.com/ewmag/proj_repair.html

    Some of us do it yourselfers might find this of use.
    1980 Mako17 Standard, 115 Yamaha 2 stroke[br]1981 Mako224 200 johnson 2 stroke Virginia Beach,Va

  • #2
    Totall agree. That is my bible. I am a big believer in Epoxy resin. If you are going to gelcoat over the epoxy repair/laminates you need to use West System. If you are just painting, then you can go cheaper and use some of the more economical epoxy resins. The economical epoxy resins in many cases are much stronger than West System (If you look at the spec sheets) but the fact that you can gelcoat over West is its main selling point for me.

    I used some epoxy resin in the house today. No fumes or smell whatsoever.
    Slidell, LA 1993 Mako 261B - Temperance

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    • #3
      Hey Ring, In what cases are other cheaper epoxys stronger ? Then I could save a little dough on other applications.

      Thanks, Ricky
      1980 Mako17 Standard, 115 Yamaha 2 stroke[br]1981 Mako224 200 johnson 2 stroke Virginia Beach,Va

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      • #4
        I've never used epoxy in repairs but I'm interested in doing it on structural stuff. From what I understand, the reason gelcoat won't work on epoxy is the amine blush, but if you wash it off with water it will cure. I've also heard that West System epoxy has more anime blush than most epoxies. So if gelcoat will work with West System, shouldn't it work with other brands, after all, it is a mechanical bond and as long as the blush is washed off it will cure.
        1973 Mako 22[br]Bahamas

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        • #5
          Here is a quick comparison between the specs of West System's 105/205 (their regular 5:1) and Several Epoxy resins from Fiberglass Coatings Inc.

          West Systems

          Shore D Hardness (PSI) - 83

          Heat Distortion ( Degrees F) - 118 degrees

          Tensile Strength (PSI) - 7846

          Tensile Modulus (PSI) - 408,000

          Tensile Elogation (%) - 3.4%

          Flexural Strength (PSI) - 14,112

          Flexural Modulus (PSI) - 461,000

          Compressive Strength (PSI) - 11,418

          FGCI 5:1 Epoxy

          Shore D Hardness (PSI) - 80

          Heat Distortion ( Degrees F) - 130 degrees

          Tensile Strength (PSI) - 14,600

          Tensile Modulus (PSI) - 497,000

          Tensile Elogation (%) - 3.4%

          Flexural Strength (PSI) - 17,700

          Flexural Modulus (PSI) - 697,000

          Compressive Strength (PSI) - 14,600

          FGCI 3:1 Epoxy

          Shore D Hardness (PSI) - 78

          Heat Distortion ( Degrees F) - 128 degrees

          Tensile Strength (PSI) - 9850

          Tensile Modulus (PSI) - 436,000

          Tensile Elogation (%) - 5.9%

          Flexural Strength (PSI) - 17,500

          Flexural Modulus (PSI) - 552,000

          Compressive Strength (PSI) - 13,300

          FGCI 2:1 Epoxy (what Bobby uses)

          Shore D Hardness (PSI) - 78

          Heat Distortion ( Degrees F) - 13 degrees

          Tensile Strength (PSI) - 8800

          Tensile Modulus (PSI) - 390,000

          Tensile Elogation (%) - 7.2%

          Flexural Strength (PSI) - 14,900

          Flexural Modulus (PSI) - 441,000

          Compressive Strength (PSI) - 12,300
          Slidell, LA 1993 Mako 261B - Temperance

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          • #6
            When I called West, they told me to sand after it cured, then wash with soap and water and you'll be able to topcoat with polyester gel-coat.
            [br]Michael R. Delgado[br]1972 Mako 22[br]http://classicmako.com/forum/topic.asp?TOPIC_ID=15745[br]1976 Mako 25[br]http://classicmako.com/forum/topic.asp?TOPIC_ID=18013&SearchTerms=mako,25[br]

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            • #7
              Correct... Thats what I do.
              Slidell, LA 1993 Mako 261B - Temperance

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              • #8
                I also prefer Epoxy Resin's mainly to avoid the pungent smell of the Resin and toxicity of the Styrene harnder.

                Epoxy I think is a lot easier to work with as well, once you have the mixing pumps and all.

                I only used West System Epoxy, do the other Epoxies smell badly? Or do all have that minor "epoxy smell" like West System or Flexcoat for rods?
                Jones Inlet, Long Island

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                • #9
                  All epoxy resins are very low on smell. I used the FGCI epoxy insid the house last weekend to do some touch-ups to the fiberglass coulmns in the foyer... Even the wife never picked up a bit of oder from the stuff.
                  Slidell, LA 1993 Mako 261B - Temperance

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                  • #10
                    With the FGCI epoxy and others, besides 5:1 being stronger than 4:1, 3:1, 2:1, what are the differences in them? Is the viscosity different or the drying time? I think I'm going to try the FGCI epoxy but not sure which one to get.
                    1973 Mako 22[br]Bahamas

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                    • #11
                      The 5:1 and 4:1 from FGCI are very strong resins. But teir working times are super short. I mean that you literally won't get 6 minutes out of a batch... Thats not near enough time to fdo anything. Their 3:1 and 2:1 are better for working time.

                      Jason Thornhill used a 3:1 epoxy from a local supplier and had excellent working time.

                      West System with the tropical hardner (209) gives good working time as well. Their 205 hardner is too fast as well.

                      All this is in our warm and sunny southern states. In cooler climates the fast hardners might give a little more working time.
                      Slidell, LA 1993 Mako 261B - Temperance

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                      • #12
                        Yes to the last statement, up here I only use the fast hardener, it takes for EVER otherwise. It also works for quick fixes. dave
                        [br]1994 Mako 215 Dual console Optimax 225[br]1978 Mako 19 with 90hp johnson[br]1996 Mako 22[br]1982 Mako 171 Angler 135 Black Max Mercury[br]1987 21b 225 Yamaha[br]1974 23 inboard Gusto gone.[br]1979m21 225johnson \"blue dolphin\" bought off this board and restored [br]with everyone\'s help!!Gone but not Forgotten....[br]1979 20 Mako 115 Suzuki gone[br]1977 19 Mako 115 Johnson gone[br]1976 23 Mako twin 140 Johnsons gone[br]1983 224 with closed transom and bracket[br]And 162 SOB (some other boats)[br]Venice Florida, Traverse city Mi.

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                        • #13
                          I used 205 yesterday 81 degrees I was humpin to get 10 minutues work time. Today I used 206, got about 15 20 minutes at 85 degrees.It worked great, no humidity
                          1980 Mako17 Standard, 115 Yamaha 2 stroke[br]1981 Mako224 200 johnson 2 stroke Virginia Beach,Va

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                          • #14
                            Anything over 85 degrees or so I use the 209 hardner. Its a 3:1 and uses different pumps. It'll give great working time in temps and humididty both in the 90's.
                            Slidell, LA 1993 Mako 261B - Temperance

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