Are there different catalyst's for gelcoat for different temperatures?

Discussion in 'Fiberglass and Composite Boat Building' started by sbklf, Dec 22, 2007.

  1. the1much
    Joined: Jul 2007
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    the1much hippie dreams

    you shouldnt need them on afterwards,,before you spray a section, move them to the next section,,then spray. watch your overspray though,, it can combust,,and cover your lights and start on fire from the overspray on your plastic cover of the lights,, i would work like heating 2 sections at a time, then move the lights over to your 3rd section,then,after your done with the first section, move the lights back to the second for a few minutes,then over to the 4th and spray your 2cnd. your garage is warm enough to keep the sections pretty warm for a while after you heat them up with ya lights. ;)
    be carful of getting them too warm,, too much heat is as bad as not enough. the sections should only be warmish to warm warm ,, not REALLY warm,, and your boat should "hold" the heat pretty good for a long while after it heated up ;)
     
  2. fiberglass jack
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    fiberglass jack Senior Member

    or you could rent a few space heaters
     
  3. hmattos
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    hmattos Senior Member

    Here in England we have wide temperature variations in the winter we struggle to get the moulds and workshop up from freezing to 15 degrees C - about 60F - so we also warm the back of the moulds and use infra red and halogen lamps to warm the gel and resin. Some builders fix pipes to the back of the moulds and pass hot water through them to warm the moulds and speed drying.
    There are many different resin / accelerator / catalyst types and our supplier ships three versions of the catalyst so we can control setting rates in Winter Spring and Summer etc.
    Our test for gel being set is when a finger " squeaks" when rubbed on the surface. It should still be tacky, but not lift gel onto your skin. This takes 40 mins to 120 mins depending upon temperature. Sometimes we have to force a job by holding a heat gun over the surface so at 80 degree C the gel is hard in 5 mins. This does not give a good gel surface and often causes vapour bubbling, so is to be avoided.

    Good Luck
     
  4. fiberglass jack
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    fiberglass jack Senior Member

    the finger trick is a recipe for desaster, the oil and waxes on your finger will come back and bite you in the arse, even a clean finger will have natural wax and oil,
     
  5. hmattos
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    hmattos Senior Member

    Correct indeed, but the finger test is always done outside the actual boat area. After all, if the gel IS still wet, we cannot afford to have a finger line in the moulding. We often put some extra brushfulls on the mould edge etc to act as test areas, while we are cleaning out the gel bucket.
     
  6. the1much
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    the1much hippie dreams

    we use cup guns for gel and keep our cups after,,,,there good indicators of your gel "kicking"
     
  7. AroMarine
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    AroMarine Junior Member

    One problem you will have doing your project in sections is once an area is cured it will have the wax film that needs to be sanded before putting on new material. If you have break points like tank deck covers or fish box lids, no problem. Leave lights on for 30min to hour after gel gets hard enough for no thumbnail print, pretty hard.
     
  8. ondarvr
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    Location: Monroe WA

    ondarvr Senior Member

    If it's already 70* then it won't need much help from the lights, as long as the surface is warm your fine. What you don't want to do is heat the surface before you apply the gel coat to the point of it curing so quick that the wax doesnt come to the surface. This is what can happen outside when parts are painted in the sun, this will leave the surface sticky.

    Testing in the lab is done by weight, but spray equipment made for resin and gel coat is metered by volume, so for the most part, either method will work.

    Gel coats can also vary a great deal in weight, white is normally the heaviest.
     
  9. sbklf
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    sbklf Junior Member

    I have good break points for working in sections and am rolling and brushing the gelcoat. How hot is too hot? The section that I did last week is pretty tack free as last night I layed paper over it and walked on it and the paper stuck a little in a spot or two but not too bad. With a non contact thermometer I was reading up to 95* F in places. One problem with lamps is that the heat is not real even. I turned them off a little before applying the gel and then back on after.

    I will think twice before working on a boat in the winter again.
     
  10. ondarvr
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    ondarvr Senior Member

    Move the lights back a little and you may get more uniform heating of the surface, anything between 85* and 95* should be fine. You may want to let the gel coat set for a few minutes before turning the lights on just to let the wax come to the surface. Also don't over roll the gel coat, if the wax comes to the surface and you roll over that area again, the roller may pick it up and remove it.
     
  11. fiberglass jack
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    fiberglass jack Senior Member

    grab a fan any household one will do this way you can blow the heat around a bit
     

  12. the1much
    Joined: Jul 2007
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    the1much hippie dreams

    make a big bombfire outside,,throw bunch of big rocks in it,,after they heat up line the rocks around ya mold ;)
    jus playing everyone ;)
     
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