Polyester Questions

Discussion in 'Materials' started by Chotu, Dec 2, 2018.

  1. Chotu
    Joined: Mar 2018
    Posts: 8
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    Location: Florida

    Chotu Junior Member

    Hi,

    I am doing some interior work. Doors, stairs, anchors for cabin soles frames, integral tanks, etc. Nothing structural. Nothing below the waterline. Most stuff indoors. The boat is floating and able to be used. The interior isn't done.

    The boat is foam core built from epoxy and glass.

    I can't use epoxy due to an allergy developed using it in an industrial setting. Even grinding cured epoxy sets off a severe allergic reaction. No idea how. Maybe heat of grinding can break down the epoxy a little?

    This leaves me with polyester to use to fabricate the parts and adhesives and screws to put things together.

    I have some epoxy help from my girlfriend for small tabbing jobs like tabbing pre built stairs to the hull. I can't go in the boat for a week or two after something like that.

    So I have lots of polyester questions since I've only used epoxy.

    1) How thick does a polyester laminate need to be in order to cure? I was going to just put a couple layers of biax with no mat on the foam for the stairs. I have read mat is required. Is it? Can I just use a little extra biax?

    2) When I make a finished product like the stairs, it's not in a mold. So how do I finish this? Polyester layers without wax, then what? Can I skim coat of Bondo on the top of the laminate while it's still green instead of using resin with wax in it? Then sand the Bondo and paint normally? Does Bondo have wax? Can it act as the top curing layer?

    3) Or... Is it more advisable to roll on gel coat as the top layer and sand that down to make the finished surface?

    Mostly I'm looking to make stairs, exterior doors, shower pans, black and fresh water tanks. Maybe some furniture.

    Extra Credit: What adhesive can I use to do the following?

    1) tab in stairs or cosmetic bulkheads.

    2) Adhere aluminum sliding door tracks to epoxy based fiberglass.

    3) Adhere aluminum window slide tracks to epoxy based fiberglass.

    4) Adhere pre built tanks to the hull in the bilge.
     
  2. fallguy
    Joined: Dec 2016
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    Location: usa

    fallguy Senior Member

    I would recommend you use some 3M adhesives for bonding. Use 5200 below WL a/o any permanent installations. You basically cut it out later it is so permanent. Otherwise; 3M 4200 is also good, but 4000 is used for in the sun and has less adhesion and more uv res. The products will not shelf forever; so buy what you need.

    Ondarvr is the local expert on polyester afaik. I stay away from the polyester due to the smell.

    You can't allow skin exposure to any epoxy products. I see people grinding on yesterday's epoxy in t-shirts. Very unwise. I catch myself now and then sanding without a mask; also bad. The idea you need to be away for a week means you are not using enough protection. It can be tough in hot climates I'm sure.

    You might discover you are not able to be in the boat at all.
     
  3. Chotu
    Joined: Mar 2018
    Posts: 8
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    Location: Florida

    Chotu Junior Member

    Thanks for the input on 5200.

    I've seen some chatter about using the other polyurethane adhesives like these.

    https://www.amazon.com/Loctite-Polyurethane-Construction-Cartridge-1390595/dp/B001E3VQBE

    Any good?

    I've taken the boat on trips with a basic interior and I've been great. I can touch cured epoxy with no issues.

    I just can be around machined or fresh epoxy. I just learned about the machined epoxy the hard way. I was in a full suit with headsock and cartridge respirator and gloves cutting/grinding it. What I was grinding has been cured up for years now. I didn't think you could have a problem with cured epoxy but I was being extra cautious. My exposure today was just opening the door of the boat and sitting outside. There was no visible dust in the main salon. Just down in a hull. I still got hit hard.

    Is it really possible that i could have a problem with cured and untouched epoxy as well?? That I may not be able to even go near the boat?
     
  4. ondarvr
    Joined: Dec 2005
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    Location: Monroe WA

    ondarvr Senior Member

    1. No need to worry about thickness if the temperature is correct, cold temps may require a thicker laminate or some heat to cure correctly.

    2. Depending on the size of the area that needs to be sanded you could use waxed gel coat (not easy to sand).
    Bondo, easy to sand, but not very water resistant. Or a product like the Duratec sanding primer. It cures tack free, is easy to apply, easy to sand and is a great substrate for any type of paint.

    CSM should be used with polyester, if don’t use it the parts may be weaker.

    Polyester can stink, but it’s not horrible, and you get used to it. Put a fan in the boat so you can get good air exchange if you’re doing more than a small amount of work.
     
  5. Chotu
    Joined: Mar 2018
    Posts: 8
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    Location: Florida

    Chotu Junior Member

    Maybe I can hire out the little bit of the epoxy work and do the bulk in polyester.

    Anyone know people in the Fort Meyers area who need a little work doing some straightforward laminating like steps, a window frame, some cleats for the cabin sole?
     
  6. Chotu
    Joined: Mar 2018
    Posts: 8
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    Location: Florida

    Chotu Junior Member

    Thank you!

    I'm happy with a styrene stink compared to all these near death experiences with epoxy and will be using a chemical cartridge mask. I also can do most of the work outside then move it inside to tab in.

    Thankfully, no shortage of heat here in South Florida.

    So for #2 above in your response, all of those 3 items will act as the necessary final layer to allow a tack free surface to prime/paint?

    Duratec sounds nice for the shower pans especially. Maybe not as necessary on the indoor steps.

    I'll make sure to get some CSM. If I have a part I'd usually put a layer of 17oz biax on, do I add a single layer of csm below that? If I have 2 layers of biax as a specification, do I just alternate between CSM and biax?

    Or just buy a roll of that 1708 stuff everyone has with the mat stitched on and call it a day?
     
  7. ondarvr
    Joined: Dec 2005
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    Location: Monroe WA

    ondarvr Senior Member

    Using 1708 is the easiest method.

    CSM needs to be used as the first layer and between each layer of 1700

    Any of those can be sanded without gummy up the paper and will hold paint.
     
  8. Chotu
    Joined: Mar 2018
    Posts: 8
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    Location: Florida

    Chotu Junior Member

    Thank you very much Ondarvr.

    Clears everything up and gives me the confidence to get some laminating done in polyester, saving the boat.
     
  9. Sparky568
    Joined: Jan 2017
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    Location: Northeast USA

    Sparky568 Junior Member

    Would recommend the 1708 as well. I found it very easy to work with. If applying to core put the mat side down first. This will ensure the roving being on top which, is easier to finish than mat unless you're really god at using mat.

    As far as bonding epoxy substrate to poly finished parts I have no experience in that so I will defer to those that do. There are a myriad of adhesives that suit nearly every scenario.

    In regards to finishing, use no wax resin then apply an easy sand to poly based fairing putty or high build primer as Ondavr recommended.

    Good luck
     
  10. fallguy
    Joined: Dec 2016
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    Location: usa

    fallguy Senior Member


    You can develop severe sensitivity that may result in not going in the boat if you fail to heed the existing one according to all I have been told. That would be more adverse reactions.

    The adhesive you showed hs varying strengths, 1x,3x,8x it appears.

    Use the right one for stairs!

    You can avoid grinding epoxy using adhesives by accepting some weight penalties and cleating with plywood/wood. Otherwise, you might consider having a professional finish the boat.
     
  11. kapnD
    Joined: Jan 2003
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    Location: hawaii, usa

    kapnD Senior Member

    Peel ply is useful over laminates that you will need to sand, it eliminates the gummy mess without having to use wax.
    On small parts I often use plastic sheeting, much cheaper, but doesn’t conform well to compound curves.
    Some of your parts may lend themselves to molding rather than stick building, melamine is my material of choice for mold making, cheap and easily workable, lay up right over it without wax, sometimes a light spray of pva to aid release.
     

  12. Chotu
    Joined: Mar 2018
    Posts: 8
    Likes: 0, Points: 1
    Location: Florida

    Chotu Junior Member


    True. I am seriously considering using some existing plywood doors as a bagging table/mold for the new doors. I guess that would also eliminate the need for a top layer since there isn't air in the bag.
     
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