Doug Hylan 15 Ben Garvey epoxy question

Discussion in 'Fiberglass and Composite Boat Building' started by ajse, May 13, 2022.

  1. ajse
    Joined: May 2004
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    ajse New Member

    Using total boat 5-1 epoxy. Chines getting 1708 biaxial inboard and outboard. 10 oz eglass inside and out. I am thinking about laying the 10 oz up to the biaxial then coming back over it all with a second layer of 10 oz cloth. My question is do I have to sand to create tooth for the second coat of epoxy to adhere to the first coat? Working alone and can't do all at the same time. Thanks for any answers.
  2. fallguy
    Joined: Dec 2016
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    fallguy Senior Member

    The best work is done wet on wet, as long as it can be done well.

    Next best is wet on green. Probably some debate here, but TotalBoat 5:1 probably provides and open window time for primary bonding. I checked and they don't show one.

    I will tell you my personal rules after using 300+ gallons of epoxy. Anytime I have an overnite cure, I sand for mechanical key.

    The reason for this is I have sanded over 'within window work' and have been displeased with the bond strength and the way the next layer tends to feather, despite the manufacturer claims otherwise.

    Because you are using a relatively light glass; I really think you should search for a helper and try to get it all done in a single go. The pot life stated for TotalBoat slow is not great, so you want to get the epoxy out of the bucket quickly and onto your surfaces. For light cloth like 10 oz and a single layer (I'd try for both), you'll want to precoat the substrate. A 50% drysuck can occur with 10oz glass. You can allow the precoat to cure or let it kick for say 2 hours, but it'll get very sticky then and then you rewet the entire surface and roll the glass off 3" tubes real careful. Requires lotsa marks and a semi-pro experienced builder. You need lengthwise marks to make sure you are not stretching and stuff.

    Otherwise, you can precoat the wood and allow it to cure and sand it all with about 60 grit or so the next day. Clean it off and then you can wet down through the laid cloth.

    If you insist on laying the cloth in two days, I would only do so after sanding, personally. Or perhaps you could do the first pass in the morning; let it cure past tacky and roll the 2nd end of day and wet down through no sanding. Certainly do not work in hot weather and no sunshine on the part.

    If it is hot and you are rightly worried about kicking off, then I'd sand the first fiberglass layer on the 2nd day. Its a scratch coat. Do not sand to make all the shine disappear or you'll be making your 10 oz into 5 oz real fast. (Or worse)

    Submit pictures if you want more clarification. I realize it is a 15' boat, but it seems like 2 layers should be doable same day. The trick is the 2nd layer comes off tubing and you use sharpies on the bottom glass so when you are rolling off you know where you need to be and if you are putting too much or too little stretch in the 2nd layer..

    I can also help you with some tips on how to make the work less stressful.

    The plywood precoat amount is 2oz/yard, plus more or less for whatever roller you use. If short, use a squeegee to cleanout the roller at the end.
    bajansailor likes this.
  3. ajse
    Joined: May 2004
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    ajse New Member

    Thank you very much for your very helpful reply. One good thing I have going for me is I am building in my shop which has heat/ac so I can control temp. Been working at 70 degrees (I am glassing all the inboard before attaching) and so far so good that way. This is really helpful and I am going to think about it this afternoon. I do think your do it in one day is the way to go and that is what I am leaning towards and if I do I guess I would have to lightly sand before a fill coat? I do have someone that is experienced in polyester glassing that I can hire (or I could get my wife to help but I can't afford a divorce :) ).
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