Layup process????

Discussion in 'Fiberglass and Composite Boat Building' started by jyoung, Aug 21, 2010.

  1. jyoung
    Joined: Aug 2010
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    Location: maine

    jyoung New Member

    I am starting a project in which I will lay up a boat from a 24' flat bottom boat mold I recently purchased. My planned lay-up schedule is:

    1. gel coat
    2. 2x 1.5 oz chopped mat
    3. 2x 1.5 0z chopped mat
    4. 1x 18/7 oz biaxle - roving/mat combo
    5. 1x 1.5ox mat

    Does this look like a good schedule for this mold?

    I was told if I used non waxed poly resin I did not need to sand between layers, is this true??

    After the gel coat cures could I lay this up in one day???

    this is my first project and any advice is appreciated.
  2. apex1

    apex1 Guest

    Not only you could lay that up in one go, you must! To achieve the best (chemical) bond between the single layers.
    Your schedule is not a good one!
    Replace the #3 with fabric (or biax) and the #4 with biax, leave the roving and mat out in these layers.
    Replace the #5 by making # 3 thicker, you don´t need mat inside.

    All in all not a very strong layup you are planning here, but I assume that was more or less a schedule given for that boat?

  3. SamSam
    Joined: Feb 2005
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    SamSam Senior Member

    Use laminating resin. It has no wax so you won't have to sand. You will have to sand or scrape a little between an old layup and a new to remove any lumps, burrs etc that might hold the laminate up off the surface and create air pockets, but that is nothing like having to sand to remove wax.
  4. CatBuilder

    CatBuilder Previous Member

    This is correct?

    Can this be used for everything normal epoxy would be used for?
  5. waikikin
    Joined: Jan 2006
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    waikikin Senior Member

    Not for epoxy, the reference is for poly/vinylester. Jeff.
  6. SamSam
    Joined: Feb 2005
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    Location: Coastal Georgia

    SamSam Senior Member

    I've never used epoxy to build boats. The OP was talking polyester. By 'old' I meant overnite to maybe later in the next afternoon, but we did not do hi-tech cutting edge construction.

    I don't know if epoxy uses wax at all. Polyster unwaxed (laminating resin) would remain slightly tacky for a day or two and sanding was not easily done. Scraping with sharpened paint scrapers was easily done to remove any random strings and strands that stuck up or especially edges of cloth that were too rough to laminate over, like on laps, which was always.

    Quickly looking I see that they have laminating and finish resin in epoxy also.

    Resins are air inhibited which means the surface exposed to air won't fully cure very quickly, so they can set up but still remain chemically receptive to the next layer, within time limits. With wax added, when curing, the wax floats to the surface and seals off the air and allows the resin to cure more fully and be easily sand-able. But it (a fuller cure) not only makes the surface not very chemically receptive to the next layer of laminate resin, it severely contaminates the surface as far as physical receptiveness, as stuff doesn't stick to wax. Trying to sand or chemically remove the wax pretty much just smears it around. Even sanding or grinding unwaxed resin leaves dust, another barrier to physical bonding.

    It's best to do wet on wet layups. The next best is minimal time after initial set and cure and that's where sharp scrapers come in very handy followed by a shop vac.

    Looking around again I only see one place that says their epoxy laminating resin remains tacky, so all this waxed, un-waxed stuff may apply only to polyester.
  7. apex1

    apex1 Guest

    You are right, it applies to poly only, and we should focus on poly only, because that was the question.

    And I concur on the rest.

  8. tunnels

    tunnels Previous Member

    Now you have given the person a lay up but have only given part of the information required . With a lay up of that amount of material all done in one swoop its going to get hot and prerelease its self specially where there are overlaps and double ups of materials .
    So tell the full story not just half of it like you usually do .
    And yes you should have a 1.5 oz bonding layer of csm on the inside as a finished layer so when the time comes to bond frames and stringers plus covers all the loose scrappy ends and edges of the fabrics etc etc .
    It is a usual lay up for a boat that size , its the framing and stringer system to make panel sizes that going to give it some guts . :p :D
    2 people like this.
  9. apex1

    apex1 Guest

    Ja, ja Tunnels

    we know..........
  10. tunnels

    tunnels Previous Member

    dont go down that Ja ja road !! not every one knows what you have left out ! Like standing in a library and saying i want a book ! :confused:
  11. apex1

    apex1 Guest


    I left out nothing.

    The layup in "one go" on a 24ft boat will hardly heat up when done by a homebuilder. He will have it hard to come around in time to lay on tacky surface.

    It was not only me BTW who recommended that! SamSam (whos knowledge is fact) backed it.

    You don´t need a inner mat over the entire surface, thats nonsense.

    Details like frames or bulkheads have not been the issue by so far, and any comment on them is just speculation. But here was advice requested, not assumptions which you like so much.

    You might have laid a few m² of glass in the past, but by so far you have not proven that you know the business, the opposite.
  12. J3
    Joined: Jun 2010
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    J3 Junior Member

    If I read this right, there is a disagreement as to whether this should/must be done in one go or not.

    How much strength do you lose if you use (air inhibited) poly resin and let one layer kick before applying the next layer some hours later or the following day?

    If it really has to be done in one go as apex1 says or else sacrifice major strength despite the air inhibited resin, are there some techniques that can be shared on how to deal with the heat when hand laminating a boat such as this?

    Edit: I should type faster as apex1 has already replied. When I read "one go" in post 2 I took that as "all layers must kick at once" whether or not you're using air inhibited resin (i.e. infusion or a big team or bust). Still a question I think is useful, at least for those of us who are not professional laminators: with air inhibited resin, how much time do you have between layers before strength drops off? In spite of the air inhibited, does the chemical bond strength decrease with time between layers in a linear or dropoff fashion? Would it be measurably stronger with 2 people laying up this hull (2x as fast) as with 1?
  13. apex1

    apex1 Guest

    It all depends as usual in our business.

    We have been asked by a homebuilder I assume. And we are talking about a 24ft hull. Therefore the layup takes a lot of time before you come to the same spot again. Meanwhile the first layer has cured to some extend and still provides full chemical bond.
    When 4 people would do the job it might happen they are at the starting point again when the resin just went to "gum" consistency. But even then the next layer can immediiately be applied without any concern about heat build up.

    More people involved, say faster layup, would have no advantage. And then the heat up argument would bite.

    Waiting longer than necessary (have a nap), would probably not provide the chemical bond any longer and weaken the structure.
    But the "open" time depends much on the resin hardener mix, temperature, layer thickness etc.
    There is no fixed time window. Some mixes provide a whole day and more, others in other conditions just several hours.

    You are right, all layers to kick at once was not meant and is not sensible in a amateur build.

    And there was not really a disagreement, those who grasped the question agreed on the "one go" issue. The contradiction was just for the contradictions sake, and far off topic in this case.

  14. tunnels

    tunnels Previous Member

    Never assume that the other person nows it all, if he did know everything he wouldnt be here asking !

    Have you got a new type of resin that dosent get warm when it goes hard ? with that thickness of material even epoxy will get hot !.

    During the whole build process you have to plan the next 2 steps ahead of yourself ,like your frames and stringers etc even fitting and sticking in the transom and other parts as well .
    The inner matt can be a 125 gram csm and a peel ply over that top .
    Makes a really nice finish on the whole of the inside and can be bonded to with a light sand paper scuff after the peel ply has been stripped off . :eek:

  15. tunnels

    tunnels Previous Member

    Dont know about anyone else but i have read this a few times and its rather confusing and controdicts its self here an there :eek: .
    Dont back peddle !!say what you mean and mean what you say :?: .
    Trouble is with laying quanties of glass in one shot is the sequance of the laps of glass down the keel line all the way from stem to stern . They are meant to interlock together , not just a bundle from one side then bundling the otherside over the top , thats bad building practises .:(

    Richard ! do you work on the floor using your hands ?? :mad:
    or do you sit in a office telling others how to do the work ?? :D
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