Timing of steps before infusion

Discussion in 'Fiberglass and Composite Boat Building' started by jiggerpro, Nov 3, 2014.

  1. jiggerpro
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    jiggerpro Senior Member

    I will soon (in a month time) be infusing my first large piece, a 33 feet (10 meter) sportfishing boat hull in a female mould, and off course I want to do things right, one my worries comes from the time lapse I can have between gelcoat application and the day the infusion itself takes place, so far our planned schedule is:

    -Day 1: Two tone gelcoat application (35 mils / 0.8 mm thick) with airless spray gear (sides: Ice Blue bottom and transom pure white)

    -Day 2: Vinylester barriercoat application (40 mils / 1 mm thick) in the morning and in the afternoon application of first light (225 g/m2) mat glass layer

    -Day 3: morning: application of one more layer of light (225 g/m2) glass mat, afternoon: last skincoat glass mat (450 g/m2) layer application

    -Day 4: Early morning, placement of all the materials to be infused, all layers of glass, foam cores in sides and transom, at the end of the day (hopefully) film bag placement, sealing and vacuum pulling and 12 hours of maximum vacuum application during the night for the total removal of gases and water vapours.

    -Day 5: Infusion

    It seems to me that 5 days is too much time between gelcoat application and infusion, and it worries me that it can prerelease due to the long time, but I can not see how could the times be reduced, without supressing steps like the barriercoat layer after the gel coat, or the two tone gelcoat.

    Any suggestions or opinions about our plans that could lead to any improvement ???

    Some forum colleagues might find interesting to take a look at our build thread and pictures here:

    http://www.thehulltruth.com/boating-outdoor-photos/372020-raptor-project.html
     
  2. ondarvr
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    ondarvr Senior Member

    Day one should be, Start early, spray gel coat, wait one hour, spray barrier coat, wait one hour, apply skin coat. This should take a full day to complete.

    Day two/three, load the mold with glass and bag. The length of time it takes to load the mold will be determined by the type and amount of glass, plus the experience of the crew.

    Day three/four infuse. An experienced crew could infuse on day three, but day four would be fine.


    The gel coat should be closer to 20 mils, 35 will be vulnerable to pre-release and cracking.
    Normal VE barrier coat should be in the 20 mils range also, by using 35 mils of gel coat and 40 mils of barrier coat you will have around 75 mils of unreinforced material, if you can get all that on and not have it pre-release before the infusion then cracking in the final part could be a real concern.
     
  3. rwatson
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    rwatson Senior Member

    Seems to me its not really 5 days from gelcoat but 2 days from the laying of last glass mat.

    I doubt you are going to have pre-release problems with that sequence, but I will be interested to hear from other more experienced builders.
     
  4. jiggerpro
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    jiggerpro Senior Member

    Hi rwatson and ondavr,
    rawtson: what you say is true from the "adhesion point of view" but not from the "avoiding prerelease point of view" off course both could be issues but I am more worried about the prerelease ....

    ondavr: In regards to gelcoat and barriercoat thicknesses, the ones I have mentioned (35 mils for the gelcoat and 40 for the VE barriercoat) are the thicknesses indicated by the manufacturer of the products (DSM largest resin manufacturer in Europe), but off course they want to sell ............ and your advise may well be much more honest, I believed the barriercoat needs to be thick because one of its functions is minimize printhorough of fibers and it sounds logical to asume the thicker it is the farther away the fibers will be from the gelcoat layer and so being more efficient as a printhorugh avoider .....
     
  5. jiggerpro
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    jiggerpro Senior Member

    And shouldn´t the skincoat be applied slowly to avoid heat build up and contractions that could cause prerelease ??

    ( I must say that my VE resin with 1.5 % MEKP takes three hours to gel, and it barely warms almost regardless of thickness )
     
  6. ondarvr
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    ondarvr Senior Member

    I looked at the linked thread, I only read the first page and the last two, I didn't have 30 pages of time right now. You have a very nice shop and appear to do very good work. Since I didn't read everything there may be details I'm not aware of, so I may be asking things that were covered in the portion of the thread that I didn't read.

    Doing a 225 g skin and then a 450 g skin is OK but....

    That first skin will cure poorly due to insufficient mass to generate the energy required to complete the cross linking. This can lead to post cure and print shortly after de-molding and being placed in the sun. The second skin will help, but the initial cure phase of the first layer is the critical step for a good surface profile. I always try for at least 450g on the first skin. The resin chosen for the skin is very important also, it needs to be a resin designed for use as a skin coat if you want the best results. Using a thicker first skin can eliminate the need for the second skin layer, but there is no harm in having two, and it can improve the surface profile of the final part to some degree.
     
  7. ondarvr
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    ondarvr Senior Member

    Typical VE resins make poor skin coats, VE tends to be very reluctant to cure completely, so by going very thin on the skin, the cure can be poor.

    Taking three hours to cure is sign of the slow and incomplete reaction, it needs to generate a certain amount of heat for the crosslinking to reach a level where there will be little movement (post cure) in the future.

    Most Marine skin coat resins designed for good to excellent cosmetics are not straight VE's, they are blends. They mix VE (slow cure and shrinks) with a different base that has tendencies to cure well and shrink very little, this gives the combination of qualities desired for a very durable yet cosmetically good surface.

    The gel time of the VE skin resin should be in the 20 minute range, and it should generate some heat. The bulk resin used for infusion can have a longer gel time and lower exotherm , there will be sufficient mass to build the heat needed for a good cure.
     
  8. rwatson
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    rwatson Senior Member

    I just cant see 80mm of layup popping without intentional persuasion
     
  9. ondarvr
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    ondarvr Senior Member

    If the supplier/manufacturer of the gel coat and barrier coat recommend those thicknesses then is should be OK, but they aren't what would be typical here in the States.

    We do make barrier coats that can be sprayed on thicker, up to 60+ mils, but they aren't VE's, and they have special chemistry to allow for it.
     
  10. ondarvr
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    ondarvr Senior Member

    Another thought.

    The learning curve on this entire project is rather steep, even experienced fiberglass people run into problems on the first part(s) when attempting something like this, I see it happen all the time.

    So, you may want to go with just one color for the entire hull on the first try, either just blue or just white, and white is easier to work with.
     
  11. ondarvr
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    ondarvr Senior Member

  12. jiggerpro
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    jiggerpro Senior Member

    Mr Watson, you are probably very right, but if you look back in your time, you might remember being a novice and being overcautious about issues that might not even exist, well that is my case right now in regards to making sucha big (for me) piece

    Mr Ondavr, I understand your points in regards to thicknesses and needed mass, but I am following the instructions (Technical user leaflets) of the products as given by the manufacturers to the letter, in the test pieces we have made we had no problems at all, in regards to the resins being pure VE or blends I do not know, all I know is that the resins we use for the different purposes ( skin, infusion ) are sold by the brand as made for the purposes we have
     

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  13. ondarvr
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    ondarvr Senior Member

    Making test panels is critical, and seeing that you're making them will ensure a much higher likelihood of success.


    There are sometimes different chemistries and techniques used in different parts of the world to achieve the same result, it doesn't mean one is right or wrong, only that the products and methods that are used need to work together to get the desired result.

    We are a global company, and when products (formulas) are moved from one region of the world to another, they frequently need to be fine tuned or tweaked for use in the way the customers of that region use them.
     
  14. rxcomposite
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    rxcomposite Senior Member

    VE resin has proved to be an industry standard for barrier coats, but does not have to be thick. To quote http://composite.about.com/od/Resins/a/Vinyl-Ester-Vs-Polyester-Resins.htm

    "Where prolonged exposure to water is likely (such as a boat hull or water tank), then by using polyester for the bulk construction with a surface barrier of vinyl ester, water penetration can be reduced considerably without a significant increase in cost."

    I use a surfacing mat after gel coat. It serves two purpose, one because it has such a high resin content and two, it serves as a reinforcing layer for the gel coat. Next would be CSM300 then CSM 450 with VE resin to reduce or eliminate print through of succeeding WR. So far no problem with high quality gel coat used (LR approved). No osmosis, no blistering. First two layers of resin rich mat was enough as a barrier coat.

    The recommendation in the early days is to use a minimum of 1x SM + 2X CSM 450 minimum. But those were the days when the resin was bad in consistency.

    There were some test made and it appeared in Marine Composites. It shows the diffusitivity of poly and VE resin in salt water test. It is unconclusive as the table shows that one type of Poly resin is superior to VE in terms of diffusivity.
     

  15. jiggerpro
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    jiggerpro Senior Member

    I have read in your suggested link towards CCP cook book the pages related to gelcoat application and found them to be extremely well written and very comprehensive, reading such good literature, makes anyone inmediately trusting the company behind.

    In fact I wanted to use CCP products, for my moulds and in the future but unfortunately the CCP distributor in spain (Gazechim) is ruled by extremely incompetent wimen that makes unfeasible doing any bussiness with them.

    I have printed and read thoroughly your advises and the related pages of the cook book, I will compare the information gathered with what my brand of resins advise and try to make an average of methods, in the hope that inbetween will be the virtue ..
     
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