First layer in making a new mold.

Discussion in 'Fiberglass and Composite Boat Building' started by Fgayford, Feb 7, 2012.

  1. Fgayford
    Joined: Nov 2011
    Posts: 43
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Cambridge Ontario Canada

    Fgayford Junior Member

    Yet another question.
    When I make a mold I spray on the tooling gelcoat and when it reaches the tacky state I apply the firsts layer of 1 1/2 oz chopped matte as the capture coat. I make this a resin rich coat so as not to get voids or air bubbles.
    Do any of you guys do things different like say, do the capture coat first layer using veil or what ever??
    Some times I think I see some matte print through in the new mold surface.
    Thanks
    Fred
     
  2. gonzo
    Joined: Aug 2002
    Posts: 15,770
    Likes: 1,197, Points: 123, Legacy Rep: 2031
    Location: Milwaukee, WI

    gonzo Senior Member

    There is a veil fabric to prevent print-through
     
  3. tunnels

    tunnels Previous Member


    Making a mould ! how big and for what ??
    You to that stage and dont know how to do the whole Job ?? wow
    THE TOOLING GEL !what is the catalyst ratio you using ?
    How thick you putting it on ?
    Better to use Tissue glass as a back up behind the gelcoat !!!
    Then 1 chopped strand matt 300 gram "P" matt
    second layer one 450 gram csm also "P" matt and after that 2 X 450 csm and carry on from there to what ever thickness you are wanting to build to .Build it slow to start off with and the first couple of layers should be cured before getting to carried away and adding lots of glass .
    Never use woven cloths on a mould as the woven pattern will show through later as the resins cure and shrinks over time !.

    You sprayed gelcoat before ?? what kind a spray equipment you got ??

    Aaaah the pva man !!!
     
  4. Herman
    Joined: Oct 2004
    Posts: 1,618
    Likes: 94, Points: 48, Legacy Rep: 1240
    Location: The Netherlands

    Herman Senior Member

    Preventing print is also about the cure state of you gelcoat. Make sure you catalyse properly, have the right working temperature, and adjust catalyst for that temperature, and apply the right thickness. All to achieve enough cure.

    I hate laminating veil, but it can help preventing the print you mention. Make sure you apply the veil with clean resin, no foamy stuff, and after cure check for larger air bubbles. Cut them open, and fill them.

    Then I suggest starting with a 225 gr/m2 mat, preferably low-tex. Lower weight mat is also OK, but make sure it is low tex. (10, 12 or so)
     
  5. waikikin
    Joined: Jan 2006
    Posts: 2,408
    Likes: 160, Points: 73, Legacy Rep: 871
    Location: Australia

    waikikin Senior Member

    This is pretty much what I do, also when using tissue there's 2 sides to it, make sure the shinier side goes to you.
     
  6. tunnels

    tunnels Previous Member






    I hate laminating veil, but it can help preventing the print you mention !!
    then lay it at the same time as a 225 gram or a 300 gram P matt Then it goes down really easy and you have 2 layers of light glass with lots a resin instead of just one at a time and even lesser of a chance of print through . Most times it just a matter of using mohair roller only so saves even more time . :D
     
  7. Fgayford
    Joined: Nov 2011
    Posts: 43
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Cambridge Ontario Canada

    Fgayford Junior Member

    Thanks Tunnel
    This mould is about 4 square feet. Tooling gelcoat 1% ratio (4.5cc per lb) 20 mil thick.
    Sprayed with a gelcoat gun. I will wet sand and polish anyway so it shouldn't be an issue. I am just interested in learning the Best way to do things, so my questions. Before the internet this sharing of information did not exist.
    I think on my next mould I will use one layer of veil and let that cure and then light sand and apply one layer of 1 1/2 ounce matte and then build up layers from there. How does that sound?
    Thanks
    Fred
     
  8. gonzo
    Joined: Aug 2002
    Posts: 15,770
    Likes: 1,197, Points: 123, Legacy Rep: 2031
    Location: Milwaukee, WI

    gonzo Senior Member

    1% is rather low.
     
  9. Wynand N
    Joined: Oct 2004
    Posts: 1,260
    Likes: 148, Points: 73, Legacy Rep: 1806
    Location: South Africa

    Wynand N Retired Steelboatbuilder

    Never had print through on a mold yet and never used surface tissue as well...

    I apply the gelcoat with brush or roller and use about 1.5 - 2.0% catalyst depending on the temperature and sometimes in the summer here like now a little less.
    I let the gelcoat cure and often check it and know its ready - when it squeals when pulling a finger over it - usually about 45 minutes to and hour. Then I apply 350gm2 CSM directly on the gelcoat and wet it out with brush only - no aluminum GRP wetting out roller used at this stage, but after the first coat gelled and second going on we wet it out with the roller.
     
  10. tunnels

    tunnels Previous Member

    Hi
    The minimum catalyst for any gel coating is 1.5% for the first coat !! use 2% for a second coat . This is any gel coat any where any time minimums % !!!:D
    If you dont use the correct ratio the gel coat will never reach it full potentual hardness . You have a couple of options ; you can use tissue or Veil as a first coat behind the gel coat or simply second coat with gelcoat again what i usually do with a second coat is use a little white or another colour and add it to the tooling gel so its easyer to see where you are applying the second coat !, Also add a little resin to the gel that make it easyer to apply either brushing or using a paint roller or even spraying because it diluted the gel has a tendancy to flow a little easyer and smooth the surface to glass over without spray or brush pattern . :)
     
  11. tunnels

    tunnels Previous Member

    Why are you quoating lbs and oz and grams and kilos in the same sentance ????.
    Its one ot the other not both . lbs and oz are history so why try to remember both when you only need to remember and deal with one !!
    1% catalyst is 10ml per kg of resin or gelcoat easy to remember and far less confusing also resins and gelcoats are measured in weight not volumn .
    About 4 sqr feet ??what sort of measurement is that ?? be accurate with any and all things when are glassing or you will be wonder why things never work properly if you keep guessing use scales and use a measuing tape . use a calculator if need be Know what you are doing dont guess !!!
    The only confussion to you day should be tea or coffee ? for breakfast !!
    Also glass is kgs and grams not pounds and oz !! this 2012 just because the rest of the world is still playing catch up and have there head buried in the sand dosent mean you have to be like them !!:D
    The usage of gel coat shold be 600 grams per sqr metre so if you know the sqr metres you will know how much gel coat to mix and the correct catalyst at 1.5% minimum plus a %of waste !!Everything costs dont waste materials !!
     
  12. idkfa
    Joined: Sep 2005
    Posts: 329
    Likes: 6, Points: 18, Legacy Rep: 79
    Location: Windward islands, Caribbean

    idkfa Senior Member

    Any required % minimum to catalyse resins? Or can one go less, not over-temp the mould cure.


    Would not sunlight & heat eventually (days) produce full cure of gel-coats & resins???
     
  13. tunnels

    tunnels Previous Member

    If i doubt do your own exsperiments Polyester resin minimum is close to 1% of catalyst so use that as a start point !! Maximum % for polyester is about 2.75% . If you catalyze to low it will go hard eventually but will never ever reach its full hardness no mater how much heat or sun you apply !. So the resin you have find where it came from and ask for specs !!
    Gel coats the minimum catalyst is 1.5% and dont go below .the upper limit is about 2.5% and the catalyst for gelcoat is normally differant to whats used for resin . It produces less gas so the gel coat wont have as much porosity !!:):p
     
  14. Fgayford
    Joined: Nov 2011
    Posts: 43
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Cambridge Ontario Canada

    Fgayford Junior Member

    Hi
    I was using 1% because that was the recommended amount on the can of tooling gelcoat. Do you use more or do you perhaps use a different gelcoat?
    Fred
     

  15. Herman
    Joined: Oct 2004
    Posts: 1,618
    Likes: 94, Points: 48, Legacy Rep: 1240
    Location: The Netherlands

    Herman Senior Member

    It that is what is on the can, who are we to disagree?

    I also think it is rather low, but the producer must have a good reason for this. Perhaps it is a high-filled resin.

    You could check with a barcol impressor to see if you reached the full potential of the gelcoat. The measurement should reach the value quoted on the TDS. If it is not quoted, I would like to see at least 40.

    Be sure to measure on a spot which has the right amount of gelcoat on it, not too thin, as otherwise you will be measuring the barcol hardness of the laminate below.
     
Loading...
Similar Threads
  1. atillayc
    Replies:
    8
    Views:
    992
  2. DogCavalry
    Replies:
    30
    Views:
    2,164
  3. Midday Gun
    Replies:
    5
    Views:
    2,305
  4. Errand
    Replies:
    9
    Views:
    2,584
  5. Davetv1423
    Replies:
    7
    Views:
    3,267
  6. omamari
    Replies:
    9
    Views:
    1,784
  7. aaronhl
    Replies:
    75
    Views:
    10,000
  8. midcap
    Replies:
    18
    Views:
    4,285
  9. idkfa
    Replies:
    5
    Views:
    1,728
  10. CatBuilder
    Replies:
    4
    Views:
    1,865
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.