Making a new plug/mold from existing mold

Discussion in 'Fiberglass and Composite Boat Building' started by mrdebian, Dec 8, 2021.

Tags:
  1. mrdebian
    Joined: Apr 2021
    Posts: 46
    Likes: 4, Points: 8
    Location: Greece

    mrdebian Junior Member

    Hi all,

    I build a mold for a sea kayak a while ago but due to zero experience in laminating before, I end up with a really good product (the kayak) but a very "problematic" mold.
    Let me explain a little bit about that. There are many bubbles in the mold which every 2-3 releases they popup and need to be repaired. They are all in very difficult shapes to fix and is been a real pain. I repair more than I release from it...
    On top of that the gelcoat that I sprayed was very thin which makes nearly impossible a good fix. When I start sanding for example a part of it with the bubble I end up going down to glass level as the gelcoat is so thin in some areas which is impossible to make the repair properly or at least I'm not aware a way.

    There is more sad history on this mold....the plug I did was really perfect. Very glossy with A quality finish (from cedar). Due to wrong wax and some other things the plug end up going out of the mold in pieces so I have no plug now. Apart from that in order to release the plug from the mold due to stress left a few areas of the deck with a mat like surface no matter well the deck polished afterwards. When I polish an item that I released from the mold you can't see it easy if you don't know it but if you do you can spot the "foggy/mat" areas straight away.

    What I'm thinking of doing is the following and I would really appreciate if you can give me your thoughts to avoid dealing with the same problems as in the past.

    I will create a new deck with a very thick gelcoat in order to be able to sand it and polish it afterwards to a A level. That deck will also have a flange like my existing mold (see attached picture) and will be used as the new plug.
    At the same day I will also create a hull.
    After 24 hours I will release both from the mold and straight away I will make a few holes in the flange in order to put both the deck and the hull in place with screws to avoid changing shape(shrink) over time.
    Then I will start sanding and polishing both (one each time).
    Once they are ready I will wax the deck first with its flange and build the mold carefully to avoid bubbles etc with lots of gelcoat on it.
    Same things goes for the hull for the next day that I will release the deck and start working on the hull.

    My questions are:
    1. Is the above procedure ok or I missed something?
    2. After releasing the deck mold from the plug would it be ok if it left as it is a day until I finish the hull before I join them with screws or it has to be reinforced straight away to avoid shrink?

    Your input is very much appreciated.

    Thanks in advance.
     

    Attached Files:

  2. wet feet
    Joined: Nov 2004
    Posts: 866
    Likes: 175, Points: 43, Legacy Rep: 124
    Location: East Anglia,England

    wet feet Senior Member

    I would begin by advising a heavy gelcoat on all moulds.Over here we normally brush on two coats to be sure there is enough,come to that we often do the same with hulls that aren't intended to be as light as possible as it gives more material to polish oxidation out of in future years.On those occasions when we are using a mould to make a new plug,it is normal to use a heavier layup that the actual component and to lay it up more gradually so that shrinkage is less of a problem than it would be if it were all done in a hurry.It may be worth using strips of coremat or similar in locations where stiffening framework will be located,also to minimise distortion.You probably won't need me to tell you that the sharp corner where the flange meets the hull surface won't be the easiest feature to wrap glass round.It may be best to use a strip of light mat on either surface,perhaps 40mm wide to effectively increase the radius that the subsequent glass has to follow.It is best to leave the plug in the mould for a day or two once the full laminate is applied to allow for a more complete cure.

    Bolts around the flanges are just about inevitable but they will wear and enlarge the bolt holes over time.It isn't easy to align two flanges with no other locating features and it isn't unusual to use conical faced tooling bobbins on a new project.It isn't really feasible to add them to your project unless you have a large template that can hold it's shape and surround the plug(s).
     
  3. mrdebian
    Joined: Apr 2021
    Posts: 46
    Likes: 4, Points: 8
    Location: Greece

    mrdebian Junior Member

    Thanks a lot for the feedback.
    How gradually you laminate? Three layers in a day for example?

    Also what is the time between the first to the second layer of gelcoat? Are you waiting like an hour to cure a little bit or less?

    Thanks
     

  4. wet feet
    Joined: Nov 2004
    Posts: 866
    Likes: 175, Points: 43, Legacy Rep: 124
    Location: East Anglia,England

    wet feet Senior Member

    I wouldn't apply more than a 1800 g/sq.m in a day by choice.As for time between gelcoats,perhaps an hour is a little soon,but certainly within two hours.
     
Loading...
Similar Threads
  1. gtcway
    Replies:
    3
    Views:
    2,740
  2. PROPGUNONE
    Replies:
    4
    Views:
    1,674
  3. Felix Gruter
    Replies:
    15
    Views:
    4,353
  4. pironiero
    Replies:
    33
    Views:
    2,288
  5. fallguy
    Replies:
    6
    Views:
    826
  6. magentawave
    Replies:
    4
    Views:
    1,000
  7. fallguy
    Replies:
    6
    Views:
    1,279
  8. JohnMarc
    Replies:
    87
    Views:
    5,483
  9. fiberglass newbie
    Replies:
    3
    Views:
    1,156
  10. Nick.K
    Replies:
    7
    Views:
    1,367
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.