Making a mould...

Discussion in 'Fiberglass and Composite Boat Building' started by JohnMarc, Feb 11, 2019.

  1. JohnMarc
    Joined: Feb 2018
    Posts: 78
    Likes: 3, Points: 8
    Location: Knysna South Africa

    JohnMarc <--- My ultimate goal

    I hear you thanks..... will do just that. In fact have now made the plug so will run a router around it .... many thanks for the tip.
     
    Last edited: Feb 12, 2019
  2. kapnD
    Joined: Jan 2003
    Posts: 437
    Likes: 29, Points: 28, Legacy Rep: 40
    Location: hawaii, usa

    kapnD Senior Member

    Your overcomplicating your mold with the addition of the second 90degree turn, which is just being discarded.
    I’d just make the vertical sides a little longer, much easier to make the fabric behave.
     
  3. JohnMarc
    Joined: Feb 2018
    Posts: 78
    Likes: 3, Points: 8
    Location: Knysna South Africa

    JohnMarc <--- My ultimate goal

    Sorry you have lost me...... not experienced enough me thinks to understand what you saying. I cannot really produce and accurate section detail as I do not know the exact thickness of the glass layup. I have had to assume a 4 mm wall thickness ... so yes it is a bit of a guessing game a section can be produced but might not to be an accurate reflection of my results. But hey we live and learn, as I said earlier more than happy to make a few mistakes......
     
  4. JohnMarc
    Joined: Feb 2018
    Posts: 78
    Likes: 3, Points: 8
    Location: Knysna South Africa

    JohnMarc <--- My ultimate goal

    Thanks and I agree but the main reason why I did this is because for the helm and drinks surface of the boat (which is what this learning experience is about) I have one or two situations very similar so I have decided to kill two birds with one stone as the saying goes and tackle the second 90 degree turn now rather than cock it up later ....
     
  5. JohnMarc
    Joined: Feb 2018
    Posts: 78
    Likes: 3, Points: 8
    Location: Knysna South Africa

    JohnMarc <--- My ultimate goal

    I am still wondering if my thinking is correct, can I not do a gelcoat with epoxy? can I only have a gelcoat if I use poly?
     
  6. tpenfield
    Joined: Dec 2016
    Posts: 144
    Likes: 9, Points: 18, Legacy Rep: 10
    Location: Cape Cod, MA

    tpenfield Senior Member

    Polyester gelcoats will not cure if applied to an epoxy surface. . . at least not without a lot of surface preparation to eliminate the 'amine blush' that remains on the surface of epoxy.

    However, on your mold and finished part, you will be putting the polyester gelcoat down first, then doing the epoxy resin with the laminates. So, that will be OK.

    You can also look into epoxy gelcoats, so there is no compatibility issues to worry about.
     
  7. JohnMarc
    Joined: Feb 2018
    Posts: 78
    Likes: 3, Points: 8
    Location: Knysna South Africa

    JohnMarc <--- My ultimate goal

    Thanks to everybody for their help, going ahead today to try my first vacuum bagging ..... one last question if I may, any comments on using denatured alcohol to thin the epoxy?
     
  8. fallguy
    Joined: Dec 2016
    Posts: 1,668
    Likes: 87, Points: 48, Legacy Rep: 10
    Location: usa

    fallguy Senior Member

    No thinning is done.

    You can lower viscosity by warming the mixture, but this will hasten gel time.
     
  9. tpenfield
    Joined: Dec 2016
    Posts: 144
    Likes: 9, Points: 18, Legacy Rep: 10
    Location: Cape Cod, MA

    tpenfield Senior Member

    I have thinned epoxy with acetone, but only slightly (5-10%). Not sure about denatured Alcohol. . . I am not sure how a thinned resin would do in a vacuum bag setup. I figure that the solvent needs to go somewhere. thinning may be better suited for an open mold situation (not sure).

    Are you going to do resin infusion? (not sure if that was asked/mentioned already) or just vacuum bagging for the curing process?
     
  10. JohnMarc
    Joined: Feb 2018
    Posts: 78
    Likes: 3, Points: 8
    Location: Knysna South Africa

    JohnMarc <--- My ultimate goal

    Very good point about solvent going somewhere? will not risk thinning ....weather warm here at the moment so should be good. I am doing vacuum infusion....I am such a newbie I had to google the difference between the two before answering you :rolleyes:
     
  11. tpenfield
    Joined: Dec 2016
    Posts: 144
    Likes: 9, Points: 18, Legacy Rep: 10
    Location: Cape Cod, MA

    tpenfield Senior Member

    Hopefully, the epoxy is thin enough for an effective infusion. The part is small, so the distance the resin has to travel is short and the cure time of epoxy is long, which will help.

    Take some pictures and post them if you can.
     
  12. JohnMarc
    Joined: Feb 2018
    Posts: 78
    Likes: 3, Points: 8
    Location: Knysna South Africa

    JohnMarc <--- My ultimate goal

    Okay so the journey begins..... As I said earlier made the plug just from MDF (particle board I think is another term for it) rounded the corners with the router and filled the inside corners with a bit of wood filler. I popped down to a paint supplier and bought some Auto paint, applied the primer after mixing with hardener etc. I will sand it down before applying the top coat which will hopefully give me a smooth enough finish for the inside of the female mould to ultimately give me a wonderful gelcoat (he says optimistically) finish on my final product....I will post a pic or two at every stage if peeps are interested, if not let me know and I shan't bother you with them.
    IMG_7548.JPG
    IMG_7549.JPG
     
  13. JohnMarc
    Joined: Feb 2018
    Posts: 78
    Likes: 3, Points: 8
    Location: Knysna South Africa

    JohnMarc <--- My ultimate goal

    Our average temperatures at the moment are in the high twenties .... (80 F) so all should be good as far as the viscosity goes..... don't know about the rest though :rolleyes: time will tell.
     
  14. tpenfield
    Joined: Dec 2016
    Posts: 144
    Likes: 9, Points: 18, Legacy Rep: 10
    Location: Cape Cod, MA

    tpenfield Senior Member

    Not sure if you are planning on waxing the mold or spraying it with PVA (polyvinyl alcohol) as a release agent for the mold.
     

  15. JohnMarc
    Joined: Feb 2018
    Posts: 78
    Likes: 3, Points: 8
    Location: Knysna South Africa

    JohnMarc <--- My ultimate goal

    Just had a giggle, your use of the word "planning" assumes a plan right? ..... So what I have on my shelf of newly procured goodies are what I think they call "Ram Wax", I have a bottle of PVA as well. I am now doing some serious you tubing to find the best way forward. So far I think I am going to hand lay the gelcoat and Chopstrand fibreglass, four or five layers then Vacuum Bag to cure, creating the female mould. Then use vacuum infusion (hence the large lip on the plug) for the hatch itself. These are my thoughts at the moment although open to suggestions.
    BTW if I use the PVA does that mean I do not need to wax?
     
    Last edited: Feb 13, 2019
Loading...
Similar Threads
  1. Felix Gruter
    Replies:
    15
    Views:
    1,565
  2. Raggi_Thor
    Replies:
    11
    Views:
    6,803
  3. scotboats
    Replies:
    2
    Views:
    2,149
  4. PROPGUNONE
    Replies:
    4
    Views:
    401
  5. fiberglass newbie
    Replies:
    3
    Views:
    408
  6. Nick.K
    Replies:
    7
    Views:
    737
  7. sailsherpa
    Replies:
    2
    Views:
    749
  8. missinginaction
    Replies:
    3
    Views:
    1,862
  9. pavel915
    Replies:
    6
    Views:
    4,227
  10. tugboat
    Replies:
    87
    Views:
    8,789
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.