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

    Many thanks, sounds like the route I am destined to take. So you have used the two part epoxy paints.... sprayable I assume.
     
  2. fallguy
    Joined: Dec 2016
    Posts: 1,902
    Likes: 105, Points: 63, Legacy Rep: 10
    Location: usa

    fallguy Senior Member

    It is a decision you must make. Gelcoats have their positives. Don't take my word for it.

    There are epoxy gelcoats as well.
     
  3. JohnMarc
    Joined: Feb 2018
    Posts: 78
    Likes: 3, Points: 8
    Location: Knysna South Africa

    JohnMarc <--- My ultimate goal

    I would very much like to make an informed decision, besides the fact that the epoxy paint is more prone to scratching I am not aware of many other pro's to poly + gelcoat. I am under the impression that Epoxy is up to 20% stronger than poly. Poly gelcoat is more sensitive to UV rays .... I would imagine that epoxy paint is easier for the occasional inevitable touch ups required to keep the craft in tip top condition. That is about all I have to make this decision, any other input would really be appreciated.
     
  4. Blueknarr
    Joined: Aug 2017
    Posts: 629
    Likes: 93, Points: 28
    Location: Colorado

    Blueknarr Senior Member

    JohnMarc

    The advantage of gelcoat:

    • Smooth finish coming out of mold requiring little additional work.
    • Film thickness 20 times thicker than paint
    • Much deeper scratches or gouges can be buffed out
    • Poly is much more UV resistant than epoxy
    • Gelcoat is easier to touch up than many paints
     
    Last edited: Feb 14, 2019
  5. fallguy
    Joined: Dec 2016
    Posts: 1,902
    Likes: 105, Points: 63, Legacy Rep: 10
    Location: usa

    fallguy Senior Member

    Most professionals would not agree with the ease of touch up. Color matching gelcoat is an artform. Paint color retention is remarkably good for typical expected lives of paint.

    Are you moulding all the parts?

    Gelcoat is also heavier.

    Epoxy paints are harder than gelcoats, but I don't have a resource. The obvious advantage is a 2mil scratch in a 20 mil coating is not all the way through; so gouges in gel have a chance to not go through; not so epoxy.
     
    Last edited: Feb 14, 2019
  6. JohnMarc
    Joined: Feb 2018
    Posts: 78
    Likes: 3, Points: 8
    Location: Knysna South Africa

    JohnMarc <--- My ultimate goal

    When you ask wether I am moulding all the parts.... if I don't use the correct terminology please understand I am total novice. What I am planning to do is use foam core (Maricell Lycell Fused Structural PVC Foam) which I will vacuum infuse (using Epoxy) for the hull deck etc.
    All of the "furnishings".... seating, helm, head etc. I plan to vacuum bag.
     
  7. JohnMarc
    Joined: Feb 2018
    Posts: 78
    Likes: 3, Points: 8
    Location: Knysna South Africa

    JohnMarc <--- My ultimate goal

    Silly question possibly but on my plug must I mask the area where the double sided tape is going to be on the plug prior to applying wax or will it stick to the waxed element of the plug. So the sequence would be to wax the "entire" plug, apply the double sided tape and then spray the PVA.
     
  8. Blueknarr
    Joined: Aug 2017
    Posts: 629
    Likes: 93, Points: 28
    Location: Colorado

    Blueknarr Senior Member

    I would:
    • Apply two layers of wide masking tape to the unwaxed plug/mold
    • Wax and PVA
    • Run a razor blade thru top layer of tape close to working side of plug/mold
    • Remove most of top layer of masking tape
    • Apply double sided tape to exposed base layer of masking tape.
    These steps help avoid:
    • Scratching plug/mold with razor
    • PVA from peeling off of plug\mold if PVA too thick
    Some people apply double sided tape directly to raw plug/mold. They risk prematurely exposing top adhesive
     
  9. ondarvr
    Joined: Dec 2005
    Posts: 1,965
    Likes: 142, Points: 63, Legacy Rep: 506
    Location: Monroe WA

    ondarvr Senior Member

    A couple of things.

    Do not thin the epoxy, adding any type of thinner can drastically reduce the physical properties of the resin, and that includes water resistance.

    You cannot use regular gel coat in-mold with epoxy, they are not compatible. You can use epoxy compatible gel coats though.

    The Duratec line of products are epoxy compatible, they can be use in-mold, or post applied. This gives you many options on the finish of an epoxy part.

    Using a combination of wax and PVA is a good insurance policy. PVA can be a bit tricky to spray, you need to just mist the first coat on and let sit for a bit. I will frequently apply it with a rag. Apply a small amount and rub in a circle until it starts to dry, it will about disappear on the surface.
     
  10. JohnMarc
    Joined: Feb 2018
    Posts: 78
    Likes: 3, Points: 8
    Location: Knysna South Africa

    JohnMarc <--- My ultimate goal

    mmmm okay this is embarrassing .... so followed all the advise I got, did the plug and religiously waxed at least ten coats, put down the double sided tape, then tried to spray the PVA....aaaagh :oops::eek: before everyone starts shouting at me, in my defence I did not watch enough you tube vid's on how to apply it...... so busy cleaning it all off, turfing the tape and now will follow Blueknarr's advise with the tape and then do the mist coats (thanks ondarvr, wish I read your post before starting ) etc. etc. Patience it seems is the key :)
    IMG_7559.JPG
     
  11. tpenfield
    Joined: Dec 2016
    Posts: 209
    Likes: 15, Points: 18, Legacy Rep: 10
    Location: Cape Cod, MA

    tpenfield Senior Member

    Sorry to say, but it looks like you tried to drown the thing with PVA. :eek: Ondarvr's suggestion on PVA application should get you there. :)
     
  12. fallguy
    Joined: Dec 2016
    Posts: 1,902
    Likes: 105, Points: 63, Legacy Rep: 10
    Location: usa

    fallguy Senior Member

    one of the pvas is too thick to spray...the purple iirc is for brushing

    I use the green for spraying.

    Maybe someone here can talk about the difference. I have both in the shop, but always use the green in the sprayer and apply the purple with a roller or chip brush.
     
  13. JohnMarc
    Joined: Feb 2018
    Posts: 78
    Likes: 3, Points: 8
    Location: Knysna South Africa

    JohnMarc <--- My ultimate goal

    I know..... ha ha ..... I have now "drowned" it in warm soapy water and will try the PVA again......
     
  14. JohnMarc
    Joined: Feb 2018
    Posts: 78
    Likes: 3, Points: 8
    Location: Knysna South Africa

    JohnMarc <--- My ultimate goal

    I hear you but I am in a little town on the arse end of Africa, this is all we have, not too sure the colour reference is relevant, it is possibly not the same range. It sprays just fine.... me thinks the problem was with the "sprayer" not the product. The guys at the shop tell me that spraying is the only way to use this product. I've just got to remind myself I am spraying a mist coat or two and not putting out a fire :(
     

  15. kapnD
    Joined: Jan 2003
    Posts: 481
    Likes: 34, Points: 28, Legacy Rep: 40
    Location: hawaii, usa

    kapnD Senior Member

    A foam roller will lay down a nice thin PVA layer, I hold a strong light in my free hand to help identify puddles of the stuff.
    A pump sprayer does a good job on small or irregular surfaces.
    When I first started using it, my standard application tool was a rolled up,sock!
     
Loading...
Similar Threads
  1. Felix Gruter
    Replies:
    15
    Views:
    1,854
  2. Raggi_Thor
    Replies:
    11
    Views:
    7,103
  3. scotboats
    Replies:
    2
    Views:
    2,194
  4. PROPGUNONE
    Replies:
    4
    Views:
    517
  5. fiberglass newbie
    Replies:
    3
    Views:
    482
  6. Nick.K
    Replies:
    7
    Views:
    805
  7. sailsherpa
    Replies:
    2
    Views:
    840
  8. missinginaction
    Replies:
    3
    Views:
    1,959
  9. pavel915
    Replies:
    6
    Views:
    4,571
  10. tugboat
    Replies:
    87
    Views:
    9,057
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.