Molding part the "wrong" way (Annular foil)

Discussion in 'Fiberglass and Composite Boat Building' started by ziper1221, Dec 29, 2019.

  1. ziper1221
    Joined: May 2018
    Posts: 28
    Likes: 5, Points: 3
    Location: florida

    ziper1221 Junior Member

    Hello, I had the idea to make an annular rudder for a foiling dinghy, both for induced drag reduction and for safety reasons. However, I couldn't come up with any east to make the part. To mold it the typical way, it would take (by my count), no less than a 6 part mold. If it were to be made with the parting line along the line of max thickness instead of along the chord line, it could be made with only a 2 part mold, CNC'd from foam. Pictures attached for your viewing pleasure. The section is exaggerated.

    Note that the actual section would be much thinner (~8% of chord) and minimally cambered. The part would be solid carbon, no core.

    My concerns are that:
    1. The trailing edge would be too fine. the mold would be difficult to machine, difficult to keep release agent on it, and difficult to pack with fiber.
    2. The draft angle would be too small, and the part would fail to release from the mold.
    Those issues could be solved with either using a sacrificial mold, or using the mold to make an oversize billet and then machining that down.

    Is there a better way to make this that I am not seeing, or is this my best option? Thank you for your responses.
     

    Attached Files:

  2. BrissoDamo
    Joined: Dec 2019
    Posts: 49
    Likes: 7, Points: 8
    Location: Brisbane

    BrissoDamo Junior Member

    make a solid core cnc machined and coat it
     
    Last edited: Dec 30, 2019
    DogCavalry likes this.
  3. fallguy
    Joined: Dec 2016
    Posts: 3,213
    Likes: 395, Points: 93, Legacy Rep: 10
    Location: usa

    fallguy Senior Member

    Oversize and machine is my vote, but I am an amateur.
     

  4. DogCavalry
    Joined: Sep 2019
    Posts: 597
    Likes: 234, Points: 43
    Location: Vancouver bc

    DogCavalry Senior Member

    Why mold it at all? The plug to form the mold on will take the same amount of time and effort, as making the part. Or almost as much. Much less than making a plug, making a mold from that, making the blank in the mold then machining it down to the final form.
     
    bajansailor and fallguy like this.
Loading...
Similar Threads
  1. fenfen
    Replies:
    10
    Views:
    2,552
  2. burke
    Replies:
    2
    Views:
    959
  3. groper
    Replies:
    13
    Views:
    3,642
  4. Fgayford
    Replies:
    2
    Views:
    2,041
  5. groper
    Replies:
    68
    Views:
    13,961
  6. ramon
    Replies:
    6
    Views:
    6,136
  7. alibi
    Replies:
    2
    Views:
    3,153
  8. octavius
    Replies:
    7
    Views:
    4,449
  9. useragentseven
    Replies:
    14
    Views:
    1,399
  10. JohnMarc
    Replies:
    7
    Views:
    709
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.