Resin infusion and gravity

Discussion in 'Fiberglass and Composite Boat Building' started by idkfa, May 2, 2016.

  1. idkfa
    Joined: Sep 2005
    Posts: 329
    Likes: 6, Points: 18, Legacy Rep: 79
    Location: Windward islands, Caribbean

    idkfa Senior Member

    I have noticed that all most all videos of infusion shows it being done from the bottom/center of the hull up to the gunwales/perimeter, and the few I've seen of infusion on a male mould, shows from the gunwales still up to the middle of the hull...

    So is this due to gravity, does it matter, isn't resin flow due to capillary action?

    NB. I do understand there is a disadvantage in going from the perimeter in, in that if there is a leak at the perimeter, it will pull air in with the resin flow. Where as if the same leak occurred with resin flow from the middle-out, there will be some loss of vacuum pressure but the air end up in the catch pot and not the laminate.... But there should be zero leaks before infusing anyway, so this should be a non-issue.
     
  2. gonzo
    Joined: Aug 2002
    Posts: 13,347
    Likes: 325, Points: 93, Legacy Rep: 2031
    Location: Milwaukee, WI

    gonzo Senior Member

    Resin is infused by a pressure differential. The reason to start at the lowest area is that the air bubbles rise, so it it easier to wet the laminate completely.
     
  3. idkfa
    Joined: Sep 2005
    Posts: 329
    Likes: 6, Points: 18, Legacy Rep: 79
    Location: Windward islands, Caribbean

    idkfa Senior Member

    True bubbles will rise if left on their own, so it will help to flow in that direction, but for sure the pressure differential will also expand the bubbles into the lower pressure of the vacuum, so it will be easy to overcome this tendency. ?Also surface tension of the resin (in the limited spaces) stops the resin from "free falling"?

    I'm fairly certain it is possible to infuse downwards successfully, so are there any other factors for flowing upwards?
     
  4. TANSL
    Joined: Sep 2011
    Posts: 5,546
    Likes: 160, Points: 73, Legacy Rep: 300
    Location: Spain

    TANSL Senior Member

    What is the function of the vacuum pump throughout this process?
     
  5. idkfa
    Joined: Sep 2005
    Posts: 329
    Likes: 6, Points: 18, Legacy Rep: 79
    Location: Windward islands, Caribbean

    idkfa Senior Member

    Without it nothing flows, up or downwards? I'm not trying to change/make a new process, just saying it will work in both directions, so why favour one over the other, for what reasons?
     
  6. gonzo
    Joined: Aug 2002
    Posts: 13,347
    Likes: 325, Points: 93, Legacy Rep: 2031
    Location: Milwaukee, WI

    gonzo Senior Member

    If the flow is up, you can think of it as filling an empty container (the void between the mold and the film. Doing the opposite, the resin will flow into the low area where the vacuum lines are and leave the upper areas dry. If you continue to run the vacuum, the lines will fill with resin.
     

  7. rob denney
    Joined: Feb 2005
    Posts: 696
    Likes: 73, Points: 28, Legacy Rep: 436
    Location: Australia

    rob denney Senior Member

    The usual reason is the worry that the resin might flow faster under gravity than under vacuum and create dry areas. Unwarranted in my experience. I usually run the feed line along the middle of the job and suck it to the edges as this way the entire laminate gets wet out and there is no need for a resin catchpot as the resin stops flowing when it reaches the edge. Whether this is up or down makes no difference.

    It is important to have the resin bucket below the lowest point of the laminate, or the hose clamped or the resin keeps flowing after the glass is wet out.
     
Loading...
Similar Threads
  1. guzzis3
    Replies:
    31
    Views:
    1,991
  2. Straycatstrut
    Replies:
    7
    Views:
    1,322
  3. hakalugi
    Replies:
    3
    Views:
    1,168
  4. KnottyBuoyz
    Replies:
    8
    Views:
    2,881
  5. KnottyBuoyz
    Replies:
    27
    Views:
    2,762
  6. nqb12179
    Replies:
    1
    Views:
    1,197
  7. rwatson
    Replies:
    16
    Views:
    2,374
  8. AMW marine
    Replies:
    3
    Views:
    1,531
  9. method_nzd
    Replies:
    15
    Views:
    4,885
  10. saladin harun
    Replies:
    3
    Views:
    1,571
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.