How should I waterproof Nomex?

Discussion in 'Fiberglass and Composite Boat Building' started by TJ Cameron, Nov 20, 2012.

  1. TJ Cameron
    Joined: Mar 2012
    Posts: 12
    Likes: 0, Points: 1, Legacy Rep: 10
    Location: USA

    TJ Cameron Junior Member

    I am designing a super-light beach cat that will be built using folded flat sandwich panels for the above the waterline hull superstructures similar to the technique described by Kurt Hughes here:

    http://www.multihulldesigns.com/pdf/hulls2lite.pdf

    I plan to score flat sandwich panels, fold the panels, install bulkheads and tape the scored areas and seams with carbon biaxial tape as shown by ACP and Hexcel here and here:

    http://www.acpsales.com/upload/Cut-and-Fold.pdf

    http://www.hexcel.com/Resources/Dat...ets/Sandwich_Panel_Fabrication_Technology.pdf

    DNA/ARC A-class cats are built using 10 mm thick, 48 kg/m3 Nomex, 300 gsm carbon cloth prepreg outside, 200 gsm carbon cloth prepreg inside and a 35 gsm waterproof sealant adhesive film between core and prepregs all layed up in female molds, vacuum bagged and autoclaved. My panel laminate schedule will be of similar weights.

    I am considering Nomex, Corecell and Divinycell for the core. If I use Nomex honeycomb, what are my options to prevent moisture intrusion into the honeycomb core?

    Will two part polyurethane paint, (Awlgrip or equal) both outside and inside be sufficient?

    The boat will never be sailed or in the water for more than 6 hours a day.

    Thanks in advance for your advice.
     
  2. upchurchmr
    Joined: Feb 2011
    Posts: 3,134
    Likes: 174, Points: 63, Legacy Rep: 579
    Location: Ft. Worth, Tx, USA

    upchurchmr Senior Member

    TJ,

    The only real waterproofing method for Nomex is to have a continuous, non porous skin inside and out.

    Paints do not typically stop moisture intrusion.
    Even aerospace quality epoxy laminates allow a minute amount of water to go thru the skin even if it is perfect. However, the amount is small, and nothing can be done about it.

    Damage will let in much larger amounts of water which cannot always be completely removed by drying before repair. But that is the best you can do.

    The only way you can tell if there is water is to weight your boat, trying to make sure you always have the same equipment in place. Actually X-ray can find water, if you can afford it and have access to specialized equipment.

    Last, don't ever put a fastener thru a honeycomb panel. Take out the Nomex and make it solid laminate in that area.
     
Loading...
Similar Threads
  1. Jim Allen
    Replies:
    0
    Views:
    728
  2. CuriousCanuck
    Replies:
    12
    Views:
    5,685
  3. fly186
    Replies:
    11
    Views:
    2,418
  4. aaronhl
    Replies:
    18
    Views:
    30,850
  5. hyboats
    Replies:
    7
    Views:
    5,440
  6. hyboats
    Replies:
    2
    Views:
    1,419
  7. hyboats
    Replies:
    5
    Views:
    1,362
  8. hyboats
    Replies:
    8
    Views:
    3,696
  9. hyboats
    Replies:
    8
    Views:
    9,473
  10. exp2000
    Replies:
    5
    Views:
    1,687
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.