bleed and feed

Discussion in 'Fiberglass and Composite Boat Building' started by Tungsten, Dec 19, 2013.

  1. Tungsten
    Joined: Nov 2011
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    Tungsten Senior Member

    Well no plans for knife cut test,the holes will save me some resin and less flow media used.Holes should only add about 8 grams a sq/ft and I make a panel all in one shot.

    Whats going to happen to the shear strength of the foam with all these holes?
     
  2. Tungsten
    Joined: Nov 2011
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    Tungsten Senior Member

    Did a test piece,12"x40" drilled the holes and found a piece of glass so I can see the underside.

    [​IMG]

    I put a little red flow media under the inlet to aid flow,again it was just a little too fast even though I held it back.On the underside you can see the glass didn't wet out 100% right under the inlet.The rest was clear.I did get some racing even though I did what I could to stop it.Glass is short of the chamfer on both sides just the peelply over laps and plenty of pleats.I assume because of such a small part that this will always happen.

    [​IMG]


    underside.

    [​IMG]

    In the end the part fully wet out ,

    [​IMG]

    I had no problem getting the distance I need and I think once I go full size I shouldn't have any problems.

    Thanks groper.Oh and any guess on what % my shade cloth is?It consumes about 40g 2^ft ....420gsm
     
  3. groper
    Joined: Jun 2011
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    groper Senior Member

    You need to get a handle on things a bit more... when you center feed, the resin will go out in all directions at about the same speed - only depends on certain types of flow media which will flow faster in 1 direction compared to the perpedicular axis.

    Therefore, you can predict that the resin will reach the sides of this panel, long before the resin gets toward the ends. So this was destined for a dry spot near the ends with the flow media stopped very short. Once the front gets to an edge, you have no idea how fast the race track will be - so you should plan your strategies to avoid this and instead design the flow strategy so that the front reaches all the edges, all at the same time ideally. So the distances from center feeder line, to panel edge, should all be the same in a center feed arrangement.

    So its the strategy which is the problem, not the panel size - and this you will learn intuitively as you do more infusions. It gets really interesting when you have very odd shape panels to do. I made all these same mistakes just the same as you whilst i was learning :D

    If your shade cloth consumes 420gsm of resin, its most likely 50% shade. I use 30% shade and it uses around 300gsm and is a bit slower. Slower is always better with infusion, too fast leads to many problems. The only limit with regards to slow speeds, is the resin gel time and getting it out of the bucket before it exotherms and tries to catch fire - been there done that too :)
     
  4. Tungsten
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    Tungsten Senior Member

    Well this was more of a test of distance and if I can seal the edges and I'm happy with it.I also forgot to offset the holes.
    Another question,any benefit to having the mold side glass exstend a little so it touches the top peelply ?Will this give any pull to the resin on the mold side?
    Also how much glass can I exspect to fully wet out on the mold side,in the test I had one layer 600gsm.Is there a limit with 1.9mm holes?
     
  5. groper
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    groper Senior Member

    No limit , but thicker laminates on the tool side increase the lag distance from top side to tool side.

    No extending the glass won't give anymore pull. The reason there is is lag is because of the difference in permeability, it's high permeability on top because of the flow media... Higher permeability = more speed.
     
  6. Tungsten
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    Tungsten Senior Member

    Well cured now and the tool side from laying on a sheet of plastic is perfict,to me anyway.peelply side is also nice.saving a layer of peelply and flowmedia on the toolside is a big plus.I have the piece in the post cure box now looking forward to some testing.
     

  7. Tungsten
    Joined: Nov 2011
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    Tungsten Senior Member

    Tried a test on bare foam and was unable to get a perfect seal,my leak detector couldn't find it.The tape was sticking pretty good so I'll have to assume its through the dry foam.

    I tried once before and was able to get a seal but it was just a small piece.So I guess it depends on the foam.
     
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