Vacuum Infusion without Bleeder "paper"

Discussion in 'Fiberglass and Composite Boat Building' started by basslover911, Feb 26, 2009.

  1. basslover911
    Joined: Feb 2009
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    basslover911 Junior Member

    I was thinking, if you were NOT to use the vacuum bag itself again, why couldn't you just "inject" all of the resin and epoxy into the bag and have it come out to a "catch can" before the pump... ?

    In other words, no peel ply and no breather/bleeder cloths; just the bag.

    This is for a very small piece (48x48" max) and the resin injection and extraction points would be all across the opposite sides (No need for flow media either).

    Why can you, or can't you do this? Just use the vacuum bag itself?
     
  2. jim lee
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    jim lee Senior Member

    The peel ply breather is very handy as a resin break. IE It gives time for the resin front to get to the corners before it finds the vent line and gets sucked out.

    Also, it makes pulling off the plumbing a -lot- easier.

    -jim lee
     
  3. AndrewK
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    AndrewK Senior Member

    Bass,
    What type and quantity of reinforcement, cored or solid laminate, viscosity & gel time of resin.
    If it is only a thin laminate, your resin viscosity is sufficiently low and you had a very long gel time >120min you should be able to infuse through the reinforcement only over the 48".
    But by placing the feed line in the middle and having vacuum lines at either side you 1/2 the resistance and the infusion time would be only approx 1/4.
    Or place the feed around the perimeter and your vacuum at the center of the job.

    But then again why take the risk if you can use inexpensive shade cloth as the resin transfer medium.

    Andrew
     
  4. basslover911
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    basslover911 Junior Member

    Ok, it is carbon fiber (2x2 weave so there is some space inside) and of course using "water" infusion resin.

    I was going to place around 4 feed lines on one side and 4 vacuum lines on the other side exactly perpendicular to each other so the resin goes "straight" (and the part is in the middle).

    The reason I don't want to use any type of peel ply is to (1) cut costs (and common we all want to do that!! :) ) (2) To have an extremely smooth surface and do MINIMAL to no sanding afterwords.

    Also, I think a lot of resin going into the vacuum tubes would be ideal (I will be throwing those away after) since they will plug the lines once everything hardens and hopefully I will be able to turn off the vacuum pump and still hold vacuum.

    ??
     
  5. JRL
    Joined: May 2007
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    JRL Im with stupid

    Just for clarification when you say "inject" you dont mean your going to use pressure to introduce the resin into the bag right?

    Also, ever think about wiring up a pressure switch to your vacuum system? I got mine for all of $14 and hooked it up to a PVC reservoir. Works perfect.
     
  6. sigurd
    Joined: Jun 2004
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    sigurd Pompuous Pangolin

    hello,

    maybe you could clamp off the vacuum line instead of waiting for the epoxy to plug it. but maybe it is better to keep the vacuum with the pump because of leaks and gasses.
     
  7. basslover911
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    basslover911 Junior Member

    JRL

    Yes I meant pressure to create a vacuum as "suck" the resin in...

    Completley kind of changing subjects, but has anyone seen how much it costs to make dry carbon fiber? (prepreg?).

    I just ran a complete analysis on costs;
    Wet Carbon;
    - Bleeder/Breather Paper
    - Peel Ply or perforated material
    - Resin flow material
    - Epoxy and Hardener (REALLY expensive if you are doing vacuum infusion)
    - Carefully placed feed and vacuum lines

    Dry Carbon;
    - Carbon Fiber
    - Umm... that's it!

    I came to the logical conclusion that I might never do wet layups ever again, and I might start from scratch making dry carbon fiber. I mean, VERY hard to mess up a part as opposed to wet layups, and even though the prepreg carbon is more expensive, it actually comes out cheaper than if you add all the extras that it takes for wet layups! CHEAPER!

    And for this I am talking about smaller (again 48x48" pieces), since you would need a huuuuge oven, for lets say, making a complete boat hull!
     
  8. sigurd
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    sigurd Pompuous Pangolin

    there exist also films that are epoxy, that you can put on non-prepreg but to cure like prepreg. But maybe very expensive. I think SP system has this.
     
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  9. JRL
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    JRL Im with stupid

    That depends on the thickness of your layup. After a 3 or 4 layers of prepreg you will want to debulk (remove excess resin) from the layup. You briefly bring the carbon up to a temp that will get the resin moving. Apply vacuum for a few minutes (i.e. a full layup). Then debag and continue your layup.

    Also, when prepreg hits a certain temperature (every manufacturer is different), the resin begins to move just like a wet layup. You will need to have material to keep the vacuum uniform....which will keep the resin moving where you want it vs. it building into puddles due to un-uniform vacuum.
     
  10. basslover911
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    basslover911 Junior Member

    Yea but thing is that shouldn't, in theory, be MUCH easier to control temp (through turning on or off heat lamps) rather than controlling the flow of resin?

    Unless you have one of those programs that models resin flow, I think the only way is to test every single part, probably destroy 2 or 3, before you can get the resin where you want it to go...

    Oh and about the layers thing, 4 layers would probably be the most that I do on these small pieces- which also keep in mind I think you can easily do 1 or 2 less layers in dry carbon than in wet carbon due to the higher strength...

    Correct me if I am wrong on all this...
     
  11. apex1

    apex1 Guest

    Sorry, yes, you´re wrong
    I made a layup of carbon EP 39% fibre: 245gsm 0°/ 245gsm -45°/ 245gsm +45°/ 245gsm 0° first attachment (test)
    second layup carbon EP 50% fibre: 245gsm 0°/ 245gsm -45°/ 245gsm 0°, second Att. test1
    third layup Carbon Ep 50% fibre: 245gsm 0°/ 204gsm -45°/ 204gsm +45°/245gsm 0°/ third att. test2

    Have a look.
     

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  12. basslover911
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    basslover911 Junior Member

    Can you explain me your tests better?
     
  13. apex1

    apex1 Guest

    I thought if I provide the graphs. it´ll be selfexplaining!?
    The first laminate simulates a handlayup with 39% fibre (most homogenous)
    The second a Vac.layup with 50%, but only 3 layers (inhomogen)
    The last a Vac.layup with 50%, but again 4 layers, using two thinner fabrics 204gsm, instead of 245. (best strentgh to hom. ratio)
    Which means you cannot reduce the number of layers!
    Regards
    Richard
     
  14. AndrewK
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    AndrewK Senior Member

    Basslover,

    I am still unclear as to what you are making, other than it is CF 2x2 weave and 4'x4' and you want smooth and glossy surfaces on both sides. Any core and how complex is the shape? or is it a flat sheet?
    I also assume you have tried hand lay up both with and with out vacuum consolidation, and you were not happy with the results?

    Placing extra inlet and vacuum lines as you suggest will not speed things up.
    I suggest you do a test on say a 4" x 48" strip to see if you can drag the resin through your reinforcement over that distance first.

    Assuming your trial proves that you can cover 48" and you decide to use infusion for the real parts turning the vacuum pump off early is not a good idea. This is because you say you want both surfaces to be perfect and if you turn off the pump early you may get some off gassing degrade the surface that otherwise would have been drawn of by the pump. You may have to degas your resin first too.

    Also if you have the $ comparison for prepreg versus wet out I would like to see this.

    Cheers
    Andrew
     

  15. basslover911
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    basslover911 Junior Member

    ^^ I am first going to make a simply road bike frame to see what shapes I can do and how strong I can do it. After I will make a kayak.

    I think I want to do prepreg because I dont have to buy the epoxy and hardener, breather paper, and I don't have to worry about the whole infusion process.

    I do like wet layups but (1) there is so much to go wrong that it always stresses me out (2) I want a lighter, stronger shell for anything I make and dry carbon is the only way to go really...

    Plus price per price (like I mentioned earlier) you dont have to buy the epoxy and stuff so the price ends up being only slightly higher for prepreg but you dont have to worry about many other things (just heating it right).
     
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