Infusion Plan

Discussion in 'Fiberglass and Composite Boat Building' started by jorgepease, Jun 4, 2012.

  1. jorgepease
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    jorgepease Senior Member

    Sorry, I mean lessening vacuum. The two stage pump doesn't want to run free for extended periods of time.

    I want to keep the pump pulling a higher vacuum by limiting air flow with a valve or something but lessen vacuum on the bag with a regulator.
     
  2. variverrunner
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    variverrunner Junior Member

    Herman,

    Was I right about your drop test comment? I don't want to steer anyone in the wrong direction.


    Allan quote:

    "He also mentioned the importance of doing a "drop test". My interpretation of a "drop test" is, after you have sealed everything to the best of your ability, shut off the vac pump. If you loose full vac within than 15 minutes you have a leak that needs to be found and fixed prior to infusion."


    Thanks for your time


    Allan
     
  3. SamSam
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    SamSam Senior Member

  4. jorgepease
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    jorgepease Senior Member

    Yes, videos and lots of pics. All my flanges are screwed down, today I will add a skim coat of filler to them and start preparing for the drop test. Im pretty confident any leaks will not be from my joints of the core so with a good bag I should be okay. More immediate is finding the MTI tube, looks like I need to order that from HP direct and finish building the resin trap. I bought tubing glands from vacmobile, they should arrive by Thursday.
     
  5. groper
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    groper Senior Member

    if your using epoxy, you dont need to reduce vacuum... infuse it at 100% vacuum with your 2 stage pump - this is what i do. If you using a vinyl or polyester, then i would not try to infuse it above 90% vacuum or risk boiling the solvents. same goes for the drop test, do it around 90% and it shouldnt drop at all in 15mins or you have a leak that needs to be found.

    If you want to reduce vacuum for whatever reason - like adjusting the bag before it pulls down tight - you can buy a needle valve from a hydraulics fittings/trade supplier. I bought a little brass one for just that... tried backing off the vacuum once infusion complete as some people advocate, didnt notice much difference...
     
  6. jorgepease
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    jorgepease Senior Member

    Im infusing epoxy so that is good to know!!
     
  7. Herman
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    Herman Senior Member

    Variverunner: yes, you were right.

    Isolate the pump from the rest of the system, and if 5% of vacuum is lost within 15 minutes, chase for leaks.

    For epoxy the problem is moisture, which causes gas once curing. This can only be addressed BEFORE infusion. When infusing below 20 mbar (the boiling point of water at 25 degrees C) I like to "up" the vacuum to 50 mbar once done.

    Controlling the vacuum can be done using a vacuum switch, which stops the pump, by using needle valves, which I do not like as these are vacuum dependant, or spring loaded valves, like Airtech "VacReg" unit.
     
  8. jorgepease
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    jorgepease Senior Member

    I am going to keep a strong vacuum on bag for at least a few hours after the leak check to see if I can get rid of moisture.

    I love the MTI hose product. That technology makes me think of another infusion plan.

    With spot placements of MTI hose and reusable infusion connectors you could eliminate a lot of spiral wrap and wasted vacuum hose plus maybe reduce imprint?

    Does this look like it would work. The resin infusion connectors would be in the center of each dotter red circle ... the off center MTI vacuum point is a drawing error.
    [​IMG]
     
  9. variverrunner
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    variverrunner Junior Member


    Jorge,

    I had never heard of MTI tubing. Thanks for the info.

    I found an interesting YouTube video about it.

    http://www.youtube.com/watch?v=8C0DkROWsiE


    What do you use for reusable infusion connectors? West System type
    "suction cups"?

    Thanks again,


    Allan
     
  10. Herman
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    Herman Senior Member

    I have re-usable feeders and vacuum ports in my program. A friend was so friendly to inject mold them in HDPE.

    Page 13 of this PDF (in Dutch, sorry. Next one will be English).

    http://www.brandscomposiet.nl/products/documentation/n/B43 Vacuummaterialen.pdf

    Spot placements of MTI hose is not needed. But actually the size of the boat is such that you do not need such a complicated strategy.
     
  11. jorgepease
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    jorgepease Senior Member

    Herman was the one who mentioned them earlier in the thread. Do you ship to USA Herman?
     
  12. rwatson
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    rwatson Senior Member

    Whats the best way to do this Herman ?
     
  13. groper
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    groper Senior Member

    hold a full vacuum until all the moisture has boiled off... you can apply heat to the dry stack under vacuum to accelerate the process aswell, esp if you in a cold climate. Then once its gone, the oil in teh pump will not be milky anymore and you can infuse as per normal...
     
  14. Herman
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    Herman Senior Member

    No problem of shipping non-dangerous goods to the USA. (shipping dangerous goods is only cost effective in containerloads)

    The best way to dry your laminate stack is 2-fold. First of all, keep your materials dry. This can be a challenge in humid climates. Actually I have a customer that has a "dry room" which is almost airtight sealed, humidity is in the 20-30% range, and temperature is in the 30s (celcius, so nice and warm, 90-100F). He makes panels with a resin which is very water intolerant.

    That is the start. Water that is not in the stack, does not need to come out either.

    When laying up, and vacuum is applied, you can boil off the water. The biggest challenge is reaching that 20 mbar. This is sometimes a real pain. First of all a normal rotary vane pump (oil lubricated) has a range which ends somewhere at 20 mbar, so they usually are no big help. A double stage pump is better in that respect (but more expensive, and usually less volume). In an ideal world you would need 3 pumps: A vacuum blower to evacuate the bulk of the air, a single stage vacuum pump for bringing the vacuum to 50 mbar or so, and a double stage vacuum pump to bring vacuum down even further.

    Airtech has very nice units to measure the airstream present in the bag. I have never used them with large objects, but for smaller objects these are useful for seeing the amount of loss. They are called "vacview10" (6th picture on page 14 of the following PDF: http://www.brandscomposiet.nl/products/documentation/n/B52 Werkplaatsinventaris.pdf)

    Also make sure your mould is really airtight. Moulds that are sufficiently thick are usually OK. Check the edges of the mould for laminate quality. Air voids can create channels into the mould cavity, and be a real pain to fix during the infusion. Usually the perimeter is the vacuum side, and your infusion will not be harmed, but you will not be able to reach 20 mbar. (or below).
    Of course the tape seam should be 100%, but that actually is the easy part. The vacuum film itself should be perfectly in shape as well. In boating, use a thick bag (75 mu, or 0,003") which should contain plenty of nylon. PE bag will not do it.
    Stand in the boat with a leak detector, and slowly point it 360 degrees round. This will give you an idea of where approximately a leak can be. Walk towards where the sound came from, and you should be able to pinpoint the leak quickly. The fix usually is simple. Check your vacuum gauge to see if your chasing had success. (I like digital gauges for that, or the fancy logarithmic ones, which unfortunately are utterly expensive) Last time I asked they were some 900 euro or so, which is why I only sell digital ones.

    Once you go through all that trouble of drying your laminate, and create a leak-free bag, please also degass your resin. Combined this will give a flawless laminate.
     

  15. jorgepease
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    jorgepease Senior Member

    I ordered some from dd-compound they have some stock in the USA.
    contact Dominik info@dd-compound.com

    it's expensive if you use it the way they show, all the way around the perimeter but if you can use small pieces in spots it can go a long way.
     
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