Infusion Plan

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

  1. Herman
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    Herman Senior Member

    MTI wants you to infuse outwards. In this case I would infuse inwards. The MTI hose would only be used in a small stretch in the middle, to create a long vacuum point. The stuff is perfect for that.

    Just keep in mind that when the resin reached the MTI hose, vacuum is basicly shut off, and the part is almost at atmospheric pressure, or even at atmospheric, when the resin line is left open. This has the advantage that leaks are not catastrophic, but weight is higher than expected. great for visual appealing carbon products.
    When you want to reduce weight, rig your resin line such that you can pull a vacuum on it. This way you will pull a considerable amount of resin from the part into your catch pot.
     
  2. jorgepease
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    jorgepease Senior Member

    I think, if I understand the literature correctly, if you clamp the resin line just as you would normally when nearing the end of the infusion the resin will continue to distribute through the part since it can not leave the mold. So if you calculate exactly the amount of resin and clamp off the line just before you get air it would seem to be the same as a normal vacuum process because the resin is not around the hose, just under it so air continues to be excavated and you still have whatever vacuum you desire to pull.
     
  3. Herman
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    Herman Senior Member

    Yes and no. You will have to be a master in calculating the resin. The larger the project, the easier it is, but you do not want to end up with just too little resin and a partially infused part. Keep in mind that runners, infusion mesh, peelply, core material, bridging in the fabric, etc take a considerable amount of resin.

    But in general you are right.
     
  4. jorgepease
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    jorgepease Senior Member

    Ok, I completely forgot about all that excess resin. Is there a rule of thumb or other calculation for calculating how much extra resin to prepare. I guess I would have to weigh before and after infusing all the consumables and that would give me a general idea and then add 5-10%
     
  5. Herman
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    Herman Senior Member

    There is no real trick on excess resin calculations. It totally depends on infusion mesh (or not), overlaps, runners used, amount of bridging, etc.

    It also is hard to calculate it as an amount per kg of resin used, as thick laminates use more resin, and have roughly the same amount of waste, so are more economical.

    I guess when infusion mesh is used, count for a kg of resin per m2. Based on nothing...
     
  6. jorgepease
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    jorgepease Senior Member

    Thanks for all the assistance. I am going to infuse some smaller components to see if I can get a feel for it.
     
  7. groper
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    groper Senior Member

    allow,

    300grams / m2 / each side to fill the surface of the corecell so 600grams for both sides;
    pi*radius of resin feeder lines^2*length of lines, for resin waste in the lines
    same as above if you have perforations in the core;
    i use 30% rated shade cloth for a flow media, which wastes 320grams / m2;
    my peel ply consumes 70grams /m2;
    laminate of stiched e-glass (triax or biax or dbl bias etc) consumes 1/2 the total weight of glass in the layup = 0.5*weight of glass reinforcement*number of plies*surface area assuming you infuse at close to 100% vacuum - you will use more resin if you infuse at less vacuum although not much difference down to 90%;
    then allow 0.5kg waste resin left in the bottom of the bucket after clamping.

    I would infuse a test peice of your flow media, then weigh it afterwards to see what it will consume - everything else will get you damn close...
     
  8. jorgepease
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    jorgepease Senior Member

    That is perfect, Thanks! Getting the pumps ready to do my first test, this is going to help me greatly!!!
     
  9. jorgepease
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    jorgepease Senior Member

    I did my first test infusion today and it failed due to various errors I think. However it was a test, not the main hull. The test was a panel 48" long by 26" wide. I laid the resin lines parallel down each side of the length and a vacuum line (MTI) running down the center. So the idea was to pull the resin across from each side to the center.

    Somethings I know I messed up
    1) The ratio 100:26 by weight Don't ask me how I got this wrong but do I assume correctly (in hindsight) that means 100 parts to 26 parts or for example 100 ounces resin to 26 ounces hardener? I put too much hardener and the resin kicked off in less than 15 minutes.

    2) When the resin on one side got to the MTI hose first ... Like Herman said ... I seemed to quit pulling which is not what the documentation says is supposed to happen.

    This might also have been the resin kicking off though I noticed the top and sides of the MTI hose was dry so the bag must have been preventing that from pulling air. Would a few strips of resin flow media have broken this seal and let air continue to flow?

    3) I T'd off the resin line outside the bag and fed each leg down the side of the panel, I wonder if I Should have run separate lines to the bucket?

    3) My resin lines were along edge of panel but not on top of or wrapped with resin flow media. Should these be wrapped with resin flow media?

    4) I only had one vacuum line 3/8 id. Maybe I was limiting how much air could be pulled from the bag?

    I was pulling 30" of vacuum and the bag had no leaks.

    Thanks for any suggestions.
     
  10. Herman
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    Herman Senior Member

    And what went wrong? Do you have a picture?

    When the resin reaches the MTI hose, at that spot it stops pulling, but on the places where the MTI hose still is dry, it keeps pulling.

    one 3/8" vacuum line is more than plenty. I once did a 9 meter boat (300 kgs of resin) with 2x 3/8" lines. Vacuum capacity is seldomly the limiting factor.

    There is no problem T-ing the resin lines, but keep in mind that especially at the first stage of the infusion this is the limiting factor, so your infusion time gets longer.

    On the resin: 100:26 indeed is 100 ounces of resin to 26 ounces of hardener, or whatever unit you want to choose (grams, kilos, stones, pounds)

    Resin lines should be in good contact with the flow medium.
     
  11. jorgepease
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    jorgepease Senior Member

    Im not sure, I think it was a combination of things.

    The resin flowed quickly on one side and not the other. I think that the resin must have raced around one side to the other since the hose was not connected to flow media maybe there was a path of least resistance?

    When the resin reached the hose on one side I thought I lost vacuum because of the MTI hose but then I checked the bucket (less than a gallon) but that had already kicked and no more was going to get through hose. I decided, since it was scrapped anyway, to cut the resin line and try to feed a new batch, when I cut the line I did not lose vacuum so the resin gelled in the hose as well I guess.

    I hope the additional hardener is what set it off, I thought this resin was supposed to last longer than 15 min in a bucket.
     
  12. Herman
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    Herman Senior Member

    OK, so it just basicly stalled because of short geltime. Keep the resin out of the sun, and always do a geltest before infusion. Especially when you have not used that resin before, started on a new batch, or just left it alone for a couple of weeks.

    Your resin is infusion resin, right? Thixotropic polyester resin (hand laminating resin) will not work.

    The infusion lines should be on or below the mesh, that way you will not experience resin cut-off.
     
  13. jorgepease
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    jorgepease Senior Member

    Thanks for your reply,
    I used Prime 20 LV from Gruit but I mixed half slow hardener with fast hardener. Maybe I will stick to slow hardener ? The error I am most sure I made was the ratio of the mix.

    After that my lines were not in contact with the flow media at all. How do you keep resin from gelling so quickly in the bucket? I see people infusing with 5 gallon buckets, mine was less than a gallon.
     
  14. Herman
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    Herman Senior Member

    Use more slow hardener. The ones I use mostly have a 4-5 hour working time (measured in 100 gram cups, which is some 3 fl oz).

    Stay accurate on mixing ratios.
     

  15. jorgepease
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    jorgepease Senior Member

    Yes I am going to switch to only Slow Hardener

    Prime 20 LV :

    FAST - 30° C - Geltime 150g in water 0:17 / POTLIFE 500g in AIR 0:16
    SLOW - 30° C - Geltime 150g in water 2:20 / POTLIFE 500g in AIR 0:45
    * The room has an ambient temperature of about 27° C

    Since my bucket had 100 ounces, the 15 minute gel time sounds about right. On next attempt I will use every means to get the resin out of the bucket faster.
     
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