Infusion Q&A

Discussion in 'Fiberglass and Composite Boat Building' started by jim lee, Dec 17, 2009.

  1. jim lee
    Joined: Feb 2007
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    jim lee Senior Member

    New question..

    Some of the boat builders around here like to let off some of the vacuum after getting an infused part "wet out". They say its so the part doesn't get resin starved. Is anyone else doing this? If so how much?

    -jim lee
     
  2. Herman
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    Herman Senior Member

    Never did that. Would need to test the effects to see what is happening.

    Reducing vacuum means the fibers want to expand a bit. Which should not be possible, as there is no resin to fill the extra space.
     
  3. 13AL
    Joined: Oct 2008
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    13AL Junior Member

    Jim, There was alot of talk about that at the ACMA show. I think the numbers were 18 to 20" but I'm not positive.
     
  4. AndrewK
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    AndrewK Senior Member

    Reducing vacuum after wet out

    Jim, some builders do reduce the vacuum to 60 - 80% after impregnation. They say it is to prevent sucking out too much resin, I disagree with the assumption that 100% vacuum will lead to resin starved laminates. In my opinion the only way you can have resin starved laminates is if there is a leak, its the incoming air that will sweep out resin regardless of vacuum level.
    I do agree that reducing the vacuum after impregnation can lead to better looking laminates (lower void content) as it reduces the amount of dissolved gas expansion.
    I am guessing that some have incorrectly attributed the slow formation of micro bubbles in the laminate after the resin lines are shut with resin starvation.
    You would have observed this, say you start with 100% vacuum and you open the resin inlet you will see that the resin in the inlet tube will be all frothy initially and then settle down to bubble free solid stream. The resin front will be bubbling most of the time, this is because you will only have full vacuum at the resin front so the mixed in air and dissolved gas will be greatly expanding at this front. Further back the absolute pressure very quickly drops off so very little or no observed gassing. You finish impregnating clamp the resin inlets and the laminate looks perfectly translucent, as any mixed in air in the resin was sucked out. But with time the absolute pressure is slowly restored from the resin front back up into the laminate causing the dissolved gas to start showing up as micro bubbles.
    In order to produce a perfect laminate at 100% vacuum I think you need to go to the trouble of degassing the resin first but I have found this to be only practical to relatively small parts with only one degassing pot. So reducing the vacuum after impregnation is only a means of overcoming this, I have found that reducing the vacuum down to 80% has only a slight increase in resin content. So the re-expansion of the laminate as Herman points out is not an issue for thin laminates as there is enough excess resin in the system as long as the reduction is done immediately after clamping the resin inlets. Better still reduce the vacuum before clamping the last resin line.
    Of course this is only my explanation, could be wrong.

    Andrew
     
  5. ahender
    Joined: Jan 2009
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    ahender Junior Member

    Alternative to resin-flow medium and a vinyl ester question

    I have a question on using resin flow materials or rather, not using them.

    Instead of using this type material, is there a downside to adding more spiral-wrap flow channels?

    Say maybe every 12 inches have a flow channel -- in a semi grid layout.

    Would this strategy cause resin flow blockages?

    Also, does using vinyl ester as the resin of choice have any downsides other than fumes?

    I have worked a lot with epoxy but know nothing about vinyl ester.

    Alan
     
  6. Herman
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    Herman Senior Member

    If you apply the flow lines as a grid, without a vacuum line in the middle of the grid, yes, you are in trouble.

    Resin will follow the easiest path. Which is your grid. So very soo you have a resin filled grid, with dry areas in between. This already is a problem when using saw-cut foam, with the sawcuts acting as runners, and leaving dry spots in the middle of the blocks. (there are manufacturers advertising this core as their "core infusion process" leaving you with the risk for dry spots, and overweight products, as there is an unexpectedly large amount of resin disappearing in the grooves.)

    Vinylester, epoxy and polyester can all be used, but make sure your resin is not thixotropic, and has the desired geltime (and test that).
     
  7. AndrewK
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    AndrewK Senior Member

    Alan
    I can not see any advantages in doing so, what is the laminate schedule and part you want to infuse? I think this strategy increases risks with out any benefits. It probably will waste more resin, leave greater inprints, be much slower and cost more than mesh spiral combination.
    As Herman said resin racing can be a problem so having only parallel feed lines can work but will be very slow and you will have many resin inlet lines to control. If you incorporate CFM into the laminate schedule it will greatly reduce the number of feed lines required.
    Using a fish bone layout will also work as long as the distance from the vacuum line and the spiral ends is greater than the spiral spacing. This way you eliminate most of the resin inlet lines.

    VE resin will have greater shrinkage on cure, lower gel time, and perhaps a bit lower elongation. May have a higher HDT and strength depending on the properties of the epoxy you are comparing it to. And will be half the cost of epoxy.
     
  8. ahender
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    ahender Junior Member

    I will be infusing a 12' canoe.

    In my first attempt at doing this, while actually creating my female mold, the actual infusion was taking forever.

    I was using MGS epoxy, which for epoxy, has a pretty low viscosity rating.

    It is also pretty expensive compared to other epoxies.

    After an hour-and-a-half, probably only infused 20% of the part before I had to bail on the process due to my resin starting to set up.

    I was using a single feed line and a single 4" wide strip of resin flow material.

    Can you elaborate more on the fish bone method and your quote "distance from the vacuum line and the spiral ends is greater than the spiral spacing."

    I have seen this diagram before, I thing with Polyworks software.

    Thanks for your help and feedback.

    Alan
     
  9. Herman
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    Herman Senior Member

    What is the maximum girth of the canoe?
    Which MGS resin do you use? (they have many). RIM135 or RIM235? Or anything else?
    What is your laminate schedule?
    Did you do a small scale test (over the maximum lenght the resin will have to travel)

    With mesh this should be an easy job. When the laminate is too dense to allow for resin travel, you will need to incorporate something that WILL allow the resin to travel. This can be CFM, foam core, Soric, infusion mats like polymat or rovicore, or disposables, like flow mesh.
     
  10. ahender
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    ahender Junior Member

    The girth is 65 inches.

    The resin I am using is MGS 335, slow hardener.

    My laminate schedule will vary a little, but the first boat I make will have 2 layers of S-2 glass, 2 layers of carbon, infuse, then apply my balsa core, and once that has cured, then 4 more layers of carbon.

    When I did my first attempt at infusing the actual mold, the number of reinforcement layers was 8 (6 oz. cloth).

    I am guilty of not doing any "real world" testing.

    Not sure what you are asking here : "Did you do a small scale test (over the maximum lenght the resin will have to travel)."

    Are you referring to half the girth? If yes, then no, I have not.

    Thanks again for you assistance.

    Alan
     
  11. AndrewK
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    AndrewK Senior Member

    Alan, if you only infused 20% of the mold in 1.5hrs, this alone tels you it is not a very efficient strategy, why don't you want to use flow mesh?
    Yes fish bone layout can be seen in polyworks promotion.
    Say you run the main feed line down the center line of the mold and if you are not using mesh then I am guessing that you would need to have the T'd side feeds at 12" spacing. Vacuum lines are along the mold edge, resin then has to only flow 6" either side of the side feed, then you would terminate the side feeds say 8" short of the mold edge. That is the distance the resin has to travel from the ends of the feeds to the vacuum line is greater than the distance it has to travel between them. If you have decent flanges on the mold or can seal the bag on the outside so that you can have say 6+" CSM as a resin break then you could terminate the side feeds just short of the reinforcement edge.
    Also if you still want to go down the no mesh path then there is no point in using fast feed lines as the reinforcement is the infusion speed limiting factor, 1/4 spiral would do the job.
    What is the viscosity of your resin? there are much lower viscosity resins than the MGS range which would help when you are infusing through the reinforcement alone.
    Personally I would also infuse the complete job in one hit.

    Cheers
    Andrew
     
  12. ahender
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    ahender Junior Member

    I'm not against using a mesh resin flow media, my initial question was could it be done efficiently without a flow media.

    The answer certainly seems to be no.

    There are many brands of flow media. What would your recommendation be?

    Also, other than Pro Set epoxy, I have not seen any other epoxy with as low a viscosity as MGS 335. Mixed it is approximately 400.

    I would love to hear about other options.

    Thanks you your feedback.

    Alan
     
  13. tunnels

    tunnels Previous Member

    HOW WOULD YOU STOP THE HONEY COMB FROM BECOMING COMPLETELY FILLED WITH RESIN ??? :confused: BY MAGIC ???:idea:
     
  14. AndrewK
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    AndrewK Senior Member

    Are you having a paint or gelcoat finish? if gelcoat I would use infusion grade VE resin.
    Since you have access to MGS resins you will find that the others like RIM 135, 235 have a lower viscosity around 300 mPas at 25'C (75'F).
    I have been using a 300 mPas resin for everithing, hand laminating, vaccum bagging and infusion. The problem with this is that it is a compromise in each process so I am going to change to two resins. Infusion resin to have a viscosity <200 and for hand laminating 600 - 900. To give you an example all other things equal a 150mPas resin traveled almost 3 times the distance that the 300 mPa resin did in the same time.
    I dont know what resins are available to you locally but I imagine the global brands like Sicomin SR 8100 and SP Prime 20ULV should be. These have a viscosity <200 at 25'C but are expensive and do require a post cure at a low temperature as do the MGS resins.

    I am using shade cloth as the flow media but did test a a number of plastic meshes.
    I suggest you do the same with the materials available to you locally and decided based on economics and properties.
    What I did was to line up 100 x 1000mm strips of various flow media and 750gm2 triaxial glass and measured the resin flow distance vs time. And also quantified the amount of resin each media consumes.
    I also strongly recommend that you use a perforated release film under the flow media so that it can be stripped off easily.

    12' canoe is not a very large area to hand laminate, have you considered just vacuum bagging?
     

  15. gages
    Joined: Jun 2008
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    gages Junior Member

    A new setup

    I have finally finished the plug and am wanting too setup for Infusion into both deck and hull moulds of my kayak

    Do I need certain size flanges for Infusion?
    Does anyone recommend any thing I should do whilst I build the mould?

    What is the best way to learn ?

    Any advice is welcomed

    Thanks in advance
     
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