Infusion Plan

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

  1. Herman
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    Herman Senior Member

    Why not use the chines as main feed, and vacuum along the centre: The boat pictured is reasonably large, and there is a height difference. I prefer to infuse upwards, not downwards (sometimes you cannot prevent it, especially at decks).

    As for the centre runner for the small boat of Jorge: 60cm could be enough, but make sure you keep the fishbones short enough then. Otherwise just use a strip of MTI over almost the complete length. Do not forget to seal it on one end, and install it into a piece of vacuum hose on the other end, leading the vacuum hose outside the bag throug a pleat. (I hate holes in the middle of bags, but again, sometimes you cannot prevent it.)
     
  2. jorgepease
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    jorgepease Senior Member

    Herman I was just trying to figure that out ...

    I think I will opt for the longer MTI hose in center, it will infuse faster that way and I can be sure the resin wont stall on me.
     
  3. jorgepease
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    jorgepease Senior Member

    With fishbones feeding in and 4 inlets, this should infuse fast! I like this plan!

    [​IMG]
     
  4. groper
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    groper Senior Member

    That looks great Jorge, and yes it will infuse quite fast, probably around 15 mins and youll be done.

    You still have 4 race track paths in all 4 corners, 2 at the bow and 2 at the transom corners. Have a plan to deal with these also - such as dont put the vac outlets there, put them in between the areas that could be vacuum blocked if it was to occur - such as in the middle of the bow and the middle of the sides etc...
     
  5. jorgepease
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    jorgepease Senior Member

    Groper,

    The transom is not installed, I don't think that will be a problem.

    About the bow, not sure what you mean about the vac outlet? I am using the MTI hose which you only need to pull on one end since no resin enters the hose.

    Maybe I should cut the corners a bit and run the resin feed from the center of bow chine at a slight angle to side chines ... Like a slight V ??

    [​IMG]
     
  6. groper
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    groper Senior Member

    Sorry i forget that the mti hose stops the resin...

    In the bow you still have 2 vertical chines no? If it race tracks up these it could vac block an area ij the center of the bow although its not likely if you can prevent it running sideways once it reaches the gunnel.
     
  7. jorgepease
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    jorgepease Senior Member

    I will modify the feed to come to a point at the bow chine, that will allow the middle of the bow to get a head start in case it race tracks in the corners ... as shown in drawing above (purple lines)
     
  8. Herman
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    Herman Senior Member

    If the 4 dots are the feeds, place them more outwards. The rear one a fishbone further, the forward one 1,5 to 2 fishbones further. All in all you want the bottom to close on you in a circular (oval) pattern.

    Infusing inwards is faster than outwards (by a factor of 4, if you look at a circle)
     

    Attached Files:

  9. jorgepease
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    jorgepease Senior Member

    Ok, I will space those accordingly.

    Wow 4 x faster!! ... okay well then my bet on infusion time will be 7 minutes. I will post a video!
     
  10. jorgepease
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    jorgepease Senior Member

    Let me start by saying Infusion Media takes years off your life!! If I ever do this again it will be with grooved core and a built in media like soric or whatever else you can use!!

    Hoses laid out.
    [​IMG]

    [​IMG]

    Infusion Media and Peel Ply over vac hoses

    [​IMG]

    Major Thick Bag - This is not going to stretch as easy as my other bag, I have to be careful with this one.
    [​IMG]
     
  11. groper
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    groper Senior Member

    I always try to avoid overlapping the media like that much, as the resin will travel at different speed through that area - think what effect that will have on your strategy :idea:

    Have you measured and checked that the distance between runners, is *less than* than half the distance between the ends of the fishbones and vacline? otherwise again, the resin front will vac block some small spots between runners...

    And just make extra sure that no resin will be able to get through the ends of that vac hose.

    Is that flow media stopped only 2 inches from the center vac line? looks more than that, make sure its not more than 2 inches... the resin will flow very slowly through that last bit - no problem just dont panic when it seems the resin has stopped moving, it will get there slowly over about 20mins and use up excess resin already contained in the laminate from the resin rich areas...
     
  12. jorgepease
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    jorgepease Senior Member

    Yikes, 20 minutes to pull 2 inches!! I would have had a heart attack LOL!! I left 3.5 inches and then put a strip of peel ply over the top but I will make it 1.5 to 2 inches and cut back the overlap.

    The spacing is confusing me ... The spacing between fishbones is currently 20" and the distance from end of fishbone to vac line is 12".
     
  13. groper
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    groper Senior Member

    That spacing will be ok.

    And yes, if you dont have any flow media the speed is greatly reduced, especially at the end of the infusion near the vac line when the resistance (distance*viscosity) is at its highest. So anymore than 2 inches starts to get dangerous as the last little bit wont infuse if the resistance is too high and the resin gels before it finally gets there...
     
  14. jorgepease
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    jorgepease Senior Member

    I have corrected the overlap and narrowed the break to about 1.5 inches on each side. The media has a break at the flange as well, about 2". I am ready to connect bag and start prepping the air hoses etc ... I was thinking ...

    Would there be any point in bonding a grid of core strips to a flat panel to make an extra stiff deck with minimal extra weight and saving a lot of money on core? I am talking about strips running both length and width and spaced every 12". It seems like you would get a much stiffer panel and use less core!

    [​IMG]
     

  15. petereng
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    petereng Senior Member

    Hi Jorge - By creating your "grillage" you are sort of defeating the purpose of the sandwich. This also applies to designs that use strips of carbon in a grillage format over glass sandwichs. It is always a bit of a toss up. Do we make a thin cored sandwich and create a beam structure to support the panels? or do we use a thicker core and have no grillage? You have to do the numbers both ways but in general the thicker sandwich wins. It wins because you can use a lighter core, the stiffness goes up by a fourth power to the thickness, so a small increase in thickness gives a very big increase in stiffness. The cost is usually small for the stiffness/strength gain. Plus add the labour involved in placing the grillage and the extra fiddly bits it creates (in a production environment where labour costs and complications go hand in hand) My vote is generally for the thickest core and thinnest skins.

    Most optimal sandwich designs limiting factor is the shear shrength of the foam. So extra foam thickness is always a good thing. Plus it depends on what failure mode you want to design to. If the core shears then its still watertight. If you create a critical grillage design the foam has to cope with assymetric shear (rolling shear) between beams and this is a difficult thing to predict but a reality in common failure modes. Cheers Peter S
     
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