Infusion technique question - height of resin reservoir

Discussion in 'Fiberglass and Composite Boat Building' started by rwatson, Aug 22, 2013.

  1. rwatson
    Joined: Aug 2007
    Posts: 5,852
    Likes: 290, Points: 83, Legacy Rep: 1749
    Location: Tasmania,Australia

    rwatson Senior Member

    Just by accident, I wandered into a quite good series of RTM ( Resin Transfer Moulding ) videos



    This particular one on the series discusses the process of infusing the FG, using vacuum of course..

    He points out that the process is not really 'sucking' resin with a pump, but more creating a pressure differential to 'push' the resin from the reservoir, through the glass.

    In his lightweight parts process, he has only one 'exhaust' manifold, and multiple inlet manifolds, to increase the backpressure on the resin, over and above what the vacuum pump can do.

    The thought that occurred to me was that, all the infusion videos I have seen have the resin Receptacle on the floor, below the actual job.

    From this video, it seems there might be a lot of advantage to placing the resin reservoir higher up than the job, to increase the back pressure on the resin, even more than the vacuum pump can do.

    Has anyone had any experience with this ?
     
  2. Cat Cruiser
    Joined: Aug 2013
    Posts: 29
    Likes: 0, Points: 0, Legacy Rep: -7
    Location: Texas

    Cat Cruiser Junior Member

    Im pretty sure scrimp methods always have the barrels of resin elivated to the higher points of a big project. Ive only done hatch doors, and the tool was a two piece that did not have inlet hoses and a resivor. Ionstead it was a floppy lid that sealed around the edges, We just skin coated the parts traditionally (the molds were already gelcoated) and the layup was continuous strand mat instead of chopped. We just poured the pre weighed amount of resin right in the middle of the part on the CS mat and then placed the floppy lid on and applied the vaccum.
     
  3. rwatson
    Joined: Aug 2007
    Posts: 5,852
    Likes: 290, Points: 83, Legacy Rep: 1749
    Location: Tasmania,Australia

    rwatson Senior Member

    Thanks for that info CC. It looks like at least some people are aware for the technique then.
     
  4. mcollins07
    Joined: Jan 2006
    Posts: 220
    Likes: 11, Points: 0, Legacy Rep: 166
    Location: Texas

    mcollins07 Senior Member

    vacuum vs gravity

    If you elevate the reservoir, then you have gravity flow.
    If you rely entirely on vacuum, you are ensured a more uniform distribution of the resin. With gravity flow, there can be pooling in lower regions.
    Depending on the part shape, part size, the viscosity of resin, and the quality of vacuum, you may find it useful to assist the vacuum flow with gravity flow.

    I sometimes place the reservoir about a foot above a relatively flat uniform part. This gives a little gravity assistance, but not a lot. I don't think I'd ever use more than a foot. Also, must be ready to shut off the resin supply.
     
  5. rwatson
    Joined: Aug 2007
    Posts: 5,852
    Likes: 290, Points: 83, Legacy Rep: 1749
    Location: Tasmania,Australia

    rwatson Senior Member

    Thanks MC. It sounds like its a viable option. I know that the gravity pressure increase dramatically with height.

    It sounds like it may be possible to get away with quite low vacuum pressure in some cases.
     
  6. Cat Cruiser
    Joined: Aug 2013
    Posts: 29
    Likes: 0, Points: 0, Legacy Rep: -7
    Location: Texas

    Cat Cruiser Junior Member

    It seems you have a reservoir -with excess, catilized excess ( wasted) when you should ONLY have enough to make the part--EXACTLY and no more-except perhaps in the inlet media lines-that are sacrificial from projects I have seen done. That way extra -puddling in the lower areas would not be a concern because there is very little or no wasted resin.
     
  7. DCockey
    Joined: Oct 2009
    Posts: 4,703
    Likes: 315, Points: 83, Legacy Rep: 1485
    Location: Midcoast Maine

    DCockey Senior Member

    I've watched a few infusion demonstrations and there is a small amount of resin left in the reservoir. It is much better to have resin left in the reservoir than risk sucking air into the part.
     
  8. Cat Cruiser
    Joined: Aug 2013
    Posts: 29
    Likes: 0, Points: 0, Legacy Rep: -7
    Location: Texas

    Cat Cruiser Junior Member

    For something like a one off hull obviously, a half gallon or a gallon is no matter. But for outfits cranking out parts like hatch doors they dont have any waste - they do it every day- all day so they cant afford wasted material.
     
  9. rwatson
    Joined: Aug 2007
    Posts: 5,852
    Likes: 290, Points: 83, Legacy Rep: 1749
    Location: Tasmania,Australia

    rwatson Senior Member

    yes. His later posts make the point that he programs his system with really precise amounts.

    I guess supervision would be critical
     
  10. ondarvr
    Joined: Dec 2005
    Posts: 2,333
    Likes: 259, Points: 83, Legacy Rep: 506
    Location: Monroe WA

    ondarvr Senior Member

    There are so many different nuances in infusion methods it can make your head spin. None of them are really right or wrong, most have situations and/or parts where they work very well, and others where they are a poor choice, or at least not the best one.

    The choice of tooling makes a big difference, rigid, or semi rigid tools at times can benefit from pressure feeding, bagged infusion is less tolerant, but done correctly it is workable in some situations.
     
  11. rwatson
    Joined: Aug 2007
    Posts: 5,852
    Likes: 290, Points: 83, Legacy Rep: 1749
    Location: Tasmania,Australia

    rwatson Senior Member

    Good point. It sounds like a lot of practical experimentation is the secret. Nice to be aware of another option I guess.
     
  12. pdwiley
    Joined: Jun 2008
    Posts: 1,002
    Likes: 86, Points: 48, Legacy Rep: 933
    Location: Hobart

    pdwiley Senior Member

    How about you experiment by making my rudder? Spring arrives tomorrow...

    PDW
     
  13. groper
    Joined: Jun 2011
    Posts: 2,467
    Likes: 123, Points: 73, Legacy Rep: 693
    Location: australia

    groper Senior Member

    yep, an easy task... heres the one i did for masalai;

    You can do all manner of things, infuse uphill, downhill, bucket above or below, its all doable... if you wanna learn whats possible, just start playing around with it...
     
  14. rwatson
    Joined: Aug 2007
    Posts: 5,852
    Likes: 290, Points: 83, Legacy Rep: 1749
    Location: Tasmania,Australia

    rwatson Senior Member

    Yeah - you're right. I have decided I cant possibly borrow your boat if it has a marine ply rudder blade, so I am going up to Island Speciality Timbers to get a couple of planks of Celery Top Pine for the blade.

    I have my standards you know ( and if you don't like them, I have others )
     

  15. Herman
    Joined: Oct 2004
    Posts: 1,618
    Likes: 89, Points: 48, Legacy Rep: 1240
    Location: The Netherlands

    Herman Senior Member

    When making boats a gallon or so wasted material is not that critical. When doing high output smaller parts, usually the complete system is changed to VARTM / RTMLight, and resin waste is dealt with by using RTM machines, which limit wasted resin to some 100 gram / 4 ounces at maximum, no matter of the size of the job (that said, job size is limited when doing RTMLight)

    On placing reservoirs higher than the part: never do it unattended, or you are in for a nice surprise at times.

    However, the point is, that the size of the inlets combined make a huge difference in infusion speed. Which is what the push-pull story is about.
     
Loading...
Similar Threads
  1. ahender
    Replies:
    8
    Views:
    154
  2. S17665
    Replies:
    4
    Views:
    370
  3. rwatson
    Replies:
    3
    Views:
    556
  4. ProBoat
    Replies:
    0
    Views:
    565
  5. GreenFreak
    Replies:
    12
    Views:
    775
  6. ahender
    Replies:
    28
    Views:
    1,033
  7. bedfordd
    Replies:
    9
    Views:
    920
  8. fallguy
    Replies:
    2
    Views:
    948
  9. KD8NPB
    Replies:
    8
    Views:
    1,029
  10. guzzis3
    Replies:
    31
    Views:
    2,938
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.