Infusion General Problems - Needs It's Own Thread

Discussion in 'Boatbuilding' started by CatBuilder, Dec 14, 2011.

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  1. CatBuilder

    CatBuilder Previous Member

    My infusions have gone down hill. No idea why.

    The first infusion I did were rudders and dagger boards:

    [​IMG]
    [​IMG]

    They came out just fine.

    Next, I did the deck and half of the outside of a hull that was already glassed inside. After plugging some core leaks, it also came out fine, infused at 25 inches Hg. (29Hg is max in these non-SI units for non-US people).

    [​IMG]

    [​IMG]



    Then, I tried infusing the inside of a half of a hull. It was just a core with gaps filled in by epoxy/microballoon bog. I couldn't get past 5 inches Hg no matter how many days I went at it. Ended up ripping all the infusion stuff off and hand laminating that hull interior. Big setback. Below is the picture of the inside of the half hull, still in the mold, but before I put glass and infusion materials on it...

    [​IMG]

    Never got below 5 inches Hg on that one and had to strip the infusion material off and hand laminate it.

    Now, I am trying to infuse the final piece of the other hull mentioned earlier where I was infusing the deck and half the hull. I'm now infusing that last half of the outside of the hull and keel area. After that, there is no more glass to put on and that hull is ready to have the bow/stern put on and then for final fairing and paint.

    Problem is... I'm only getting to 11 in Hg!

    Here is a picture of the area I am trying to infuse - the entire area facing the cameral, plus up and over the keel, plus around the sheer that is close to the camera and low to the ground, to meet the edge of the deck.

    [​IMG]

    Problem is... I'm only getting to 11 in Hg!

    QUESTIONS:

    How much area should a 6CFM vacuum pump be able to pull down?

    Is my 45+ft x 12ft area too large for it to pull down?

    I mean, if there are tiny leaks (as there always are when infusing a single side of a part) and you are doing a smaller area (say, 22' x 12'), you are going to have half the air flow from your leaks for the vacuum pump to deal with. If you double the area you infuse, you double the CFMs the vacuum pump has to move in order to keep up with small leaks.

    So... is that 6CFM pump enough for a 45' x 12' area?

    I have an ultrasonic leak detector and nearly every inch is now scanned and not leaking. All audible leaks are plugged. I can pick up faint whispers here and there on 100x amplification (it has 1x, 10x, 100x), but there is not much leaking at all.

    Any ideas on why my infusions have gone down hill?

    Can pumps go bad? Can gauges go bad?

    It is very depressing to tear off infusion materials and hand laminate something you have already set up for infusion. I don't want to do this again... :confused::confused::(:(:(:(:(

    Any thoughts?
     
  2. JRD
    Joined: May 2010
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    Location: New Zealand

    JRD Senior Member

    I dont know infusion, but a bit about pumps. if its an oil lubricated vane pump they can spit out all the oil when you run them for a long time with coarse (low) vacuum, though I'd assume you check the oil level if it is one.

    Can you do a test pull with same size bag over the laminate but no resin lines attached, or even just make sure the pump can pull to its specified vacuum level with a closed line at the inlet.

    Gauges - go bad when you fill them with some kind of substance that goes hard when you let it get it inside........ cant imagine that happening here tho.... come to think of it so do pumps

    Good luck
     
  3. CatBuilder

    CatBuilder Previous Member

    Thanks, jrd. Did all the sanity checks including trying the backup pump. It's the hull leaking, as usual. Getting ready to cut my forward water tight bulkhead out now to access the inside of the bow.

    I wouldn't wish single side infusing on my worst enemy.

    Hundreds of wasted hours.
     
  4. CatBuilder

    CatBuilder Previous Member

    Can't get below 11.5 on the last infusion of the finished hull. No idea what to do.

    Can't find any more leaks even with the ultrasonic leak detector. I think it is microscopic holes through the "already" infused part and/or the hand laminated interior.

    What happens when you infuse at 11.5?
     
  5. CatBuilder

    CatBuilder Previous Member

    Has anyone on this forum ever infused a single side of a hull?

    Does anyone here know exactly what happens if you infuse at 11.5 instead of 29?
     
  6. CatBuilder

    CatBuilder Previous Member

    Ok, answering my own thread for the benefit of Google readers.

    I am trying an idea I got from another site tomorrow. I'll be putting my primary 6CFM pump on in parallel with my backup 6CFM pump, creating a 12CFM capability and increasing the whistle/hissing of leaks that have been difficult to find.

    This should get another set of pinhole leaks in the core and glass to present themselves (hopefully) and maybe I can get over 20inHg.
     
  7. AndrewK
    Joined: Mar 2007
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    Location: Australia

    AndrewK Senior Member

    CatBuilder; you have already proven that the 6CFM pump is more than enough for the job, 0.6cfm would be enough for the job. Agree that higher capacity pumps do make it easier to find the small leaks with the detector as they do become more audible with higher vacuum levels.
    You must have many small leaks if you can not detect them with the leak detector.
    Do not do the infusion unless you can get full vacuum that your pump is capable of delivering. Don't get too hung about the accuracy of the gauge or the vacuum that your pump can deliver. Look at the pump output, can you fit a small tube to the output? if you can put this hose into a shallow container with 1'' of water in it. This will give you a good indication of the total volume of the leaks. This is what counts not the ultimate vacuum level. Just remember to take the tube out of the water before shutting the pump down or you will suck the water into the pumps oil sump.

    If you are only getting 11.5" your pump will be putting a lot of air at the outlet, if you were to do the infusion under these conditions you can just picture the damage that this quantity of air being dragged through your laminate is going to make over the time it takes for the resin to set.

    Good luck
    Andrew
     
  8. P Flados
    Joined: Oct 2010
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    Location: N Carolina

    P Flados Senior Member

    It sounds like you are moving lots of air, but that you are NOT finding much in the way of leaking locations.

    I ran into a problem with "gas permeability" before. It was a different application entirely, but was an interesting subject. It is kind of amazing how much air can flow through a surface that looks "non-porous".

    Your method of finding leaks (audible) relies on air moving at a good velocity through individual crevices. What you may be facing is a large surface with a high density of very small (microscopic) flow paths that allow low velocity air flow. In other words, you have a porous surface with respect to air leakage.

    As can be noted in general vacuum bagging discussion, some sheeting materials are too porous and can cause problems.

    The infusion process is very efficient but I am pretty sure that normal applications are very prone to the results you are seeing.

    Painting (or priming) the backside surface, covering it with plastic sealed around the edges, coating it with something removable (wax, rubbery coatings, cornstarch-water mixtures, thinned out white glue) are all things that could be considered to reduce the overall leakage. As you reduce the exposed area of your "porous surface" you should see your leakage flow rate drop and your vacuum improve.

    I would bet that some have learned to go ahead and do the basic prep and prime of the first surface made before relying on it to be air tight. The more common approach is probably to just to leave everything in the mold until all vacuum bagging is done.
     
  9. CatBuilder

    CatBuilder Previous Member

    Thanks guys. I took the advice and kept at it.

    The advice I received here was 100% correct. Not only is 6CFM plenty, but also, there is a gas permeability issue.

    I found more leaks with the two pumps (12CFM) total, but I have also identified a HUGE problem.

    The laminate I have already infused, since it has pinholes and what not, is where it is leaking. I can hear faint noise there, not enough to register on the meter, but I can hear it. I think that is where my air is coming in. Everywhere else is sealed and very quiet.

    So, I am thinking about bogging (with a very wet bog) the area. Basically thinking about painting it with slightly thickened epoxy to try and plug some of these holes.

    Now, I have a regular question:

    Can I just apply my bog right over the infused surface that has the holes in it and also has peel ply recently ripped off?

    It is very grooved by the peel ply and has plenty of pin holes. Can I get away with this?

    I ask because the boat is upside down. The deck is about 8 inches from the floor on blocks. I don't want to have to move the hull to paint the deck with epoxy. So... can I just pain the epoxy on and not worry about sanding it?
     
  10. AndrewK
    Joined: Mar 2007
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    Location: Australia

    AndrewK Senior Member

    Yes, runny bog that you can paint on by brush or roller will do the trick and still be sandable later.
     
  11. CatBuilder

    CatBuilder Previous Member

    Whew! That's good news. Wasn't looking forward to moving the hull to sand the deck before applying the very thin, paintable epoxy bog. Thanks!

    Will do this tomorrow morning.
     
  12. CatBuilder

    CatBuilder Previous Member

    Ok, used a roller to apply some very runny bog today to the area I had already infused. Should be ready for another pull down in the morning.
     
  13. CatBuilder

    CatBuilder Previous Member

    Bogged in part of the hull as a test today (it needed a lot of prep) and tried the pull down this afternoon.

    The needle moved! It moved up to about 12.5 inches Hg and I bogged maybe 25% of the required area in.

    Indeed, I have microscopic leaks through the part of the hull that was already infused. I am failing to see how this can save you any time at all over hand laminating. You still have to fill in pin holes and such, so why bother?
     
  14. P Flados
    Joined: Oct 2010
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    Location: N Carolina

    P Flados Senior Member

    Some amount of surface work will be required regardless.

    If you just plan a round of bog and prime before the one-sided work, there is not that much extra effort. Just a different sequence.
     

  15. CatBuilder

    CatBuilder Previous Member

    Thanks P Flados. That's what I'm thinking too.

    Infusion has the same amount of surface prep work but you then have to add all that work (and expense) of putting all that infusion material on.

    Seems cheaper and faster to hire some help and hand laminate to me.

    It's not like the infused laminate is actually any better than hand laminating, since you have to pile the bog on both of them.

    Where it really gets tricky is the zero sided work - infusing to one side of a core with nothing on the other side.
     
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