resin infusion foam scored one side

Discussion in 'Fiberglass and Composite Boat Building' started by guzzis3, Mar 18, 2018.

  1. guzzis3
    Joined: Nov 2009
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    guzzis3 Senior Member

    Hi all,

    I hope this hasn't been discussed before. If it has a heads up to where would be appreciated.

    I have been reading everything I can find on resin infusion. I'm thinking of going down the scored foam/no bleeder path. Dry spots concern me so I was wondering if anyone had tried scoring on one side only (the invisible side) in the hope that will flood first and if any dry spots develop they are more likely on the visible side and therefore can be addressed.

    So the layup would be: Table, peel ply, glass, foam scored side down and perforated of course, glass, peel ply, bag.

    Is this likely to work ok or am I completely off track ?

    Also anyone care to guess what weight of vinylester I should allow for the foam per square meter ? Divinycell 80 gram.

    Thank you in advance.
     
  2. Tungsten
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    Tungsten Senior Member

    Should work just fine, this way you keep the resin in the part ,not throw it away with the flow media.Perimeter feed with center vac would be my choice.The hard part with center vac is getting it air tight,any tiny leaks and you'll get air forming around the vac.
     
  3. rob denney
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    rob denney Senior Member

    The scoring will almost certainly show through the paint if the mould side sees any sun. Plus, the feed (spiral) allows faster dispersion if it is on top of the job rather than alongside it. Dry spots are caused by vacuum problems, not resin problems, so I doubt that scoring the underside will help. Make sure all your perforations are clear before you start.
    If you have the vac on the job, make sure it is well spread and you have a collection pot in case the infusion is uneven.
    I allow 200 gsm per side for resin to fill the foam, plus the volume of the scores and perforations.
    Vinylester stinks and is flammable. Not ideal for garage use.
     
    Last edited: Mar 20, 2018
  4. rwatson
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    rwatson Senior Member

    Too true. It is really disgusting, and I dont know how you could use it without a separate air supply.
     
  5. guzzis3
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    guzzis3 Senior Member

    Thank you for the reply. I'm not at all worried about fast infusion unless speed helps the result. I wouldn't care if it took 24 hours to saturate. If going slow increases the chances of a panel failure though then it matters.

    I've spent many hours reading everything I can on infusion, so hopefully have avoided asking the same old silly questions that have already been answered many times. Hopefully.

    Scored and perforated foam ends up about the same cost per square meter as bleeder.

    I am planning to make some flat panels and joining them into a big box slide on camper for my ute. In theory these should be easier to make and aren't as critical to get perfect, so if they have some dry spots or whatever I can still use them. Once I've got a feel for it then the hulls.

    I was going to use 2 small ebay vacuum pumps. A 2 stage to pull a good vacuum and a single stage to help pull down initially and to maintain a lesser vacuum during the actual infusion. From what I've read if I keep the higher vacuum I'll risk boiling the resin, or the styrene in it anyway. I was going to vent the pumps outlets well away from people, so the only fumes would be off the mixing bucket ?

    Epoxy is too dear so vinylester seemed a good compromise..

    Any thoughts appreciated.
     
  6. rwatson
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    rwatson Senior Member

    Yes you are worried. You don't HAVE 24 hours - it can start to gel off in 20 minutes if you are out on your mixtures a bit. Epoxy is much more forgiving.

    Fair enough, but do a small test batch on as associated part to really understand the problem.
     
  7. rob denney
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    rob denney Senior Member

    I get infusion epoxy for aboyt the same price a vinylester, but have to buy it by the drum, which is way more than I need at the moment. If you want to share a drum (I am on the Gold Coast), drop me a line at harryproa@gmail.com.

    rob
     
  8. guzzis3
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    guzzis3 Senior Member

    Again thank you for the replies.

    Mr Denny:

    I am in Brisbane and I was planning on buying a drum. The quotes I got put epoxy almost twice the price. I will email you the details, I don't know if it's appropriate to discuss quotes here on the forum ? I would be very happy to share an order. I'd also appreciate any tips on cheaper suppliers.

    rwatson: I understand the limits of cure time. I was hoping to bias my mixtures for slow cure. One of the nice things about epoxy is the slow formulations.
     
  9. CloudDiver
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    CloudDiver Senior Member

    I don't know how wide or long your infusion will be, but try the serial infusion technique. Helps avoid dry spots and you mix smaller batches of resin. This process is also easier on a single person to pull off without assistance.
     
  10. guzzis3
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    guzzis3 Senior Member

    Thank you for the comment but it's a 25' catamaran. I think serial infusion would add complication and not really help.

    If I go with epoxy I don't have to worry about resin boil. I was planning on buying 2 cheap vacuum pumps and pulling from both the vacuum line and resin line until I start the infusion. That hopefully will help eliminate trapped air. 2 stage pumps should get me a good vacuum provided I eliminate leaks. This is one of the reasons I favour infusion. I can take my time and only involve resin once I'm 100% happy with the setup.
     
  11. CloudDiver
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    CloudDiver Senior Member

    I understand you want to avoid additional complication, but you already seem willing to use two pumps so that in and of itself is added complication. While serial infusion requires several more resin paths with the associated spiral tube, valves, entry pucks, etc.... overall it still simplifies the process by mixing smaller batches of resin. If your concern is dry spots over a large surface area this is the best way to avoid it and control resin path. Even using epoxy, you can still have a large batch cook off in the pot if you aren't careful.
    If you don't believe me, please ask others or check media resources. I know of at least one good video showing a single technician executing a serial infusion on a long hull surface. I'm at work so I can't copy the video link to post it.
     
  12. guzzis3
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    guzzis3 Senior Member

    Unfortunately life has got in the way of progress on this but I've come full circle and thinking maybe plain foam and an infusion medium is a better approach.

    So there are dedicated materials and there is shade cloth. I have searched but not been able to find much on the pros and cons of the purpose made fabrics vs shade cloth. I have also not been able to find what weight of shade cloth to use. Do you use the dense 90% shade cloth ? the 30% or something in between ?

    I know this will use more resin, but there are swings and round abouts for every option. At least I've got the epoxy sorted...

    Thoughts appreciated.
     
  13. Tungsten
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    Tungsten Senior Member

    I think the one I used was 50%. You’ll have to try a few and see. Remember resin viscosity will half with a 10c increase in temp. So keep the goo warm for it to work with shade cloth
     
  14. guzzis3
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    guzzis3 Senior Member

    Thank you for the comment.

    I've got epoxy with an infusion specific hardener so it's pretty runny anyway, but at this rate I'm going to be infusing in brisbane's summer so lack of heat isn't going to be a problem.

    The scariest thing is getting the foam to conform to the mould.
     

  15. VadimGo
    Joined: Aug 2006
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    VadimGo Junior Member

    May I ask what it is you are building? I do apology if I missed the thread, Pls.
    I like very much the questions you were asking on the designs, and am curious what is the answer you've come with.
     
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