edges of panel under vac

Discussion in 'Fiberglass and Composite Boat Building' started by fallguy, Sep 6, 2017.

  1. Tungsten
    Joined: Nov 2011
    Posts: 468
    Likes: 10, Points: 18, Legacy Rep: 75
    Location: Canada

    Tungsten Senior Member

    I would do one of Robs suggestions and make a few more holes in the release film.You can up the vac then also.
    Just fold the plastic as much as you can and drill some 1/8 holes through all the layers.
    I wouldn't bother with tests of only glass one side with perforated foam.
     
  2. fallguy
    Joined: Dec 2016
    Posts: 2,302
    Likes: 179, Points: 63, Legacy Rep: 10
    Location: usa

    fallguy Senior Member

    What is the minimum amount of open time you would allow friends? 80 minutes on 120 minute gel time?
     
  3. fallguy
    Joined: Dec 2016
    Posts: 2,302
    Likes: 179, Points: 63, Legacy Rep: 10
    Location: usa

    fallguy Senior Member

    What if I have a leak in a vacuum table panel join? .... I'm betting I'd get bubbles in my part regardless of the gel times... My table is mdf. 1" mdf with epoxy and cabosil seams, then two lifts of epoxy over the top. I am going to test my table tomorrow.
     
  4. fallguy
    Joined: Dec 2016
    Posts: 2,302
    Likes: 179, Points: 63, Legacy Rep: 10
    Location: usa

    fallguy Senior Member

    I tested one join and did a visual of the others and while my test did not hold forever; I had full vacuum and nothing more than system dropoff. Meaning when I isolate the bag from the system; dropoff is similar.
     
  5. rob denney
    Joined: Feb 2005
    Posts: 723
    Likes: 86, Points: 28, Legacy Rep: 436
    Location: Australia

    rob denney Senior Member

    Having a minimum time is no help as there are too many variables, and once you have started, it doesn't matter anyway. Work as fast as you can until the vacuum is on. If you don't make it, then find a resin supplier with longer cure time resin.
    If you have table leaks, fix them as it makes it much easier to find leaks in the bag, plus the higher the vacuum, the better the . Ensure you have bleeder or cloth over the entire table when you test it. 2 coats of epoxy on mdf should be airtight. Any air through the table will head for the nearest core perforation then through the top laminate and into the bleeder and should be visible in previous panels as bubbles in the laminate, but is unlikely to be critical, if the bag pressure is finger and thumb pull proof.
     
  6. fallguy
    Joined: Dec 2016
    Posts: 2,302
    Likes: 179, Points: 63, Legacy Rep: 10
    Location: usa

    fallguy Senior Member

    Thanks all. I ran samples yesterday. We turned the vac on at about 60 minutes. I ran full pressure for 8 hours.

    2- 4' x 20" pieces, all xslow resin 120% bottom, 100% top, all samples with rebates, all peelply both sides
    #1 glass both sides, 300g/m^2 core wetout
    veil on half with breather film and single bleeder, 300g/m^2 veil
    no veil with double bleeder and no breather film other side of same part

    #2 glass one side only, peelply wetout at 35g/m^2 top side,
    breather film & single bleeder one side
    no film, single bleeder other side


    RESULTS

    Zero bubbles all parts.

    Laminating defect where veil and valley between zero strands exist. It is an air bubble of sorts, but not between the core n glass, but between veil and glass. The best course is to ditch the veil.

    The nonuse of perf plastic is a major no no. Release of the bleeder is nearly impossible. Doubled, it was worse.

    My breather film has holes 10mm spacings. No need to drill it.

    SUMMARY

    Well, pretty likely my resin gelled on the other part and/or I did not run the pressure up high enough.

    I also learned my core and glass wetout amounts are really high (glass with the veil). The wetout of core at 300 was great plenty on the bottom and the top can be done at 250 or less because it is pretty wet from bubble up already.

    I am going to tell my crew we need to have the part bagged at 60 minutes. There is no reason we can't. We did one at 70 already.

    Only question is if there is a boil risk on my epoxy.

    I am going to ask S3.

    Thanks.

    Rob-I am going to read up on the infusion link after I get my new part made. I am curious about it; especially for more intricate parts where the details could be vaccumed dry and watched. I was terrified of starting to learn infusion on the blind side of panels.
     
  7. rxcomposite
    Joined: Jan 2005
    Posts: 1,987
    Likes: 176, Points: 63, Legacy Rep: 1110
    Location: Philippines

    rxcomposite Senior Member

    Veil is hard to wet out and it is stiff as I have mentioned before. Those who had good results laminate the veil first then let it partially cure before proceeding with the next step.

    When we were doing prepreg aerospace parts, we would full vacuum the part and remove the quick release. The bagged part stays tight for 4 to 6 hours unassisted. If it becomes loose before that, we have a leak. We have good airtight molds so we know the bagger has done a sloppy job.

    In wet bagging, we release the vac lines 1/2 to 1 hour after the part has cured. That is a total of 1 1/2 to 2 hours per part that the vac is on. less than 1 hour working time, 1 hour after curing. We add more people if we could not finish the part within the working time of the resin. No need to hold the vac as the resin has cured. It has nowhere else to go and compacting it further is useless. We rely on the residual vac to hold it together during full cure.
     
  8. fallguy
    Joined: Dec 2016
    Posts: 2,302
    Likes: 179, Points: 63, Legacy Rep: 10
    Location: usa

    fallguy Senior Member

    A little less pump time would be good. I think I will experiment with the smaller bulkheads n such. I know if I try to remove the parts at 6 hours a disaster ensues as the epoxy is in a wierd state of soft and hard combined and it will not release from the table. So my parts stay on the table a minimum of 15 hours with xslow resin. The other resins offered by S3 required immediate postcure at higher temps like 90F. They were designed for Abu Dhabi; not Minnesota!

    I think the bleeder valve next to the vac pump was creating lots of issues for me. Gonna run on max.
     
  9. Tungsten
    Joined: Nov 2011
    Posts: 468
    Likes: 10, Points: 18, Legacy Rep: 75
    Location: Canada

    Tungsten Senior Member

    Lol!

    Turn down your shop temp to 50f this will buy you some time , keep your resin at the same temp that your usally at. Room temp I assume. You can turn the temp back up once your all sealed and sucked.
    Do a test piece infusion on glass, you get to see everything.
    Sounds like your back on track,happy building.
     
  10. fallguy
    Joined: Dec 2016
    Posts: 2,302
    Likes: 179, Points: 63, Legacy Rep: 10
    Location: usa

    fallguy Senior Member

    The only thing I hate about leaving the vac pump running is I don't sleep because the pump gets hot, so if I turn the vac on late in the day, say 6pm, I don't sleep until 2am because I have been strictly following an 8 hour rule on the pump.. I went out at midnite last part and there was still some tackiness to the epoxy that ran through the perforations on the table plastic. Maybe after I build the next panel and start building some smaller stuff, I can try to run the vacuum time down to 6 hours, then 5, then 4. It'd be really nice to shut it off at 4 hours. The working time on the epoxy is 2 hours. and the gel time says 2 hours and tack free says 6 hours, but it actually went a little longer (shop might be a little cool). I guess there isn't much point in running past the tack free time of 6 hours is there? I think the gel time reflects a 100 gram solid mass, so a thin layer of epoxy would be longer, say like ?2.5 hours.
     
  11. Tungsten
    Joined: Nov 2011
    Posts: 468
    Likes: 10, Points: 18, Legacy Rep: 75
    Location: Canada

    Tungsten Senior Member

  12. fallguy
    Joined: Dec 2016
    Posts: 2,302
    Likes: 179, Points: 63, Legacy Rep: 10
    Location: usa

    fallguy Senior Member

    I only have a resin trap. No vac switch. On my large table, I'd probably get a great gauge of the leaks if I had a pressure switch. As of right now, the only way to gauge leaks is for me to walk over and flip the switch, which is difficult if I am standing by a leak I just fixed.
     
  13. AndrewK
    Joined: Mar 2007
    Posts: 463
    Likes: 29, Points: 28, Legacy Rep: 344
    Location: Australia

    AndrewK Senior Member

    When infusing at 100% vacuum rather than performing drop tests I put tubing on to the pump output and put the tube end into a shallow water. This will tell you instantly if you have leaks somewhere in the system. If you do this take the tube out of the water before shutting the pump down otherwise you will get water into the pump.
    If you already havent done so direct a fan on to the pump.
    I have a foil backed bubble wrap skirt around my table and have an electric heater under there. On top I cover with electric blankets first followed by insulation. If you dont want to mess with electric blankets then cover with any insulating material to keep the exotherm temperature in. This reduces the resin viscosity while infusing and greatly reduces the gel time.
    Pressure switch is only good if the hysteresis is very small, you dont want the clamping pressure of the bag rising and falling.
     
  14. fallguy
    Joined: Dec 2016
    Posts: 2,302
    Likes: 179, Points: 63, Legacy Rep: 10
    Location: usa

    fallguy Senior Member


  15. AndrewK
    Joined: Mar 2007
    Posts: 463
    Likes: 29, Points: 28, Legacy Rep: 344
    Location: Australia

    AndrewK Senior Member

    I can not comment, I had confidence in my pump being able to run continuously so chose the zero variation approach.
    100% vacuum for infusion, pump is a high quality two stage with almost perfect vacuum and previously to me inheriting it continuously ran for 3 years non stop. I still direct a fan on to it.
    80-85% for vac bagging, utilizing a small diaphragm pump at its full capacity rather than wanting to achieve that particular vacuum.
     
Loading...
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.