epoxy primer sprayed on green epoxy laminate?

Discussion in 'Boatbuilding' started by bntii, Oct 11, 2006.

  1. bntii
    Joined: Jun 2006
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    bntii Senior Member

    Anyone know of a spray primer which can be applied over green epoxy layup?

    I am laying out laminate with System Three 'Silvertip' epoxy.

    I am glassing the whole hull of a 40' sailboat and want to save the grind out on raw glass before applying primer. Thinking of 545 sprayed on as soon as I run the hull and the epoxy has tacked. Awlgrip calls 545 a epoxy polimide.
    System three tech does not know but thinks it should be fine.... Anyone know??

    Thanks,

    T
     
  2. catmando2
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    catmando2 Malaysia bound....soon

    Wouldnt you have to bog it first.????

    Dave
     
  3. Jimbo1490
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    Jimbo1490 Senior Member

    Many different epoxy products (and polyurethanes too, for that matter) can be recoated during 'green cure'. Some are even designed to work that way. The non-sanding Mil Spec epoxy/polyamide primers are an example that comes to mind. What you are supposed to do is apply, then wait at least X amount of time but no longer than Y amount of time, to recoat. Then the two products will bond and cure together. This actually gives you FAR better adhesion than if you let the substrate coating go to full cure first, then abraded and applied the second coating. Gives you chemical bond adhesion rather than just mechanical adhesion in the sand scratches.

    So this should work fine**BUT**, It's so easy to make a small test panel to be sure that it will before you commit to the entire hull. The stakes are high here! You can't afford a failure!

    If both epoxy products had polyamide curing agents then I would say "Absolutely yes, go for it". But that is not likely the case. The laminating resin most likely has amine type curatives, and the results are a little less predictable since there are SO MANY different amines.

    Make a test panel!

    Jimbo
     
  4. bntii
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    bntii Senior Member

    Thanks Jimbo

    I am calling Awlgrip today to get what advice they can offer. In my dealings in the past with their tech support, they will not recommend anything which is not already spelled out in the 'application' guide they publish. This is a topsides lay-up on an existing hull. I am laying out a 1208 with a 6ox finishing cloth over. I layed up one side of boat & have ground out to fair/ready for prime. Trying to avoid that much raw glass grinding when I run the other side of boat :(. Do you think a test would reveal to the eye such problems which might exist?

    Who has their Oz to English dictionary handy?

    Bog: Peaty bits at the wet end of a field in which failed boat projects are
    buried. :)
     
  5. catmando2
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    catmando2 Malaysia bound....soon

    Any boats I've built and worked on get a bog slurry trowled into the glass as it goes green. Micro-balloons or Q-cells mixed in with the epoxy is what I use. gives you something nicer than glass to sand when fairing. THEN when the hull is fair, we spray highbuild with about 25% Q-Cells in it and it works the same as Awl grip and Sterlings incredibly expensive spray bog [putty]. Hit this with the torture board and 80 grit for final fair. After that final highbuild.

    We found Awlgrip does not work any better than Ameron Coatings or Jotun paints and of course these are much more cost effective.Also the colours last much longer.

    Pics of my last paint job

    Have fun

    Dave
     

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  6. bntii
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    bntii Senior Member

    Ok-thanks

    I had thought of trowel on but am running one man and am beat by the time I finish the layup. Having sanded out the one side, I now see that any effort is worth it to avoid the raw glass grind out. I was hoping for a spray product as I could spray on at the end of a long day with so little effort. The System three folks have a ready mix epoxy fairing sold in pails, may give this a try.

    Complaining about boats in Maryland,

    T
     
  7. catmando2
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    catmando2 Malaysia bound....soon

    Hey, know how ya feel, did the glassing on the 50 footer myself as well. I just did it in sections and bogged as I went. Next day feather of the edge and start again.

    At the end of the day you still have to mix the system 3 stuff and put it on. There is a reason pro builders dont use these products, but if thats what you want to use............

    Pic of current project

    Dave
     

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  8. bntii
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    bntii Senior Member

    Ya-Chasing self with a broom as we are running out of weather to do glass work here in md:

    Note to self- "Glass the whole frigging side of boat today or else!"

    Works, but makes for a long day.

    Funny- I've done plenty of glass work over the years but when the project gets to be the whole boat side the application details make a big difference.

    Took me 8 hours to grind out the one side on raw glass :(
    That was no fun at all
     
  9. catmando2
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    catmando2 Malaysia bound....soon

    Gee only takes me 1/2 an hour to feather the edge on the boat in the pic

    Dave
     
  10. bntii
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    bntii Senior Member

    Tough guy :)
     
  11. JR-Shine
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    JR-Shine SHINE

    I have done what catmando describes with the Silvertip Epoxy. After Im happy with the lamination of glass, and while the epoxy is still green, I mix some fairing mix into the same silvertip epoxy. This makes a "fairing slurry" that will fill in the weave and leave a good surface to begin the real fairing. This slurry is going to be a thinner viscosity than what you would normally use when fairing. It saves time.

    Personally, I would not take the chance in putting another brand of epoxy primer over still green epoxy of another brand. Silvertip cures quickly and is no-blush so there should not be too much prep work needed when you ready for the primer.

    Joel
    E-boat
     
  12. catmando2
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    catmando2 Malaysia bound....soon

    Thanks for the back up JR-Shine, it's all pretty basic stuff. Never used silvertip epoxy, but the principal is the same with ANY glass job.

    Dave
     

  13. bntii
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    bntii Senior Member

    Catmando2, others

    Thanks very much for the excellent advise. I layed up the starboard side on Saturday. Took me about six hours to get both layers of glass and trowel the 'bog' on this 40' hull. On Sunday I sanded the work out. BIG difference sanding out the light fairing as apposed to grinding out the glass on the other side. The whole boat is ready to go with coat of 545 and see what I've got. I ended up using the Silvertip epoxy premade fairing product. Has a 10 min work time. Perhaps exspensive at about $35 USD/1.5 gallon but smooth as butter and quick to mix. I used about 1.5 gallons on side to fill the cloth quick and dirty. Could have been less if I was not beat. I sanded allmost all off the next day. The product was too fast for the large batches I was using. I would have liked fairing based on the slow hardener I used for the laminating: ~30 min pot life.

    Thanks again,

    T
     
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