Plug and Mold for 18' sailboat

Discussion in 'Fiberglass and Composite Boat Building' started by John Merritt, Oct 1, 2018.

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  1. John Merritt
    Joined: Oct 2018
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    Location: Ada, MI

    John Merritt Junior Member

    The (endless) longboard sanding is going well but I have run into a problem. There are many ( hundreds) of little pinholes where there were tiny bubbles in the fairing compound. Does anyone have a good idea of how to fill them ? Any advice would be very appreciated. Thank you.
     
  2. KD8NPB
    Joined: Mar 2018
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    Location: South Carolina

    KD8NPB Junior Member

    Yes, stop using microballoons ;)

    Duratec 707-002 will fill it in.
     
    ondarvr likes this.
  3. Blueknarr
    Joined: Aug 2017
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    Location: Colorado

    Blueknarr Senior Member

    I just stated my opinion that micro balloons are simply micro blisters waiting to grow on another thread.

    Your pinholes are most lickly mini clumps of balloons which didn't disperse during the mixing of the epoxy. It takes hours of mixing to fully declump powders added to resins or paints.

    Two solutions. Remove it all and start the fairing process over.
    Paint with high build epoxy primer and hope blisters don't form.
     
  4. ondarvr
    Joined: Dec 2005
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    Location: Monroe WA

    ondarvr Senior Member

    Below the waterline epoxy.

    Above the waterline you have more options, that’s where the Duratec products can come into play.
     
  5. John Merritt
    Joined: Oct 2018
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    Location: Ada, MI

    John Merritt Junior Member

    Is the Duratek 707-002 product able to be brushed on ? As this is only a plug does the waterline matter ? Is there another, easily sandable, filler I could make that wouldn't use microballoons ?
     
  6. ondarvr
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    ondarvr Senior Member

    I forgot it was the plug.

    It can be brushed, but the results are better when sprayed
     
  7. Blueknarr
    Joined: Aug 2017
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    Blueknarr Senior Member

    The pinholes problem isn't purely caused by microballons. It is the clumping of them that caused the problem. Any compound not shaken for hours will have clumping of the added powder.

    Even premixed compounds have some pinholes. 3M markets a "glazing" compound formulated specifically to fill pinholes and scratches.

    Or use an extra coat of primer as a surface filler.
     
  8. KD8NPB
    Joined: Mar 2018
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    Location: South Carolina

    KD8NPB Junior Member

    it could, but it’ll lay pretty flat if you spray it.

    If you’re wanting to start sanding above P400, I’d change to spraying on about 50-60 mils of Duratec 707-002.
     
  9. John Merritt
    Joined: Oct 2018
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    Location: Ada, MI

    John Merritt Junior Member

    this is going to sound very strange but here goes. Right now I am starting to apply the second coat of fairing compound to the plug (which is the last coat). I did a small test area using 5% wax added to the fairing compound before catalyzing. But the surface still seems pretty gummy...and goes through my sandpaper very quickly. I understand that perhaps this is because with the microballoons added it is harder for the wax to float to the surface and provide the air barrier required.... Now the silly part... would it be possible to spray on a layer of oil ( yes, I'm thinking Pam) to provive that air barrier which could then be easily washed off ? Has anyone tried it? Should I just increase the % of wax in the fairing compound ? Inquiring minds want to know.....
     
  10. tpenfield
    Joined: Dec 2016
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    Location: Cape Cod, MA

    tpenfield Senior Member

    How about PVA instead of oil ?
     
  11. gonzo
    Joined: Aug 2002
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    Location: Milwaukee, WI

    gonzo Senior Member

    Oil will make a sticky mess out of the fairing compound. PVA will work, but if you have a lot of pinholes, it will cause problems later. The PVA is softer than the mold, so it will show on the hull. Microballons are the wrong product for a final coat. As the name implies, they are hollow balls. When you sand them, each will leave a hole. Check Duratec website for an explanation of the different layers and products to get a good mold. Hawkeye Industries http://www.duratec1.com/Hawkeye/
    They can help you with the job. Basically, you have a bunch of mismatched layers. It is unlikely the mold will be good. However, it is a learning experience. The best is always to use only one method and not to mix and match to re-invent the wheel.
     
  12. John Merritt
    Joined: Oct 2018
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    Location: Ada, MI

    John Merritt Junior Member

    To be clear, the final coats prior to the mold will be Duratec, but I want to spray the Duratec onto a very fair surface. The bigger air pockets ( size of a grain of rice or two) I am filling with the fairing compound ( easy to do and only 100 or so). It is the tons of smaller ones I'm worried about. I was thinking about a thin epoxy to fill all the tiny holes , perhaps pushed into the holes with the end of the brush.... Any ideas about a thin epoxy ?

    As an aside, this is what finally worked on the second coat. I heated the garage to 80F and added 3% wax and 1.5% catalyst to the fairing compound. Had to work quickly and used a 4" wide plastic putty knife . After it hardened I removed the top waxy/gummy layer with 80# on an orbital sander ( picking off the stuff stuck to the paper with a chisel every 10 minutes or so ) BTW big box of those sanding pads pretty cheap at Harbor Freight. After that outer layer was removed it was very easy to long board w/o gumming up the paper. Hull is now really looking like a boat. Next is to cut out a 3in wide strip down the middle in order to facilitate the shaping / placement of the keel..... then, of course, more sanding. Will try to add some pictures soon
     
  13. ondarvr
    Joined: Dec 2005
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    Location: Monroe WA

    ondarvr Senior Member

    Skip filling the defects with epoxy, just use Duratec, that’s what it’s designed for.
     
  14. John Merritt
    Joined: Oct 2018
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    Location: Ada, MI

    John Merritt Junior Member

    OK! Just ordered the Duratec primer. Any hints about application? I hate to admit this but I have never used spray gun . Since it is epoxy can the gun be used more than once? What grade ( grades ) of sandpaper should I order for use after spraying the Duratec? Does anyone know of a supplier that is reasonably inexpensive? Also, an HVLP sprayer is recommended for the Duratec, but they are very expensive, has anyone had good luck with another type of sprayer and if so, what? Thanx.
     

  15. ondarvr
    Joined: Dec 2005
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    Location: Monroe WA

    ondarvr Senior Member

    Duratec is not epoxy, they make polyester and VE primers.

    Find the cheapest spray gun on amazon that has a 2.5 mm tip. You’ll probably find one for around $40.00

    You can use the gun for ever if you clean it thoroughly between uses.

    For this size job order some of the Duratec 39GELX-01

    This will extend the pot life enough for you easily spray it before hardens in the gun.
     
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