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
    Posts: 36
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    Location: Ada, MI

    John Merritt Junior Member

    Trying to post some pics.
     

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  2. Chris Rogers
    Joined: Apr 2020
    Posts: 24
    Likes: 9, Points: 3
    Location: Boston, MA

    Chris Rogers Junior Member

    Looks like a neat project! I'm not sure if you're still having pin-hole issues, but I have found spraying (or rolling I guess) the first shot of Duratec and then sqeegeeing it over the surface will press it into the pinholes and displace the air. Just spraying will not fill all the pinholes. You've got to be quick or do it in zones because Duratec will gel in 15-20 minutes. You can go on spraying a few more rounds to build some thickness - there will be some ridges here and there from the squeegee but they will sand off quickly with 80-120 grit and then you won't be chasing them forever. Pinholes, fairness and smoothness are three different sets of challenges!

    Once you're in Duratec all your fills will be polyester putty so things will go fast. I find it takes a minimum of three spray sessions followed by finer and finder sanding to get to a polish-able surface. It's frustrating but I haven't found any shortcuts yet - let me know if you do!
     
  3. John Merritt
    Joined: Oct 2018
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    Location: Ada, MI

    John Merritt Junior Member

    Thanks for your input Chris, the sqeegee method sounds like it will work... I will try that. Was there any particular product that seemed to work well to do the Sqeegeeing? Also, The mold is now going to have three parts, Port, starboard and transom. I think I have a fair grasp of what's necessary for the mold itself but have LOTS of questions about how to go about constructing A good cradle that splits in half on unmolding, can be easily moved and possible be rotated to facilitate ease of lay up..... And remember this IS a garage project and my budget is very limited. If anyone has such a cradle I would love to see some detailed pictures of it as I can't seem to find any. Thanks.
     
  4. John Merritt
    Joined: Oct 2018
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    Location: Ada, MI

    John Merritt Junior Member

    Oh, I almost forgot, I would like to have the option to do infusion molding. Is there anything (other than having a wide flange at the shear for tubing) special that I need to consider when constructing the plug or the mold?
     
  5. ondarvr
    Joined: Dec 2005
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    Location: Monroe WA

    ondarvr Senior Member

    The mold(s) need to be stiff enough to not flex when you pull a vacuum.

    It also needs to be air tight, so joining the mold sections correctly gets far more critical.
     
  6. John Merritt
    Joined: Oct 2018
    Posts: 36
    Likes: 1, Points: 8
    Location: Ada, MI

    John Merritt Junior Member

    Just a quick update. Applying the Duratec with a brush and am able to fill all the little pinholes by dragging the brush over the same spot several times. Sands to a really nice finish. Once the "pinhole coat" is sanded I will spray the next coat. Looks like I may be able to start the mold itself before the weather cools off too much to work in the garage. Thanx to all for the help and advice.
     
  7. ondarvr
    Joined: Dec 2005
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    Location: Monroe WA

    ondarvr Senior Member

    Use a plastic squeegee (bondo spreader) to fill the pin holes, and there's no need to sand after this step, go straight to spraying.
     
  8. John Merritt
    Joined: Oct 2018
    Posts: 36
    Likes: 1, Points: 8
    Location: Ada, MI

    John Merritt Junior Member

    OK! All the pin holes are now filled and it's time for spraying... which leads to my next problem. From what I've read, HVLP is "the" way to go to shoot Duratec and gelcoat. Unfortunately a turbine just isn't in the budget ( was out of work for 3 months thanks to Covid - back now but the damage to the bank account was grim). So, is it possible to use a regular spray gun? Is it possible to use a cup gun? I can't seem to find a cheap gun with a large enough nozzle.... any advice on where I could find one.... cheap? Thanks again.
     
  9. Chris Rogers
    Joined: Apr 2020
    Posts: 24
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    Location: Boston, MA

    Chris Rogers Junior Member

    Yes, a cup gun with a 2mm+ nozzle will work fine. You may need to thin the Duratec - they make a thinner that works great - and make sure to mix/shake the cans really well because it settles. I have used the cheap cup guns from Home Depot and they work fine - got to clean them pretty well though - which is true for any spray gun!

    If you let it flash for 30 minutes (depending on temperature and catalyst) or so then you can spray on a few coats (that you mix and catalyze separately) in an hour or two. Their EZ-Sand product works pretty well for heavier but not high-build type fairing - and best not to let it sit for days or it will harden more and sanding will be more work! The surface will be better with the standard surfacing primer (or the VE) though.
     
  10. John Merritt
    Joined: Oct 2018
    Posts: 36
    Likes: 1, Points: 8
    Location: Ada, MI

    John Merritt Junior Member

    Thanks Chris! a Titan Pro300 HVLP just popped up on Craigslist near me. Does anyone know if this system would handle gelcoat with a 3.0mm nozzel? When you say a cheap gun, is that HVLP or a standard spray gun with air compressor?
     
  11. Chris Rogers
    Joined: Apr 2020
    Posts: 24
    Likes: 9, Points: 3
    Location: Boston, MA

    Chris Rogers Junior Member

    I've never used one like that but if it is easy to clean then it might be ok - this stuff gels hard compared to normal paint and if you don't clean it before it gels you have trouble!

    I meant one like this: Husky Gravity Feed Composite HVLP Spray Gun-H4850GHVSG - The Home Depot https://www.homedepot.com/p/Husky-Gravity-Feed-Composite-HVLP-Spray-Gun-H4850GHVSG/203497641

    Has a 2.2mm nozzle which should be fine. Needs a compressor but even a small compressor will do if you are not painting something huge - and take a few short breaks for it to catch up. They used to have a cheaper one with multiple nozzles - like $40 but its been a few years since I bought one.
     
  12. John Merritt
    Joined: Oct 2018
    Posts: 36
    Likes: 1, Points: 8
    Location: Ada, MI

    John Merritt Junior Member

    Do you think the turbine on the Titan Pro300 would work ?
     
  13. KD8NPB
    Joined: Mar 2018
    Posts: 95
    Likes: 19, Points: 8
    Location: South Carolina

    KD8NPB Junior Member

    Pressure feed is best.

    Gedu High Pressure Spray Gun with 1000cc Cup, 2.5mm Nozzle, Sliver https://www.amazon.com/dp/B01JIEZMAG/ref=cm_sw_r_cp_api_i_4z49Eb8RS6VEN

    remove the cup.

    Use this for fluid pot
    Shop Fox W1799 2-1/4 gallon Paint Tank https://www.amazon.com/dp/B005W1CE4W/ref=cm_sw_r_cp_api_i_SA49EbPMYFV6T

    use these for fluid lines
    Brennan PCNY2405-08-06 PBT Push-to-Connect Tube Fitting, Adapter, 1/2" Tube OD x 3/8" NPT Female https://www.amazon.com/dp/B004I43AW4/ref=cm_sw_r_cp_api_i_MC49EbB08Z4NW

    ATP Value-Tube LDPE Plastic Tubing, Natural, 3/8" ID x 1/2" OD, 100 feet Length https://www.amazon.com/dp/B000CDCLJ8/ref=cm_sw_r_cp_api_i_yD49EbRK0D2JN

    use whatever you want for air line, 3/8 minimum ID.

    theory;
    Remove suction cup
    Attach push to connect to gun
    Attach push to connect to pot fluid outlet
    Use 1/2” ldpe tube for fluid hose

    When ready to spray, buy $1 plastic 1gal pails. Mix your Duratec in the pail and place the pail directly inside the pot.

    the fluid line is disposable, so all you have to clean is the pot pickup and the gun. The pail acts as a liner so the inside of the pot stays clean.
     
  14. John Merritt
    Joined: Oct 2018
    Posts: 36
    Likes: 1, Points: 8
    Location: Ada, MI

    John Merritt Junior Member

    Wow KD8... that was VERY specific and very helpful. You have shot Duratec this way I assume... Can you tell me how much Duratec you are able to mix at a time? Did you use the additive to slow the kick down? How long of a line between the pot and the gun can be used? Can this same setup be used to spray tooling gelcoat? Thanks!
     

  15. KD8NPB
    Joined: Mar 2018
    Posts: 95
    Likes: 19, Points: 8
    Location: South Carolina

    KD8NPB Junior Member

    Use gel extender. Spray at night or early morning. Prep everything, use a drill mixer when introducing MEKP. Try to mix, insert, close pot, pressurize, and spray within 1 minute.

    Going off Binks literature, I think they recommend 50 ft max for 3/8 ID?

    The spraygun is an Inest Iwata W77 knockoff. If you need finer atomization / less fluid, screw the needle in further to restrict fluid output.

    I use this setup for specialty colors. The push to connect fittings eventually crap out, but they’re cheap and it cuts back on acetone / potential contamination. After I had to scrap and remake a $1500 project due to gelcoat contamination (black flecks of hose debris in light gray gelcoat), I got a little more careful.

    one warning ; to atomize thick coatings, it’s going to use a lot of air. You need about 15 cfm @ 50 psi.
     
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