Efficient Fiberglass Repairs

Discussion in 'Ask All Sailors' started by Project_Mayhem, May 22, 2019. Add this thread to a FAQ

  1. Project_Mayhem

    Project_Mayhem

    Joined Sep 24, 2018
    381 posts, 73 likes
    O'Day 25
    US Waukegan
    I've been doing a lot of fiberglass work lately and I've come to the conclusion that I am not going about them in the most efficient way. My general technique has been grind down (usually to the filler of a keel or centerboard), fill it back in with filler, grind to a smooth surface, start using cloth/mat, grind down to correct mistakes/voids/unsaturated cloth, fill voids in with filler or resin, sand smooth again, add more cloth, add resin/filler and sand to smooth surface and finally paint. Does anyone have any tips (@dlochner this sounds like it's right up your alley) or recommended reading material?
     


  2. dlochner

    dlochner

    Joined Jan 11, 2014
    3,785 posts, 1,758 likes
    Sabre 362
    113 US Fair Haven, NY
    1872289_1024x1024@2x.png

    (Courtsey of Mads and his Sail Life You Tube channel.)

    There really isn't much of a short cut. It is not necessary to use fairing compound between layers of fiberglass. Just keep laying up the glass until it is thick enough and then fair it. Andy Miller at Boatworks Today will put on a coat of sacrificial gelcoat to help with the initial sanding. It helps to see the high and low spots. Here's a video of him making a test panel for a paint demo he will be doing.

     


  3. Project_Mayhem

    Project_Mayhem

    Joined Sep 24, 2018
    381 posts, 73 likes
    O'Day 25
    US Waukegan
    I've been adding filler in between layers to fill in voids. I discovered that mixing in paper trays (the type that you'd get a hot dog or nachos in) drastically helps reduce the bubbles versus using a cup. Hopefully this will reduce the number of voids I've been seeing.

    I checked out some of the Boatworks Today videos. He recommended a filler called Adtech P-14. It's a fast curing filler that comes pre mixed with some sort of resin (just add a few drops of hardener). He recommended buying from expresscomposites.com. Wow! So much cheaper than West products.
    While I was on their website I bought some chop strand mat (also recommended by BWT) and discovered a fabric called veil. The veil is a fine finishing mat that looks similar to a dryer sheet. Hopefully I'll learn a few things as I play with these new materials
     


  4. FastOlson

    FastOlson

    Joined Apr 8, 2010
    1,107 posts, 176 likes
    Ericson Yachts Olson 34
    US Portland OR
    Before you start evaluating resins for their "cheap" qualities. .....
    be aware that West Systems EPOXY is waaaaay different than inexpensive polyester resin for strength. Epoxy is usually easier to use, as well. The reaction time is more forgiving.
    As for fillers, once you have the repair done, you can indeed use cheap fillers, even the oft-insulted "Bondo" for filling surface dings.
    Veil is good for some things, and very fine weave "surf board cloth" is also good. Nowadays most of us use "Bi-Axial cloth for structural work. Great stuff.

    Read and re-read all of the West Systems booklets and watch their videos. They 'know a thing or two because they've seen a thing or two', as a popular commercial jingle sez on the telly.
     


    jssailem likes this.
  5. Project_Mayhem

    Project_Mayhem

    Joined Sep 24, 2018
    381 posts, 73 likes
    O'Day 25
    US Waukegan
    I picked up a gallon of West Resin and have been using less expensive cloth/mat. I currently have some standard woven cloth and 1708. I actually find epoxy's working time too long. That may change as it gets warmer outside.

    I just realized that P-14 is a polyester based product. Is it compatible with West's resin?
     


  6. agprice22

    agprice22

    Joined Aug 3, 2012
    2,375 posts, 595 likes
    Performance Cruising Telstar 28
    302 US Watkins Glen
    Wipe well with acetone before glassing. Do it twice. Lots of bubbles are formed around dust and impurities. Make sure to use rollers to get the air out of your layups. The voids are air trapped beneath your mat. Do not bother to fill between layers. Keep working the epoxy til it is too hard to move easily. You will be able to fix problems as the epoxy hardens. Fussing over epoxy and filler as it cures can help you smooth ridges, remove bubbles, etc. Once it won’t move easily, stop fussing. You will only make things worse from there on.
    If it is taking too long to cure, use a faster hardener.
    Tape to contain your repairs. Make gutters out of brown craft paper to catch stray or running epoxy. Squeeze epoxy out of your layup. It is common to have a resin rich layup. It just adds to the mess and the sanding.
    Start with 40, go to 80 or 120, finish with 220 or 320 grit depending on how visible the area will be. Sanding is no fun.
    Got a drip of epoxy? Either wipe it up immediately with acetone, or wait for it to dry and pop it off with a razor. Do not smear it if you are not going to sand and paint that spot. Biaxial mat is strong. CSM is weaker but easier to form.
     


    jssailem and FastOlson like this.
  7. dlochner

    dlochner

    Joined Jan 11, 2014
    3,785 posts, 1,758 likes
    Sabre 362
    113 US Fair Haven, NY
    Most chopped strand mat does not do well with epoxy because the fibers are held together with a styrene based adhesive. CSM is designed to be used with polyester resins, the styrene in the polyester resin dissolves the adhesive and allows for easier cloth saturation. Epoxy can be forced in to CSM, but it results in a resin rich lay up.

    A cloth like 1708, which is BWT favorite cloth has the mat stitched to the fabric so it can be used with epoxy.

    It is not necessary to wait for one layer of glass to cure before adding more, just keep building up the layers until the laminate is as thick as you want.

    Yes, you can put polyester products over epoxy and vice versa. However, the laminate will be strongest if each layer of the laminate has the same resin and is laid up before the layer beneath cures.

    In order for polyester resins to cure, they must be sealed from air. Some resins have wax in them, the wax floats to the surface and seals it. Or, after the surface can be sprayed with PVC. Either way works, it is probably easier to wash off the PVC as it is water soluble than to remove the wax.
     


  8. Project_Mayhem

    Project_Mayhem

    Joined Sep 24, 2018
    381 posts, 73 likes
    O'Day 25
    US Waukegan
    I did not know that impurities can cause air bubbles. I've been quickly wiping with iso alcohol

    I like adding it when the previous layer is sticky but that usually requres me to wait for it to start kicking. At what point does out gassing become an issue when adding multiple layers or lots of filler?
     


  9. dlochner

    dlochner

    Joined Jan 11, 2014
    3,785 posts, 1,758 likes
    Sabre 362
    113 US Fair Haven, NY
    That's going to vary with temperature and the hardener being used and the particular application. The tasing (exothermic reaction) occurs when the resin gets too hot. On large flat surfaces the heat generated by the reaction can dissipate pretty quickly and so having the resin go exothermic is not a big issue. When filling a deep hole or void, it becomes more of an issue because the heat can't dissipate as easily. When working with epoxy it is better to have the epoxy in a large flat pan rather than a cup. The working time will be longer in a shallow pan.

    When epoxy and hardener are mixed, the chemical reaction generates heat. The speed of the reaction (cure time) decreases with higher temperatures. This is how you get a run away reaction. The resin gets warm as it gets warm, the reaction speed increases, which generates more heat, which speeds up the reaction thereby generating more heat. At some point the reaction gets so hot the resin starts to gas and foam.

    It is probably safe to lay up 4-6 layers of glass with out much issue. If a deep void is being filled, then it is necessary to put thickened expoxy in several layers waiting until the prior layer is being to set up, but not fully cured. In these cases, a ¼" of thickened epoxy is about the most you'll want to use at a time. Wait a few hours and use the fingernail test, a thumb nail should leave an impression, but the resin should not be tacky.
     


    agprice22 likes this.
  10. dlochner

    dlochner

    Joined Jan 11, 2014
    3,785 posts, 1,758 likes
    Sabre 362
    113 US Fair Haven, NY
    Just to clarify 2 of my statements.

    tasing is autocorrect for gassing. :mad:

    The speed of the reaction increases resulting in the cure time decreasing. Cure time and reaction speed are inversely related, faster reaction, shorter cure time; higher temperature, faster reaction, shorter cure time.
     


  11. Crazy Dave Condon

    Crazy Dave Condon

    Joined Jun 8, 2004
    7,339 posts, 820 likes
    -na -NA
    US Anywhere USA
    Resin rollers to flatten out the glass and get air bubbles out
     


    agprice22 likes this.


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