Fibreglass Finishing Questions

Discussion in 'Powerboats' started by mike marchetti, Jul 10, 2018 at 2:36 PM.

  1. mike marchetti
    Joined: Jul 9, 2018
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    mike marchetti New Member

    hi, i recently replaced the transom on my 1987 Mako 224 i cored out the old wood material with a arbor bit and refilled core with trk2000, built up inner and outer transom with 4 layers of 1708 with poly laminating resin, and thought i had everything smoothed out pretty well, but after applying the 2nd and 3rd gelcoat layer, i can see that alot of the weave is showing thru in areas, And im unsure as to best solution. Do i sand off the gelcoat and add a surface layer of resin to fill in the weave more ? add another layer of 6 oz. cloth, then gelcoat ?
    or is it ok to simply keep adding more layers of gelcoat until the weave is filled in. i know gelcoat shouldnt be that thick, but what is considered acceptable ? I'm pretty sure i should not add a resin layer over the gelcoat to fill, then gelcoat over that again ? any help is greatly appreciated.
     
  2. JosephT
    Joined: Jun 2009
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    JosephT Senior Member

    Hi Mike, for canoes & kayaks the glass & layers are fine. Larger fishing & runabouts have a rougher weave. It's Ok to add a few layers of gel coat until all the fiber weaves are filled. May take 2+ coats to achieve that depending on the thickness of your weave.
     
  3. Blueknarr
    Joined: Aug 2017
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    Location: Colorado

    Blueknarr Senior Member

    Welcome

    Pictures are worth thousands of words.

    How thick was the gelcoat applied?
    How was it applied?
    How much texture remains?
    How deep are the valleys, pits?
    What color?

    Hard to give good advice with incomplete information.
     
  4. ondarvr
    Joined: Dec 2005
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    Location: Monroe WA

    ondarvr Senior Member

    Use a high build polyester sanding primer to get the surface smooth again, this will be much easier to work with than gel coat or resin, and don't use straight resin, it won't work well.

    The other option to make an easier sanding filler with the resin you have, micro-spheres and Cabosil will make something you can work with.
     
  5. Rurudyne
    Joined: Mar 2014
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    Rurudyne Senior Member

    While it may take creativity for some craft that aren't made of developed surfaces there's a trick using, IIRC, Mylar and a real good squeegee or roller to compress down the fibers that may help reduce that.
     
  6. JosephT
    Joined: Jun 2009
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    Location: Roaring Forties

    JosephT Senior Member

    Yes that's a good trick. Generally it takes a few coats though on a flat surface. Below is a good video (pardon the elevator music).

     
  7. Rurudyne
    Joined: Mar 2014
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    Location: North Texas

    Rurudyne Senior Member

    Many years ago I stepped onto an elevator completely unprepared for what I was about to experience: a full choral in harmony version of AC/DC's Hell's Bells with tinny silver bells.

    I'm not a fan but it was just wrong on so many levels. A friend who was fan just shook his head in disgust.

    So it could be worse I suppose.

    This has been an Official Rurudyne Totaly Random Digression (tm).
     
  8. mike marchetti
    Joined: Jul 9, 2018
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    Location: Kona hawaii

    mike marchetti New Member

    thanks for reply's, i have been applying gelcoat with a short nap 4" roller and layers are going on fairly thin, rolling it out so no lines, its leaving a slight stipple, but i know thats un-avoidable. id have to say depest part of weave may be 1/16 to 1/8" max i already have rolled on 4 layers of gelcoat, sanding between layers to knock down any high spots and have been having issues where after just a min. the nap starts pulling off roller and gets stuck into work, where i have to pick it out and try to re-roll over it without making a mess of area, coats 3-4 filled in weave quite a bit,so as long as its ok, will keep adding more coats, will prob. stop after next 2 coats and call it a day. i did spread some epoxy/aerosil mix that i had extra from another project into the thickest weave parts as filler, will sand and give it 2 more coats of gelcoat today if weather holds. thanks for all your advise. will try to post pics tomorrow a.m. then on to next project, rebuilding dash....
    cut out slant area, now have to get backing board and seal it up with glass, the fun never stops...
     
  9. mike marchetti
    Joined: Jul 9, 2018
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    Location: Kona hawaii

    mike marchetti New Member

  10. mike marchetti
    Joined: Jul 9, 2018
    Posts: 4
    Likes: 0, Points: 1
    Location: Kona hawaii

    mike marchetti New Member

    darkened some of the pics to show more contrast, let me know what u guys think - thanks
     
  11. Blueknarr
    Joined: Aug 2017
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    Blueknarr Senior Member

    Me thinks you forgot the fairing step of the process.

    Forgive me for not scrolling back to the start. Did you say if you ate using waxed or straight up gelcoat?

    How close to flawless perfection are you striving for?
     

  12. ondarvr
    Joined: Dec 2005
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    Location: Monroe WA

    ondarvr Senior Member

    Hopefully you used gel coat with no wax in it.

    Don't use a roller, use a squeegee (yellow plastic Bondo spreader type thing), apply some gel coat to the surface any way you can, it will be a little difficult on a vertical surface. Use the squeegee and spread the gel coat onto the surface, this fills the low spots and doesn't add anything to the high spots, a roller adds more material to all surfaces. You can put it on with the roller then squeegee it.

    You may need to do this a couple of times.

    Thickening the gel coat slightly helps, you can get even better results by using micro balloons in the mix along with cabosil, easier to apply, easier to spread and easier to sand.

    That will get rid of the glass pattern, but you may still have a somewhat wavy surface, to eliminate the waves and irregularities you need to use higher build fillers and a long board. This would be done before doing the prior mentioned work.

    The good thing is you are the only one that needs to be satisfied with the results, so you can stop at any stage and call it good enough, then bolt the motor back on.
     
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