Foam strip plank help

Discussion in 'Fiberglass and Composite Boat Building' started by SURRYEQUIP, Oct 20, 2017.

  1. SURRYEQUIP
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    SURRYEQUIP Junior Member

    I am glassing some hull extensions that are rounded, made of 3/4 corecell strips, flat cut, not bead and cove. Here is the holdup: The grooves between planks are tedious to fill completely. I am glassing with 2 or 3 layers of 1708 and rolling all the air bubbles out is mighty slow. Tips? Vacuum bag? Infuse? Thanks
     
  2. fallguy
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    fallguy Senior Member

    I am the king of air bubbles lately! I don't understand your post. Can you explain it a little better? It seems like if you have a fair line, or create a fair line with cabosil and balloons, you'd not have many bubbles to worry about. If you have an uneven surface, vac bagging isn't going to make a difference. Perhaps I don't understand.

    I like to use a drywall surform to get corecell more even, then after that, you could do some fairing, unless I am misunderstanding.

    If you are having trouble with the fill sagging, you need to mix it on a hawk until it stops sagging.
     
  3. PAR
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    PAR Yacht Designer/Builder

    Agreed, we'll need a little more information about the troubles you're having. Generally, the strip gaps need to be full or you can guarantee bubbles and voids. Are you using epoxy or styrene based resins? combi fabrics aren't necessary with epoxy and just add a lot of weight, with little strength improvements, in spite of the bulk the mat provides. How are you applying the resin?
     
  4. SURRYEQUIP
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    SURRYEQUIP Junior Member

    Sorry I did not make myself clear. The first problem is the gap between strips on the outside of curves. I though it would be easy to fill them (this is 3/4 corecell) but unless they are filled completely bubbles develop. I am filling them with west 105 and 3M microballoons mixed thin so it will flow to the bottom of the gap. I don't really want any voids but the gaps vary from almost none to maybe 3/16 depending on the amount of curve. I had considered loading up a syringe to fill but some gaps are so narrow no tube will go in them. I maybe should have filled them better as I was glueing up over molds but the info I saw said it was real easy to fill them so don't sweat it. I wish now I had sweated it or gone bead and cove. I am going to handle this by just keeping after it but I wish I had done something different. This is just a small project but I need to do better on bigger projects or it will beat me. On the fabric- The fabric has a light layer of mat. I am hand laminating- spreading 105 epoxy on the corecell with a thin mix of microballons a frosting so to speak, then wetting out layers as we go. Squeegee and "bubble buster" roller. It seems to take a lot of time and rolling to get the fabric wetted out completely. Would bagging it get the air out quicker? Or still need much rolling and the bag would just compact it? Sorry to ramble on- just trying to do a better job here. Thanks
     
  5. fallguy
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    fallguy Senior Member

    Not a fan of the thin mix. I would try for a thicker mix that you force into the gaps with a trowel after you pastry bag. Tedious or no; that is the job. That would not sag and create a place for voids.

    Also, I would first use a sureform a bit to take off any high spots on the core on the outside. Then I would fair the curves and create a flat surface grinding or sanding before any glass work. Your bubble mix should sand ez unless you use too much epoxy, which sounds to be the case.

    As for the mat, not a huge fan. Mat is really resin thirsty stuff and not meant for epoxy wirk. You would need a very wet prewet to help with the wetout to keep the fabric the right way (glass out) and you are going to end up heavy. Mat backing is designed for other resins or when stiffness is needed, aka tapes. So you are using the wrong fabric on an uneven surface and that is making for a very poor lamination and difficult working condition.

    You need to do better prep of the surface and use the right glass. If you used a really firm mix; you could work wet on wet even; that is; you could fill and glass after the fill tacked a bit unless you need to sand it smoother first.

    Anyhow; you are doing a couple things wrong. The strength of the core joins is mostly all in the glasswork.

    Mix up your fill material on a board with a trowel and make sure it doesn't sag or it is too thin for filling and you will just make a mess. I think you want about 3:1 to start. And that is balloons to epoxy, not the other way. (By vol)
     
    Last edited: Oct 21, 2017
  6. fallguy
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    fallguy Senior Member

    If you are stuck with the mat backing; try wetting the mat side out on a table and rolling it up on a cardboard tube and then bringing it to the job if possible. If you need it to be movable or you need absolute references; use a sharpie on the hull on chines or reference marks before moving to the table.

    Vac bagging won't deal with an uneven surface. It will still have bubbles where you are too uneven. Trust me; this I know!
     
  7. PAR
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    PAR Yacht Designer/Builder

    The real trick with filling gaps is technique, not necessarily materials. I agree a thin mix isn't a good idea. It needs to be stiff enough to remain in place. The method I use is to physically force it in with a plastic auto body filler applicator, after an initial wetout with neat goo. It's a rolling motion with your hand, pressing the thickened goo into the grooves. I don't bother with pastry bags and similar. I find I spend more time filling them than applying epoxy and it dramatically shortens pot life, massed in a bag. I usually overfill than quickly come back and knock it down, moving accumulated goo to places where I need more. This is fast and easy to control. Bubbles result from moving too fast and not insuring the goo truly fills the gap. If I see these areas, I push the edge of the applicator into the groove and apply more goo.
     
  8. SURRYEQUIP
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    SURRYEQUIP Junior Member

    On a related subject- what does everyone say is the best epoxy for hand laminating heavy or multiple layers. What wets out best?
     
  9. fallguy
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    fallguy Senior Member

    Blush free is all that matters to me.

    Good luck with Silvertip, MAS, and had a little trouble with one brand bubbling. It will rename unnamed.
     
  10. PAR
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    PAR Yacht Designer/Builder

    RAKA seems to have one of the lowest viscosities of the usual choices. It's not very costly and wets out quickly, which can be a good or bad thing, depending on what you're doing. There's really no such thing as "blush free". Some formulations are less likely to blush, but given the right environmental condisions, it still will. For most novice laminators, you're best to assume your shop condisions aren't sufficiently controlled (humidity and temperature), to insure a blush free layup.
     
  11. fallguy
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    fallguy Senior Member

    Thank you PAR. I have never had an issue with the low blush formulations; it is good to be reminded.
     
  12. TeddyDiver
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    TeddyDiver Gollywobbler

    Depends also some of the working conditions as the viscosity of epoxies varies with temperature. I've used West with fast hardener and Ampreg 21 both at 19 to 20C temperature. While Ampreg wet outs better it has a draw back as without after curing (not possible untill later) it remains a bit "sticky" and is a pain to sand (mainly on the sides in some places where some fibers stick up) which is not an issue with West. So I use West doing smaller patches and Ampreg for larger areas to get most benefit of both. As PAR mentioned the type of fiber is more of an issue as thick multilayer fabrics are harder to wet. Best material to wet in my experience is Basalt fibers, much better than any glass fiber..

    BR Teddy
     
  13. Jim Allen
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    Jim Allen Junior Member

    There's not a comparison in fiberglass to basalt. I've been using basalt now for over a year and the benefits of it over fiberglass is insane. The strength isn't even close, weight is about the same, basalt isn't affected by elements, last much longer, I'm curious to see what others say. I'm actually looking into building my first hull out of basalt material. And may sound crazy but looking at using basalt rebar in between the basalt fabric therefore creating a hull that has no ribs. I'm building a small version of it now just to see how it will work
     
  14. TANSL
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    TANSL Senior Member

    Ribs may be necessary even if the basalt laminate is extraordinarily strong. The torsion, or shear stress, that the hull can experience could, in some cases, make the ribs necessary.
     

  15. Jim Allen
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    Jim Allen Junior Member

    That is true but my thinking was if I use the deck to reinforce the sides it might actually work..I'm gonna try it on a mini boat
     
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