Alternative schedule to 1708 for a deck?

Discussion in 'Fiberglass and Composite Boat Building' started by leaky, Oct 15, 2019.

  1. leaky
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    leaky Senior Member

    I've got a ~ 16 X 9.5 foot deck of 3/4 Coosa I'd like to laminate and tab the topside of the deck on in one piece, maybe adding an extra layer of tabbing to the hull, but otherwise I'd like to run the lamination of the deck continuously up the sides of the hull in one shot. The resin will be VE. With 1708, which is kinda the no-brainer otherwise, and is the ballpark schedule I want (ie with a veil of 3/4 ounce mat over it), it will be really difficult to do with any respect for cosmetics on such a large area.. but on the topside I can't go very light on the glass either as that's an impact barrier for day to day wear & tear..

    What is a good alternative to 1708 here? Would alternating 2 layers of some sort of 8 ounce cloth/weave and 3/4 ounce mat be a sane way to do it? In that case I could nicely shuffle along the length of the deck, keeping the minimum schedule but without having giant overlaps from 1708 since the edges of the lighter cloth & mat could alternate.

    Some other details on the build here..

    There are 4 stringers creating spans of 28 inches or less, with some supports spanning the beam too. It's fiberglass 32 foot downeast..

    The plan is to lay down the deck in 3 sections - ie 3 pieces that are about 16 feet long and ~36 inches wide for instance. Initially two sections cut from 4X8 sheets will be laminated as one piece on the bottom, and lightly tabbed on the top, to make a continuous 16 X 3 foot sheet - then installed in the boat.. On an aside I'll round over the edges that will face the hull and steering bulkhead, and wrap them over with glass too..

    The plan is then to set the 3 long pieces down atop fiberglass angle that is bolted to the stringers, and when doing so use an adhesive atop the fiberglass angle (likely epoxy but have to make sure I can mitigate any problems when I go to laminate atop with VE, if some epoxy squirts up to the topside).. The idea of these details is essentially after the topside lamination the the deck then becomes one 16 X 9.5 foot sheet.

    Thanks in advance!

    Jon
     
  2. fallguy
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    fallguy Senior Member

    Relief the overlaps using an electric planer. Plane at 1/8" depth.

    You can buy a planer for like 50-100$ brand new.

    If you get/use 38" fabric, the reliefs will be on the edges of the panels...

    Not sure the entire edge plan, but if you relief all four sides of the panels; theoretically you can fair only the reliefs and still use 1708.

    you could also laminate the panels ahead of time and tape the seams...that way you could even vac bag the job; although they are gonna get kinda heavyish
     
  3. fallguy
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    fallguy Senior Member

    Basically, think sheet rock tape rebate.
     
  4. leaky
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    leaky Senior Member

    Thanks for that, its a way to do it, and I've resorted to the same basically when patching over a deck post fuel tank replacement - but really would like to avoid the 1708 here as unless I hit those reliefs just right (which I may in theory but won't in practice :) ) its gonna be ugly until filler and fairing on the deck, which Id really prefer to avoid...

    There's no schedule of lighter weave and mat that makes sense for this sort of thing?

    The killer with 1708 for me here is #1 its real hard to work in dry, so I gottta really jump through hoops to even span the deck with one piece (ie pre wet bottom and unfold as you go game).. #2 its the entire schedule I want in one shot so no way to avoid ugly overlap.

    Was thinking with alternating lighter cloth and mat I can both work big spans that are set down dry (because its thinner layers that go faster) and I never have that 34 ounce overlap. A 16 ounce overlap for instance I can tolerate and mostly smooth out anyway by sanding down the peak which is just veil anyway. No sense to it? I ask here because I just never hear of people doing it this way with VE or PE, maybe for good reason?
     
  5. fallguy
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    fallguy Senior Member

    An alternative to 1708 that wets out easier is two layers of 12 oz biax.

    You will still need to roll it off tubes as wetout is easier onto wetted surface. But you can try a tops down wetout only for the first layer.

    personally, I'd laminate the 3' sections with a reliefs under vac then tape them together by hand...if you have help; you could dry fit and build them the whole length

    or you can hand lay it all same way

    I am no fan of 1708 either, but it won't snake skin on you like the 12 oz biax and has its place for sure. If you prelaminate with 12 oz biax X2 layers; that would be super ez as panels that you join.

    to join; use 1208 tapes or 1708 tapes
     
  6. leaky
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    leaky Senior Member

    Thanks, would it be wrong to do the same with 12 ounce biax and 3/4 ounce mat for instance? Like does it have to be stitched together to be any good?

    I know for instance I could wet that weave by itself easier than with the mat on it and if I can alternate the layers using longer pieces of mat it helps cut down on the surface irregularity.
     
  7. fallguy
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    fallguy Senior Member

    I am unfamiliar with mat and VE and mostly use epoxies; test the glass plan first on your offcuts. The rebates will save you tons of fairing work and allow the panel laminations on a table.

    Others here might offer more ideas regarding the schedule.

    i would want to be sure the mat portion did not bunch or behave poorly and that the stitching of the biax didn't print through it.

    If you are asking about 1208; that seems wise, but I don't know if you need two layers of mat. A single layer of 1208, then 1200 would work. All 1208 will be pretty thirsty.
     
  8. leaky
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    leaky Senior Member

    Thanks again! I was wondering if you maybe only used epoxy because you kept recommending only stitched products without mentioning what was wrong with using the same products separately.

    By "biax" above I meant a straight weave with no mat. Basically if its sane Id really like to separate the mat from the weave and with VE its fully compatible with the dissolving binders so I don't need stitched products.

    I get the rebates idea I just dont see my work landing in the rebates so nicely and want to end up with something that ends up looking ok (for a basically commercial fishing boat) without use of fillers and fairing versus something that ends up looking perfectly molded after fairing.

    My hesitation to fillers is basically the ones compatible to the VE/PE system Im using will tend not to do well as far as cracking on a well used deck over time. Id want to glass them back over again with at least some mat, which I guess is an option but rather would do a smoother layup initially that suffices in cosmetics and avoid it.

    Print through is a total non issue since after 3 coats of gelcoat rolled on, with the last nonskid, anything like that is more than hidden away.

    Jon
     
  9. ondarvr
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    ondarvr Senior Member

    I’m going along with fallguy.

    Cut the wood to shape, cut the reliefs for the overlaps, glass the the wood before its installed, once in place glass the relief cuts to match the surrounding surface.

    You may need to lightly sand it, but no fairing on fillers will be required.

    The multiple coats of gel coat will hide any minor surface irregularities.
     
  10. leaky
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    leaky Senior Member

    Thanks again guys! Guess Im getting a little more sold on the reliefs as in the end there are only 2 running the hull length that Im obliged to hide, which are just tape really so may be able to hit that..

    But then Im still trying to layup/stage 16 foot panels so they are ok on top. I guess I could relief those too but is there no substitute for stitched-together products where I can use multiple layers of lighter mat and weave for good results?

    It would make the layup so much easier even during the staging if for instance I could run 3/4 mat across the panel, then 8 ounce weave, then mat again, then weave, then mat. Versus pre wetting while unfolding a long piece of 1708 and racing the curing resin.

    It would result in an extra layer of mat but Id eat it for the ease of effort, if its a sane way to do it?

    Just looking for a way to slow the layup down. In my working environment I can do about 3 yards of 1708 on a batch but that's my limit, but I cant get a veil on it wet and bubble rolled after reliably. 2 yards I can. But we are talking over 5 yards.

    Jon
     
  11. Sparky568
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    Sparky568 Junior Member

    Giving this a quick read it seems to me 3 X 16 single piece may be tough to handle. You mentioned cross beam supports. Any chance you can shorten the segments at the cross beams and do an additional rebate? I realize it's more work but you'll be able to manage the single layup on smaller segments much better.
     
  12. Rumars
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    Rumars Senior Member

    Leaky, 1708 is composed of two layers stiched togheter for convenience, one 17 oz./sq. yard +-45 biaxial and one 8 oz./sq.yard CSM (=3/4 oz./sq. ft CSM). That means you are laminating 25oz./sq.yard of material at once. You can reliably do 2 yards at a time, meaning 50oz at once. So instead of laminating it all at once buy and laminate each layer separatly. That way you can do aprox. 6 yards of CSM and 3 yards of biax at once. In reality it will be more since you don't have to work as hard.
     
  13. leaky
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    leaky Senior Member

    Thanks! The short anwer is it could but haven't quite worked it out between sub deck rigging, storage, and exhaust, and the hull doesn't require it.

    Possibly it ends up partitioned out at about 4 and 12 feet if I just added them logically where there are structures in the center now (ie if I carried structures connecting center stringers to outside stringers, to hull, up to deck level).
     
  14. leaky
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    leaky Senior Member

    Thanks! And yes that is what I was hoping to do basically, but was thinking of stepping down to lighter biax. I assumed there must be something wrong with the idea because nobody commented on it, maybe Im explaining it poorly?

    Honestly could skip the biax all together on top if I wanted, most of these hulls only use csm on the deck.. I just know even a thin continuous fiber is so much more rigid so I don't want to skip it.

    How about if I got a straight 12 ounce biax and sandwiched it between layers of csm? May do something like a 3/4 ounce under and a 1.5 over. That would really allow me to slow the process down.

    Edit - to add to that, its what I was getting at thinking maybe a couple layers of alternating 8 ounce cloth and 3/4 ounce csm.
     

  15. ondarvr
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    ondarvr Senior Member

    You can use a lighter Biax or cloth with a 3/4 oz CSM in each side of it.

    I wasn’t sure if you were relying on the 1708 as a structural component, or just a covering.
     
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