Alternative schedule to 1708 for a deck?

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

  1. fallguy
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    fallguy Senior Member

    Use 1208.

    12 oz biax with 3/4 mat...

    Easier wetout; waterproof.

    glass each coosa panel separate and then use the 1208 offcuts to tape it all up

    a bit of fairing in the reliefs and done
     
  2. leaky
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    leaky Senior Member

    Thanks! My thinking is if I can make something more rigid and stronger for about the same weight then its a better way to go. I don't like stacking up csm rather once I consider over 1.5 ounces of csm Id rather put something more structural in there.
     
  3. leaky
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    leaky Senior Member

    Thanks! But what is the difference between that and running them separately? It would be much easier I think to use separate layers of the two, would let me slow down and wet them out in place.
     
  4. fallguy
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    fallguy Senior Member

    you can try that, but even 12 oz biax works best with a wetted out surface

    the best way is to roll out resin say 30% of the weight of the glass with a pvc tube roller or paint roller; then roll the glass out onto reference lines off a 3" tube

    the only thing about 1200 is it can be a bit snaky which is great for compound work, but less great for flat work

    if you are gonna roll resin on the bottom and roll the glass off a tube; not sure why you'd want an extra layer to do...

    if you try to do the whole job alone and in a single go; it will be tough

    I did a two layer lamination alone with some compound curves and I had to pour it a littl resin heavy cuz it started to kick.

    This was two layers of 12oz biax and 60" of glass at the wide part and 20' long. doing it alone was a bear running both sides of the table. You won't have the compounding, but it is similar..
    E9B2852D-CBF6-43CF-BF22-CAD575F55BFD.jpeg
     
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  5. Rumars
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    Rumars Senior Member

    Well I'll admit it took me a while to understand what you are talking about. If I'm right you are planing to use Coosa like plywood, put it over the deckbeams glued or screwed then cover the outside with fiberglass. No glassing on the underside other than tabbing to hull and deckbeams, and some tape over the joints.
    You basicly have two scenarios here:
    1. Coosa has the needed structural properties for using it as decking material. In that case any fiberglass on top is strictly for abrasion and CSM only is plenty. No need for overlaps either, just butt it and sand anything that sticks out flush before gelcoating.
    2. Coosa does not have the structural properties and needs fiberglassing both sides. In wich case using Coosa for the whole deck is unnecessary expense, use regular PVC foam for the core with some high density inserts (like Coosa or G10) under any mounting points.

    It really comes down if you believe Coosa's claim about not needed to be glassed on the underside when used in decks. I would want to know from them what the maximum unsuported panel size is for a given thickness in order to arrange deckbeams and stringers acordingly.

    What are we talking about here anyway, replacing a glassed plywood deck or a new construction?
     
  6. leaky
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    leaky Senior Member

    Idea #1 I call "half glassed" :) and it's something I really despise in a fiberglass boat of any value; my feeling is glass on the top dictates glass on the bottom, no matter what the core is made from. Maybe Coosa really is so impervious to water it's a non consideration (I don't buy that either :) ) but if you skip the glass on the underside you are giving up a whole lot of strength and rigidity, actually the glass on the underside ends up loaded as much if not more than the glass on top is how I understand it...

    Additionally I never really like the idea of the core "hanging" on the sides where it meets the hull (which is the effect if you do not have a flange of some sort actually on the hull on the outside and you just glass it over on top, very commonly seen). So I will run the glass right around the outside corners of the panels where they meet the hull during the staging process - then the tabbing on top will basically be holding the top and bottom edge of the coosa to the hull.

    It's new construction, the consideration for avoiding the hassle of overlaps on the bottom is almost nil (other than it will make the interface between the supports underneath the decking and the support I will glue the decking down to a bit bumpy, but any adhesive can take up a 1/20th inch that a layer of 1708 amounts to).. So on the bottom maybe I will glass it just like the top, excepting I will leave the veil out (who cares if weave prints through on the bottom), or maybe I will just use a layer of 1708 done with shorter pieces overlapped.

    Jon
     
  7. Rumars
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    Rumars Senior Member

    If it's a new construction the designer should be the most qualified to help you.

    Now if I would be faced with the problem I would give infusion a chance. Place the foam over temporary deckbeams (to get the chamber) then tab the foam to the hull on the inside, that effectively creates a flange for the foam to sit on and seals the joint. Now infuse the whole outside deck at once. Put overlaps into a rebate in the foam. Make the rebate just a hair deeper then your overlaps and after infusion build up with CSM by hand then sand flush. On the inside remove the temporary deckbeams and sand the tabbing. Now you can infuse the whole deck overhead (you need to use some adhesive spray to tack the glass in place) including the permanent deckbeams if you want.
    Or laminate by hand in sections between the temporary deckbeams if that seems simpler to you.
    Do you have the means (space, lifting) to do the whole deck off the boat on a jig then put it in place as one unit? That way you avoid laminating overhead and just have to do some tabbing on the inside and outside, but the tabbing would be on the hull not the deck.
     
  8. leaky
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    leaky Senior Member

    Just to make sure no more confusion, by deck I mean cockpit sole.

    Its a 32 downeast, pilot house , keeled boat, semi displacement, very flat in stern, only 2 feet or less sub deck. Gunnels and pilot house do not allow a one piece deck install.

    So deck goes on "blind" in 3 to 6 long pieces normally, which is why I will be setting the 3 long panels atop angle fiberglass angle bolted to stringers and then bonding the deck to it.. I could also bolt the deck down counter sunk where Im going to tab over, but have had mixed results with bolt heads hiding under fiberglass.

    The owner of the mold in this instance uses wood framing usually to hold the deck up, mechanically fastened to stringers, plywood mechanically fastened to framing, then fiberglasses over the top of the deck...

    Other finishers do it all different ways. These are 40 year old designs by royal lowell intended originally as fast commercial lobster boats but are used and finished for every purpose under the sun. Basically just saying there is no standard way.

    What I did was I brought the stringers up about 5 inches just a bit under deck level (which are 1 inch coosa glassed over) to alleviate the need for framing. By bolting angle fiberglass to the stringers it both provides a way to make precision alignment in deck pitch/level as well as a demolition plan if the deck ever has to come up that only destroys the deck and the angle fiberglass.

    Attached picture I have in my phone here was not intended to show the whole cockpit area but gives a general idea I hope of the setup.

    20190622_170851.jpg

    Thanks for your help!

    Jon
     
  9. Rumars
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    Rumars Senior Member

    Ok. Now I understand. Make the fiberglass angle with a wide flange to act as a butblock and and join the panels on it. The panels I presume are already glassed on the underside. The curved hullside I presume also gets it's own fiberglass angle laminated in place to act as a shelf.
    How do you plan to have the joints, fore and aft or awarthships or both?
    A simple way would be to make rebates, glass the panels on the bench on both sides then glue them to the angle and join them with tape on the upper side. If you feather the rebate sides a little and use CSM as the last layer you can sand that nicely flush.
    I would use a T profile "angle iron" (or two L's back to back), do a dry run for fit, then a layer of biax tape in resin on top of the T and drop and screw the panels down. Then remove screws and glass the top.
     
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  10. fallguy
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    fallguy Senior Member

    We have some corelite panels and I am glassing them for added stiffness and abrasion resistance.

    They are a little more flexible than same thickness ply, so kinda nice to glass them a bit.
     
  11. leaky
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    leaky Senior Member

    Thanks again!

    Yes I will pre-glass the bottom and topside on the panels and then install them - originally I was thinking I'd do the bottom first then the top in the boat but you guys convinced me otherwise. The fiberglass angle, I have some madeup but went a little overboard on the schedule so may not use them except if I have a reason for something that strong someplace.. Was thinking the interface under the edges of the deck would be about 4 inches wide.

    On the steering bulkhead, there will be a mechanically fastened fiberglass angle (ie bolted through the steering bulkhead) - so the two outside panels will sit on that on the ends, no brainer.. I'll run a fillet and glass on the topside.. On the center just aft of the engine, I owe a brace that connects the stringers together to the structure - I will similarly bolt a piece of angle fiberglass to that.

    At the stern and sides of the hull, my plan is when I'm making the panels up, likely before I glass the faces, I will round the edges that face the hull off (ie using a mini router then hand sanding to make it fairly perfect), then I will wrap the edges in a similar schedule as the top/bottom. Once the panels are set down I'll round a fillet using about a 1.5 inch tube, to spread the structure across a wider flange where it meets the hull and to make it a tight fit that is easy to run glass over, then I'll just tab it in on the topside - since the edges will be wrapped I think it will be a fairly well done tab there as essentially it will be holding the top and bottom of the encapsulated Coosa..

    As far as the tabbing holding the deck to the hull, both on the deck and hull itself, sides, fore, and aft - I just don't care about having the raised area from the tabbing showing there. I'll attach it all with 2 layers of 1708 and a veil of csm, if there is anything really ugly I'll grind it down. My only cosmetic concern is I just don't want tabbing showing across the middle of the deck.

    Jon
     
  12. Rumars
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    Rumars Senior Member

    Sounds like a plan. Good luck.
     
  13. leaky
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    leaky Senior Member

    I feel like coosa, even the glass reinforced 26 lb stuff ive got, is the same way. Plywood is strong stuff.
     
  14. fallguy
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    fallguy Senior Member

    I'd love a picture of the whole boat.
     

  15. leaky
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    leaky Senior Member

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