What Order is Best? Fairing/Glassing/Hull Construction

Discussion in 'Boatbuilding' started by CatBuilder, Apr 2, 2011.

  1. CatBuilder

    CatBuilder Previous Member

    My second hull half is coming along well and is going to be ready to pair with the first half I built in just a short time. This leads to a logistics question:

    How do people usually go about the construction/fairing/finishing process? What order do you go in?

    In a bit, I'll have a complete catamaran hull (port side) with bulkheads installed and the interior glassed, sitting in a mold.

    What next?

    Do I?...

    a) None of the below. ;)

    b) Bog/Fair the foam on a single side of the hull exterior and glass that, then take it out and lay it down low and do the other side?

    c) Take the hull out without glassing and lay it on some low foam bits or blocks to hold it while I bog/fair the foam and glass one side, then flip it over on the same supports to do the other side?

    d) Take the hull out and leave the bare-foam hull sitting around, then build the starboard hull... fairing, bogging and glassing them both at the same time in parallel?



    Bonus round:

    When do I prime/paint/seal?
     
  2. waikikin
    Joined: Jan 2006
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    waikikin Senior Member

    Catbuilder, finish the glass sandwich(outer skin) to the first half hull asap , use your peelply to minimize sanding & damage to fibers in prep for final fair & paint---- I think? thats what you mean in point b? The
     
  3. michael pierzga
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    michael pierzga Senior Member

    Hmm..... completly finishing the hull sounds correct. I never worked with a catamaran. Is the hull now upside down ? Post a picture of the hull on its mold.
     
  4. cthippo
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    cthippo Senior Member

    Hull is out of the mold, or, half of it is anyway.

    [​IMG]

    Not that I would claim to have any great insight on this, but depending on how long you think it will take to build the other half I think you should glass them both together at the same time. On other words, D, protecting the foam.
     
  5. rberrey
    Joined: Oct 2010
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    rberrey Senior Member

    Cat, I dont know either, but you should be able to do a quicker build on the second half, so i would tend to agree with cthippo. My fear is if I build one ama first and the second after the main hull I will have one ama lighter and looking better than the other, my boat might limp and be ugly on one side. I think if you fair and prime the whole hull at once you will have both sides looking and finshed the same. rick
     
  6. hoytedow
    Joined: Sep 2009
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    hoytedow Wood Butcher

    Retracted first bad advice. Don't glass a half-hull. Glass 1 complete hull at a time, but glass the first complete hull before starting the second.
     
  7. michael pierzga
    Joined: Dec 2008
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    michael pierzga Senior Member

    Again... I dont know, I have never worked with a cat. .

    One thing is clear...your present partially skinned hull in pliable. Joining two pliable hulls together must be easier than joining two rigid hulls of slightly different shape.

    How do you join two hulls together ??
     
  8. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    Fairing one side of the hull, then doing something else, just to come back and setup for fairing the opposite side seems not the best utilization of time and materials. Build the other side of this hull, you're setup for this now, then marry the hull halves, so you can setup for the next phase of the project on this hull, which is smoothing and fairing in prep for the external skin.

    Smoothing and fairing before then skin goes on can save you a whole lot of touch up and fairing after you've skinned it. I always try to do things in stages, so if you're setup for laying foam in molds, they lay foam until you're done. Then move to the next stage. Going back and forth would drive me nuts and is wasteful of time, setup and materials.
     
  9. CatBuilder

    CatBuilder Previous Member

    PAR, thanks. This is what I was thinking with choice "D" from the list.

    Make the hulls, then glass them both at the same time, in parallel, after I throw out the mold. My thought, as well, was that doing similar things all at once saves time because you don't have to retool. Mass production.

    Many, many people on this thread don't understand my build process. I'm sorry it's not clear to you. I will try to make it clear now. Please take another look at my original post after seeing these pictures:

    First, just as Cthippo says, I have half a hull out of the mold right now. I have already reversed the mold (to create its sister) and am about 1/3 of the way done foaming the sister. So, the shop looks like this picture, with another 1/3 of a sister half in the mold.

    [​IMG]

    So, the next big event is bringing that first half hull I completed over and putting it on top of the one in the mold I am working on now. This will produce a hull (NOT HALF HULL) with all bulkheads installed and the entire interior finished - glassed. I was very consistent calling things "hull" or "half hull" in my original post, but many didn't follow that. So, I will have a complete catamaran hull (the port hull) that will just need to have the exterior foam faired and bogged, then glassed. This hull will be sitting in the mold at the next big moment in the build. It looks like this, and has no fiberglass on the outside of the hull - just bare foam that needs bogging and fairing:

    [​IMG]

    NOW... we are at the point of my questions. I'll paste them in here again so that it all makes sense and you don't have to scroll back up. Hopefully, this is less confusing now to those who didn't understand the build process:

    Do I?...

    a) None of the below.

    b) Bog/Fair the foam on a single side of the hull exterior and glass that, then take it out and lay it down low and do the other side?

    c) Take the hull out without glassing and lay it on some low foam bits or blocks to hold it while I bog/fair the foam and glass one side, then flip it over on the same supports to do the other side?

    d) Take the hull out and leave the bare-foam hull sitting around, then build the starboard hull... fairing, bogging and glassing both completely hulls at the same, time in parallel?



    Bonus round:

    When do I prime/paint/seal?
     
  10. rberrey
    Joined: Oct 2010
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    rberrey Senior Member

    Cat will you have a finish glass over the trix? rick
     
  11. CatBuilder

    CatBuilder Previous Member

    No, I won't. Keeping weight to a minimum. I'll be putting a layer of bog on as the final piece of layup. It is pressed *very* firmly on and makes a kind of "zebra stripe" effect.

    What the bog is doing is filling in the weave of the heavy triax that still exists even if you use peel ply. So, where there is a strand of 0deg triax, you see a clear spot. Where there is a pit between the strands of zero deg triax, you see dark brown. It provides a smooth surface.

    So, the steps I have to take to finish the outside of the hulls is to:

    1) Fill in any gaps and dings in the foam with bog.
    2) Sand the bog and foam as fair as I can get it.
    3) Glass the hulls
    4) Squish in that very thin, weave-filling bog layer
    5) Final fairing, priming and painting.
     
  12. p_smith
    Joined: May 2010
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    p_smith Junior Member

    keep up the good work cat!

    my vote is this, bog and fair the uppper hull half once it is joined to the lower, then glass as much of the exterior that you possibly can while the hull is in the mold.

    At that point pull the hull, reverse the molds and lay the hull back into the molds temporarily while you finish glassing the exterior.

    I am still very concerned about introducing waves and distortions into the hull and this is your best chance to avoid them.

    After that, just pull the entire hull, set it aside, leave the finish bogging until both hullls are complete and you can do them both together.
     
  13. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    Complete the one hull sufficiently so it can tolerate sitting outside for a while. Don't leave the foam exposed too long. If it was me, I'd make the one hull, then move it out, so you can make another. The second will go easier, as you'd learned all the lessons on the first.
     
  14. CatBuilder

    CatBuilder Previous Member

    No hulls will be outside. They will come off the mold and directly into final position - port hull will go to the left in the pictures, up against the wall. Starboard hull will come off the mold to the right in the picture, going into place against that wall.

    Nothing will ever go outside in this build.
     

  15. Brian2009
    Joined: Jan 2011
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    Brian2009 Junior Member

    CatBuilder - how long do you plan to wait before you put the thin layer of bog onto/into the voids in the triax weave? When the glass/epoxy is hard but not yet cured so you get a chemical bond? Or later, but you can't sand within the weave, so a mechanical bond would be challenging?

    Do you think you could combine the above step with a portion of the final fairing step (material buildup, not sanding) at the same time - i.e. put on a slightly thicker layer of bog where you know you will need it? (To reduce an intermediate stage of sanding)

    Also, I enjoy reading your posts and following the project - keep up the good work! It's very educational for those of us who are also involved in a build.
     
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