Couple Questions on Glassing and Bogging

Discussion in 'Boatbuilding' started by CatBuilder, Feb 22, 2011.

  1. CatBuilder

    CatBuilder Previous Member

    Would you believe it??

    It's already a couple days away from laying my first inner glass! :cool:

    I am working in 1/3 hull units to make it easy to reach everything. Starting with the bilge, then topsides, then deck.

    I'm done foaming the bilge 1/3 and also have bogged 1/2 of that in.

    Two questions:

    1) When laying up Corecell on a batten mold/form, you end up with some gaps between the sheets. You are supposed to use a bog of microballoons to fill them up and make for a very fair surface for glassing.

    How crucial is it to have the bog go all the way through to the other side of my 1" (2.54cm) foam? It goes all the way in some areas, most of the way in other areas and just shy of 1/2 way in different areas. Of course, where the foam is a perfect fit, there is no bog at all because it can't get in between the sheets.

    What is the bog's purpose? Just to even out the surface for glassing? OR... will it be holding my hull together while I'm moving it around before the outer glass goes on?

    2) Anyone have any last tips for me about glassing before I begin?? :eek:

    I'm glassing the from bow to stern, doing the bilge radius area.

    I'll be working by myself, mixing epoxy and doing a hand layup along the length of the boat - 45ft (17m). One sheet of 34oz triaxial, special low viscosity laminating resin.

    Anything I need to remember before I start that?
  2. rberrey
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    rberrey Senior Member

    Looks like were not going to learn much tonight Cat. I think I read somewhere not to fill the cracks between the foam all the way, may have had to do with the other side. rick
  3. rberrey
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    rberrey Senior Member

    I did,nt post that just right, you finish filling the gaps when you bog the other side.rick
  4. CatBuilder

    CatBuilder Previous Member

    Ok, thanks Rick.

    That's the best answer I have so far. It seemed like it would be no problem to fill them in the rest of the way when I did the outside of the hull, but I wanted to make sure I wasn't going to have the hull fall apart when I went to lift it out with partially filled gaps.

  5. Herman
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    Herman Senior Member

    Fill the rest when you turned the hull, do not worry about it. The bog will prevent stres cracking during the boats life, but during construction it does not really serve a purpose.

    As I told you by PM, take some time to organise your laminating. Precut the glass, as this saves a lot of dragging high weight rolls around. Also make sure you have the mixing and measuring of the resin sorted. Either pre-weigh batches of resin, ready for mixing, or figure out something else which you feel comfortable with.
  6. CatBuilder

    CatBuilder Previous Member

    Thank you, Herman. Your input is greatly appreciated.

    I am taking an afternoon to do some practice lamination. I have some Corecell that I burned on one side that I have cut into two pieces and thermoformed.

    I have bogged the pieces together (like the real hull) and will lay up the 34oz triax on it tomorrow.

    I noticed when testing for using a bog syntactic layer or not (another thread) that I had quite a few areas without resin between the large strands of the triax.

    I am going to lay this triax up with the 45/45 against the foam instead of the 0deg against the foam to prevent this from happening again. I will need more bog outside, but it is better, IMO than possible strips of neverbond between fiber bundles.

    I will heed your advice to organize, organize, organize. I am laminating one large piece of a full roll of glass in this case, so no cutting (maybe 10-20cm) is all that is needed. I will dry- fit the glass in place, then cut anything required off, roll it up and save it for later use somewhere.

    I need to recalculate the weight of all the layup so I can have the appropriate amount of resin on hand and put into the layup.

    After this, it will feel like I really have a boat, not just a boat shed. :)
  7. CatBuilder

    CatBuilder Previous Member


    I am getting ready to apply the 34oz triaxial to the foamed and bogged hull.

    I am thinking a couple moves ahead, which is always good to do...

    I plan to apply the triaxial with the +/-45deg side against the Corecell, leaving the very thick 0 deg side up. My reasoning is that during some test laminations I did (both with bog and without), I ended up with incomplete bonding between the very large strands of 0 deg fibers.

    So... if I put the +/-45 down against the foam and have those large strands facing out, I will most certainly need to bog those up.

    My question is.... how?

    Do I try to bog them while I'm doing the layup? The layup is 1 layer of 34oz triax, from bow to stern, full roll width in the bilge curve. It's also my first big layup. I'm thinking I'll never be able to bog and do this layup at the same time.

    How then, do I bog it later? I have to sand before bogging, but I can't sand down into the spaces between the large weave of the glass, so how does the bog stick? Won't the unsanded area (the majority of the area) between each fiber hold onto the fairing bog?

    Ideas? Help?

    I'm kind of lost on this point.
  8. rberrey
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    rberrey Senior Member

    With wet on wet it,s my understanding you can put another layer on the next day without sanding , depending on temps. If this true then you can bog the next day without sanding.You might get someone to chime in on time frame of wet on wet. Glass into the night get a few hours sleep and bog. rick
  9. CatBuilder

    CatBuilder Previous Member

    Oh yeah!

    Somewhere I remember reading the System Three SilverTip I'm using on the hull lamination had like a 36 hour time where you can still achieve a primary chemical bond.

    There are so many things to keep track of when building, some of these details seem to seep out of my brain.

    Thanks for the reminder.
  10. AndrewK
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    AndrewK Senior Member

    Gluing of foam planks. Are you trying to force the bog into the gap after the foam has been screwed down? You should be buttering the edge first before you push it in place and scraping of the excess from either side. It will not take long to work out exactly the right amount of bog required and then you will have no wastage.

    You do want full bond lines for your type of construction, but do not lose sleep over what you have done so far.
    The reason why you want full glue lines is that this helps during the half hull turning while you only have the inner laminate.

    When you first release the half hulls from the mold and lift them out with the lifting gear say attached to the rear beam and mast beam bulkheads the inner laminate will be under tension so all good. But as you roll the hull over the over hangs of each hull will put the inner laminate into compression, and because at this stage you do not have the outer laminate its the foam surface that will be in tension. Any partially filled bond line is a potential folding point.
  11. CatBuilder

    CatBuilder Previous Member

    Foam planks:

    Yes, I'm thermoforming the foam into place, then using a cake decorating bag to force the bog into the gap like a caulking gun would. It is working, I just haven't been loading them up so bog is all spilling out the other side. I thought it was best not to have it all spilling out the other side... ? Some are fairly full, others are kind of short on bog.

    If this is an issue, I can always fill those bog lines in from the outside of the hull using the same technique, but squirted in from the outside. Next time, I'll be sure to fill the gaps better for safety upon turning hulls.


    About bulkheads: I would like to install the real bulkheads in the hulls straight away to help support the hull halves.

    My bulkheads will be 12mm Okoume for speed of construction and cost purposes. Very little weight difference between those and the full composite laminate ones with foam. I was surprised when I did the math. Maybe 200lbs or so for the entire boat's bulkheads.

    What is the best way to get these all in place on each half hull, have them line up properly upon meeting and to join the bulkhead halves to be strong and secure?

    Any tips on how to do this best so that everything comes out right?
  12. gonzo
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    gonzo Senior Member

    I don't mean to insult you, but many of these questions should be answered by the building plans. Are you designing as you go, or did you buy a design?
  13. CatBuilder

    CatBuilder Previous Member

    No insult taken. When it comes to building a boat hull, I'm here to learn... I'm starting from zero knowledge, but getting up to speed finally.

    I have a design. It's a Kurt Hughes catamaran.

    Which questions are supposed to be spelled out in the design, specifically? It would be good for me to know that, so I can organize a bit more.

    If you are talking about the bulkheads, the design is available in foam/glass or in epoxy/wood construction. I had a failed epoxy/wood build where my hull split on fold up (like Charly had problems with, but he fixed). I opted to get the foam/glass plans and start over. I cleared some crossovers from the foam/glass and epoxy/wood build with Kurt. Specifically, I cleared 12mm Okoume bulkheads, both standard and main strength ones that span the boat, holding the hulls together. I will also likely build the cross beam aft and forward beam out of wood/epoxy, but haven't fully decided yet. I was going to keep the wood/epoxy stuff inside the boat (which is foam/glass) since it is well protected in there. I will epoxy coat all the bulkheads to keep them from absorbing moisture.

    So which things were supposed to be in the design that I'm asking? I better get that straightened out right away since I'm getting pretty far in now.
  14. AndrewK
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    AndrewK Senior Member

    Gluing; no you dont want excess glue spilling out the other side, you always want to minimize the glue & bog you get on the foam. The reason is that even when you highly load the bog with microspheres it is still harder than the foam. So when you sand it to get rid of gloss you can easily create hollows in the neighbouring foam. For this reason keep your glue lines just that, lines. Only fair areas that require it, small dents and screw holes fill just before a glassing job so its wet on wet.
    The glue lines should be full, thermoform your piece first then remove and butter up the edge with bog with a paint scraper and form it into a small ridge. Then fit and push into place and scrape excess off, there should be very little.

    Bulkheads; fitting and aligning is easy, after you have planked and glassed the entire half hull screw battens along the two top edges of the stations. Then measure and mark the bulkhead positions on both sides. Also put reference marks on to the battens and stations so that when these are taken off to make the next hull they can be returned to the same position later to save all the re measuring.
    Because the stations are level and square place a 4x2 across the top of the mold aligned with the b/h position marks, drop the b/h in, check that its vertical with a spirit level or your laser and clamp into position against the 4x2.

    Re joining the connecting beams / bulkheads; in foam its easy as they are simple tape joins.
    For plywood talk this through with Kurt but I dont see any reason why it would not be the same. After all your plywood is in 8' x 4' sheets so you will have scarf joins, all you need to do is to make one of these joins along the hull side.

  15. CatBuilder

    CatBuilder Previous Member

    Nice strategy on aligning the bulkheads. Thanks!

    Great info.
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