What joint to use in bulkheads??

Discussion in 'Boatbuilding' started by CatBuilder, Jun 3, 2011.

  1. Nurb
    Joined: Jan 2011
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    Nurb Junior Member

    Yea, on a serious note, I've looked at some of your threads with interest. I thought you are building a one-off boat for yourself in limited space (a tent structure). And I thought you were building this with no other workers? I define a "boatyard" as a place where many boats are built by professional workers. If you've done it before and are doing it again you will have more forethought --- hindsight from the last job --- and planning in place than if you are building a one-off. Materials tested from previous jobs. Lots of different materials and tools on hand to test with. ETC. It is harder to build a one-off than do something you have done many times before. That's a fact of life.

    You sound like you need some encouragement right now, so keep your chin up. There is a lot to be learned from your threads. I respect that you are man enough to share your questions and how you worked past each problem.
  2. Landlubber
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    Landlubber Senior Member

    ...hey, thanks PAR for trying to lead a horse to drink.....I re read your comments and simply find them straightforward and very advisable (and honest)....maybe that is where you have gone "wrong"......sometimes the horse simply does not want to drink...

    ...oh well, you can only try...i feel your pain when doing this sometimes, you only comment to help people not to make the mistakes that we see sooooooo regularly, but they seem to have already made up their mind that they know what they are doing and only wish for comments that authorise their own ideas.

    ...you are very right that NO professional would use bog as a glue, simply put, that is why we have bog and glue, horses for courses.
  3. Nurb
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    Nurb Junior Member

    Agree with that. If a lot of money and time is at stake, there is no substitute for your own testing. With your own hands, Then you know.
    2. If you have the answer from the designer you trust, he is the one who engineered your whole boat.
    3. Opinions from the internet give a lot of different advice from people with a lot of different experience. You don't want to second guess every thing or try to build one boat four ways based on free advice. Advice from other professionals you are not even paying for their time on the internet is an opportunity. Was the question understood fully? Has there been a misunderstanding or miscommunication? Is there a better way to do it? Is it applicable? Worth reconsidering the current plan or taking a second look? Free advice is free advice, not gospel nor final judgment.
  4. Charly
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    Charly Senior Member

    What I am taking away from this thread is the fact that there is a big distinction between "filler" and "adhesive".

    I believe the original miscommunication between PAR and catbuilder revolves around this distinction, and how it relates to what gores into the "Payson butt joint". It seems Cat envisioned it as filler and Par envisions it as adhesive.

    As catbuilder has stated in other threads, one of his big concerns is the tendency of other fillers to absorb water. I believe this is why his emphasis is on those "bomdo like" elements of the "bog"...

    I sure hope you both stick around. Some of us "backyard builders" are sure benefitting from your exchanges:D

    Hey Cat. Sounds like it is time for another "bender" break. Then come on back and show us some more pics! And maybe, if you add a dose of chopped fibers to that peyson butt joint mix it will be just right. Is that about right PAR?
  5. AsterixDeGaul
    Joined: Mar 2011
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    AsterixDeGaul Junior Member

    Scarf... Take the time and do it right, that way you have nothing to regret later. Scarfing is easy enough and quite fast when using a jig. ie: router jig or even using a Gougeon skilsaw jig.
  6. sabahcat
    Joined: Dec 2008
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    sabahcat Senior Member

    and as such, what you are using for foam core is fine, more than as it only needs to be as strong as the foam.

    Timber core is stronger than foam, so a stronger filler is needed, again, it need only be as strong as the core so this is what I have used previously West System 411 (click) which is a filler, but also has some fibre
    (I make my own version )

    Plywood is stronger than foam and lightweight timber core, so a stronger adhesive again is needed (in my opinion) Previously, I would have used West System 403 (click) which is high density and a ***** to sand, so definitely no good for foam and even light timber but very good for ply.
    Again, I make my own version saving considerable dollars which I have tested
    Joints have never broken in the glue line
  7. PAR
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    PAR Yacht Designer/Builder

    I use three basic types of thickened epoxy mixtures: a structural fillet mix, which is also a very strong glue, a light structural fillet mix, which is a moderate glue, but fine on lightly loaded areas and a cosmetic fillet/fairing mixture which is mostly smooth particulates in suspension (balloons, spheres, etc.) and only intended to make a surface fair, no load carrying capacity.

    Again, My intent wasn't to piss of Catbuilder, but the list of "interesting dilemmas" as I worded it, that he's shared here about this build is extensive to those following the threads. A "back yard build" means a novice is at work, not that the project is necessarily in someone's back yard. I also think it goes without saying that "forethought and planning" typically aren't part of a back yard build. As for the rest of it, possably some was harsh, though not intended to be, so much as straight up and too the point, which is typical for me.

    I've made very few posts on this and the other Catbuilder threads, most having been covered by other and I'll add all watching with considerable anticipation of such a adventurous project. Major balls (meant in a good way) is the only good description I can surmise of Catbuilder, as he'd had to have them just to consider this, let alone get started. This places him in the 1% category as far as boat builders go, which is a pretty elite column to reside. The remaining 99% of people actually building a boat can only sit and watch as Catbuilder continues down the very lumpy path towards completion (it's always a lumpy path). Good luck Cat and don't let my poor choice of adjectives and prepositional phrases deprive everyone else of a unique and inspirational thread . . .
  8. masalai
    Joined: Oct 2007
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    masalai masalai

    The title of this thread is "What joint to use in bulkheads... Well what comes to mind nor is possibly a good portion of marijuana - the variety with plenty of THC - not the sort (Indian Hemp), used for making quality rope ... and have a loooong smoke break...
  9. waikikin
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    waikikin Senior Member

    C'mon Mas', anyone that knows about these things will tell you that if you use marijuana in your joints they always spliff.........:D
  10. PAR
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    PAR Yacht Designer/Builder

    I think a joint anywhere near a just completed bulkhead is a big waste of a perfectly good spliff. In the tiki hut with a beer in one hand and scantily clad teenagers dancing on the beach in front of you is a much more appropriate location for enjoying a fatty.
  11. troy2000
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    troy2000 Senior Member

    My job is designated 'safety sensitive' by the fed's because it involves high-pressure gas pipelines, compressors and the like; that makes me subject to random drug tests. I've never actually been tested, but I'm careful not to even walk downwind of someone with anything but a cigarette lit...
  12. CatBuilder

    CatBuilder Previous Member

    Well PAR, it's official.

    Not only do a number of well known designers (Kurt Hughes, Derek Kelsall, Chris Ostlind, etc...) agree with what I'm doing, but it would appear the Gougeon Brothers agree with me as well.

    Have a look:


    I'm using 406 (colloidal silica) with some 407 (microballoons) to make fillets for bulkheads and for that Payson joint. According to everyone (except you), this is the right way to do it. When necessary, I also add chopped fibers in for extra strength.
  13. Charly
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    Charly Senior Member

    Well I'm glad that's settled.:D

    Now how about some pictures:)
  14. PAR
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    PAR Yacht Designer/Builder

    I'm glad you're back Catbuilder. My impression of your bulkhead joints (which certainly may have been miss interpreted) was you had a high percentage of phenol balloons and some silica to stiffen the mixture.

    As an average, what are the percentages of balloons to silica in your "bog", because again and according to the filler selection chart you've linked, balloons are not used in bonding applications except in small quantities to ease sanding. The adhesive portion (assumed, as bulkhead joints would seem to require an adhesive) is the silica.

  15. Deering
    Joined: Feb 2005
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    Deering Senior Member

    Based on the color of the filler in some of the photos of the joints posted here, it looks like a pretty high percentage of microballoons. Anything I want to stick together - plywood joints, layers of glass, etc - I don't use any microballoons unless I intend to sand it. Wood flour, silica, or microfibers add strength, balloons don't. Maybe the designer feels that those applications don't need a lot of adhesion/strength so he's fine with balloons.
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