SibLim update

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  • 07 Apr 2019 06:09
    Reply # 7263892 on 4315719

    I've just posted my latest update.  I've been laying the teak deck, which is very slow and not that photogenic, so it's only a short read.

  • 24 Mar 2019 19:27
    Reply # 7242232 on 7241825
    David wrote:

    I see the hinges on the forehatch on the forward side, but can't see the hinges on the galley hatch. I might have considered putting them on the aft side, so as to get a good down draught when you go to Fiji. Anyway, it's good to have both on the steeply angled part of the deck so that water won't lie on top of them.

    The hinges are inboard on the galley hatch, David.  It should be able to be open most of the time at anchor, even when it's raining, in this position.  I'll have the pram hood to scoop down air when I'm sailing to Fiji!
  • 24 Mar 2019 08:07
    Reply # 7241825 on 4315719

    Looking very good, Annie. If Noel isn't commenting on the joints, it must be because they're perfectly acceptable. No false modesty, please, young lady, it's all going very well, this is a boat to be proud of.

    I see the hinges on the forehatch on the forward side, but can't see the hinges on the galley hatch. I might have considered putting them on the aft side, so as to get a good down draught when you go to Fiji. Anyway, it's good to have both on the steeply angled part of the deck so that water won't lie on top of them.

  • 24 Mar 2019 05:53
    Reply # 7241798 on 4315719

    Looking really good! A hatch above one's bunk is the way to go. Being woken up by the first few drops of an incoming rain storm one of life's little pleasures. 

  • 24 Mar 2019 05:06
    Reply # 7241777 on 4315719

    I've finally managed to find the time to update my blog.  Starting to play with bits of teak now, which is fun!

  • 04 Mar 2019 20:41
    Reply # 7199048 on 4315719

    Annie: The second layer of ply makes for a good butt block!

    Exactly. That was all I meant, really. You were absolutely right to stagger those butt joins.

    Last modified: 04 Mar 2019 20:43 | Anonymous member
  • 04 Mar 2019 20:03
    Reply # 7198970 on 7197323
    David wrote:I could wish that you had built the deck in the way that I originally envisaged, with longitudinal deck beams and closely spaced stringers (Gougeon Brothers pp 260 - 262), not laminated deck beams, and with single layer ply, longitudinally orientated, on the planar side decks and double layer ply on the curved centre of the deck. You would have found it much quicker and easier to build, and just as strong. But it's all done now, and the final result will  be very serviceable.

    You decided against the extended "eyebrow" above the companionway, and that's fine, but it will still be good to incorporate some form of drip rail here, so that water doesn't migrate along the underside of the deck. Look at the underside of a windowsill on a house, and you will generally find one or two grooves, to disrupt that migration path.

    I did actually more or less follow the Gougeon Bros advice and they do use beams as well as stringers, ie a grid pattern.  The reason for the thickness of the material was to assist in attaching the deck liner.  The plans that you gave me - you may have revised the deck structure since designing the smaller Sib-Lim only gave me two large stringers.  This wouldn't have given me sufficient wood to fasten the plywood to, or for the panels to achieve the desired shape.  I added extra stringers, if you recall, but even so, I had to add another couple for the deck between the bilgeboard cases, because the plywood naturally created a hollow.  I also like that fact that the way my deck has turned out looks like one constant camber rather than two flats and a curve.

    Surprisingly, it was very difficult to bend the 6mm ply in the bilgeboard area - it was much easier to get it to sit nicely using the longer sheets, hence the extra, extra stringers mentioned above.

    I am probably going to finish both the forward and after ends of the deck as we did on Badger.  At the companionway there will be a small timber for the acrylic to rest against and I suspect that will make an effective drip rail  However, the water can only go as far as the little fore and aft bulkheads because of the deck beam. Don't know nuffink about houses and window sills, but I do know about leaky companionways!!

    By the way - the Gougeon Bros do not use butt blocks, they scarf on their dainty beams.  I felt quite happy to butt on my wider beams.  The second layer of ply makes for a good butt block!

  • 04 Mar 2019 17:41
    Reply # 7198717 on 4315719

    David Tyler. I'm sure your correct with your longitudinal construction of Deck Beams aand stringers. When we were building relatively high speed planning Launches in timber, if the longitudinal members of the hull (Chines, stringers, etc were let into the bulkheads, we had problems with broken stringers on occasions, when a Launch fell off a wave at speed. When we ran the longitudinal timbers of the hull over the top of the bulk heads, we did not experience these failures as the bulkheads could not create a hard spot to the same degree. Pretty much the essence of Cold Molded Multi Skin Construction. However, Annie's approach is the traditional method for plywood decks and boats I was involved with building 40 years ago using similar construction to Annie's's are still going strong. As with all things Boat, Timely Maintenance is the Key.   



      

  • 04 Mar 2019 08:33
    Reply # 7197323 on 4315719

    Building a multi-layer deck, and staggering the butts, is undoubtedly going to be much stronger, stiffer and longer lasting. There is an obvious design flaw in building a single layer deck with butts landing on a narrow bulkhead, and clearly the butts  on that scow should have had a wide butt block underneath them, whether or not they were landing on bulkheads.

    Annie, you've made a deck that will last a long time. The two layers of ply with staggered butts, + the longitudinal teak, will be strong and stiff. I could wish that you had built the deck in the way that I originally envisaged, with longitudinal deck beams and closely spaced stringers (Gougeon Brothers pp 260 - 262), not laminated deck beams, and with single layer ply, longitudinally orientated, on the planar side decks and double layer ply on the curved centre of the deck. You would have found it much quicker and easier to build, and just as strong. But it's all done now, and the final result will  be very serviceable.

    You decided against the extended "eyebrow" above the companionway, and that's fine, but it will still be good to incorporate some form of drip rail here, so that water doesn't migrate along the underside of the deck. Look at the underside of a windowsill on a house, and you will generally find one or two grooves, to disrupt that migration path.

    Last modified: 04 Mar 2019 10:50 | Anonymous member
  • 04 Mar 2019 05:00
    Reply # 7197194 on 7196944
    Annie wrote:
    Graeme wrote:

    I think you did absolutely the right thing, and I disagree with your remark that it was “hardly necessary” to cover the 6mm butts.

    By coincidence, just this afternoon Marcus and I were discussing the failure of the plywood deck on the old scow I built 50 years ago. (I did not make the deck, the next owner did it). It was a single skin deck, with butt joins landed on bulkheads. The bulkheads are actually 3.5 inches thick so no butt straps were used. 40 years later cracks appeared at all these joins – and later, rot set in. Bulkheads are hard spots of course, and I think the joins would have been better between the bulkheads, and done with plywood butt straps. To make matters worse, the deck was then just dressed with canvas and paint.

    I think we are, perhaps, at slight cross purposes here, Graeme.  What I meant was that I didn't believe that staggering the joints would make the deck stiffer or more stable. I don't think that in a reasonably flat (fore and aft) deck, the bulkheads should be creating  a hard spot.  I would have thought that is more of an issue in the curving surface of the hull.

    What you appear to be talking about is water ingress in the joints.  From my reasonably extensive experience and ownership of plywood boats, my conviction is that the difference between plywood boats that rot and plywood boats that don't, is epoxy, carefully and correctly applied.

    Still, 40 years is pretty good going!

    I think that a large part of the problems with Graeme's plywood joins over the bulkheads is that there would have been inadequate landing for each plywood sheet, There must be a formula somewhere which states how wide the butt strap should be for a given planking thickness. But as way of example the designed butt strap width for the 6mm thick plywood on my little catamaran is 120mm, so a landing of 10 times the width of the plywood. As the plywwod is worked and walked on with Graeme's scow, movement within the joint would result, which would lead to the cracking and degradation of the joint. I don't know that even the use of epoxy would have helped in this situation. 

    Having seen the deck that Annie is building I very much doubt there will be any degradation of the plywood joins for many years. In fact Annie you can probably give a genuine 'lifetime warranty' with your creation.

    Last modified: 04 Mar 2019 05:30 | Anonymous member
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