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Re: [bolger] Re: Whalewatcher double bottom construction

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  • philbolger@comcast.net
    I don t think I understand how you do the Payson-Joint without doing the Payson-Joint ? Many of Phil s smaller to midsize plywood-based designs are based
    Message 1 of 16 , Aug 18, 2012
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      I don't think I understand how you do the 'Payson-Joint' without doing the 'Payson-Joint' ?

      Many of Phil's smaller to midsize plywood-based designs are based on multiples of standard sheet-size in either 4 or 8-foot 'rhythm.  
      Traditional 12:1 scarfing loses that much per sheet-length, throwing the economies off in both materials and man-power.  On a 1/2 sheet you are losing 6" per sheet by turning those into saw-dust.  Ergo our preference for the up-dated (power-planer-based) 'Payson Joint' in which you always get 32-feet panel-length after you joined four 8-foot lengths.

      Susanne Altenburger, PB&F
      ----- Original Message -----
      From: Eric
      Sent: Friday, August 17, 2012 11:50 PM
      Subject: [bolger] Re: Whalewatcher double bottom construction

       

      My project was big enough that a gear pump would have been a good investment, except I changed epoxy companies and epoxy mixes which would have made the gear pump useless to me. A boat builder friend uses a scale effectively and that is used for the three different types of epoxies he uses. I didn't often have to do large batches of epoxy. Not having a gear pump nor scale, my method for doing big jobs was to buy paper cups of two different colors. One color for resin. One for hardener. (No thinking during the epoxy spreading rush.) I then pre measured all the epoxy I needed into the cups. When laminating my masts I had a helper mix the epoxy for me (along with a measured amount of thickener) so I could just spread. All the helper had to do was dump a hardener cup into a resin cup and mix it. The mixed epoxy was poured into a larger spreader cup into which the correct amount of thickener had been measured, and that was mixed to the proper consistency. I then traded empty spreader cup for full cup until the mast joints were coated. Then my helpers helped me get a few ties on the mast to hold it together until I could tighten hose clamps and spanish windlasses around the mast to clamp it together.

      I scarf plywood together in the same manner Susan describes plus scrap wood "clamps" top and bottom of the scarf. (Plastic keeps the scrap wood clamps from becoming part of the scarf.) I have a power planer and belt sander to cut the scarfs with. They do not have to be anything like perfect. I find this to be no more trouble to do than a neatly done Payson joint. On the finished piece the joint cannot be seen after filling and sanding any imperfections in the joint.

      Eric

      --- In bolger@yahoogroups.com, <philbolger@...> wrote:
      >
      > ...then, once you have your strong-back set up to carry the accumulating loads you get to lift the full-length 1/2-thick panel up and then over the sequence of frames and molds. You'll enjoy how that half-thick bottom drapes in a smooth non-dishing arc. You cat will 'play house' underneath in no time...
      >
      > Then use the pre-cut ply-pieces for the second layer to just bed them in epoxy in a 50% overlap pattern on the 'master-layer', shooting temporary dry-wall screws as you march the transverse-oriented ply-piece by piece along her length. To not have any risk of 'hard points' where the second layer just butts up against each other, you'll shoot a higher density of screws in a double-row to pull the edged smooth with each other.
      >
      > 6-8 hrs after you shot all these screws, you better get up at whatever indecent hour and get on with reversing that process. If you wait 12+ hours, each screw may balk at you, making you wish you'd done that job sleep-walking. If you do it in time, you get to walk all over that full-thickness bottom without sticky soles as you just pull them out in your driver's high-gear. Pulling them is always faster that shooting them.
      >
      > Then with thickened epoxy you'll march over it against spackling each hole with a drop. Otherwise glassing the bottom may see some of the screw-holes drool the precious stuff below. Remember that you should use hardened dry-wall screws for reliable driving in and out. And those only come in sizes 1" and longer. We found the most reliable hold with coarse-thread 1 1/4" screws for the 1" bottom lamination. Ergo holes going right through. Furthermore, any frozen drip on your bulk-heads below will have to be ground off.
      >
      > We found that without a go-fast (mega-cost) gear-pump we would have been in serious trouble producing a smooth lamination on bottom and our double-layer topsides. Ditto for the glassing of the bottom several times in one long session each. As a minimum you have to have an automatically-metering pump to have a second person do mostly the pumping and mixing. You'll consume a lot of the stuff running that 6'6 x 30' surface-length. Our gear-pump cost less than any serious challenge during that lamination-process in material, epoxy and man-hours would have cost. That pump is treated with great respect with the intent of having it last 'forever'...
      >
      > There's always more to talk about. Those two gantries came in handy many times, handy well beyond lifting and turning over the completed full-size bottom structure. Bolted together you can take them apart and pass them along, or just stow them in a modest bundle of pieces.
      >
      > Susanne Altenburger, PB&F
      >
      > ----- Original Message -----
      > From: philbolger@...
      > To: bolger@yahoogroups.com
      > Sent: Thursday, August 16, 2012 1:51 PM
      > Subject: Re: [bolger] Whalewatcher double bottom construction
      >
      >
      >
      >
      > Good question.
      > But first. Measure again. WHALEWATCHER is closer to 6'6" wide on her bottom.
      >
      > On her hull-assembly, I've just been through this last summer on the SACPAS-3 project with a Vee-nose Sharpie hull measuring 34'x7' net.
      >
      > I used the Payson-Joint option to assemble the first 1/2" layer of the double-layer bottom flat on the shop-floor. See MAIB Vol.29 #3 July 2011 pp.46-48 for the sequence. It requires bracing the whole assembly with temporary 2"x4" on edge to allow lifting and turning over of the floppy piece without breaking the half-joints. Then complete the joint's other side. Then lift that assembly to 90-degrees on edge and brace the piece securely in that position. We used two home-made 2x-type gantries and trailer-winches for all that large-panel handling.
      >
      > Check out MAIB Vol. 29 #6, p.42-43 for one way of doing your hull. And whenever you do build the strong-back, do not assume the floor is true...
      >
      > I could go on for hours...
      >
      > Susanne Altenburger, PB&F
      >
      > ----- Original Message -----
      > From: thewildernessvoice
      > To: bolger@yahoogroups.com
      > Sent: Thursday, August 16, 2012 2:07 AM
      > Subject: [bolger] Whalewatcher double bottom construction
      >
      >
      >
      > I have never tackled a project as big as whalewatcher before, it is almost 30'long. The bottom is doubled plywood, I am looking for ideas of support for the bottom and also a strategy for epoxy joining all the sheets. If you recommend a book i likely have it. It is 6' wide, so likely to save plywood will sue a 2ft wide strip and a 4 ft wide strip to save plywood, of course staggering the joints. I may be just over thinking this, in that I simply bevel the plywood and tape with epoxy. Going longitudinal with the plywood would allow me to use full sheets but of course with 2 ft waste and eliminate alot of taping. Then for the second layer, just epoxy and drive some screws to hold it together while it dries.
      > Anyway, experience is a wonderful teacher and so for those of you who have faced this challenge and have experience, there may be something I can learn or maybe fear has caused me to over think this?
      > -Jim
      >

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