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Re: [bolger] More Mast Alternatives

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  • hwal@aol.com
    In a message dated 8/2/2000 8:33:08 AM Eastern Daylight Time, marka@online-pro.com writes:
    Message 1 of 6 , Aug 2, 2000
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      In a message dated 8/2/2000 8:33:08 AM Eastern Daylight Time,
      marka@... writes:

      << Looking at Sam Rabl's old 'Boatbuilding in Your Own Back
      Yard' got me thinking that, in the same way plywood is
      partly an alternative to scarce, great timber for planking, it
      might again do the same for hollow, wooden masts. >>

      I have a borrowed copy of this same book - and remember seeing the section on
      plywood masts - and at the time I wondered if this was for real! It hardly
      seems like it would strong enough. Wow - what a great idea - if it works. I
      mean - if it's in a book it has to work right? Steve Anderson ( the notorious
      MJ Landroval)
    • Jim Goeckermann
      Regarding mast alternatives, thought the source eludes me, I recall seeing an aluminum tube reinforced by a wooden X that was driven down the center. If you
      Message 2 of 6 , Aug 2, 2000
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        Regarding mast alternatives, thought the source eludes me, I recall seeing
        an aluminum tube reinforced by a wooden "X" that was driven down the
        center. If you have access to aluminum tubuing this sure merits
        considering. Anyone else recall where on the net this was detailed?
        Jim
      • Mark Albanese
        Sam Rabl was very esteemed, a Bolger of his day. The plywood spars in his book all have shrouds, hence the plug to help one stand alone. Not even an amateur
        Message 3 of 6 , Aug 2, 2000
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          Sam Rabl was very esteemed, a Bolger of his day. The plywood
          spars in his book all have shrouds, hence the plug to help
          one stand alone.

          Not even an amateur scientist, I can only ask:
          Isn't plywood strong enough to replace a plank twice its
          thickness? Isn't there more strength in the size and shape
          of a section than in the mass of material involved?

          Wood inserts for aluminum tubes are seen in Stevensen designs.

          Mark

          hwal@... wrote:
          >
          > In a message dated 8/2/2000 8:33:08 AM Eastern Daylight Time,
          > marka@... writes:

          > I have a borrowed copy of this same book - and remember seeing the section on
          > plywood masts - and at the time I wondered if this was for real! It hardly
          > seems like it would strong enough. Wow - what a great idea - if it works. I
          > mean - if it's in a book it has to work right? Steve Anderson ( the notorious


          Jim Goeckermann wrote:
          >
          > Regarding mast alternatives, thought the source eludes me, I recall seeing
          > an aluminum tube reinforced by a wooden "X" that was driven down the
          > center. If you have access to aluminum tubuing this sure merits
          > considering. Anyone else recall where on the net this was detailed?

          >
          >
          >
          > Bolger rules!!!
          > - no cursing
          > - stay on topic
          > - use punctuation
          > - add your comments at the TOP and SIGN your posts
          > - add some content: send "thanks!" and "ditto!" posts off-list.
        • Lincoln Ross
          ... snip ... Not unless you mean across the grain of the original plank. With the grain the plank is stronger. Wood is much weaker across the grain. If you
          Message 4 of 6 , Aug 2, 2000
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            --- In bolger@egroups.com, Mark Albanese <marka@o...> wrote:
            snip
            >
            > Not even an amateur scientist, I can only ask:
            > Isn't plywood strong enough to replace a plank twice its
            > thickness?
            Not unless you mean across the grain of the original plank. With the
            grain the plank is stronger. Wood is much weaker across the grain. If
            you need strength in both directions at once, plywood is better. If
            you are making a mast, I think you would end up with a lot more
            weight
            with plywood than with regular planks. Also, the thickness, position,
            and grain direction of each layer matters a lot.

            Isn't there more strength in the size and shape
            > of a section than in the mass of material involved?
            >
            That's not very precise, but I'd give it a yes, sort of, unless the
            load is pure tension. That's why you don't see hollow stays.
            snip
          • Mark Albanese
            Or then, there s the stitch-n-glue spar: Cut thin plywood staves on given taper. Fix to four sides of plug. Pull together full length. Putty and tape to round
            Message 5 of 6 , Aug 2, 2000
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              Or then, there's the stitch-n-glue spar:

              Cut thin plywood staves on given taper. Fix to four sides of
              plug. Pull together full length. Putty and tape to round the
              corners. Plug at the top.

              Mark
            • Mark Albanese
              Had a look through some old How To Build 20 Boats . In with the mix between runabouts with fins and Sea Scout cruisers by William Garden and other serious
              Message 6 of 6 , Aug 4, 2000
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                Had a look through some old 'How To Build 20 Boats'. In with
                the mix between runabouts with fins and Sea Scout cruisers
                by William Garden and other serious boats there are lots of
                drawings re: rectangular box spars.
                I actually didn't find more than one plywood mast. Which
                makes me think these might really be more of a Sam Rabl
                innovation than I thought.

                The examples in the 3 mags mostly specified the purest Sitka
                Spruce, and none was free standing. I noticed that, while
                they had various fillers here and there, none had a big
                solid plug at the bottom. That's further confirmation to me
                that for a freestanding wooden mast, a substantial solid
                plug is very important.

                There was one boat showing another way to have a plywood
                mast. This was 'Guppy', cuter than a Swan shaped pedal
                boat. a 5' x 32" children's sailboat. Meticulously laid out,
                deep keel, washboards, paddle and all come from one sheet
                each 3/4 and 1/4 inch plywood. The rig is is the four sided
                sprit, something under 16 sq. ft.

                A pair of blanks for the 5' x 2 1/2" mast come from one
                edge of the 3/4" sheet. Glued together and tapered
                for'n'aft, it isn't kidding for this little boat.

                Keep safe,

                Mark
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