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Re: [bolger] Re: Chebacco help...

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  • derbyrm
    Yeah, I did all that, then cut a pattern for the inner stem from scrap plywood. It still ended up as a SWAG/eyeball/file-to-fit item. Looks fine. As you say,
    Message 1 of 3 , Apr 20, 2007
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      Yeah, I did all that, then cut a pattern for the inner stem from scrap plywood. It still ended up as a SWAG/eyeball/file-to-fit item. Looks fine.

      As you say, those bevel angles aren't measured in any plane that's obvious to a wood butcher.


      ----- Original Message -----
      From: Jamie Orr
      To: bolger@yahoogroups.com
      Sent: Friday, April 20, 2007 12:21 AM
      Subject: [bolger] Re: Chebacco help...


      I missed the original post, so I hope I'm answering the right
      question. I'm also not at home so I don't have my plans handy, but I
      seem to recall doing a lot of measuring with a scale rule. This may
      have been where I drew a vertical line near the plan, along with
      horizontal lines every six inches (starting from a place I could find
      on the plywood, like where the top of the side plank lands on the
      stem). Then I measured along each horizontal line from my drawn line
      to the stem. This gave me a series of points that I could draw full
      size then run a line through that was the same shape as the stem.

      I'm going from memory, but the method will work. Draw and measure as
      carefully as you can but remember you can fine tune once you have the
      stem in hand. To get the angles you can extend them on the drawing,
      then borrow your kid's school protractor and measure them. Remember
      that the angle you get is in the horizontal plane, and
      not "perpendicular" to the point on the stem you are measuring. Does
      that make sense?

      As you can guess, my plans had a lot of pencil marks on them before I
      finished, but it all worked out in the end.

      Jamie Orr

      --- In bolger@yahoogroups.com, "derbyrm" <derbyrm@...> wrote:
      > As to the stems, forget it. Make a pattern that's close for the
      inner stem, cut a bevel that's way wider aft, and secure it to the
      building jig. Then as the strakes get close, pare it down so they
      lie pretty flat. The beauty of wood flour filled epoxy is that you
      don't have to be perfect. Once the strakes are on, pare the stem to
      a nice curve and build up "deadwood" so you have a little more than
      needed for the outer stem. Drop vertically (up since the hull's
      upside down) from the bow top for a ways, then make a smooth curve to
      the keel. When building up the deadwood I used biscuit joints to
      keep the epoxy-buttered chunks from sliding away. A few drywall
      screws augmented the clamps. After the epoxy's hardened for a few
      days, pare the lower portion of the outer stem towards the desired
      pointyness (3/4" ?). Leave the upper portion square.
      > What I'm saying is that lofting on paper and then transferring to
      wood isn't worth it for a small boat unless it's a racing "class"
      that has to meet specifications. I used a cheap laser level clamped
      to the keel as a reference and various 3', 4', and 8' "yard sticks"
      to find the desired points in space. Loft it in 3D, full size, on
      the building form. The pieces fit the available lumps of wood.
      Between high school and college I had three years of drafting
      classes. The stem would have been a great final exam question.
      > On http://home.insightbb.com/~derbyrm/Dayawl.html drop down to
      August of last year and earlier and you'll see my scheme for securing
      the inner stem to the building jig. A 2x4 screwed to what I call
      bulkhead "A" positioned a chunk of chipboard which was epoxy'd to the
      inner stem. After the lower strakes are secured to the stem, the
      chipboard & 2x4 are removed (chisels, gouges, sanders and battery
      driven circular saw). Remember that this is the inside of the anchor
      storage space and a fancy finish is not required. I've filleted the
      strakes to the inner stem with thickened epoxy to add strength. Jack
      Aubrey could deal with sprung butts, but I don't want to.
      > I found the CB trunk pretty straightforward, but there is one
      gotcha (or gotme). The external shape is different for the "Cruising
      Conversion" as opposed to the day sailer. For the Cruising
      Conversion the top should parallel the waterline. It makes a
      footrest for those sitting on the head and/or tending the cookstove.
      For the daysailer, the top slopes down aft.
      > You have the shape of the CB itself, right? The inside of the
      trunk is an inch or so bigger. Swing radii about the location of the
      pivot until you get to vertical, then drop down to the external edge
      (bottom of the keel).
      > Send me your e-mail address and I'll send some images of my
      loftings of the parts. (but I didn't use the drawings much when
      > Roger
      > derbyrm@...
      > http://home.insightbb.com/~derbyrm
      > ----- Original Message -----
      > From: boylesboats
      > To: Bolger@yahoogroups.com
      > Sent: Wednesday, April 18, 2007 1:40 AM
      > Subject: [bolger] Chebacco help...
      > I swear that I could not get any accurate answer(s) for lofting
      > inner and outer stems of Chebacco..
      > Another question is, centerboard trunk.. Does anybody figure out
      > pattern?
      > Everything else is fine...
      > [Non-text portions of this message have been removed]

      [Non-text portions of this message have been removed]
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