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50283Re: Digest Number 5325

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  • Mark Albanese
    Aug 20, 2014
    • 0 Attachment

      Ah, then; may this help.

      http://www.wb-sails.fi/Portals/209338/news/SailPowerCalc/SailPowerCalc.htm

      Or Jim Michalak's background material.

      https://www.google.com/url?q=http://www.boatbuilding-links.de/Jim-Michalak/sail-math-and-thoughts-of.html&sa=U&ei=FSP1U5_UM-S7igKG14DYCw&ved=0CA0QFjAB&sig2=ZOZjOC87UKPSIFhde6Qmcw&usg=AFQjCNEr2q_ByP9xHUkr4YMmwAuYF2tfBA

      Mark
      "Don't just do something; stand there!"

      On Aug 20, 2014 12:51 PM, "G Cook songdog1760@... [boatdesign]" <boatdesign@yahoogroups.com> wrote:
       

      Thanks for the reply.

      I should have added that I stretched the foot of each sail 10% and the foresail gaff was lengthened the same. I have worked the combined CE and the relationship with CLR has not changed. Just in case my math is off there is a bowsprit that can carry a jib to cure too much weather helm. Both mast have rake adjustment built into their steps. We will have to see. I've been building a little over 2-1/2 yrs. I am ready to get on the water and try it out. She is a Bill Garden designed cat schooner. He passed away not too long after I bought the plans. I just forged ahead and built the boat.

      Thanks again,
      Glenn


      On Wednesday, August 20, 2014 2:22 PM, G Cook <songdog1760@...> wrote:


      Thanks for the reply.

      I should have added that I stretched the foot of each sail 10% and the foresail gaff was lengthened the same. I have worked the centers on the combined CE and the relationship with CLR did not change. Just in case my math is off there is a bowsprit that can carry a jib in case of too much weather helm. But that will have to wait until I've sailed and checked the balance. The rake of both masts has some adjustment built into the mast steps. We shall see. I have been working on the boat for a touch over 2-1/2 years. I am ready to get into the water and try it out! By the way, she is a Bill Garden designed cat schooner. He passed away about the time I bought the plans. I was unable to get his OK for the modification.

      Thanks again,
      Glenn


      On Monday, August 18, 2014 2:37 AM, "boatdesign@yahoogroups.com" <boatdesign@yahoogroups.com> wrote:


      There are 2 messages in this issue.

      Topics in this digest:

      1a. Re: mast diam.   
          From:  pvanderwaart
      1b. Re: mast diam.   
          From: Mark Albanese


      Messages
      ________________________________________________________________________
      1a. Re: mast diam.
          Posted by:  pvanderwaart@... pvanderwaart
          Date: Sun Aug 17, 2014 10:38 am ((PDT))

      The precise answer, which I think I don't know enough to work out, depends on the kind of wood, stability of the boat, and the standing rigging. I looked through a couple of my Bolger books. The closest example I could find was the Folding Schooner for which both main and mizzen are specified to be 3" in diameter. I suspect that had as much to do with available material as anything since it could be made from a couple of 2x4s glued together.  The FS rig is actually smaller than what you describe, and the boat is light and unballasted.Although the FS masts are solid, Bolger tended to design masts that are, basically, two board separated by spacers. Or to put it differently, masts based on a three layer lamination where the middle layer has a gap, leaving the the middle of the mast hollow. Again, I'm not sure that he was going for the virtues of a hollow mast so much as making efficient use of common materials.Peter



      Messages in this topic (3)
      ________________________________________________________________________
      1b. Re: mast diam.
          Posted by: "Mark Albanese" marka97203@... marka97203
          Date: Sun Aug 17, 2014 12:47 pm ((PDT))

      Glenn,

      Adding 10% to length doesn't add much to stability. You haven't said you
      added to the sail area.

      This suggests to me that increasing spar diameter will only add to weight
      aloft. No advantage in that.

      Mark
      On Aug 17, 2014 10:38 AM, "pvanderwaart@... [boatdesign]" <
      boatdesign@yahoogroups.com> wrote:

      >
      >
      > The precise answer, which I think I don't know enough to work out, depends
      > on the kind of wood, stability of the boat, and the standing rigging. I
      > looked through a couple of my Bolger books. The closest example I could
      > find was the Folding Schooner for which both main and mizzen are specified
      > to be 3" in diameter. I suspect that had as much to do with available
      > material as anything since it could be made from a couple of 2x4s glued
      > together.  The FS rig is actually smaller than what you describe, and the
      > boat is light and unballasted.Although the FS masts are solid, Bolger
      > tended to design masts that are, basically, two board separated by spacers.
      > Or to put it differently, masts based on a three layer lamination where the
      > middle layer has a gap, leaving the the middle of the mast hollow. Again,
      > I'm not sure that he was going for the virtues of a hollow mast so much as
      > making efficient use of common materials.Peter

      >




      Messages in this topic (3)





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