Re: [bolger] Re: Spar making
An excellent analysis -- useful to me in future projects, I think.
Doug Pollard wrote:
> Wanna say a little more about spar making. I would say that spar
> size is more a matter of how you think than any size a designer can
> decide on. A rig designer has to make his decision based on the idea
> that we very unprofesional boat builders will use a piece of wood that
> is not perfect and maybe even worse than that. Normally you figure that
> something has to carry a certain load then you double or even tripple it
> to allow for all the things you can't calculate. A step ladder for example.
> So the builder decides and he makes that decision at the lumber
> yard. If he can find a perfect piece of very light strong wood he can
> make the spar smaller than called for. If the wood selected is mediocre
> the spar needs to be what the designer calls for. If you pick a louzy
> piece of wood you better make the spar plenty heafty and in which case
> you will wind up with a heavy rig that may even be weaker than the
> designer intended.
> The guy who designs things from wood faces a really difficult
> problem where strength of material is concerned. He likely has a table
> that gives the strength of a piece of wood of a certain kind . The
> problem is the figure on that table is only for the piece of wood
> tested. Or maybe an average of a bunch of differencet pieces.
> The test for a mast has traditinally been to set the ends on a
> sawhorse and stand in the middle if it doesnt break it's good,but then
> that depends on how big the mast is. If your mast is for a 14ft boat
> you will likely break then all.
> If you're not going to put much thought into buying wood I would
> say make it as strong as called for because very little thought and
> little understanding of wood is what the designer was counting on.