Thanks, Tony. Good information. I'm looking forward to trying your Dark
Star (or derivative) some day.
Take care,
--Bill
>From: tony estep <[EMAIL PROTECTED]>
>To: Bill Harris <[EMAIL PROTECTED]>
>CC: [EMAIL PROTECTED]
>Subject: Re: [RCSE] spars and wing joiners
>Date: Tue, 5 Jun 2001 07:09:18 -0700 (PDT)
>
>The stress in a spar concentrates at the upper surface (compression)
>and the lower surface (tension). You can spread it over two or more
>spars or have a single spar, but the determining factor is the
>cross-sectional area of the caps * the compression (or tension)
>strength of the material in the caps. For the formulas governing spar
>strength, see
>http://www.charlesriverrc.org/articles/allegro2m/spar_sizing.txt
>It turns out that the an excellent all-around deal is a single spar
>made out of solid balsa with the grain top to bottom, capped with
>carbon 1x thick on the bottom and 2x thick on top, where x is
>determined by spar height, width, and the desired load on the wing. The
>load in turn depends on span and how hard you zoom.
>
>The Dark Star web page
>http://www.mvsaclub.com/articles/dark_star2.htm
>shows the easiest way to make and install such a spar in a D-tube wing.
>
>
>--- Bill Harris <[EMAIL PROTECTED]> wrote:
> > I've been toying around with some ideas on spar/wing joiner design.
> > Let me
> > run a couple of ideas by you.
> >
> > Given: a built-up polyhedral wing, two piece, bolt-on to the fuse.
> > Spruce/CF/shear-web spar at 1/3 chord with a 5/16" steel wing rod at
> > the
> > spar. This is more or less the conventional wing construction.
> >
> > Here is a modification of this basic design: put in a lighter
> > "secondary
> > spar" at 2/3 chord and use two 1/4" wing rods at the primary and
> > secondary
> > spars. The wing would be stronger and the loads would be distributed
> >
> > between the two spars and the two wing rods.
> > Yep, I just got through refurbishing an Oly 99 and that how Renaud
> > did the
> > spars/joiners on the Oly.
> >
> > Second: What stresses are present in a wing, especially during the
> > critical
> > time of launch loadings? Looking at a straight dihedral wing, it
> > would seem
> > that the greatest stress is at the center at the wing joiner and
> > decreases
> > to the wing tips. I think that the stresses would be similar in a
> > polyhedral wing, I'm nor sure if there would be a stress
> > concentration at
> > the poly joint.
> >
> > Thanks,
> >
> > --Bill
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