At 02:57 AM 7/3/2004, you wrote: >The shear load is not affected. It is always the total weight that is >being carried by the spar. Increasing the spacing between the spar caps >does not affect the shear. > >I Sometimes I see the neutral axis far away from the forces and thus the >plane where loads are least - then again, logic (mine) suggests that >loads must be the highest opposite forces along the NA.
This is not correct. The neutral axis is very near the center of the spar and it is the best place to put holes. >Where we need a 2 to 3" hole through the spar in the web surfaces (for >control runs etc.) is it better to avoid the centre of the web? I am >tempted to fit a filler block (extra pillar) between the ply webs in the >area of the hole, but worry about creating a stress break (riser?). > >Pending a better solution, my intention is to place a reinforcing ring >of the same ply around the hole - maybe change the grain direction. A reinforcing ring is an excellent idea. I used them in the few places that I had to pierce the shear web. You should feather the edge (make it thinner) at the outer edges of the ring. This will prevent creating what is called a stress riser. Don Reid - donreid "at" erols.com Bumpass, Va Visit my web sites at: AeroFoil, a 2-D Airfoil Design And Analysis Computer Program: http://www.eaa231.org/AeroFoil/index.htm KR2XL construction: http://users.erols.com/donreid/kr_page.htm Aviation Surplus: http://users.erols.com/donreid/Airparts.htm EAA Chapter 231: http://eaa231.org Ultralights: http://usua250.org VA EAA State Fly-in: http://vaeaa.org
