X-Mozilla-Keys:                                                                                 

Paul wrote:

This is more what Mike had in mind. He wanted to use
channel instead of a 1/2 inch plate for the back bulkhead.
I prefer 1/2 plate with a large hole as it is stable   
in shear. The channel system relies on the bolts
to stabilize the bulkhead in shear resulting in somewhat
higher stress in the bolt hole area.

ingenuir@ix.netcom.com wrote:

Mike, my FEMAP pre/post processor and ME/NASTRAN finite element
analysis programs mesh (pun intended) nicely with drawings from my
ACAD 14. When you want to get specific about thicknesses and lines of
action, my company offers a preliminary analysis special for $200
that, while limited, should warn you against serious problems and
check stresses and deflections for several load cases.

My main concerns are:

1) Weights, strengths, and stiffnesses of welded truss structures are
hard to beat.

2) I think you need shear bracing on the sides for gravity loads and
torque.

3) It's hard to lock bolts against continuous vibration.

4) Transfering reactions to the firewall hard points still should use
a truss structure.

5) Peak stresses result from several simultaneous flight load
components, i.e. wrap-up turns or pullouts with engine torque and prop
gyro forces.

Gary Moir
GAMA Ingenuirity
ingenuir@ix.netcom.com

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