That may be overkill, if the 1/8 was almost strong enough. Assuming that
the wall is pretty thick, 1/4" would be 8X as strong and 16X as stiff,
if I'm not mistaken. I wonder if the problem is that the rod is not very
strong crosswise, so if there's a hint of a sharp edge, maybe it will
crunch. A steel tube might be a good compromise, though the yield
strength, unless you go pretty high tech, will be maybe half or less
that of music wire. Presumably the diameter would make up for that,
given the right wall thickness, etc. (I'm assuming you'd use a little
piece of 4130 or something from Aircraft Spruce)
I wonder if one glued short lengths of brass tubing over the carbon at
the appropriate places if that wouldn't help keep local loads from
messing it up. Especially if you ground the edges to a taper. Or maybe
that's just too much trouble.
The 1/4" carbon might weigh 7 grams or so if it was 4" long.. A 1/8"
steel rod would weigh about the same for the same length. The carbon
would be much stiffer, of course. And if you loaded it carefully, with
only smooth edges, a heck of a lot stronger. However, assuming a 24"
stab with 100 square inches or so, the 1/8" joiner on the tail would
stand up to an airspeed comparable to that of a 1/2" steel rod of the
same yield strength on the wing. However, music wire tends to have a
really high yield strength. (plus or minus a lot depending on design
details)
: <[EMAIL PROTECTED]> wrote: Ray, I have used 1/8 cf rod
for stab axles, and had them break. This was on my Yardbird design,
130". I went back to steel rather than try to go to a bigger tube. My
latest will use 1/4 cf tube for stab axles. Jack
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