I posted new photos of the LED tail strobe, now with the circuit
completed, at
http://w1.lancair.net/pix/led-strobe

i also posted the schematic.

the particular component choices give a 1 second period and
50% duty cycle. tinker with values to get your favorite flash pattern

i used monolithic ceramic capacitors because they are small, but
they do have a bit of variattion of C with temp. might be
better to use something more stable. as the circuit warms it flashes
faster.

The circuit works quite well, but after some soul-searching I have
tenatively decided NOT to put the system on the LNC 360.

reasons:
-its heavy...235 grams. Installing the strobe will require more than 3
times its mass added to the rudder counterweight. perhaps a kilogram
total. all this at the maximum rearward moment arm. yuck.

-it gets quite warm. after a minute or two the temp is maybe 40C at
the
base of the LEDs and thats with a fan pushing air past at about 10
MPH. in still air it overheats. if i forget to turn it off on
landing,
I could possibly slag my rudder.

-the system satisfys the FAA Regs, but with no margin...I prefer a
safety factor 2.

-its a complicated system. lots of machining. tight fits. odd angles.
no finesse.

it just doesnt seem like a bulletproof system to me, so i may just
chalk
this one up to experience and develop plan B.

Plan B: get a bunch of 5 mm diameter superbright white leds and
mill the hemispherical ends off the plastic cases. this will give
them a
lambertian pattern. no need to polish the ends, might even sandblast
them
to make the pattern even broader.

glue these into holes drilled in the curved trailing
edge of the lancair wingtip. i will need many more of these LEDS than
with
luxeons, but that will help distribute the thermal dissipation.

the weight might actually be lower this way than with luxeons since
the
aluminum heat sink will no longer be needed. and the weight will be
near the center of lift, and will not require a counterweight.

or maybe i will come up with plan C...

-Jeff