Based on the recent discussion of drilling aileron counterweights, this task
was approached with some misgivings. After priming, the weights were drilled
initially with 8 each 1/4 inch holes (to within 1/8 inch of the opposite
side), bringing the angle to about 20 degrees. Each 1/4 inch hole lightened
the weight by about 11 grams. 16 holes, 8 per weight, changed the angle
about 16 degrees.
Drilling in lead was more difficult than anticipated because the swarf stuck
in the flutes of the drill. Used a variable speed electric drill at slowest
speed. Dipping the bit in water periodically helped (oil would be preferred
but could cause a problem with paint adherence) but seemed to cause chatter
while drilling. Apparently heat from drilling warms the lead enough to cause
it to stick to the sides of the hole as it comes up the drill flutes.
Lubricating the flutes with graphite using a pencil helped. Ultimately,
putting a few grains of graphite lubricant (the type used on the self
aligning pitch cross tube bearings) into each hole after getting 2/3 through
solved the chatter problem.
Each coat of finish paint caused the angle to improve by about 3 degrees,
leaving a need for considerable further adjustment on completion of painting.
The 1/4 inch holes were bored out to 11/32. Due to poor planning, the holes
were not perfectly spaced so at this point some holes were nearly touching.
The 3 holes in each weight with the most space around them were bored to
13/32, however breakthroughs to adjacent holes occurred.
Further lightening required the Dremel and was very slow to remove material
compared to drilling. Adjacent holes which had broken through were further
opened such that a large hole about 2cm square resulted in each weight in
addition to several drilled holes not connected.
I tried to save the swarf produced during lightening and did capture most of
it although 5% to 10 % escaped. Total collected was 443 grams or about one
pound per aileron. Unfortunately, I had not recorded the weight of the lead
pieces prior to installation. If anyone has loose weights I would appreciate
knowing their weight prior to drilling.
Given the effort required to remove the lead from the weight, I wonder if it
might not be easier and faster to do it the other way around. That is, by
making the form of foam, then drilling 1/4 inch holes and inserting pieces of
lead rod or lead shot? Alternatively, perhaps shortening the foam which
holds the weight a bit would help - it seems like the 45 degree initial angle
called for in the instructions could be reduced to good effect.
John A044
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