REFLECTOR: Suprise in my duct

[Scott Derrick]

Today one of my projects as to open up the left hand duct so I could 
prepare the oil line for my secondary oil cooler/cabin heater 
installation. 

This under the back seat oil cooler will be connected so its gets the 
oil first, the nose cooler is second in line, have two 100 CFM fans, 
with an air diverter to provide recirculated cabin heat or dump the air 
overboard for additional engine oil cooling in the summer.

I cut a 12 inch piece of the duct off and started to pull wires out of 
the way and noticed some really weird looking stuff that completely 
filled the cavitys between the oil lines, vacume line, throttle/mixture 
cables, etc.  It looked like burnt wood chips or something? 

It turned out to be rust particles from the throttle/mixture cables. 
water/moisture had entered the duct and sat in the low spot and attacked 
the steel wraps on the cables.  The outer wrap was completely gone and 
it was working on the inner wrap.  The cables operation showed no 
symptoms of an impending failure. The rust area was about 18 inches 
long. I ended up opening up more of the duct  so I could get all that 
corrosion crap out of there.  The cables are of course junk.

I had heard of people talking about drain holes in the ducts and though 
yeah, that would be nice....

It would be more than nice, it should be mandatory!  If you don't have 
them you should make it a priority!

Any suggestions on how to make the drain holes? 
I thought of drilling a 1/4"  hole, than flox in a thin straw through 
the hole, then cut off the straw when cured?  Any better method?

Scott