|
|
Posted for "N320GG" <n320g@hotmail.com>:
I am hoping someone on the group will be able to help Johnnes.
Gary
Johnnes,
I am impressed with your pressure cowl, it looks fantastic! I am also
impressed with your detective work, using the airspeed indicator! I am
sending a copy of this post to the LML, I am sure some of the great minds
there will provide us with some ideas. I will forward any ideas that I get
Gary Melton
LNC2 N320GG 600 hours
----- Original Message -----
From: Johannes Schredl
Hi Gary,
even for me it was partly not easy to understand! But itīs realy fun! It
shows the child in us (even in pilots! ;-)
We are still suffering under a long an cold winter: still about 32°F and
some snow. Spring time is requestet urgently to start flight season!
Here are some information about my "cooling problem" (high CHT) and what I
did in the meantime:
1. I made a pressure cowling:
Bevore
After
I made the pressure cowling out of carbon fibre sandwich using a 360°F
prepreg system (was a lot of work!)
Result: no siginficant change!!!! Beleve me: I was frustrated!
Positive: the weight of the pressure cap is about 0,4 lbs which is about the
weight of the removed silicone rubber! And: it looks like "high tech" (donīt
ask about the hours to make it)
2. I tryed to make more professional investigations by checking the pressure
situation above and beyond the cylinder head:
I run two thin tube form "above cylinder head" and "below cylinder head"
into the cockpit to a Airspeed Indicator to compare it with the aircraft air
speed during flight.
I expected: having a good pressure cowling, the "speed above cylinder head"
should be about the value of aircraft speed; the "speed below cylinder head"
sould be about zero (ideal below zero-> suction)
Result: "speed above cylinder head" is about 75% form indicated aircraft
speed which is pretty good i think!
But: "speed below cylinder head" is about 35% form indicated aircraft speed
which is much to high!!!!
Why is below the cowling a positive pressure but there should be a slight
suction?
My opinion: there is a perfect (and sufficient) pressure "above the cowling"
but very bad conditions (positive pressure) "below the cowling". Goal is it to
reduce this pressure...
3. My exlanation: there are turbulences under my cowling which prevent air
form escaping! I suspected my nose gear cut out to cause turbulences:
Now I modified the cowling and added a small door which closed the nose gear
cut out after retrection of the nose gear.
In a new flight I measured the pressure again "speed below the cowling"
Result: no significant change!!! (Frustration)
This is situation right now and I think about other sulutions to reduce
positive pressure below the cowling...
Any idea?
Johannes Schredl
D-ESWS
|
|