Thoughts about air scoops.

[Ed Miller]

Having run my fair share of YS 4 strokes all I can say is place one on a test bench, run it for awhile and touch the case in the rear bearing area while it is running. The only one that was ever hot to the touch that I've run was a SC. An ill fitting/installed rear bearing will generate excessive heat. I've tried this with a ST2300 and found the case barely above ambient temperature. I think what is happening with the YS is being it is a supercharged engine, at full throttle it requires a substantial supply of intake air. The scoop(s) in the engine bay area supply additional air that the engine needs to produce full power. Look at the nose of our planes and where the intake is on a YS. I believe cooling is a good thing up to a point, just feel the power increases seen are largely due to the increased supply of air for the engine to ingest then cooling. Ever run one of the "air filters" on the YS and notice a power decrease ??
Ed M. 
  ----- Original Message ----- 
  From: Thomas C. Weedon 
  To: discussion at nsrca.org 
  Sent: Wednesday, February 05, 2003 5:06 PM
  Subject: RE: Thoughts about air scoops.


  I had a mid-air this last summer that slightly damaged the nose of my plane. Eric H. suggested that when I repair the nose, I should add an air scoop just above the rear bearing of my YS-120FZ. He said that it would help cool the rear bearings and would improve my top RPM. Guess what? He's right! My engine had a little more power. The rev's increased about 100 to 150 RPM on the ground and I noticed an improvement in the verticals. So, now I'm finishing a new fuse and I'm adding another air scoop over the rear of my YS-140FZ. I think it will help.
  Tom Weedon
    -----Original Message-----
    From: discussion-request at nsrca.org [mailto:discussion-request at nsrca.org]On Behalf Of Adam Quennoz
    Sent: Tuesday, February 04, 2003 8:34 PM
    To: Pattern List
    Subject: Thoughts about air scoops.



    It seems the trend these days are air scoops.  Before a scoop is effective, the area of the air exit must equal or exceed that of the air intake thus allowing a positve air flow to occur.  With all the scoops people are putting on the nose of the aircraft, there must be a pretty good sized hole somewhere for the air to escape.  There are cheek scoops, chin scoops and now with the concern of cooling the crank cases, there are scoops above the engine compartment.  I call them "nose scoops".  

    Has anyone thought of making EXITS on the top of the nose above the engine, and/or exits on the cheeks?  Basically put the scoops on backwards.  The air flowing over the backward facing scoop would actually create lower pressure inside the engine compartment allowing a larger volume of air to enter the chin scoop.  The air entering the chin scoop can flow all around the engine as it makes way to the exits of the engine compartment, and what's left can flow down the pipe tunnel.  

    I'd like to hear what others have to say about this idea.  I'm thinking of trying it on my pattern plane.

    Regards,
    Adam Quennoz
    AMA 383866
    IMAC 2439
    NSRCA 3546

-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.f3a.us/pipermail/nsrca-discussion/attachments/20030205/949dd71e/attachment.html