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Re: Europa-List: Jab cooling

Subject: Re: Europa-List: Jab cooling
From: D.Hetrick <gdh@isp.com>
Date: Mon, 1 Oct 2007 09:23:48
Hi John,
I want to add to Al Stills request of showing us how you made and 
installed the turbulators.  Sounds like an interesting approach to my 
cooling problems.  I did put an "eyebrow" on the left air intake but it 
didn't seem to make much difference.
Thank you.
Dale Hetrick
  ----- Original Message ----- 
  From: TELEDYNMCS@aol.com 
  To: europa-list@matronics.com 
  Sent: Monday, October 01, 2007 6:30 AM
  Subject: Europa-List: Jab cooling


  In a message dated 10/1/2007 2:58:40 AM Eastern Daylight Time, 
europa-list@matronics.com writes:
    Concerning the Jabiru, there is little room between the prop and the 

    front cylinders to provide a correct diffuser, so the inlet must be 
of 
    larger size, and the efficiency will be lower.
    But the engine can be adequately cooled all the same, at the price 
of a 
    little more drag, of course.

  Hi Gilles and all,

  I've had a chance to test my turbulators installed at the mouth of my 
left cooling intake and they worked exceedingly well. I've seen, on 
average, a 25F drop in CHT's on the left side now that I have turbulated 
the airflow entering the left side intake. One cylinder dropped 45F and 
went from being the second hottest of the six to the coolest. 
Interestingly, the engine is now running in the 240F-260F range on all 
CHT's, but the delta pressure did not change! This has left me with the 
impression that all this talk about 6" of water column being needed for 
adequate cooling is a bunch of bullshit put forth by the engine 
manufacturers to make you go away and be quiet.

  I still have 3" WC on the right at cruise and the hottest CHT is about 
250F. The coolest CHT on the right is 219F in cruise. I still have 5" of 
WC at cruise on the left side and the highest CHT is now about 260F, 
down from 295F on the hottest cylinder in cruise. The coolest on the 
left is now 235F, down from 275F prior to the turbulators.  All of my 
testing results indicate that pressure is the absence of flow, not a 
sign of flow. Internal cooling duct pressure, measured against static 
pressure inside the cowl, seems to be have an inverse relationship to 
flow, if indeed it has any relationship at all. My test results show 
pressure is meaningless and FLOW is what we're after.

  I think ultimately what I'm going to do here is dimple the area around 
my intake ducts like a golf ball. The zigzag tape is ugly and I can't 
think of a way to make it pretty, so I think dimples are the answer. 
Should make for quite a conversation piece, don't you think?

  Clearly, Andy Silvester used the Lancair cowls as a model for his 
Europa cowl set. I've studied close up pictures of the Lancair cowl to 
try and find out what the difference between the two really is. The only 
thing I notice is the Lancair inlets protrude about 1" farther in front 
of the cowl than mine do.,  I think this has something to do with the 
pressure wave I've observed in front of my left intake with my crude 
string tests. So Gilles, you are likley correct in your analysis.

  FWIW, every Sonex cooling suggestion I've tried has lead to hotter, 
not cooler temps. So, Jabiropaphiles, my suggestion is don't bother with 
anything Sonex has to say. 

  The moral of this story is: for better FLOW, excite the area just 
outside the hole. Almost pornographic, isn't it? (notice how I didn't 
say for better PRESSURE?)

  Now, I'm back to analysis of boundary flow on the wings.......

  Regards,

  John Lawton
  Whitwell, TN (TN89)
  N245E - Flying 


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