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09-06-2012, 03:13 AM
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Join Date: Jan 2009
Location: Verona, Italy
Posts: 59
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Circular air vents for engine cowling
Hi guys, can anyone tell me if the circular vents for the engine cowling (watch the pic) are an optional that should be selected when you purchase the kit, or is it a change that can be done after?
Thanks, regards.
Ettore
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Ettore ”Hector“ Bellini
B737NG Senior First Officer
RV-8 planned, to become real sooner or later.
Verona, northern Italy.
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09-06-2012, 03:21 AM
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Join Date: Jan 2005
Location: SC
Posts: 12,887
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Brian has a Sam James cowl and cooling plenum. Search the forum for "james cowl" then Google it.
When you order your FwF kit delete the Van's cowl. There is very little cost difference between the two cowls.
One word of caution, they are a good bit more work than the stock setup.
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Bill R.
RV-9 (Yes, it's a dragon tail)
O-360 w/ dual P-mags
Build the plane you want, not the plane others want you to build!
SC86 - Easley, SC
www.repucci.com/bill/baf.html
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09-06-2012, 04:56 AM
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Join Date: Jan 2009
Location: Verona, Italy
Posts: 59
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Quote:
Originally Posted by N941WR
Brian has a Sam James cowl and cooling plenum. Search the forum for "james cowl" then Google it.
When you order your FwF kit delete the Van's cowl. There is very little cost difference between the two cowls.
One word of caution, they are a good bit more work than the stock setup.
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Thanks Bill!
__________________
Ettore ”Hector“ Bellini
B737NG Senior First Officer
RV-8 planned, to become real sooner or later.
Verona, northern Italy.
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09-06-2012, 06:59 AM
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Join Date: Oct 2005
Location: 08A
Posts: 9,500
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Quote:
Originally Posted by Ettore
Hi guys, can anyone tell me if the circular vents for the engine cowling (watch the pic) are an optional that should be selected when you purchase the kit, or is it a change that can be done after?
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You can buy a cowl or modify the stock cowl. It's just fiberglass.
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Dan Horton
RV-8 SS
Barrett IO-390
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09-06-2012, 07:23 AM
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Join Date: Dec 2007
Location: Flagstaff, AZ
Posts: 2,653
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Dan is not wrong but he's making light of what is actually a big task. The SJ inlets are aluminum; you would have to fabricate your own. Also, Sam has spent a lot of time developing his design and the associated plenum; it was not without difficulties to get to the current end result. Obviously it can be done or we wouldn't have the innovations we see in the third-party market. But it's not 'just fiberglass'; done wrong, you can cook an engine or worse.
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Patrick Kelley - Flagstaff, AZ
RV-6A N156PK - Flying too much to paint
RV-10 14MX(reserved) - Fuselage on gear
http://www.mykitlog.com/flion/
EAA Technical Counselor #5357
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09-06-2012, 08:46 AM
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Join Date: Mar 2005
Location: Elkhart, Indiana
Posts: 1,186
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Quote:
Originally Posted by DanH
... It's just fiberglass.
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Good one, Dan! You know, we are not all Composite Wunderkinds like you. You might as well have said, "It's just quantum physics." 
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Don McNamara
Peoria, AZ
Builder: RV-8 "Smokey"
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09-06-2012, 12:21 PM
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Join Date: Dec 2005
Posts: 182
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Round Engine Inlets
Kelly Johnson once said: "Round engines like round air."
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09-06-2012, 01:24 PM
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Join Date: Jan 2008
Location: Ashland, OR
Posts: 2,573
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round inlets and plenums
Bear in mind that the primary reason for the round inlets is to make a simple interface for the plenum to connect to. The rings nest into groves in the mating cowl rings. It is easiest to do this with round holes, so you can turn the rings on a lathe.
But, many have used plenums and adapted to the more stock inlet shape.
There is no intrinsic aerodynamic advantage to the round cooling inlets, and if not done right (size, lip radius) it is possible for them to be a disadvantage. The stock inlet shape spills flow very gracefully and does not cause much spillage drag. At high speed, there is sometimes flow coming out near the spinner, and going in over the outboard portion of the opening.
For some, it is probably an aesthetic thing.
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Steve Smith
Aeronautical Engineer
RV-8 N825RV
IO-360 A1A
WW 200RV
"The Magic Carpet"
Hobbs 625
LS6-15/18W sailplane SOLD
bought my old LS6-A back!! 
VAF donation Jan 2020
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09-06-2012, 04:50 PM
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Join Date: Oct 2005
Location: 08A
Posts: 9,500
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Quote:
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Bear in mind that the primary reason for the round inlets is to make a simple interface for the plenum to connect to.
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Fair to note a ducted plenum connection isn't really required with a low velocity (large diameter) inlet. An example might be the Mooney Acclaim, or the 0.3F inlet in CR3405.

__________________
Dan Horton
RV-8 SS
Barrett IO-390
Last edited by DanH : 09-06-2012 at 04:54 PM.
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09-06-2012, 04:53 PM
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Join Date: Jun 2006
Location: St. Louis (Eureka), MO
Posts: 283
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Buon giorno - benvenuti al mondo di Van's Aircraft.
To add to the above comments, the Sam James cowl needs little exterior finishing from the example I saw today - very smooth. But, in looking at speed and temperature data, with and without the Sam James plenum (sold by a different location in Florida), I have truly seen negligible differences. For me, it is a matter of aesthetics, with the SJ cowl much sexier looking, albeit at the price of more work (though I'm not at this stage yet, a builder today told me that the Van's baffle kit is wonderful and fits well with their cowl. With the SJ cowl, there will be many hours more work).
As an aside, there are a dozen or so RV builders in Italy. There is a Luca P not far from you, but don't know him and if he still has his flying RV. Not too far from Verona south of Milano near Lodi is Lucio Castrogiovanni, building an RV-7. I visit him every year - a great guy. Message me if you want his contact information.
Arrivaderci,
Carl
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