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HelicopterCentury Radikal G20-30 N640 Hawk Predator › CSpec and fan shroud fit...
09-04-2003 03:37 PM  14 years agoPost 1
sreuss

rrApprentice

Ontario, Canada

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Hi,

I'm finishing the installation of a cspec in my PMax and have cut the fan just upstream of the fins on the cylinder head. Unlike Payton's shroud, which is cut so that the sides of the shroud still extend down to the fins (i.e. the cut out is semi-circular), my cut is square.

My original idea was to mount a G10 extension to the outside of the existing fan shroud. The extension would then fit over a greater part of the cylinder head.

I'm wondering now if I may be better off to leave it as is, and not make the extension. The logic here is that:
- air is still being re-directed over the cylinder head, and
- this flow/jet will entrain more of the relatively cool ambient air

Does anyone have any (potentially strong) optinions and/or experiences along these lines?

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09-04-2003 03:42 PM  14 years agoPost 2
MG

rrKey Veteran

California

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sreuss,

I wish I had pics of John Benario's setup. He made a fan extension out of plastic that basically extends over the C-Spec head. It really looks good and offers much better cooling than just cutting the shroud. Maybe he will chime in and give you more details.

Time wasted = Life not lived to the fullest.

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09-04-2003 07:14 PM  14 years agoPost 3
Lift

rrElite Veteran

Houston, TX

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sreuss,
The majority of the heat on a glow motor is on the fins closest to the glow plug area. Having taken temperature readings it is easy to determine where the airflow is most criticle.

When I trimmed the Predator fan shroud I left the sides of the shroud intact so that air would be pushed THRU the fins. The top two rows of fins are not directly cooled but that is not as important since this is a rear facing engine and the Predator has alot of frame cut out back there. Whether flying forwards or backward the airfoil will get to the head surface and help cool too.

While it would be fine to build a shroud that extends over the entire head I don’t feel it’s critical on the Predator. Also, I don’t know if you noticed but the Predator has a pretty high volume airflow. You can place you hand under the engine when idling and notice it and at 13-15k rpms cooling WILL be a non issue on this machine. So, IMHO you will be fine.

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HelicopterCentury Radikal G20-30 N640 Hawk Predator › CSpec and fan shroud fit...
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