Cowl Air Routing and Possible Forces  
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Cowl Air Routing and Possible Forces - 5/28/2002 7:48:24 PM   
Jazzy



Posts: 1106
Joined: 1/8/2002
From: Erie, PA, USA
Status: offline 		I currently have a 1.08 two stroke mounted sideways in a Cap 232. The engine fits completely within the cowl. When looking at the cowl from the front, the right cowl opening basically doesn't cool anything, allows air to simply pass through the cowl, around the Pitts muffler, and out the bottom.
The engine tends to run a bit 'hot.'
Would ducting the air coming in the afore mentioned cowl opening across the front of the cowl, (inside), to help cool the head cause the plane to veer to the left in flight?
Would it be better to just block it off?
I'm trying to find the most efficient way of using the already available air stream to help cool the engine without affecting flight.
I understand the force of the vectored air may be inconsequential but, I thought I'd ask anyway.

Thanks for any suggestions or help.

Jeff

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Aww $#!^.... I left the )@#& transmitter at home!
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Cowl Air Routing and Possible Forces - 5/29/2002 12:55:11 AM   
Al Stein



Posts: 968
Joined: 1/7/2002
From: Johnstown, PA, USA
Status: offline 		If you have room to effectively direct the airflow, it may help.

The two things that seem to make the biggest difference I know of is directing the air over the cooling fins and out (not letting it wander around the inside of the cowl unguided) and making sure that the airflow exit is two or three times as big as the entry.

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. . . Aim High!

(in reply to Jazzy)
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Cooling Air Exit/Intake Area - 6/13/2002 9:00:09 PM   
Schwing RC



Posts: 36
Joined: 6/2/2002
From: Mercerville, NJ, USA
Status: offline 		Jeff,
You should have about 2/3 more exit area as intake area for good air flow around the fins. Engine heated air expands a lot under the cowl, if it has nowhere to go you'll get less flow by the cylinder. You could try a baffle in the left cowl front, or make sure you have a gap all around the firewall at the rear of the cowl. This worked well with some of my radial warbirds where a plastic dummy radial engine works as a baffle, with one or two dummy cylinders removed near the glow engine's cooling fins. No driving around though, get up to speed quickly on hot days.

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Tom Schwing, Schwing RC

(in reply to Jazzy)
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force the air - 6/14/2002 2:30:39 AM   
Johng



Posts: 1821
Joined: 1/24/2002
From: Deland, FL, USA
Status: offline 		The way to cool the engine is indeed to force all the air coming into the cowl to go past the engine. This would be done by baffling the cowl so the air has to travel thru the fins of the motor.

Imagine slicing the front of the plane off, thru the center of the engine. If you made a plywood baffle to fit the shape of all the cross sectional area here except for that taken up by the cylinder, motor mount, etc it would close off all possible airways except for the cylinder fins. It would be glued inside the cowl, so that it wouldn't interfere with access to the motor or whatever when the cowl is off. It's the easiest mounting solution too.

You may want to oversize the motor cutout a bit and then use some hi-temp gasket material to make a direct air seal around the perimeter of the cylinider. That will allow relative motion between the baffle and cylinder and make it easier to get the cowl on and off.

BTW- you may think this increases drag, but it actually decreases drag by reducing the amount af air that actually scrubs thru the cowl. Not that drag reduction on an aerobat is necessarily a good thing either.

_____________________________

John

(in reply to Jazzy)
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Cowl Air Routing and Possible Forces - 6/16/2002 12:07:20 AM   
Jazzy



Posts: 1106
Joined: 1/8/2002
From: Erie, PA, USA
Status: offline 		Thanks for the ideas.
Looks like I've got some tinkering to do...


Jeff

_____________________________

Aww $#!^.... I left the )@#& transmitter at home!

(in reply to Jazzy)
       Post #: 5

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