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Old Jun 29, 2007, 11:05 PM
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El Cajon, CA, USA
Joined Feb 2001
801 Posts
Question
Effect of air temp on engine power

So I left San Diego earlier this week and went to Phoenix to visit a friend. I put hawk up in the air and it was super gutless. Now mind you it's never got much power (OS .32) but this was rediculous. The thing could barely get outta its own way.

The temp was up over 110 and I know that effects power since less oxygen is in each stroke and poor heat dissipation but I didn't think it would be THAT bad.

I know....I need to move up to a .37. That will happen quite soon.

Just curious what you guys think of power and heat.

Thanks
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Old Jun 29, 2007, 11:11 PM
I don't want to "Switch Now"
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Toronto (Don Mills), Canada
Joined Dec 2002
16,942 Posts
Two problems - less power from the motor and less lift from the blades.
Also SD is more or less at Sea level , Phoenix about 1100 feet.

More nitro and/or a bigger motor

Pat MacKenzie
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Old Jul 06, 2007, 09:14 PM
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Joined Aug 2006
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The hotter air is, the more water vapor it contains, which lowers its density which gives your engine and blades less air to bite into, which equals less power.
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Old Jul 07, 2007, 12:12 AM
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Christchurch, New Zealand
Joined Jun 2006
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Not quite... water and temperature are separate problems (although there can be a lot more water in hotter air, I bet there wasn't in Phoenix).
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Old Jul 07, 2007, 01:02 PM
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El Cajon, CA, USA
Joined Feb 2001
801 Posts
All I know is that the thing was running pretty dang hot until I richened it up. Then the power fell and it was difficult to maintain headspeed while doing much of anything.

My .37 arrived yesterday. About stinking time. I've been cheap and pushed that .32 to the limit. I'm tired of gimping around.

Thanks guys

Daniel
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Old Jul 08, 2007, 01:46 PM
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Hi Andrew, do you mean to get your density altitude?
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Old Jul 08, 2007, 07:05 PM
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Christchurch, New Zealand
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Density altitude first, and then correct for humidity (I forget the correct name for that).
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Old Jul 08, 2007, 09:34 PM
Kamikaze Heli Pilot
Japan
Joined Jul 2005
466 Posts
This document may be of interest

http://www.raptortechnique.com/highaltitude.htm
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Old Jul 10, 2007, 03:23 AM
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Been 3 years since CPL Met
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