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Old 07-30-2012, 01:58 AM   #1
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Default 10x7sf or 10x7 standard prop

I have a Eflite Alpha 450 with a 450 motor. My question is in a wind above 5 kts which prop is best? I was flying at my club a couples day's ago with the standard 10x7 prop, when the wind came up fast and the plane was hard to handle. Should I have used the 10x7sf?
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Old 07-30-2012, 03:44 AM   #2
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Probably not. The 10x7 Slow Flyer prop would give you more thrust at slower motor speeds (part throttle), and a slightly lower top speed because the wider blades load the motor down more. If you were having trouble flying in wind, lack of thrust at low speed with the standard 10x7 was probably not the problem.

Flying in wind takes experience. Gusts make the plane do things you didn't command. Planes seem twitchy flying upwind and sluggish flying downwind. It's very common for the pilot to misjudge the plane's speed flying downwind, and slow the plane till it's on the point of stalling while it appears to the pilot to be moving plenty fast.

The simple solution for flying in wind is to fly just a little faster than usual, the whole time. That smooths things out. For that, your standard 10x7 may actually be a slightly better choice. In practical terms, there won't be all that much difference.

I meant to do that! Anyway, I can fix it.
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Old 07-30-2012, 07:31 AM   #3
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I run a 10X5 on mine, but I'm running a 240 watt headsuprc power up 450 sport motor. Its fairly comparable to the eflight motor for less then 1/2 the cost. It is a 1100kv motor though. While I was playing around with props and the watt meter, I could tell very little differance in top speed going to higher pitch props. I think the airframe isn't capabile of much over 50 mph. I'd guess I'm 45 mph top level speed.

The plane is really a floater, and even a small gust of wind can make it hard to handle if your not expecting it. I'd run whatever you feel comfortable normally and go from there. You don't want the plane to fly dfferent or change props because of wind.

I generally fly at 5-15mph winds lately. 10-15mph its not much fun. 45 seconds up wind, then 10 seconds down wind if you want to keep it semi close in a full circle.

How do you have your rates and expo setup? I just guessed on mine, and added a bit of extra rudder till I got what I thought looked right. I don't use any computer radio fancy stuff, except I did mix in the other aleroin with an extra channel. You can try adding flapperoins, but I didn't care for them much. The flapperoins just slow the plane down and require more throttle to keep moving forwards.

Here's a couple of video's to show you how well the plane can fly slow and easy once you get used to it.
http://youtu.be/0j2uhcxDeIQ
http://youtu.be/YKa9mqKVzog
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Old 07-30-2012, 07:23 PM   #4
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thanks for the help
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Old 07-30-2012, 07:51 PM   #5
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whatever you do DO NOT fit a slow fly prop to that plane. Slow fly props are for low speed low RPM applications and you risk them throwing off blades if you over-speed them.

APC state an RPM limit for their SF props of 65,000 divide by diameter (in inches).

That means for a 10" prop the limit is 6,500RPM. Your 890kv motor on a fresh 3s battery will spin that prop at about 7500 - 8000RPM on the ground and maybe close to 10,000RPM in the air

Anyway, the prop wont make a jot of difference to how the plane handles the wind. It's really down to getting experience of flying in the wind, it can be a lot tougher than flying on calm days but all the props in the world wont change that.

Steve
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