RE: Predator II ??  
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RE: Predator II ?? - 5/7/2006 2:39:50 AM   
Lifes a Drag



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Status: offline 		I had to think about this for a second. But if I remember correctly, going back to high school physics, the terminal velocity between the two would be greater with the heavier weight. Therefore, given equal power sources, equal forces, and all other thigs being equal besides weight, the lighter object would indeed result in higher speed if neither ever reached the maximum velocity of the lighter object.

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RE: Predator II ?? - 5/7/2006 4:43:40 AM   
BUDMAN27



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RE: Predator II ?? - 5/7/2006 5:07:00 AM   
Airbike


 

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Status: offline 		Sorry Ron, I'm with Budman..Say What?


High school physics; if you dropped two Predators from 1000' nose first, straight downline, the heavier one would hit the ground first.

F=ma bigger mass=bigger force acting on it while aerodynamic drag stays the same for identical objects.

Lighter plane creates less induced drag from less lift required.

But I thought the final conclusion was that a better flown line will have much greater impact on lap times than a slightly heavier plane.

Oh I understand the thought process of stacking everything you can in your favor, but for a newbie like me, I'll just do the simple things and not worry about the bugs on the leading edge or a couple of extra ounces.

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RE: Predator II ?? - 5/7/2006 5:16:51 AM   
djlyon



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Status: offline 		Airbike you slept through high school physics and you never read Newtons laws if you think the heavier object will hit first when the aero drag is the same.

Denis

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RE: Predator II ?? - 5/7/2006 5:54:27 AM   
HighPlains


 

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Status: online 		Sometimes HS physics is not enough.

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RE: Predator II ?? - 5/7/2006 5:55:55 AM   
HighPlains


 

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Status: online 		But airbike is correct as to which airplane would hit first.

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RE: Predator II ?? - 5/7/2006 6:05:21 AM   
Airbike


 

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Status: offline 		Djlyon,

did I miss something? heavier objects of the same size fall faster IN AIR (or other fluids too).

Whoever dropped the stuff off the leaning tower of Pisa just couldn't measure accurately.

....but then there was this giant threadmill...



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RE: Predator II ?? - 5/7/2006 12:57:18 PM   
BUDMAN27



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Status: offline 		Sounds like we need to get the TV show Myth busters involved with our problem, if you want to call it that.

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RE: Predator II ?? - 5/7/2006 3:44:31 PM   
HighPlains


 

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RE: Predator II ?? - 5/7/2006 4:41:32 PM   
Lifes a Drag



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quote:

ORIGINAL: BUDMAN27

Say what?


Budman, your lighter air rifle pellets traveled at a higher fps than the heavier ones given the same force.

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RE: Predator II ?? - 5/7/2006 4:56:59 PM   
Lifes a Drag



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Status: offline 		Dan,

Wrong theory. We’re not dropping planes from a building. Point A and point B are 90 degrees opposed to gravity. Gravity plays only a part in velocity.

Picture this. Two Predators exactly alike in every way, both being pulled by a power source, which produces exactly 6lbs. of thrust, only one plane weighs 3lbs., the other weighs 5.5lbs. Assuming both leave point A at exactly the same time and travel a perfectly straight line, which will arrive at point B first?

Weight is the enemy.

< Message edited by ***Reno*** -- 5/7/2006 4:58:20 PM >

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RE: Predator II ?? - 5/7/2006 5:46:18 PM   
BUDMAN27



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From: Galveston, TX, USA
Status: offline 		But like he was saying . Thats in a perfect world. What about a windy day. shouldn,t a heavyer plane be able to say on track better.

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RE: Predator II ?? - 5/7/2006 6:01:04 PM   
Lifes a Drag



Posts: 957
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From: La Habra, CA, USA
Status: offline 		Hi Budman.

Mass and drag coefficients come to mind. I am just thinking Newtons first and second laws of motion.


Anyway if you're interested and have the time, check out this link for some really good reading.

http://www.auf.asn.au/groundschool/index.html




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RE: Predator II ?? - 5/7/2006 10:03:19 PM   
djlyon



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Status: offline 		You didn't miss anything Airbike. I missread what you wrote and then tried to cancel my post but I guess I failed.

Denis

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RE: Predator II ?? - 5/8/2006 12:31:50 AM   
Airbike


 

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Status: offline 		I think everybody agrees that a heavier plane will be slower for the same conditions. I don't even think the heavier plane is noticeably more stable in windy weather (we're talking just a few ounces here).

Reno, you missed some impromtu laps at Whittier last Sat afternoon. However, the local club guys got all upset at not following the AMA rules. (Well, really at a novice flyer that flew so wide, he was basically over the pits). They didn't get upset when we were doing laps really tight at the runway.

Anyways, its almost like no flying behind the "standard pilot flight line" except during an official event. So technically, no lap practice except the afternoon before the race and during the race. All other times, its against AMA rules.....

I think if we kept safety in mind, it shouldn't be a problem. We waited until others had landed before we launched. It's probably best to do lap practice only when there is hardly anyone there. A while back, the park police gave another flyer a hard time when he did some "laps" while standing on the runway.


What's the optimum CG for a quickie? I'm just trying to adjust battery location so that the plane will fly level without elev trim (drag). Is it better to be a bit nose heavy (perhaps more stable)? or is it better to have the CG farther aft (perhaps less tail downforce, less drag)?

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