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Mar 11, 2002, 11:41 PM
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soholingo's Avatar

Power:weight for 3d planes


What is the ideal power to weight ratio for 3d planes?

would 1 to 1 be adequate or would there need to be more?

Hovering is the important thing to me...

Thanks
Jay
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Mar 12, 2002, 12:47 AM
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iankraus's Avatar
I would start with a minimum of 1.2:1 static anything less is borderline.
1.5:1 static is a much more usable proposition
2:1 static. !!

Unlike on a gas plane spining a small low pitch prop fast, geared epowered planes can spin a much bigger prop. I have found it best to use a prop with a decent amount of pitch. It unloads in the air a lot and you can fly 1/2 power without running out of pitch speed. If you try and use less pitch like on a gas plane you run out of forward speed at too high a throttle position. All the above applies to a geared motor setup.

I know some may have hovered on less than 1.2:1 but you stated that hovering was important to you. If you really want have fun I would aim for at least a computer predicted static thrust of 1.5:1 with a minimum of 40 mph pitch speed for a mid sized plane.
Mar 12, 2002, 06:40 AM
Product Manager at Hobbico
GWRIGHT's Avatar
1.2 to 1 is about minimum if you want to hover. when you get to 1.4~1.5 or greater, things get really "fun" This level of thrust/weight is really not that hard to accomplish, assuming the plane is designed to fly without a lot of speed,..i.e. it's not too difficult to get a lot of thrust from an electric,..whereas it is a bit difficult (or just expensive) to get a lot of speed. ensure that you have at least 2.5 times the stall speed in static pitch speed,.. and you're Ok. Within that paramater, gear high and swing a really big prop and get as much thrust as you can while still maintaining at least a 2.5 to one pitch speed to stall speed ratio. If you want true 3D performance with knife edge loops and such,..you will need a bit more than 2.5 to 1 in the speed realm,..more like 3 to one or so. Use a wattmeter, tach, calculator,.. and start with motocalc to get you in the ballpark,.. then try the top 10 to 15 combinations that appear to fit the requirements in motocalc. You'll find that motocalc's best guess is generally not the best performance,..but one of it's top 10 or so will get you where you want to be.
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Mar 12, 2002, 08:09 PM
Registered User
Aviron's Avatar
In the stock E3D setup, what is the thrust and pitch speed?

I am trying to figure a comination with some motors I already own and would like to know the target values. I'm looking for at least comparable performance.
Mar 13, 2002, 05:27 AM
Product Manager at Hobbico
GWRIGHT's Avatar
it's just a touch below that 1.2 to one number in thrust which means to hover you can't waste a lot of energy by wiggling the wiggly bits on the tail a lot, because you lose a touch a vertical component of thrust everytime you move a control surface . pitch speed is in the 50's (over 3.5 times stall speed). With the 14X7 on the hacker setup i havent' actually measured thrust but if feels like around 1.5 to one,.. as it will stop and pull vertical from a tailslide. pitch speed is down in the high 40's with that setup.
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